US3355605A - Crossed field plasma device - Google Patents

Crossed field plasma device Download PDF

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US3355605A
US3355605A US310608A US31060863A US3355605A US 3355605 A US3355605 A US 3355605A US 310608 A US310608 A US 310608A US 31060863 A US31060863 A US 31060863A US 3355605 A US3355605 A US 3355605A
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gas
electron
mhd
generator
ionization
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Ernest C Okress
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American Radiator and Standard Sanitary Corp
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02KDYNAMO-ELECTRIC MACHINES
    • H02K44/00Machines in which the dynamo-electric interaction between a plasma or flow of conductive liquid or of fluid-borne conductive or magnetic particles and a coil system or magnetic field converts energy of mass flow into electrical energy or vice versa
    • H02K44/08Magnetohydrodynamic [MHD] generators

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  • Cooler 58 60 Gas Purifier Regenerator 50 54 MHD Generator Primary Heat Source Faraday Electron Collector Electrode (Anode or Accelerator) E J F: D n 0l nu mu M 5 mm t. A
  • This invention relates generally to (thermal to electric) gaseous energy converters and more particularly to a cross field non-equilibrium plasma-type referred to generally as a non-equilibrium magneto-hydrodynamic (MHD) generator.
  • MHD magneto-hydrodynamic
  • Common MHD generators utilize thermodynamic equilibrium or thermal ionization of the Working medium, which is commonly seeded (combustion) gas in open cycle operation. Because of the extremely high temperature of the working medium which would be required for MHD generator conditions with gas alone (e.g., 5800 F. 1 mho/m., 6900 F. mho/m. and 8500 F. 100 mho/m.) to ionize most gases because of the relatively high ionization potential required to achieve the desired electrical gas conductivity, seeding material (e.g., 1% molar alkali, such as potassium or cesium), which ionizes at a relatively lower gas temperature, is generally added to the gas.
  • gas alone e.g., 5800 F. 1 mho/m., 6900 F. mho/m. and 8500 F. 100 mho/m.
  • seeding material e.g., 1% molar alkali, such as potassium or cesium
  • the purpose of ionization of the working medium is to obtain suificiently high electrical conductivity for the purpose of achieving optimum MHD generator performance and tolerable MHD generator sizeespecially with respect to its dominant physical parameter, the electrical conductor or ionized gas duct length.
  • crucial material limitations arise because of the high gas temperatures associated with combustion MHD generators which tax the endurance of available (electrode and confining wall) materials to so drastically limit the duty of operation and life of the MHD generator and associated system as to require impractically low values of these parameters.
  • Commercial apparatus is invariably continuous or full (i.e., 100%) duty, relatively high impedance, alternating current type, with generally long reliable life characteristics.
  • Equilibrium vs. non-equilibrium gas ionization denotes whether the ion species temperature is comparable with or higher than, respectively, the gas or more properly the related stagnation temperature (by virtue of the isentropic expansion relation).
  • This feature requires extremely short (i.e., order of state of art millimicrosecond) pulse durations, but at corresponding high duty to mitigate the correspondingly rapid recombination rate and so as not to depart significantly from continuous (full duty) operation conditions.
  • FIGURES 1A, 1B, 1C and 1D are schematic and vector diagrams of various electrode configurations appropriate for use in MHD generators
  • FIGURE 2 is a flow diagram of a closed cycle MHD generator
  • FIGURE 3 shows salient MHD quantities involved in the description of MHD energy converter operation
  • FIGURE 4 is a schematic representation of an MHD generator or an MHD motor in accordance with the principles of the invention.
  • FIGURES 4A through 4E illustrate alternate electrode pair means of applying pulsed ionizing voltage to interaction space of the MHD generator or MHD motor illustrated in FIGURE 4;
  • FIGURE 5 is a perspective view representing schematically a mechanical nozzle or convergent-divergent gas duct with electrodes for an MHD generator of the type shown in FIGURE 1C and FIGURE 4;
  • FIGURE 6 is a longitudinal sectional view of an illustrative embodiment of an MHD generator in the form of a straight constant cross-section gas duct;
  • FIGURE 7 is an external elevational view of the device shown in FIGURE 6;
  • FIGURE 8 is an external end view of the device as viewed in FIGURE 6;
  • FIGURE 9 is a partial view of an electrical connector of low heat transmission characteristics as viewed along the line 99 in FIG. 6;
  • FIG. 10 is an clevational view of an insulating (e.g.,
  • FIG. 11 is a cross-sectional view taken along the line 1111 in FIG. 6;
  • FIGS. 12 and 13 are fragmentary views of duct walls grooved and preshaped to receive short-circuiting straps as shown in FIGS. 6 and 11;
  • FIG. 14 is a schematic showing of an arrangement for applying a magnetic field to a gas duct by means of ordinary (or superconducting) solenoid electromagnet in which wrought iron pole pieces are saturated and, consequently, no yoke is used;
  • FIG. 15 is a cross-sectional view taken along the line 15-45 of FIG. 16;
  • FIG. 16 is a schematic cross-sectional representation of a compound crossed field electron gun with strip cathodes and multiple vane control electrodes for injection and modulation (for alternating current operation of the MHD generator) of an electron beam in a gas duct;
  • FIG. 16a is a cross-sectional representation of a crossed field electron gun for direct current operation of the MHD generator, this structure being substituted for the electron gun of FIG. 16 when direct current Operation is desired rather than alternating current operation;
  • FIGURE 17 is a schematic plan view taken along the line 17-17 in FIGURE 16;
  • FIGURE 18 is a schematic cross-sectional representation of a compound crossed field electron gun with multiple plasma-cathodes for injecting an electron beam into a gas duct;
  • FIGURE 19 is a schematic plan view taken along the line 1919 in FIGURE 18;
  • FIGURE 20 is a schematic cross-sectional representation of a dual compound electrostatic electron gun with strip cathodes, for injecting electron beams into a gas duct along the direction of the applied magnetic field in an MHD generator (or motor);
  • FIGURE 21 is a schematic cross-sectional representation of a dual compound electron gun with plasma. cathodes, for injecting electron beams into a gas duct along the direction of the applied magnetic field in an MHD generator (or motor);
  • FIGURE 22 is a schematic representation of a helically wound gas duct of an MHD generator (or motor) with ordinary (or superconductor) solenoidal windings for providing the required magnetic field, an outer solenoid being partially cut away.
  • MHD generator or motor
  • ordinary (or superconductor) solenoidal windings for providing the required magnetic field, an outer solenoid being partially cut away.
  • FIGURE 23 is a schematic representation of the device as shown in FIGURE 22 in longitudinal cross-section;
  • FIGURE 24 is a schematic cross-sectional representation of a helically wound gas duct of an MHD generator (or motor) with saturated magnet iron pole pieces and ordinary (or superconducting) solenoids disposed between adjacent turns of the helically wound duct.
  • MHD generator or motor
  • saturated magnet iron pole pieces and ordinary (or superconducting) solenoids disposed between adjacent turns of the helically wound duct.
  • FIGURE 25 is a schematic diagram of typical electrical connections suitable for connecting an MHD generator of the type shown in FIGURE 1C to an MHD motor of the type shown in FIGURE 1D.
  • thermal energy in a suitable unseeded gas derived from a primary heat source can be directly converted into commercial, direct or alternating current electricity, depending upon the ultimate application.
  • a primary heat source e.g., fossil fuel, solar energy or gas cooled nuclear reactor
  • Crossed field electron beam and interdependent periodic ionizing electric field impulse gas ionization means are utilized to provide a device whose gas temperature does not tax the endurance of the associated materials.
  • an MHD device which can operate continuously at full (i.e., 100%) duty and still have a long operating life is provided.
  • a suitable gas is nonequilibriumly or electrically ionized to make it optimumly electrically conducting, by crossed field means, involving electron injection, and/or by periodic ionizing electric field impulse means, thereby enabling the device to convert directly a major part of the thermal or kinetic energy, of the gas imparted to it by a suitable primary heat source, directly into electricity.
  • the rate of extraction of enthalpy from the gas by the MHD generator derives from the usual energy balance, which shows that it depends strongly (i.e., square) on the gas velocity-magnetic field product, for a given efi'lciency, conductivity, Hall parameter, degree of nonuniformity and ion slip, neglecting heat loss to the exterior and changes in kinetic energy in the gas.
  • the energy transfer means is in accordance with the equivalent Hall or Faraday generator principle, taking cognizance of the fact that whereas the energy transfer via a metal electrical conductor is by virtue of the positive ions anchored to the crystal lattice, in a gas electrical conductor energy transfer occurs only by virtue of attractive electrical forces and predominately axially directed collisions between (unanchored) ions and (neutral and excited) gas molecules.
  • This invention is also capable of directly converting electricity to mechanical (directed kinetic) ener y of the gas, in accord with the equivalent Faradays motor principle.
  • the resulting MHD motor or pump, accelerator or compressor does not depend on any moving mechanical parts and, therefore, it eliminates the need for any mechanical components in the whole system.
  • the energy required to operate the MHD motor is derived from a tolerable fraction of the MHD generator output.
  • Either fossil fuel, direct solar energy or a gas cooled nuclear reactor may serve as the primary heat source for heating the gas or working fluid of the proposed energy converter.
  • the electrical power output can be con tinuous or full (100%) duty (i.e., direct current), or intermittent (i.e., pulsed), or alternating (e.g., sinusoidal) cur rent.
  • duty i.e., direct current
  • intermittent i.e., pulsed
  • alternating e.g., sinusoidal cur rent.
  • low drive of a voltage controlled electrode system of the crossed field (or electrostatic) electron gun used for injecting the electrons into the gas at high efficiency for complete absorption and ionization of the gas
  • pulsed modulation various pulse durations and repetition rates can be utilized.
  • alternating current modulation various frequencies, including commercial or utility frequencies, can be realized.
  • the life of the non-equilibrium MHD motor is not limited in duty or life by the state-of-art materials of the (metallic) electrodes and confining (dielectric) duct walls.
  • highly efiicient nonequilibrium electrical gas ionization i.e., 90%
  • equilibrium or thermal (high temperature) gas ionization instead of equilibrium or thermal (high temperature) gas ionization and the required doping or seething with easily ioniza-ble material (e.g., potassium, cesium, and the like).
  • gas temperature of 3500 to at least 4000" F. are required by thermal or equilibrium MHD generators in obtaining desirable electrical con ductivity of the seeded gas.
  • the temperature of the gas is approximately 2500 F. as it need mainly be adequate for good thermodynamic (cycle) efficiency (e.g., -45%) and, suitable with respect to duty and life of the primary source of heat, such as a gas cooled nuclear reactor. It is possible to obtain high generator efficiency (i.e., theoretically about 95%) and high cycle efficiency (i.e., '-45% at 2500 F.).
  • the upper practical limit of the generator efiiciency is dependent upon the maintenance of an adequate uniformity and stability, -(e.g., avoidance of spark channels) in the plasma. Spark channels and consequently excess channel ionization can be alleviated, especially in the crossed field guns, :by resort to periodic (rectangular) impulses of extremely short (i.e., order of a nanosecond) pulse duration and rise time (within state of art capability of a decinanosecond and centinanosecond, respectively) at high duty, so as to mitigate the effects of recombination rate and provide virtually continuous (full duty) operation.
  • pulse duration somewhat longer than this serves to substantially supplement the degree of gas ionization afforded by the crossed field electron injection since all the electrons in the gas are involved.
  • the MHD generator and MHD motor are capable of self excitation and possess rapid starting characteristics.
  • the performance features of the MHD generator are best realized especially with respect to the electron beam gas ionization means alone when the Hall (effect) parameter, B (i.e., product of electron mobility, and magnetic field B), is dominant.
  • B i.e., product of electron mobility, and magnetic field B
  • the requirement of high electron mobility including considerations relative to the primary heat source, as well as to (high) specific heat/thermal conductivity and (low) molecular weight, on account of thermodynamic and aerodynamic condsiderations, are satisfied by using noble gases at low pressure.
  • High magnetic field reduces generator size, reduces losses proportional to Wall area and enables quicker extraction of power.
  • electrical non-equilibrium ionization of the gas is efiiciently initiated and maintained with negligible, if any, gas flow obstruction or at the expense of magnetomotive force of the magnets.
  • This gas ionization means is achieved dually by crossed field electron beam injection means supplemented by periodic ionizing electric impulse means in the guns and interaction duct. While the former is characterized by a finite number of electrons the latter involves all the electrons in the gas.
  • the electron beams can be injected into and guided in the MHD generator (or MHD motor) interaction space, for example, by means of an applied (electric-magnetic) crossed field (short, long, space charge, ramp or magnetron optic) electron guns, it being understood however, that the electron emitting source is not restricted to a solid state type (e.g., plasma).
  • the term short or long" crossed field electron gun refers to the length of the electron guns cathode along the electron orbit direction in vacuum. When the vacuum length is less than a half (and in particular a quarter) cycle the gun is termed short optic. When otherwise (i.e., several half cycles) the gun is termed long or adiabatic optic.
  • the electron beam can also be injected electrostatically into the MHD generator (or MHD motor) interaction space, along the (applied magnetic field axis which acts as a beam focusing field).
  • MHD generator or MHD motor
  • the electron beam must permeate the gas interaction space completely and continuously, due to the inherently rapid gas ionization decay rate and for sake of uniformity, especially at injection sites. This means provides a finite number of electrons into the gas and so its ability to provide the desired gas electrical conductivity is correspondingly limited.
  • the applied periodic rectangular ionizing electric impulses are applied to all the electrons in the gas since this field is impressed between the electron emitters (i.e., cathode) and electron collectors (i.e., anodes or accelerators) and are of such duration (e.g., order of a centimicrosecond) that, together with the injected electron beams, competitive non-equilibrium and uniform gas electrical conductivity (e.g., 10 to 1000 mho/m.) may be achieved without sparking and consequeut excess ionization.
  • This supplementary means is inherent in the operation of the system.
  • This invention avoids all of the thermal or equilibrium MHD generators material problems by using a gas temperature that is substantially lower and below the thermal endurance limitations of materials, consistent with reasonable thermodynamic (cycle) efficiency. With this invention it is not necessary to seed or dope the gas and, naturally, the problem of recouping the seeding material is eliminated. However, it is not here implied that seeding or doping the gas cannot be used, since there may not be need for recouping the seed material in closed cycle operation.
  • the proposed system can be used with various (fossil fuel, gas cooled nuclear reactor or solar) primary heat sources due to the relatively low gas temperature, it is very adaptable for use with an advanced gas cooled nuclear reactor having unclad fuel elements as primary heat source, taking cognizance of the fact that state of art nuclear reactors operate in the vicinity of 1,0- F.
  • a Rankine rather than a Joule cycle is indicated, hence a condensible working medium (e.g., Ce) may be incorporated.
  • this invention also embraces an MHD motor or pump or accelerator or compressor having no mechanical moving parts and which is capable of moving gas at velocities from subsonic, to supersonic and even hypersonic magnitudes. While the MHD motor, pump, accelerator or compressor component is used for moving the gas in a closed cycle system for generation of electric power, it can be adapted for use in an open cycle system for providing MHD propulsion of space vehicles.
  • the normally linear structure of the MHD generator for electrical gas conductivities significantly less than about mho/m., can be rolled into a helical structure as a conventional helix delay structure of an appropriate electronic tube (e.g., traveling wave tube) or folded into a meander structure, as an interdigital delay line (of such an electronic tube) in order to avoid unwieldly structures and objectionable and even impractical overall dimensions, while utilizing such length of the gas duct, or electrical conductivity of the gas.
  • conservation of magnetomotive forces can also be affected in the production of the required uniform magnetic field in the interaction space.
  • the helical structures can be referred to as periodic magnet helix MHD generators (or motors). While the helix (or meander alternative) duct structures are not here considered further, it should be remembered that this invention can also assume these configurations.
  • the voltage and current or power is taken off longitudinally or axially by appropriate electrodes in the interaction duct, which conveys the electrically conducting gas.
  • the transverse currents provide the necessary physical resistance to the gas flow.
  • the physical power density expended by the gas flow by pushing against the electromagnet forces is represented by the sealer product v BI (where v denotes the gas velocity, B denotes the magnetic field and I denotes the transverse current density).
  • Substantially similar structural configurations can be used in the MHD generator and the MHD motor or pump or accelerator or compressor, except in the latter case appropriate structural and electrical alterations are dictated and the voltage is applied across the electrodes of the desired configuration, illustrated in FIGS. 1A, 1B, 1C, 1D.
  • the electrically conducting gas is heated to the appropriate temperature by the primary heat source and forced through the magnetic field to generate electric power output in the manner discussed in the text and in accordance with the Hall or Faraday generator principle in which the major current flows perpendicular to the strong magnetic field. Furthermore, it is essential that the energy loss to the duct walls be kept to a tolerable low level compared with the generated or dissipated energy in the volume of the gas. This implies maximizing the gas pressure-cross section product. Finally, it is essential to maintain uniform ionization at an adequate level. In the case of the MHD motor, the Hall or constant K electrode configuration also can be used with appropriate external voltages impressed across the electrodes.
  • the output ends of the MHD generator and MHD motor are combined in a unitary structure to form a regenerative heat exchanger (or regenerator and preheater, respectively), wherein heat from the residual hot gas discharged from the MHD generator is conducted to the colder gas leaving the MHD motor or pump or accelerator or compressor to preheat the gas which is on the way to be reheated by the primary heat source.
  • a regenerative heat exchanger or regenerator and preheater, respectively
  • Energy transfer in this case can result only from attractive forces and collisions between molecules in the gas conductor. Charges are generally equally divided in number between electrons and ions, therefore, in transferring their energy to an external load they are decelerated at the expense of their directed kinetic energy. However, for the sake of high conversion efiiciency, the essentially neutral gas molecules must also be decelerated by transferring energy to the charges. Now, the electron mobility is high relative to that of the ions and hence the electrons are responsible for the major electric current flow. Also, electrons under the influence of an appropriate electric field decelerate promptly, due to their low mass, and form a space charge. This electron space charge exerts electrostatic forces on the positive ions.
  • the gas stream in forcing the charges through the applied fields, is decelerated and, furthermore, continually replenishes these charges.
  • the reduced kinetic energy of flow appears as electric energy at the terminals of the generator in accord with Faradays generator prin ciple.
  • the effective collision cross section of ions with electrons is enormously greater (e.g., by thousands of times) than that between electrons and neutral gas molecules. Consequently, the electric gas conductivity at about a tenth of one percent ionization may be considered to be effectively equivalent to that at complete ionization. Therefore, essentially three mechanisms of gas retardation or braking by charges may be considered to be as follows: Namely by electrons alone, by positive ions alone and by electrons and positive ions together, with the gas atoms.
  • Electrons experience strong interaction or coupling with the magnetic field, and so are promptly braked by it, due to their relatively small mass.
  • positive ions experience no relatively significant interaction or braking by the magnetic field because of the strong interaction or coupling between the transverse moving positive ions and the gas atoms by virtue of their comparable masses and collision cross sections. Nevertheless, because of their comparable collision cross sections, positive ions experience strong interaction or coupling with the gas atoms and hence effectively retard the gas atoms by directed elastic collisions. Strong coupling or interaction between electrons and positive ions by virtue of their electrostatic forces serves to join these two mechanisms so as to effectively retard the gas atoms.
  • the (eflicient) process of controlled crossed field electron beam injection into the gas is proposed as one of two interdependent gas ionization provisions as the gas enters the cross field interaction space of the MHD generator (or MHD motor).
  • this gas ionization means is supplemented by application of periodic ionizing electric field pulses below the sparking limit (i.e., order of decimicrosecond) to ionize the gas to the required degree in order to achieve the desired electrical gas conductivity (i.e., 10 mho/m.).
  • the gas ionization so produced can be made relatively uniform across and along the interaction region to avoid excess ionization (e.g., at electron injection orifices, or by too long ionizing voltage pulse, depending on ionization means) and simultaneously combat the relatively rapid ionization decay rate.
  • the time for ionization to reach the desired level is extremely short (augenblicklich), so that for typical MHD generator operation excess ionization and sparking would be expected in the order of a microsecond and inadequate ionization in the order of a nanosecond.
  • the decay of the ionization from its established level is likewise rapid, so that the electrical gas conductivity under typical MHD generator operation can be reduced to such an extent that it is no longer useful in the order of a demisecond.
  • Control of the gas conductivity by the proposed means are such that it can be maintained within an optimum range. That is, not too low, for good efficiency and tolerable generator size (especially duct length) at a given power, and also not too high, so as to avoid severely distorting the cross sectional flow front of the gas stream and severe entropy changes due to excessive Joule heating losses from currents in undesirable paths.
  • Using the crossed field electron guns and periodic ionizing electric field pulses here disclosed it is possible to achieve uniform ionization and electron injection efficiences approaching high values (e.g., percent).
  • gas velocity should also be high, for the sake of high power density and (minimum) generator size (especially duct length), there is the frictional pressure drop and other aerodynamic problems to be considered.
  • a gas velocity in the subsonic range is indicated; it being understood, however, that other than subsonic gas velocities can be used.
  • the generator efficiency (i.e., theoretically 90%) and thermodynamic or cycle efiiciency (i.e., order of 50%) of energy conversion are correspondingly high.
  • the device is capable of continuous (i.e., 100%) duty operation with long competitive (power station) life, since the materials of electrodes and confining walls are not taxed to or beyond their thermal endurance by the relatively moderate (i.e., order of 2,500 F.) operating gas temperature.
  • crossed field gun operation involves pulsing the ionizing electric field at such short pulse duration (e.g., order of decimicrosecond for typical MHD generator operation) that sparking and nonuniformity in gas ionization are not encountered and at such high duty as to mitigate the deleterious ionization decay rate so as to approach full duty operation of the MHD generator.
  • the required high purity of the noble gas is maintained by effective (physical, chemical and/or electrical) continuous gettering of gas impurities (e.g., polyatomic molecules) in the interaction space of the MHD generator or MHD motor or pump or accelerator or compressor so as not to significantly degrade the electron energy by inelastic collisions.
  • gas impurities e.g., polyatomic molecules
  • the methods of gettering can include electrical crossed field methods as well as purely physical and chemical methods. Continuous monitoring or measuring of the actual purity of the gas is necessary and can be accomplished by means of magnetron and mass spectrometer, together with appropriate diagnostic determinations of electrical conductivity and other relevant parameters of the plasma associated with the performance of the devices disclosed.
  • FIGS. lA-lD there is shown schematically various electrode configurations and associated vector diagrams which can be employed in MHD energy converters.
  • FIG. 1A will be termed the elementary Faraday (E) type configuration. This is a transverse or shunt type, that is, the voltage, current or power extraction in the case of the generator of this type is transverse.
  • the electrodes are continuously conductive along the length of the gas duct and are connected to a single load.
  • the (not necessarily) uniform magnetic field intensity, in the MHD interaction space is indicated perpendicular to the plane of the paper and the gas velocity, v is represented by an arrow as directed. This configuration of magnetic field intensity and gas velocity is assumed to be the same in each of the FIGS. lA-lD.
  • FIG. 1B will be termed the multi-load-shunt (or 1r) Faraday segmented type utilizing transverse or shunt power extraction.
  • the electrodes are segmented and each electrode pair is connected to a separate isolated load R
  • FIG. 1C will be termed the Hall (or H) type. It utilizes longitudinal (or series) power extraction.
  • the electrodes are also segmented and connected to a single load, while the individual opposing electrode pairs are strapped as indicated.
  • FIG. ID will be termed the modified Faraday segmented or constant K (or K) type. It also utilizes longitudinal (or series) power extraction.
  • the electrodes are also segmented and connected to a single load in a wave pattern, a cathode of one opposing electrode pair connected to the anode of an adjacent pair, as indicated.
  • the electric field in the interaction space in this type is in a fixed direction, independent of the loading factor, K.
  • the value of the loading factor is restricted to that value which makes the strapped electrodes of equal voltage before strapping.
  • the Hall parameter for ions is denoted by B, where ,u is the ion mobility of the positive ions of the gas and B denotes the magnetic field intensity.
  • the Hall parameter for electrons is denoted by E, where M is the electron mobility as referred to previously.
  • E the Hall parameter for electrons
  • the efiiciency of the K-type is better than that of the 1r-type for high loading (K 0.5). Its power density under load is the same as that of the vr-type. However, as noted above, this type is restricted to a specific value of K. For a particular value of K, the 1r-type and the K-type work with the same power density and related parameters.
  • the E-type performs well with respect to etficiency and power density at values of B 1, that is, at moderate or small (i.e., ,u B 0) values of Hall parameter for electrons.
  • the 1r-type performs well not only at intermediate (i.e., Kn B l0) Hall parameters, but in fact at all positive values of ,u B (i.e., Oe B- a) and so is less restricted than E-type in this respect.
  • the Hall-type performs best when the Hall parameter for the electrons is dominant, that is, when 10 n B 10. All of these three types have high efficiency and high power density in their good performance range.
  • FIG. 2 shows schematically an illustrative example of a closed cycle MHD generator in accordance with the principle of this invention.
  • monatomic (noble) gas at relatively low gas pressure i.e., 10 to 30 pounds per square inch absolute
  • a suitable primary heat source 52 such as a gas cooled nuclear reactor, conventional fossil fuel burner, solar heat source, or other means.
  • the hot gas at the exhaust of the primary heat source or inlet to the MHD generator is at maximum system temperature, T typically, in this invention, at about 2,500 F.
  • This gas temperature does not tax the endurance of the associated materials exposed to the hot gas, yet it provides the desired cycle efficiency, typically about 45%. However, this gas temperature does not impart significant ionization to the gas alone to make it an adequate electrical conductor as required, namely about 10 or more mhos/meter.
  • the hot gas can be directed at subsonic gas velocity, for the sake of tolerable frictional pressure drop, to (a properly convergent-divergent) MHD generator duct, shown schematically at 50, for simplicity as a straight duct.
  • MHD generator duct shown schematically at 50, for simplicity as a straight duct.
  • This gas ionization is at the expense of a tolerably small fraction of the MHD generator output.
  • the MHD generator 50 directly converts physical or axially directed kinetic energy of charged particles and neutral particles (via collisions with positive ions) into electrical energy, by virtue of deceleration of the charged particles (i.e., transfer of their kinetic energy into (induced) electrical energy in the coupled circuit).
  • axial rather than transverse voltage and current or power extraction or coupling is utilized in this system, it being understood, however, that this invention is not limited to this type of power extraction or coupling.
  • the Faraday generator principle and Ohms law apply, providing one takes cognizance of ion slip, Hall effect and the fact that the ions are not longer anchored as in a crystal lattice of a solid electrical conductor.
  • the gas exhaust of the MHD generator is directed into a heat exchanger or re-generator, 54, wherein the residual heat of the gas is thermally conducted to a preheater, 56, which heats the gas that is being returned to the primary heat source, 52, to repeat the cycle. This measure improves the cycle efficiency or otherwise conserves heat energy.
  • the residual heat of the cooled gas from the re-generator is directed to a cooler or refrigerator 58, wherein the gas is further cooled to the lowest practical temperature, T in order to obtain the maximum cycle efiiciency, regarding the system as a carnot heat engine.
  • the gas is passed to a primary gas purifier, 60, wherein the residual gas impurities, other than the chosen gas, may be remove-d.
  • the cooled and purified gas is passed to the properly convergent inlet of an MHD motor or pump or accelerator or compressor, 62.
  • This device can be similar to the MHD generator 50, except that it is operated as a motor by application of appropriate potentials to its terminals.
  • the gaseous electrical conductor is then electrically forced along its (properly divergent) duct, obtaining supplementary electrical energy needed to return the gas to the primary heat source from the MHD generator, 50, by connections not shown in this figure, but detailed in FIG. 25 as an example.
  • the discharge from the motor or pump or accelerator or compressor, 62 is directed to the preheater, 56, where it is preheated by the exhaust heat from MHD generator, 50, as aforesaid, before it is returned to the inlet of the primary heat source, 52, where the cycle is repeated.
  • the gas purifier, 60 can be of any suitable type, electrical, physical or chemical or a combination thereof.
  • FIG. 3 illustrates elementary relations between various components involved in the MHD generator and MHD motor action.
  • v represents vectorially the gas velocity and B the applied magnetic field, the latter directed perpendicular and out from the plane of the paper. Due to the forcing of charges through the magnetic field by the gas stream via axially directed elastic collisions with them and the electrostatic forces between the electrons and positive ions, an electric field is induced at right angles to both the velocity and the magnetic field vectors shown vectorially as E, equal to E XF.
  • the resulting induced current density is shown as IT, and is equal to @E, where a is assumed (approximately) as a scaler (rather than properly as a tensor) electrical gas conductivity, assuming an isotropic plasma in spite of the magnetic field, for simplicity of illustration. Due to the action of the plasma being forced through the magnetic field an induced EMF 1 results equal to 7 x1? directed parallel but opposite to v as shown.
  • the figure also shows that in the case of a motor, an applied electric field intensity E directed oppositely to T, but orthogonally to E and 5
  • E an applied electric field intensity
  • the resulting conduction current I] due to the applied E is equal to 0E.
  • the net measurable current density through the plasma is consequently j e-(F-FE XF).
  • the action of the current density I gives rise to a Lorentz force F, of value 7X? or (E-kflxl?) X15.
  • IE is greater in magnitude than E, the device acts as a motor; otherwise it acts as a generator.
  • phase angle For continuous Faraday electrodes and Hall effect a phase angle of currents with respect to the electric fields occurs. The magnitude of this phase angle depends upon the ratio of the electron cyclotron frequency to the collision frequency, whereas the electric fields remain as indicated. For segmented Faraday electrodes and negligible Hall effect, the currents are as shown. With Hall effect, a phase angle departure of electric fields with respect to the currents occurs as shown in the vector diagrams of FIGS. 1A, 1B, 1C.
  • FIG. 4 shows schematically an elementary embodiment of the MHD generator 50 of FIG. 2.
  • the principle of operation depends upon the Hall effect which is predominant and requires electric coupling of, or power extraction by, longitudinal or axial voltages and currents, as in the Hall-type configuration shown in FIG. 10, while the transverse currents provide the necessary physical resistance to the ionized gas flow.
  • Neutral gas of high electron mobility characteristics namely a monatomic or noble gas such as helium or argon at lower than atmospheric pressure, so that attachment/recombination losses are not excessive, enters the generator from the primary heat source at the left, as shown in the figure by an arrow 64.
  • the compromising temperature, taking cognizance of material limitations and good cycle efliciency, of the gas is chosen about 1645 K. (2500 F.) and for the sake of tolerable fractional pressure drop, its speed subsonic, at about 1000 meters/ second.
  • the gas first passes an unobstructing primary crossed field electron gun region 66, between a cathode assembly, comprising an electron emitter 68, a Wehnelt electrode 102 and control grid 63 and an accelerator electrode of the electron gun which is shown as a short type crossed field electron gun.
  • the primary crossed field electron gun controls the gas ionization by means of controlled electron beam injection and periodic ionizing electric field pulses as previously described so as to minimize excess ionization within it by application of proper ionizing pulse duration and repetition rate and electric gradient at the cathode aperture, to minimize recombination energy loss.
  • the anodes shown shorted to the emitting soles, for longitudinal coupling
  • the anode accommodates not only the output power (terminals) and shorted transverse voltage and current (shorting straps), but also independently the pulsed ionizing voltage, with respect to the emitting soles; identically with that applied between the accelerator and cathode of the primary crossed field electron gun.
  • the anodes are structurally composite and independent or,
  • blocking or chokes are inserted in the output terminals and shorting straps so as to not only prevent the flow of pulse current through these circuits, but to prevent shunting of the pulse voltage that is applied between each anode and sole pairs.
  • the composite anode may comprise one set of interdisposed and connected elements for the pulse voltage, and the other set for the output power and shorted transverse voltage and currents.
  • these can be inserted in the output terminals and shorting straps so that the subject pulsing voltage applied to the anodes behaves as though the output terminal and shorting straps are absent, yet does not interfere with their individual functions.
  • the subject pulsed electric field gas ionization means supplements that achieved by means of the electron beam.
  • the two non-equilibrium gas ionization means working together provide promise of attaining the desired range of electrical gas conductivity and other benefits previously mentioned.
  • FIGS. 6 and l720 Various type crossed field electron guns, as illustrated by FIGS. 6 and l720 in accordance with the principles of this invention, can be substituted for the type of gun shown. It should be noted that although FIGS. 6 and 17 illustrate primary cathode heaters, this is not necessary since the hot gas is at adequate temperature for the cathodes contemplated, especially since the nonthermal electron emission properties of the cathode are emphasized.
  • the electron gun in FIG. 4 employs crossed periodic pulsed ionizing electric field and direct current magnetic fields, the periodic pulsed ionizing electric field being provided by means of a source (i.e., MHD generator) of electric potential represented arbitrarily by a keyed battery, 72, connected between the accelerator, 70, and the cathode assembly 68, 63, 102.
  • a source i.e., MHD generator
  • This cathode assembly with or without the control grid, 63, and Wehnelt electrode, Hi2 may comprise (not shown) the emitting soles, 78, 84, 91 if desired.
  • the magnetic field can be provided by one or more conventional or superconducting solenoids (or by one or more permanent magnets, not shown, which are not likely to be practical due to the high MMF requirements of Hall generators).
  • the magnetic field distribution is generally substantially uniform throughout the MHD interaction space and the electron gun regions of the MHD generator (and MHD motor). However, certain situations may indicate modified (non-uniform) magnetic field distribution at the ends of the electrodes along the flow so as to increase the local charge density.
  • the magnetic field is indicated by an arrow, 74, shown perpendicular to the paper.
  • the applied electric field in the electron gun region is governed by Paschens and crossed field laws.
  • the effects of the former law are mitigated (by utilizing pulse durations of the order of a nanosecond at typical nonequilibrium MHD conditions) and controlled so as to increase the gas conductivity beyond the limit of electron beam injection alone by utilization of periodic pulsed ionizing electric field at appropriate pulse duration (e.g., order of decimicrosecond as previously discussed), and at a repetition rate to mitigate ionization decay rate and for the sake of full (100%) duty operation, and to avoid the deleterious eifects of gas discharge and consequent non-uniform gas ionization.
  • the relative intensities of the electric and magnetic fields can be such that only insignificant electron current flows to the accelerator, 70, and consequently quite modest electron current need by demand of the illustrative periodic pulser, 72, in energizing the electron gun. Provision against reverse electron current can also be made by means common to the state of the gas discharge art.
  • a control grid electrode, 63 is incorporated for alternating current operation. It is used with a Wehnelt electrode, 102, as shown in conjunction with the cathode, 68, the electrode, 63, being appropriately biased, (i.e., with intermittent (pulsed) or alternating potential) with respect to the cathode, by means of a biasing source represented arbitrarily in the figure by modulator 65.
  • the purpose of the electrode, 63 is to control the electron beam. Although separate sources for the electron gun are illustrated, these very low power sources of potential are energized by the MHD generator.
  • the cathode, 68 is a non-thermal and thermal type electron emitter, in the latter case deriving its heat from the hot gas flow in which it is in contact.
  • Electrons emitted from the cathode, 68, are drawn away toward the accelerating electrode, 70, under the influence of the periodic pulsed electric field and direct current magnetic field, by application of appropriate sources mentioned-In addition, modulation of the grid for alternating current operation can be included. Thereupon the electrons, except for any captured by the accelerator electrode, are immediately constrained to move in magnetron paths, due to the combined eflfect of the orthogonal crossed electric and magnetic fields.
  • the pulsed electric and continuous magnetic field intensities are preferably adjusted so that the paths of the electrons in the gas starting at the extreme left of the cathode will just barely graze the accelerator plate and will not be substantially collected thereby but will be further constrained to continue substantially parallel to the accelerator plate in accordance with crossed field constraints, before, at, and after passing the throat of the electron gun.
  • the result is substantially a smooth electron flow forming a stream of electrons emerging from the throat of the electron gun, in magnetron paths, all substantially along the plane of the electrodes.
  • FIGURE 4 shows schematically the electron stream from the primary crossed field electron gun, 66, as it is injected into the gaseous stream in the interaction space of the generator.
  • the moving gas passes between a series of electrode pairs anode, 76, cathode, 78, anode, S2, cathode, 84, anode, 88, cathode, 90, etc. of parallel electrodes separated by insulating spaces without plates.
  • the upper plate in each pair, as shown in the figure serves as an anode while the lower plate of each pair serves as a crossed field cathode similar to that of the electron gun and is referred to as electron emitting sole.
  • the emitting soles are non-thermal and thermal or thermionic type (i.e., cermet or dispenser) type-deriving their optimum operating temperature for the thermal or thermionic portion for electron emission from the flowing hot gas with which they are in contact. They can also be, as the cathode of the primary electron gun, indirectly heated to meet any additional heat requirement on account of any inadequacy on the part of the hot gas.
  • the emitting soles are preferably highly productive of secondary as well as primary electrons.
  • a succession of many short electrodes is employed instead of long continuous electrodes in order to break up the longitudinal circuit and so prevent large axial or longitudinal surface currents which would otherwise flow in the electrodes, due to the Hall effect which is made dominant for the purposes of this invention, a circumstance which would cause large ohmic losses. Furthermore, since at high magnetic fields or high Hall effect parameter, the current density tends to peak at the trailing edges of the electrodes, appropriate design considera tions have been applied to minimize erosion thereat.
  • the emitting soles 78, 84, 90, etc. supply the electrons to the gas or plasma in the interaction space as required to make up for electron loss and those passing to the :load.
  • electrical conducting straps, 80, 86, 92, etc. are provided outside the interaction space between the anode and the emitting sole.
  • the axial or longitudinal current, voltage and power are taken otf through a load circuit, 94, connected between the first and last pairs of electrode pairs, as shown.
  • the magnetic field, both in the electron gun and in the interaction space is in the same direction but not necessarily the same magnitude and perpendicular to the plane of the paper and that of the ionized gas fiow and electron beam flow.
  • Both the applied magnetic field and the injected electron beam are made as substantially uniform as possible throughout the interaction regions between facing pairs of electrodes.
  • the energy required to maintain the desired degree of gas conductivity by electrical ionization namely conductivity in the order of mho/m. or more, is moderate; it being of the order of a base percentage the useful power output of the generator. It is known in the art and as has been pointed out previously that the electric power generated is less than a percent of the total energy associated with the gas. That is, the total energy is equivalent to a small fraction of an electron volt at typical MHD conditions. Since the ionization potential of ordinary gases are relatively high, only a few percent of the atoms at the most would be ionized under ideal conditions of the available energy extracted and utilized. Nevertheless, the electrical conductivity of the gas when ionized to the extent of a small fraction of a percent is substantially as high as for the completely ionized gas.
  • the pair of electrodes nearest the electron gun comprises the anode, 76, and the electron emitting sole electrode, 78, connected together outside the gas duct by the electrical conductive strap, 80, which is of negligible resistance.
  • the opposing faces of the electrodes of each pair are parallel to the direction of the magnetic field.
  • An intermediate electrode pair comprises the anode, 82, and the electron emitting sole, 84, connected by a like strap, 86.
  • the pair of electrodes farthest from the electron gun comprises the anode, 88, and the electron emitting sole, 90, connected by a like strap, 92.
  • the output terminals of the generator, 50 comprise the electrode pair, 76, 78, and strap, 80, which constitute the generator terminal conventionally called the negative terminal, for direct current operation, and the electrode pair, 88, 90, and strap 92, which constitute the positive terminal.
  • the electrical load connected to the generator terminals is represented in the figure by the impedance, 94.
  • the gun forms an electron beam which substantially permeates uniforrnally the entire interaction region of the gas duct as previously discussed.
  • the electron beam moves to the right as shown in the figure, while ionizing the flowing gas, moving in the same direction, with the aid of the applied periodic pulsed ionizing electric field between cathode and anode or accelerator.
  • the plasma is subjected to a strong Hall eifeet, which induces both transverse and axial or longitudinal current and voltage in the plasma.
  • the transverse currents serve to provide the necessary physical resistance to flow.
  • the load, 94 is coupled through the longitudinal currents and voltages. Thereby, desired high rather than low impedance output characteristics are realized.
  • the electron beam injection and applied pulse duration, amplitude and repetition rate of the ionizing electric field can be controlled so that the ionization effect of the electron beam and pulsed electric field is substantially uniform and limited to the desired interaction region of the gas duct.
  • the plasma deionizes very rapidly as previously discussed, due primarily to recombination/ attachment losses.
  • Residual charges are collected at the ion collection/regenerator 98, which in a very simple form can comprise one or more plates arranged edgewise to the gaseous stream.
  • the ion collector/regenerator, 98 primarily serves the purpose of absorbing residual heat energy from the exhaust gas.
  • the neutral gas leaving the ion collector/regenerator, 98 is in turn exhausted toward the right in the figure as indicated by the arrow, 100.
  • an alternating voltage represented by a modulator 69
  • a modulator 69 is impressed between the control electrode, 63, and the cathode, 68, as shown schematically in FIG. 4.
  • the action of the electron gun is the same as described previously, except that the electron flow is modulated instead of steady.
  • the periodic pulsed non-ionizing electric field bias voltage, 65 can be applied, but is optional. Its pulse duration is so short (order of a nanosecond) that no significant gas ionization occurs on its account.
  • the alternating voltage from modulator, 69 can be superimposed on this for alternating current power output from the MHD generator.
  • a switch, 67 is shown whereby the modulator, 69, can be included in the circuit or not, depending upon whether direct current or alternating current component operation is desired. It will be evident that the modulated or alternating current output from the MHD generator obtainable by use of the modulator can be converted by means of a transformer in conventional manner and that all known intermittent or pulsed or alternating current te hniques can be employed in the utilization of the power output of the generator. Direct current operation especially at commercial voltages, is applicable in practice.
  • Alternating current operation could also be obtained, in principle at least, alternatively by modulating the current in the solenoids producing the impressed magnetic field (especially in the case of a superconducting solenoid) but with much more drive required (except in the case of superconducting solenoids) and much less economy compared to low drive voltage modulation of the control electrodes of the primary cross field electron gun and secondary crossed field emitting soles.
  • FIGS. 6, 8 and 11 show an illustrative embodiment of coaxial ducts, primary crossed field electron guns and electrode structures for use in an MHD generator (or MHD motor) according to the invention.
  • the emitting soles thereof can be replicas of the primary cathode assembly or can be simpler, as discussed previously.
  • the coaxial duct is built on the Dewar principle with two spaced walls and thermal insulating space between the walls to minimize heat loss from the inner duct.
  • the inner duct wall is a suitable dielectric (e.g., ceramic) with matching metal (e.g., tantolium, etc.) inserts on the inside to form the electrodes and joining members of sections.
  • Electrodes that are cathodes and emitting soles can be directly heated (via the hot flowing gas) or indirectly heated (via an auxiliary heater) thermionic and non-thermal electron emitter, as previously described. They can have a coating or a layer or comprise a body of electron emissive material such as a dispenser or cermet type.
  • Suitable dielectric (or ceramic) spacers are provided between the inner and outer walls at intervals along the duct for the purpose of isolating and supporting the inner duct in the outer one.
  • the outer duct wall is of suitable metal (e.g., stainless steel) with suitable dielectric (or ceramic) inserts at locations where electrical connection is made to an electrode inside the duct.
  • the ducts can be made in demountable setcions which can be welded (e.g., heli-arc) together to make up any required length, and separated (e.g., by grinding off the welds) a number of times and rescaled as before as desired.
  • FIG. shows in three-dimensional diagrammatical form a general convergent-divergent duct or nozzle which involves consideration of the Joule-Thomson (Ioule-KeL vin) effect.
  • Such nozzle can be used in practice for converting the random motions of the gas into more axially directed motion within the electron gun and interaction spaces in the gas duct in an MHD converter.
  • the crossed field electron gun cathode 68 the first sole electrode 78 in the interaction space, for simplicity a few intermediate sole electrodes, and the last electron emitting sole electrode, 90.
  • a much larger number of intermediate emitting sole and anode electrodes will be required, depending upon design requirements.
  • the electron gun accelerator electrode 70 In the far vertical wall of the divergent portion of the duct are shown schematically the electron gun accelerator electrode 70, the first anode electrode 76 in the interaction space, a few intermediate anode electrodes, and the last anode electrode, 88.
  • the sole electrode of each opposing pair of electrodes in the interaction space in shown strapped to the respective anode electrode of the pair, the first strap and the last strap 92 constitute respectively, the negative terminal and the positive terminal for the load impedance 94 for direct current operation.
  • the relative directions of the gas velocity, v and the magnetic field intensity, B are shown by arrows in the figure.
  • FIG. 6 shows a longitudinal or axial cross section of a simple MHD generator.
  • the coaxial ducts therefore, in a central plane perpendicular to the magnetic field. This plane is also perpendicular to the planes of the opposed electrodes.
  • FIGS. 7 and 8 show external appearance at side and one end, respectively.
  • the inner duct may be tapered, for example as illustrated in FIG. 5, so that where C and /gf denote cross section dimension and final gas velocity, respectively.
  • the dielectric (or ceramic) inner duct wall that is uppermost in the figure is designated, 200, and the lower inner duct wall is designated, 202.
  • the upper metal duct outer wall is designated, 204, and the lower, 206.
  • the electron cathode assembly of a simpler illustrative type of crossed field short electron gun suitable for direct current operation is shown generally at 208.
  • the cathode of the gun need not have an indirect heater assembly since the hot flowing gas is at adequate gas temperature for optimum thermionic operation.
  • Other electron guns e.g., those disclosed in FIGS. 17 through 22
  • a simplified cathode 210 is shown comprising electron emissive material either coated upon a suitable base metal or comprising a cermet or dispenser type unit.
  • the cathode 210 can operate by virtue of heat of the hot (e.g., 2500 F.) inert gas or its own accord, thermionically by means of a suitable integral electrical heat source. It can also be primarily a non-thermal type of emission cathode.
  • the indirectly heated (optional) cathode 210 is shown in the form of an inverted metal box separated on all sides from the main portion of the inner wall 202 by a gap 212. Inside the cathode, 210, are located a plurality of electrically heated heater elements indicated schematically at 214. All the heater elements 214 are connected in parallel in conventional manner and brought out through an insulating tube 220 to a pair of heater connections 222. The heaters are held in place by a cover plate assembly 224 through which the tube, 220, projects.
  • a Wehnelt electrode, 226, generally surrounds the sides of the cathode 210.
  • the electrode 226 comprises a sheet of metal inserted into the wall 202 to the left of the cathode, folded downward over the edge of the wall 202 at the gap, 212, passing under the cathode and back up opposite the cathode at the right of the cathode to fasten to the wall 202 at the right of the gap 212.
  • a suitable dielectric (or ceramic) spacer ring 228 permits the cathode to be insulated and supported by the control electrode.
  • An access side duct 230 for cathode connections is inserted in the lower outer wall 206.
  • the duct 230 is provided with a suitable cover plate 232 and a suitable dielectric (or ceramic) electrode base press 234, sealing a hole in the plate 232, through which the heater connections 222, a cathode connection 236 and a control electrode connection 238 are brought out.
  • the modulator 69 and the biasing voltage 65 can be inserted when required between the cathode connection 236 and the control electrode connection 238 in a manner similar to that shown in FIG. 4 between the electrodes 68 and 63 of that figure.
  • the accelerator for the elementary short electron gun is shown generally at 240.
  • the accelerator plate 242 is a metal (e.g., tantalum) plate inserted (i.e., brazed) in the upper inner duct wall 200.
  • the plate 242 extends opposite the control electrode 226 and the cathode 210.
  • Electrical connection is made to the plate 242 by way of a metallic pin 244, which can be integral with the plate, the upper end of which makes a suitable engagement with a nut 246.
  • An access hole in the upper outer wall 204 opposite the nut 246 is sealed by a metal-dielectric (e.g., metal-ceramic) plug assembly 248, which can be sealed (e.g., heli-arc welded) to a metallic collar 250.
  • a metal-dielectric plug assembly 248 Through the plug assembly 248 extends a shouldered metallic pin 252, the lower end of which makes a (e.g., set screw) locked engagement with a nut 254 to permit ang
  • Hairpin type electrically conducting wires 256 are inserted into holes in, or otherwise secured to the peripheries of the nuts 246 and 254.
  • a set screw (not shown) is provided in the nut 254 for securing the nut in correct angular position on the pin 252 so as to align the placements or holes for the wires 256.
  • a plan view of the nut 246, hairpin wires 256 and without the set screw is shown in FIG. 9.
  • the shouldered end of the pin 252 is provided with suitable means for engaging an external electrical connector 260.
  • the metal and ceramic parts are joined in vacuum-tight manner as known in the art, so that the space between the inner duct and the other casing can be evacuated by known means and operated under high vacuum to reduce heat transmission from the inner duct to the outer casing and the ambient medium.
  • a sole electrode for the electron gun is shown at 262. It can be an electron emitter or not, depending upon the application. In any event, its construction can be simple for direct thermionic electron emission by means of the hot gas or it can be primarily a non-thermal electron emitter independent of the hot gas. Its form can be generally similar to that shown for the accelerator electrode 240.
  • An auxiliary anode electrode for the electron gun is shown generally at 264.
  • the construction of the auxiliary anode electrode can be substantially the same as for the accelerator 240.
  • the auxiliary anode electrode is flush with the upper wall of the duct as shown.
  • An anode electrode for either an MHD generator or an MHD motor with an electrical connection external to the duct, is shown generally at 266.
  • the construction of this anode electrode can be substantially the same as shown for the electrode 240, except for current capacity and because at the high Hall parameter or magnetic field characteristic of the Hall generator (FIG. 1C) the trailing edge of the anodes (and cathodes) with respect to the gas flow must be made more erosion resistant due to the concentration of electric current there.
  • the anode electrodes are inserted into the upper wall of the duct.
  • the external electrical termination of anode electrode 266 is used only at the two generator terminals that are to be connected to the electrical load of the generator.
  • the first of these, from left to right, is the negative terminal of the generator for direct current operation. It is the first anode electrode to the right of the primary electron gun.
  • the second terminal is the positive terminal of the generator and is the last anode electrode shown generally at 268 at the extreme right hand end of the interaction space of the generator, the construction of which is substantially the same as shown for the other anode electrodes that have external electrical connections.
  • all the anode electrodes and emitting soles may require external electrical connections.
  • the electron emitters of the cathode of the electron gun and sole in the MHD generator can be operated either as a non-thermal thermionic emitters, actuated by the passing hot gas stream, or as indirectly heated emitters, actuated by impressed external heat source, shown in the drawings only for the cathode of the primary electron gun.
  • the magnetic field can be readily supplied by permanent magnets, however, because of the high mmf. requirements it may be desirable to generate the magnetic field by means of electromagnets, conventional or superconducting.
  • the non-therrnal thermionic electron emitters can be refractory dispenser or cermet types, having an operating temperature of about the ambient gas temperature (or 2500 F.). Operating these emitters at their optimum temperature insures long operating life.
  • An anode electrode that has no electrical connection through the outer duct wall is shown generally at 278.
  • the structure comprises a metallic plate 272 inserted in the upper inner duct wall 200.
  • a metallic pin 274 which can be integral with the plate 272 makes electrical contact with the plate 272 on the upper face thereof and extends upwardly to the upper surface of the wall 200 into a strap groove 302 (FIG. 12) for connection to a strap 288, as will be explained presently with reference to FIG. 11.
  • An electron emitting sole electrode that has no electrical connection through the outer wall of the duct is shown generally at 276 (FIG. 6).
  • the structure comprises a composite metallic plate 278 inserted in the inner lower wall 202 of the duct.
  • the upper surface of the composite plate 278 can be impregnated or coated with a thermionic or secondary electron emissive material to promote copious emission of electron as required.
  • the strap 288 lying in a strap groove 302 (FIG. 12) is connected to the plates 278 and 272 as shown in FIGS. 11 and 6.
  • the structure is generally similar to that shown for the anode electrode 270, except that a pin corresponding to the pin 274 extends sufficiently beyond the upper surface of the wall 208 to form a support or axle for a thermal spacer such as a wheel 282.
  • the rim of the wheel 282 is displaced laterally from the axle to such an extent that the rim bears against the inside surface of the upper outer wall 204, while the axle bears against the outer surface of the upper inner wall 268.
  • the spacer or wheel 282 can have a plurality of spokes which extend diagonally between the axle and the rim.
  • An electron emitting sole electrode similar in size to the anode electrode 280, is shown generally at 284. This electrode is inserted into the lower inner wall 202 of the duct and the thermal spacer or wheel 286 corresponding to the spacer or wheel 282 spans the region between the outer surface of the inner lower wall 202 and the inner surface of the outer lower wall 2%.
  • FIG. 11 shows a cross section of the duct through the anode electrode structure 286 and the electron emitting sole electrode structure 234.
  • the view ShOWs the inner and outer walls of the duct in cross-section, together with the thermal and electrical isolators and spacers shown as the wheels 282, 286.
  • the view further shows the short-circuiting strap 288, which corresponds generally to any one of the straps 80, 86, 92 shown schematically in FIG. 4 for connecting an anode electrode to an opposing electron emitting sole electrode by an electrical conductive path outside the inner wall of the duct; specifically over the outer surface of the inner wall of the duct.
  • the anode end of the strap 288 is electrically connected to a metallic pin 290 that forms the support for the isolator and spacer wheeel 282.
  • the strap 288 lies in a groove in the outer surface of the inner wall 260' of the duct, extending upwardly as shown in FIG. 11 and over the top outer surface of the inner wall, and thence downwardly to an electrical connection with the metallic pin 292 that forms the support for the isolator and spacer wheel 286.

Description

LmWla m Nov. 28, 1967 E. c. OKRESS CEOSSED FIELD PLASMA DEVICE Filed Sept. 23; 1963 9 Sheets-Sheet 1 Fig. IA. Fig. IB. Fig. lC. Fig. IB
Pulsed Electnc Ionizing Field Applied to All Electrode Pairs As- Per FIG. 4A or 4B or 46 or Neutral 40 or 4E. Ions Eleclrons loniggd Gus, Electrons, Posmve lens and Negative Ions Electron Emission Surfaces 1967 E. c. OKRESS CROSSED FIELD PLASMA DEVICE 9 Sheets-Sheet 2 Filed Sept. 23, 1963 F la. 2.
Cooler 58 60 Gas Purifier Regenerator 50 54 MHD Generator Primary Heat Source Faraday Electron Collector Electrode (Anode or Accelerator) E J F: D n 0l nu mu M 5 mm t. A
Electrons Ions \I i' l Faraday Electron Emitter Electrode (Cathode) INVENTOR Ernest C. Okress Fig. 3.
ATTORNEY E. c. OKRESS 3,355,605
CROSSED FIELD PLASMA DEVICE Filed Sept. 25, 195 9 Sheets-Sheet 3 Nov. 28, 1967 INVENTOR Ernest G. Okress wnw 5 wmm RN vmw SM mm mum W Em wk 8% $3 vmN mum mvw (say- 7 v ATTORNEY www mmw m w Nov. 28. 1967 E. C. OKRESS CROSSED FIELD PLASMA DEVICE Filed Sept. 25, 1963 Fig. I4.
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INVENTOR Ernest C. Okress Nov. 28, 1967 E. c. OKRESS 3,
CROSSED FIELD PLASMA DEVICE F'led Sept. 23, 1963 9 Sheets-Sheet 5 s s m m H 0 N m3 mum m R mum v w m o r 11111 3w 9 m a A own .Qwn m MW 6km 9mm 9mm Nbm vmm m 28 M ,.v.. v m ovoc m b29532; cum =4 20E 23502 ..282304 NR 16 3 mm wh m a 20m aEom f SH 3w mun E 9 E Nov. 28, 1967 E. c. OKRESS CROSSED FIELD PLASMA DEVICE 9 Sheets-Sheet 6 Filed Sept. 23, 1963 INVENTOR Ernest C. Okress Om E ATTORNEY E. C. OKRESS Nov. 28, 1967 CROSSED FIELD PLASMA DEVICE 9 Sheets-Sheet 7 Filed Sept. 23, 1963 INVENTQR Ernest C. Qkress ATTORNEY Nov. 28, 1967 c, OKRESS 3,355,605
CROSSED FIELD PLASMA DEVICE Filed Sept. 25, 1963 9 Sheets-Sheet 8 D 8 L'- g Q wv v v- N b v v 3 Q 8 &
- I INVENTOR Ernest C. Okress Ll. BY
ATTORN EY 1967 E. c. OKRESS CROSSED FIELD PLASMA DEVICE 9 Sheets-Sheet 9 Filed Sept. 23, 1963 Fig. 25.
Anodes Soles MP0 Generator INVENTOR Ernest C. Okress ATTORNEY United States Patent 3,355,605 CROSSED FIELD PLASMA DEVICE Ernest C. Okress, Elizabeth, N.J., assignor to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 23, 1963, Ser. No. 310,608 18 Claims. (Cl. 310-11) This invention relates generally to (thermal to electric) gaseous energy converters and more particularly to a cross field non-equilibrium plasma-type referred to generally as a non-equilibrium magneto-hydrodynamic (MHD) generator.
Common MHD generators utilize thermodynamic equilibrium or thermal ionization of the Working medium, which is commonly seeded (combustion) gas in open cycle operation. Because of the extremely high temperature of the working medium which would be required for MHD generator conditions with gas alone (e.g., 5800 F. 1 mho/m., 6900 F. mho/m. and 8500 F. 100 mho/m.) to ionize most gases because of the relatively high ionization potential required to achieve the desired electrical gas conductivity, seeding material (e.g., 1% molar alkali, such as potassium or cesium), which ionizes at a relatively lower gas temperature, is generally added to the gas. Unfortunately, even with seeded combustion gases the temperature is still too high for continuous full (100%) duty and long life operation at MHD conditions (e.g., 3500 F. l mho/m., 4200 F. l0 mho/m., 5100" F. 100 rnho/m.) when compared with non-equilibrium MHD conditions (e.g., for appropriately seeded nonatomic gas at 2200" F. an order of magnitude higher electrical conductivity can be achieved compared with combustion seeded gas at 5000 F.).
The purpose of ionization of the working medium is to obtain suificiently high electrical conductivity for the purpose of achieving optimum MHD generator performance and tolerable MHD generator sizeespecially with respect to its dominant physical parameter, the electrical conductor or ionized gas duct length. Aside from the problem of recouping of the seeding material, particularly in open cycle operation, crucial material limitations arise because of the high gas temperatures associated with combustion MHD generators which tax the endurance of available (electrode and confining wall) materials to so drastically limit the duty of operation and life of the MHD generator and associated system as to require impractically low values of these parameters. Commercial apparatus is invariably continuous or full (i.e., 100%) duty, relatively high impedance, alternating current type, with generally long reliable life characteristics. Hence, power supplies to be competitive with state of art, must not only approach these characteristics, but must do so reasonably economically in all respects. Consequently, non-equilibrium gas ionization resolves the major problems of MHD generator and associated components of higher electrical gas conductivity and lower gas temperature than is possible with equilibrium or thermal means. Therefore, it offers much better prospects for realizing most of the power source requirements than thermal MHD generators do, in spite of the formers comparative primitive state of development.
As an alternative, therefore, to thermal (i.e., equilibrium) means of gas ionization, a non-equilibrium and in particular novel electrical means are utilized in this invention. Equilibrium vs. non-equilibrium gas ionization denotes whether the ion species temperature is comparable with or higher than, respectively, the gas or more properly the related stagnation temperature (by virtue of the isentropic expansion relation).
It is an object of this invention to provide a device which can operate at continuous or full (i.e., 100%) duty and with long life not limited by thermal endurances of available materials.
It is another object of this invention to provide a device which can be continuously or intermittently operated at arbitrary pulse duration and average power, up to and including duty.
It is another object of the invention to provide a device which can generate either direct current or alternating (i.e., sinusoidal) current component at commercial or domestic frequencies and voltages.
It is another object of the invention to provide a device whose direct current or alternating current output voltage is suitable for operation with commercial distribution systems or transformers, respectively.
It is another object of this invention to provide a device which does not require (condensable) seeding of the gas, but which can be used depending upon the thermodynamic cycle required for a specific application (e.g., Rankine vs. Joule cycle).
It is another object of this invention to ionize the gas by crossed field electron beam injection, at the expense of a tolerable or small fraction of the power output of the MHD generator.
It is another object of the invention to provide crossed field electron beam injection along the interaction duct, especially in sufficiently high magnetic field regions thereof in a convenient and practical manner.
It is another object of the invention to minimize excess ionization especially at electron injection ports by use of controlled cross field electron guns and so minimize recombination energy losses.
It is another object of this invention to supplement the degree of ionization atforded by the crossed field electron guns by periodic electron heating on account of the inherently required pulsed ionizing electric field in the guns sufficiently below the sparking limit to avoid excess ionization. This feature requires extremely short (i.e., order of state of art millimicrosecond) pulse durations, but at corresponding high duty to mitigate the correspondingly rapid recombination rate and so as not to depart significantly from continuous (full duty) operation conditions.
It is another object of this invention to provide a device which is efficient and competitively simple in design, fabrication and operation.
It is another object of this invention to provide a device and associated closed cycle system which is portable in nature.
It is another object of this invention to provide a closed cycle system which has no moving mechanical parts.
It is another object of this invention to provide a device wherein the degree and uniformity of ionization of the gas is under control and independent of the temperature of the gas.
It is another object of this invention to provide a device wherein the gas is ionized in a uniform and continuous manner.
It is another object of this invention to provide a device wherein an MHD generator and an MHD motor (or pump or accelerator) are self-exciting.
It is another object of this invention to provide a device which can start operating practically instantaneously.
It is another object of this invention to provide a device that is not affected by its orientation.
It is another object of this invention to provide a device that is operable on or in the land, sea, air or space.
It is another object of this invention to utilize an electrode configuration best suited to but not rigidly restricted to high Hall parameter operation.
It is another object of this invention to provide a system which can be made to operate open cycle at supersonic or hypersonic gas velocity as an efficient electrical propulsion device for space applications.
It is also an object of this invention to provide a type of cathode such that its non-thermal and thermionic electron yields are adequate and whereby the thermionic portion is derived from cathode heating by the hot flowing gas in the duct.
It is also an object of this invention to achieve the required gas ionization by simultaneous electron beam and periodic ionizing electric impulses and thereby mitigate the dependence on a finite electron supply, tolerance of recombination coefiicient and electron mobility which are so inherent in the former means of gas ionization with respect to the latter.
It is also an object of this invention to utilize a Hall (segmented) electrode rather than a Faraday (segmented) electrode configuration due to desire for operation at high Hall elfect parameter or high magnetic field, because the Hall configuration requires less control, is more reliable and simpler than the Faraday configuration. Furthermore, the Hall configuration is not subject to the requirement of fixed loading or multiple loads. Finally, the Hall configuration provides a significant reduction in electron retardation or larger electron braking on account of employment of the magnetic field with transverse electric field. Also a high magnetic field, and relatively low gas velocity contemplated, improves the momentum transfer between electrons and gas atoms.
It is another object of this invention to provide gas ionization means which is not an ionizing radiation hazard.
It is another object of this invention to provide a device which can operate at minimum gas temperature consistant with desired thermodynamic (cycle) efficiency and material endurances for full duty long life operation.
It is another object of this invention to provide a MHD motor or pump or compressor or accelerator so as to eliminate mechanical moving parts in the closed system.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the apparatus becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
FIGURES 1A, 1B, 1C and 1D are schematic and vector diagrams of various electrode configurations appropriate for use in MHD generators;
FIGURE 2 is a flow diagram of a closed cycle MHD generator;
FIGURE 3 shows salient MHD quantities involved in the description of MHD energy converter operation;
FIGURE 4 is a schematic representation of an MHD generator or an MHD motor in accordance with the principles of the invention;
FIGURES 4A through 4E illustrate alternate electrode pair means of applying pulsed ionizing voltage to interaction space of the MHD generator or MHD motor illustrated in FIGURE 4;
FIGURE 5 is a perspective view representing schematically a mechanical nozzle or convergent-divergent gas duct with electrodes for an MHD generator of the type shown in FIGURE 1C and FIGURE 4;
FIGURE 6 is a longitudinal sectional view of an illustrative embodiment of an MHD generator in the form of a straight constant cross-section gas duct;
FIGURE 7 is an external elevational view of the device shown in FIGURE 6;
FIGURE 8 is an external end view of the device as viewed in FIGURE 6;
FIGURE 9 is a partial view of an electrical connector of low heat transmission characteristics as viewed along the line 99 in FIG. 6;
FIG. 10 is an clevational view of an insulating (e.g.,
circular) spacer taken as indicated by arrows 1tl-10 in FIG. 6;
FIG. 11 is a cross-sectional view taken along the line 1111 in FIG. 6;
FIGS. 12 and 13 are fragmentary views of duct walls grooved and preshaped to receive short-circuiting straps as shown in FIGS. 6 and 11;
FIG. 14 is a schematic showing of an arrangement for applying a magnetic field to a gas duct by means of ordinary (or superconducting) solenoid electromagnet in which wrought iron pole pieces are saturated and, consequently, no yoke is used;
FIG. 15 is a cross-sectional view taken along the line 15-45 of FIG. 16;
FIG. 16 is a schematic cross-sectional representation of a compound crossed field electron gun with strip cathodes and multiple vane control electrodes for injection and modulation (for alternating current operation of the MHD generator) of an electron beam in a gas duct;
FIG. 16a is a cross-sectional representation of a crossed field electron gun for direct current operation of the MHD generator, this structure being substituted for the electron gun of FIG. 16 when direct current Operation is desired rather than alternating current operation;
FIGURE 17 is a schematic plan view taken along the line 17-17 in FIGURE 16;
FIGURE 18 is a schematic cross-sectional representation of a compound crossed field electron gun with multiple plasma-cathodes for injecting an electron beam into a gas duct;
FIGURE 19 is a schematic plan view taken along the line 1919 in FIGURE 18;
FIGURE 20 is a schematic cross-sectional representation of a dual compound electrostatic electron gun with strip cathodes, for injecting electron beams into a gas duct along the direction of the applied magnetic field in an MHD generator (or motor);
FIGURE 21 is a schematic cross-sectional representation of a dual compound electron gun with plasma. cathodes, for injecting electron beams into a gas duct along the direction of the applied magnetic field in an MHD generator (or motor);
FIGURE 22 is a schematic representation of a helically wound gas duct of an MHD generator (or motor) with ordinary (or superconductor) solenoidal windings for providing the required magnetic field, an outer solenoid being partially cut away. Such a structure is more complex than its linear counterpart for sake of compactness;
FIGURE 23 is a schematic representation of the device as shown in FIGURE 22 in longitudinal cross-section;
FIGURE 24 is a schematic cross-sectional representation of a helically wound gas duct of an MHD generator (or motor) with saturated magnet iron pole pieces and ordinary (or superconducting) solenoids disposed between adjacent turns of the helically wound duct. Such a structure is more complex than its linear counterpart for sake of compactness;
FIGURE 25 is a schematic diagram of typical electrical connections suitable for connecting an MHD generator of the type shown in FIGURE 1C to an MHD motor of the type shown in FIGURE 1D.
Similiar reference characters refer to similar parts throughout the several views of the drawings.
Briefly, in this invention thermal energy in a suitable unseeded gas derived from a primary heat source (e.g., fossil fuel, solar energy or gas cooled nuclear reactor) can be directly converted into commercial, direct or alternating current electricity, depending upon the ultimate application. Crossed field electron beam and interdependent periodic ionizing electric field impulse gas ionization means are utilized to provide a device whose gas temperature does not tax the endurance of the associated materials. Thus an MHD device which can operate continuously at full (i.e., 100%) duty and still have a long operating life is provided.
In this invention a suitable gas is nonequilibriumly or electrically ionized to make it optimumly electrically conducting, by crossed field means, involving electron injection, and/or by periodic ionizing electric field impulse means, thereby enabling the device to convert directly a major part of the thermal or kinetic energy, of the gas imparted to it by a suitable primary heat source, directly into electricity.
The rate of extraction of enthalpy from the gas by the MHD generator derives from the usual energy balance, which shows that it depends strongly (i.e., square) on the gas velocity-magnetic field product, for a given efi'lciency, conductivity, Hall parameter, degree of nonuniformity and ion slip, neglecting heat loss to the exterior and changes in kinetic energy in the gas.
The energy transfer means is in accordance with the equivalent Hall or Faraday generator principle, taking cognizance of the fact that whereas the energy transfer via a metal electrical conductor is by virtue of the positive ions anchored to the crystal lattice, in a gas electrical conductor energy transfer occurs only by virtue of attractive electrical forces and predominately axially directed collisions between (unanchored) ions and (neutral and excited) gas molecules.
This invention is also capable of directly converting electricity to mechanical (directed kinetic) ener y of the gas, in accord with the equivalent Faradays motor principle. The resulting MHD motor or pump, accelerator or compressor does not depend on any moving mechanical parts and, therefore, it eliminates the need for any mechanical components in the whole system. The energy required to operate the MHD motor is derived from a tolerable fraction of the MHD generator output.
Either fossil fuel, direct solar energy or a gas cooled nuclear reactor may serve as the primary heat source for heating the gas or working fluid of the proposed energy converter. The electrical power output can be con tinuous or full (100%) duty (i.e., direct current), or intermittent (i.e., pulsed), or alternating (e.g., sinusoidal) cur rent. In those instances where alte'nating current or modulation is desired, low drive of a voltage controlled electrode system of the crossed field (or electrostatic) electron gun (used for injecting the electrons into the gas at high efficiency for complete absorption and ionization of the gas) is utilized. In the case of pulsed modulation, various pulse durations and repetition rates can be utilized. In the case of alternating current modulation, various frequencies, including commercial or utility frequencies, can be realized.
The life of the non-equilibrium MHD motor (i.e., pump or compressor or accelerator) is not limited in duty or life by the state-of-art materials of the (metallic) electrodes and confining (dielectric) duct walls. This is a consequence of the fact that highly efiicient nonequilibrium electrical gas ionization (i.e., 90%) is utilized, instead of equilibrium or thermal (high temperature) gas ionization and the required doping or seething with easily ioniza-ble material (e.g., potassium, cesium, and the like). However, even with seeding, gas temperature of 3500 to at least 4000" F. are required by thermal or equilibrium MHD generators in obtaining desirable electrical con ductivity of the seeded gas. In this invention the temperature of the gas is approximately 2500 F. as it need mainly be adequate for good thermodynamic (cycle) efficiency (e.g., -45%) and, suitable with respect to duty and life of the primary source of heat, such as a gas cooled nuclear reactor. It is possible to obtain high generator efficiency (i.e., theoretically about 95%) and high cycle efficiency (i.e., '-45% at 2500 F.).
The upper practical limit of the generator efiiciency is dependent upon the maintenance of an adequate uniformity and stability, -(e.g., avoidance of spark channels) in the plasma. Spark channels and consequently excess channel ionization can be alleviated, especially in the crossed field guns, :by resort to periodic (rectangular) impulses of extremely short (i.e., order of a nanosecond) pulse duration and rise time (within state of art capability of a decinanosecond and centinanosecond, respectively) at high duty, so as to mitigate the effects of recombination rate and provide virtually continuous (full duty) operation. In fact, pulse duration somewhat longer than this (e.g., order of a centimicrosecond) serves to substantially supplement the degree of gas ionization afforded by the crossed field electron injection since all the electrons in the gas are involved.
Due to the use of electrical non-equilibrium ionization means, the MHD generator and MHD motor are capable of self excitation and possess rapid starting characteristics. The performance features of the MHD generator, particularly power density and conversion efficiency, are best realized especially with respect to the electron beam gas ionization means alone when the Hall (effect) parameter, B (i.e., product of electron mobility, and magnetic field B), is dominant. The requirement of high electron mobility, including considerations relative to the primary heat source, as well as to (high) specific heat/thermal conductivity and (low) molecular weight, on account of thermodynamic and aerodynamic condsiderations, are satisfied by using noble gases at low pressure. High magnetic field reduces generator size, reduces losses proportional to Wall area and enables quicker extraction of power. There is also a significant reduction in electron retardation (i.e., much larger electron braking) on account of the magnetic field employed with a transverse electric field. Furthermore, a high mag netic field and relatively low gas velocity improves the momentum transfer between electrons and gas atoms.
Need for high magnetic field on account of need for high Hall effect parameter calls for a Hall configuration Which requires less control, is more reliable and simpler than the Faraday configuration and is not subject to the complexity of multiple loads or fixed loading (constant K type). Low gas pressure contributes toward minimizing the predominant recombination-attachment losses. It also reduces wall heat loss and viscous pressure loss. On the other hand, heat exchange size and non-equilibrium ionization time are increased.
In this invention, electrical non-equilibrium ionization of the gas is efiiciently initiated and maintained with negligible, if any, gas flow obstruction or at the expense of magnetomotive force of the magnets. This gas ionization means is achieved dually by crossed field electron beam injection means supplemented by periodic ionizing electric impulse means in the guns and interaction duct. While the former is characterized by a finite number of electrons the latter involves all the electrons in the gas.
The electron beams can be injected into and guided in the MHD generator (or MHD motor) interaction space, for example, by means of an applied (electric-magnetic) crossed field (short, long, space charge, ramp or magnetron optic) electron guns, it being understood however, that the electron emitting source is not restricted to a solid state type (e.g., plasma). The term short or long" crossed field electron gun refers to the length of the electron guns cathode along the electron orbit direction in vacuum. When the vacuum length is less than a half (and in particular a quarter) cycle the gun is termed short optic. When otherwise (i.e., several half cycles) the gun is termed long or adiabatic optic. The electron beam can also be injected electrostatically into the MHD generator (or MHD motor) interaction space, along the (applied magnetic field axis which acts as a beam focusing field). However, this is at the expense of considerable design, fabrication and operational complications and disadvantages and additional magnetomotive force requirement on the part of the magnet. In any case,
the electron beam must permeate the gas interaction space completely and continuously, due to the inherently rapid gas ionization decay rate and for sake of uniformity, especially at injection sites. This means provides a finite number of electrons into the gas and so its ability to provide the desired gas electrical conductivity is correspondingly limited.
In contrast, the applied periodic rectangular ionizing electric impulses are applied to all the electrons in the gas since this field is impressed between the electron emitters (i.e., cathode) and electron collectors (i.e., anodes or accelerators) and are of such duration (e.g., order of a centimicrosecond) that, together with the injected electron beams, competitive non-equilibrium and uniform gas electrical conductivity (e.g., 10 to 1000 mho/m.) may be achieved without sparking and consequeut excess ionization. This supplementary means is inherent in the operation of the system. It involves essentially imparting periodically a relative low average energy to all the electrons in the gas for such brief intervals (e.g., order of centimicroseconds for typical MHD conditions) so as to suificiently ionize the gas, but not excessively so as to cause sparking or arcing and energy dissipation. The net energy expended in producing each ion pair decreases as the electron temperature becomes much greater than that of the gas.
This invention avoids all of the thermal or equilibrium MHD generators material problems by using a gas temperature that is substantially lower and below the thermal endurance limitations of materials, consistent with reasonable thermodynamic (cycle) efficiency. With this invention it is not necessary to seed or dope the gas and, naturally, the problem of recouping the seeding material is eliminated. However, it is not here implied that seeding or doping the gas cannot be used, since there may not be need for recouping the seed material in closed cycle operation.
Although the proposed system can be used with various (fossil fuel, gas cooled nuclear reactor or solar) primary heat sources due to the relatively low gas temperature, it is very adaptable for use with an advanced gas cooled nuclear reactor having unclad fuel elements as primary heat source, taking cognizance of the fact that state of art nuclear reactors operate in the vicinity of 1,0- F. Thus, it can be readily seen that it is Well suited for remote applications and even for vehicles for land, sea, air or space. In the latter application a Rankine rather than a Joule cycle is indicated, hence a condensible working medium (e.g., Ce) may be incorporated.
As mentioned previously, this invention also embraces an MHD motor or pump or accelerator or compressor having no mechanical moving parts and which is capable of moving gas at velocities from subsonic, to supersonic and even hypersonic magnitudes. While the MHD motor, pump, accelerator or compressor component is used for moving the gas in a closed cycle system for generation of electric power, it can be adapted for use in an open cycle system for providing MHD propulsion of space vehicles.
The normally linear structure of the MHD generator (or MHD motor), for electrical gas conductivities significantly less than about mho/m., can be rolled into a helical structure as a conventional helix delay structure of an appropriate electronic tube (e.g., traveling wave tube) or folded into a meander structure, as an interdigital delay line (of such an electronic tube) in order to avoid unwieldly structures and objectionable and even impractical overall dimensions, while utilizing such length of the gas duct, or electrical conductivity of the gas. In such compact forms, conservation of magnetomotive forces can also be affected in the production of the required uniform magnetic field in the interaction space. The helical structures can be referred to as periodic magnet helix MHD generators (or motors). While the helix (or meander alternative) duct structures are not here considered further, it should be remembered that this invention can also assume these configurations.
In the type of MHD generator configuration disclosed herein (i.e., Hall generator, for the sake of one of the two means of gas ionizationcrossed field electron beam injection) the voltage and current or power is taken off longitudinally or axially by appropriate electrodes in the interaction duct, which conveys the electrically conducting gas. The transverse currents provide the necessary physical resistance to the gas flow. In effect, the physical power density expended by the gas flow by pushing against the electromagnet forces is represented by the sealer product v BI (where v denotes the gas velocity, B denotes the magnetic field and I denotes the transverse current density). Substantially similar structural configurations can be used in the MHD generator and the MHD motor or pump or accelerator or compressor, except in the latter case appropriate structural and electrical alterations are dictated and the voltage is applied across the electrodes of the desired configuration, illustrated in FIGS. 1A, 1B, 1C, 1D.
In the MHD generator, the electrically conducting gas is heated to the appropriate temperature by the primary heat source and forced through the magnetic field to generate electric power output in the manner discussed in the text and in accordance with the Hall or Faraday generator principle in which the major current flows perpendicular to the strong magnetic field. Furthermore, it is essential that the energy loss to the duct walls be kept to a tolerable low level compared with the generated or dissipated energy in the volume of the gas. This implies maximizing the gas pressure-cross section product. Finally, it is essential to maintain uniform ionization at an adequate level. In the case of the MHD motor, the Hall or constant K electrode configuration also can be used with appropriate external voltages impressed across the electrodes. It should be mentioned that in the Hall configuration, with respect to motor or generator, non-uniformity has greater influence in reducing the effective gas conduc tivity and useful range of the Hall parameter. In any event, the electric field so established works with the impressed magnetic field to move the electrically conducting gas along through the duct by cross field interaction at the desired velocity.
The output ends of the MHD generator and MHD motor are combined in a unitary structure to form a regenerative heat exchanger (or regenerator and preheater, respectively), wherein heat from the residual hot gas discharged from the MHD generator is conducted to the colder gas leaving the MHD motor or pump or accelerator or compressor to preheat the gas which is on the way to be reheated by the primary heat source.
It is appropriate to clarify the mechanism involved in crossed field electrically conducting gas interaction in the following manner: Since only electric charges can interact with electric and magnetic fields, an efficient mechanism must exist for transferring the directed kinetic energy from the charged particles to the neutral gas molecules and vice versa. Otherwise, the efliciency of the MHD generator or MHD motor cannot exceed the fractional ionization. The reason for this lies in the fact that most of the kinetic energy in the gas resides in the flowing neutral gas molecules.
Energy transfer in this case can result only from attractive forces and collisions between molecules in the gas conductor. Charges are generally equally divided in number between electrons and ions, therefore, in transferring their energy to an external load they are decelerated at the expense of their directed kinetic energy. However, for the sake of high conversion efiiciency, the essentially neutral gas molecules must also be decelerated by transferring energy to the charges. Now, the electron mobility is high relative to that of the ions and hence the electrons are responsible for the major electric current flow. Also, electrons under the influence of an appropriate electric field decelerate promptly, due to their low mass, and form a space charge. This electron space charge exerts electrostatic forces on the positive ions. The latter, because of their relatively enormous mass, compared to that of the electrons, are correspondingly less influenced by the applied electric field. Thus, a positive ion space charge also forms. The electron and positive ion space charges constitute the plasma. Now, the collision cross section of positive ions and neutral gas molecules are similar. Hence, the positive ions by virtue of efiicient axially directed momentum, transfer via direct (axially directed) elastic collisions appropriate forces on the neutral gas molecules. Hence, reliance on the electrons alone for transferring energy to neutral gas molecules (being a relatively inefficient mechanism on account of the electrons relatively inferior collision cross section) is dispensed with. Thus, the gas stream, in forcing the charges through the applied fields, is decelerated and, furthermore, continually replenishes these charges. The reduced kinetic energy of flow appears as electric energy at the terminals of the generator in accord with Faradays generator prin ciple. Furthermore, the effective collision cross section of ions with electrons is enormously greater (e.g., by thousands of times) than that between electrons and neutral gas molecules. Consequently, the electric gas conductivity at about a tenth of one percent ionization may be considered to be effectively equivalent to that at complete ionization. Therefore, essentially three mechanisms of gas retardation or braking by charges may be considered to be as follows: Namely by electrons alone, by positive ions alone and by electrons and positive ions together, with the gas atoms.
The relative collision cross section of electrons and positive ions with gas atoms are such that Whereas an enormous (typically number of collisions with gas atoms are required in the case of electrons to affect significant momentum transfer, only a few collisions are required in the case of positive ions. Hence electrons alone affect only a marginal braking of the gas even in the case where the magnetic field is high and gas velocity low.
Electrons experience strong interaction or coupling with the magnetic field, and so are promptly braked by it, due to their relatively small mass. In contrast, positive ions experience no relatively significant interaction or braking by the magnetic field because of the strong interaction or coupling between the transverse moving positive ions and the gas atoms by virtue of their comparable masses and collision cross sections. Nevertheless, because of their comparable collision cross sections, positive ions experience strong interaction or coupling with the gas atoms and hence effectively retard the gas atoms by directed elastic collisions. Strong coupling or interaction between electrons and positive ions by virtue of their electrostatic forces serves to join these two mechanisms so as to effectively retard the gas atoms. In any event, little momentum transfer between charges and gas atoms can account for the prevailing MHD power generated since it is such a small fraction 1%) of the total energy associated with the gas flow. With transverse electric field, a significant retardation of electrons occurs. This dictates shorted electrode pair configuration and hence Hall rather than Faraday type generator. The foregoing may also be viewed with respect to the degree of the Hall current involved. In the case of no Hall current, every time a Hall field develops which couples the positive ions and electrons together, the electrons are responsible for the electric current to the extent of the cathode capacity. The momentum transfer is predominantly through the positive ions and gas atom collisions. In contrast, with Hall current, the positive ions and electrons act independently. The electrons are still responsible for the electric current. The momentum transfer is, however, predominantly through electron and gas atom collisions.
To provide the required optimum electrical conductivity of the gas at a moderate gas temperature (e.g.,
l0 mho/m. and more at about 2,500 F. for the sake of good thermodynamic performance and generator length) so as not to tax the endurances of the refractory materials, departure from the prevailing thermal ionization practices in several respects is necessary. For the sake of tolerable recombinations/attachment loss the average ion density should be made low. However for the sake of power output density, the electron mobility should be made high. These requirements suggest a low gas pressure and essentially (pure) monatomic noble gas, possessing low molecular weight and high specific heat/thermal conductivity. Polyatomic molecules degrade electron energy by inelastic collisions. To ionize the gas, Without experiencing a serious frictional pressure drop and magnetomotive force sacrifices, the (eflicient) process of controlled crossed field electron beam injection into the gas is proposed as one of two interdependent gas ionization provisions as the gas enters the cross field interaction space of the MHD generator (or MHD motor). As previously described, this gas ionization means is supplemented by application of periodic ionizing electric field pulses below the sparking limit (i.e., order of decimicrosecond) to ionize the gas to the required degree in order to achieve the desired electrical gas conductivity (i.e., 10 mho/m.). The gas ionization so produced can be made relatively uniform across and along the interaction region to avoid excess ionization (e.g., at electron injection orifices, or by too long ionizing voltage pulse, depending on ionization means) and simultaneously combat the relatively rapid ionization decay rate. The time for ionization to reach the desired level is extremely short (augenblicklich), so that for typical MHD generator operation excess ionization and sparking would be expected in the order of a microsecond and inadequate ionization in the order of a nanosecond. Also, the decay of the ionization from its established level is likewise rapid, so that the electrical gas conductivity under typical MHD generator operation can be reduced to such an extent that it is no longer useful in the order of a demisecond. Control of the gas conductivity by the proposed means are such that it can be maintained within an optimum range. That is, not too low, for good efficiency and tolerable generator size (especially duct length) at a given power, and also not too high, so as to avoid severely distorting the cross sectional flow front of the gas stream and severe entropy changes due to excessive Joule heating losses from currents in undesirable paths. Using the crossed field electron guns and periodic ionizing electric field pulses here disclosed, it is possible to achieve uniform ionization and electron injection efficiences approaching high values (e.g., percent).
For the sake of high power density, a high magnetic field is indicated. This measure also reduces the MHD generator (and motor) size, including losses proportional to wall area. Of course, a high magnetic field must be bought at the expense of magnetomotive force across the gas gap, which is a serious problem even for the electrical gas conductivity contemplated. As a matter of fact, the minimum gas electrical conductivity is largely governed by the magnet solenoid regardless of its resistivity, due to cost and weight factors. In any event, both high electron mobility and high magnetic field means a high Hall (effect) parameter. Hence, longitudinal or axial voltage and current or power extraction, without restriction on loading factor, is indicated. The Hall (or H) configuration illustrated in FIG. 10 seems best suited to meet the foregoing requirements. Hence, this indicates the use of segmented electrodes with desirable single high impedance load or voltage operation, suitable for commercial applications. It should be mentioned that non-uniformity is a more significant factor in this type of generator than displayed by the other types mentioned. This restriction tends to reduce the useful range of the Hall parameter and effective gas electrical conductivity. Furthermore, for high efficiency a high electron mobility and high uniformity are required. Hence, ideal performance may be more difficult to achieve as the Hall parameter is increased. Also, at high Hall parameters the ions begin to absorb significant energy and begin to display significant ion mobility or ion slip. In other words, conditions in which the mean free path of the neutral gas molecules becomes large enough so that they begin to pass through the plasma without appreciable interchange of momentum.
Although the gas velocity should also be high, for the sake of high power density and (minimum) generator size (especially duct length), there is the frictional pressure drop and other aerodynamic problems to be considered. As a preliminary compromise, therefore, to reduce this drop to a tolerable level, a gas velocity in the subsonic range is indicated; it being understood, however, that other than subsonic gas velocities can be used.
In this invention, the generator efficiency (i.e., theoretically 90%) and thermodynamic or cycle efiiciency (i.e., order of 50%) of energy conversion are correspondingly high. Furthermore, the device is capable of continuous (i.e., 100%) duty operation with long competitive (power station) life, since the materials of electrodes and confining walls are not taxed to or beyond their thermal endurance by the relatively moderate (i.e., order of 2,500 F.) operating gas temperature.
By means of low drive (power) modulation of the control electrode of the crossed field electron gun and periodic ionizing electric field, intermittent (i.e., pulsed) or alternating (sinusoidal) current component power output can be obtained. Continuous (i.e., 100%) duty direct current output is available in the absence of such modulation. As previously mentioned, crossed field gun operation involves pulsing the ionizing electric field at such short pulse duration (e.g., order of decimicrosecond for typical MHD generator operation) that sparking and nonuniformity in gas ionization are not encountered and at such high duty as to mitigate the deleterious ionization decay rate so as to approach full duty operation of the MHD generator.
The required high purity of the noble gas is maintained by effective (physical, chemical and/or electrical) continuous gettering of gas impurities (e.g., polyatomic molecules) in the interaction space of the MHD generator or MHD motor or pump or accelerator or compressor so as not to significantly degrade the electron energy by inelastic collisions. The methods of gettering can include electrical crossed field methods as well as purely physical and chemical methods. Continuous monitoring or measuring of the actual purity of the gas is necessary and can be accomplished by means of magnetron and mass spectrometer, together with appropriate diagnostic determinations of electrical conductivity and other relevant parameters of the plasma associated with the performance of the devices disclosed.
With reference to the FIGS. lA-lD, there is shown schematically various electrode configurations and associated vector diagrams which can be employed in MHD energy converters. FIG. 1A will be termed the elementary Faraday (E) type configuration. This is a transverse or shunt type, that is, the voltage, current or power extraction in the case of the generator of this type is transverse. The electrodes are continuously conductive along the length of the gas duct and are connected to a single load. The (not necessarily) uniform magnetic field intensity, in the MHD interaction space is indicated perpendicular to the plane of the paper and the gas velocity, v is represented by an arrow as directed. This configuration of magnetic field intensity and gas velocity is assumed to be the same in each of the FIGS. lA-lD.
FIG. 1B will be termed the multi-load-shunt (or 1r) Faraday segmented type utilizing transverse or shunt power extraction. The electrodes are segmented and each electrode pair is connected to a separate isolated load R FIG. 1C will be termed the Hall (or H) type. It utilizes longitudinal (or series) power extraction. The electrodes are also segmented and connected to a single load, while the individual opposing electrode pairs are strapped as indicated.
FIG. ID will be termed the modified Faraday segmented or constant K (or K) type. It also utilizes longitudinal (or series) power extraction. The electrodes are also segmented and connected to a single load in a wave pattern, a cathode of one opposing electrode pair connected to the anode of an adjacent pair, as indicated. The electric field in the interaction space in this type is in a fixed direction, independent of the loading factor, K. The value of the loading factor is restricted to that value which makes the strapped electrodes of equal voltage before strapping.
It can be shown that the performance of each type of MHD converter with respect to power density and efiiciency depends upon the Hall parameter both for electrons and for ion-electrons. The Hall parameter for ions is denoted by B, where ,u is the ion mobility of the positive ions of the gas and B denotes the magnetic field intensity. The Hall parameter for electrons is denoted by E, where M is the electron mobility as referred to previously. In the case of (n B)( t B) l, the performance of all types is poor. This is because the collision mechanism between positive ions and neutrals is weak.
In the case of (,t B) (,u B) 1, the performances of the four types are individually differentiated, depending upon the value of B. It should be noted that when (#e (MB) the E-type has good efiiciency for low values of rt the ir-type has good efficiency for both high and low a but not as good as the K type at low values of K. In addition, the performance of the 1r-type is independent of the value of B. The efficiency of the Hall type under the condition of .t B)(,u B) l, is good for high values of Therefore, it must operate at peak efficiency. However, it has twice the duct length of the rr-type for large B and the same efficiency. The efiiciency of the K-type is better than that of the 1r-type for high loading (K 0.5). Its power density under load is the same as that of the vr-type. However, as noted above, this type is restricted to a specific value of K. For a particular value of K, the 1r-type and the K-type work with the same power density and related parameters.
The E-type performs well with respect to etficiency and power density at values of B 1, that is, at moderate or small (i.e., ,u B 0) values of Hall parameter for electrons. The 1r-type performs well not only at intermediate (i.e., Kn B l0) Hall parameters, but in fact at all positive values of ,u B (i.e., Oe B- a) and so is less restricted than E-type in this respect. The Hall-type performs best when the Hall parameter for the electrons is dominant, that is, when 10 n B 10. All of these three types have high efficiency and high power density in their good performance range.
Closed cycle system FIG. 2 shows schematically an illustrative example of a closed cycle MHD generator in accordance with the principle of this invention. In this system, monatomic (noble) gas at relatively low gas pressure, (i.e., 10 to 30 pounds per square inch absolute) for the sake of tolerable recombination/attachment loss, is supplied to the MHD generator proper 50 after being heated by a suitable primary heat source 52 such as a gas cooled nuclear reactor, conventional fossil fuel burner, solar heat source, or other means. The hot gas at the exhaust of the primary heat source or inlet to the MHD generator is at maximum system temperature, T typically, in this invention, at about 2,500 F. This gas temperature does not tax the endurance of the associated materials exposed to the hot gas, yet it provides the desired cycle efficiency, typically about 45%. However, this gas temperature does not impart significant ionization to the gas alone to make it an adequate electrical conductor as required, namely about 10 or more mhos/meter.
The hot gas can be directed at subsonic gas velocity, for the sake of tolerable frictional pressure drop, to (a properly convergent-divergent) MHD generator duct, shown schematically at 50, for simplicity as a straight duct. Here it is electrically uniformally ionized by simultaneous crossed field electron beam injection and periodic ionizing electric field pulses below the sparking limit as previously described. This gas ionization is at the expense of a tolerably small fraction of the MHD generator output.
The MHD generator 50 directly converts physical or axially directed kinetic energy of charged particles and neutral particles (via collisions with positive ions) into electrical energy, by virtue of deceleration of the charged particles (i.e., transfer of their kinetic energy into (induced) electrical energy in the coupled circuit). In particular axial rather than transverse voltage and current or power extraction or coupling is utilized in this system, it being understood, however, that this invention is not limited to this type of power extraction or coupling. In effect, the Faraday generator principle and Ohms law apply, providing one takes cognizance of ion slip, Hall effect and the fact that the ions are not longer anchored as in a crystal lattice of a solid electrical conductor.
The gas exhaust of the MHD generator is directed into a heat exchanger or re-generator, 54, wherein the residual heat of the gas is thermally conducted to a preheater, 56, which heats the gas that is being returned to the primary heat source, 52, to repeat the cycle. This measure improves the cycle efficiency or otherwise conserves heat energy. The residual heat of the cooled gas from the re-generator is directed to a cooler or refrigerator 58, wherein the gas is further cooled to the lowest practical temperature, T in order to obtain the maximum cycle efiiciency, regarding the system as a carnot heat engine. From the cooler, 58, the gas is passed to a primary gas purifier, 60, wherein the residual gas impurities, other than the chosen gas, may be remove-d. The cooled and purified gas is passed to the properly convergent inlet of an MHD motor or pump or accelerator or compressor, 62.
This device can be similar to the MHD generator 50, except that it is operated as a motor by application of appropriate potentials to its terminals. The gaseous electrical conductor is then electrically forced along its (properly divergent) duct, obtaining supplementary electrical energy needed to return the gas to the primary heat source from the MHD generator, 50, by connections not shown in this figure, but detailed in FIG. 25 as an example. The discharge from the motor or pump or accelerator or compressor, 62, is directed to the preheater, 56, where it is preheated by the exhaust heat from MHD generator, 50, as aforesaid, before it is returned to the inlet of the primary heat source, 52, where the cycle is repeated.
In some cases, it may be desirable to substitute another type of pump or accelerator or compressor the MHD type. However, when freedom from moving mechanical parts, absence of lubrication problems, etc., are important considerations the MHD device has decided advantages. Electrical input to the motor, 62, can if desired, be supplied from any suitable electrical source other than generator, 50.
The gas purifier, 60, can be of any suitable type, electrical, physical or chemical or a combination thereof.
FIG. 3, illustrates elementary relations between various components involved in the MHD generator and MHD motor action. In the figure, v represents vectorially the gas velocity and B the applied magnetic field, the latter directed perpendicular and out from the plane of the paper. Due to the forcing of charges through the magnetic field by the gas stream via axially directed elastic collisions with them and the electrostatic forces between the electrons and positive ions, an electric field is induced at right angles to both the velocity and the magnetic field vectors shown vectorially as E, equal to E XF. The resulting induced current density is shown as IT, and is equal to @E, where a is assumed (approximately) as a scaler (rather than properly as a tensor) electrical gas conductivity, assuming an isotropic plasma in spite of the magnetic field, for simplicity of illustration. Due to the action of the plasma being forced through the magnetic field an induced EMF 1 results equal to 7 x1? directed parallel but opposite to v as shown.
The figure also shows that in the case of a motor, an applied electric field intensity E directed oppositely to T, but orthogonally to E and 5 The resulting conduction current I] due to the applied E is equal to 0E. The net measurable current density through the plasma is consequently j e-(F-FE XF). The action of the current density I gives rise to a Lorentz force F, of value 7X? or (E-kflxl?) X15. In case IE is greater in magnitude than E, the device acts as a motor; otherwise it acts as a generator.
The flow of electrons, e, and positive ions, i, in the interaction space, together with the resulting ionization of the gas is also illustrated in FIG. 3.
For continuous Faraday electrodes and Hall effect a phase angle of currents with respect to the electric fields occurs. The magnitude of this phase angle depends upon the ratio of the electron cyclotron frequency to the collision frequency, whereas the electric fields remain as indicated. For segmented Faraday electrodes and negligible Hall effect, the currents are as shown. With Hall effect, a phase angle departure of electric fields with respect to the currents occurs as shown in the vector diagrams of FIGS. 1A, 1B, 1C.
Longitudinally coupled generator FIG. 4 shows schematically an elementary embodiment of the MHD generator 50 of FIG. 2. The principle of operation depends upon the Hall effect which is predominant and requires electric coupling of, or power extraction by, longitudinal or axial voltages and currents, as in the Hall-type configuration shown in FIG. 10, while the transverse currents provide the necessary physical resistance to the ionized gas flow. Neutral gas of high electron mobility characteristics, namely a monatomic or noble gas such as helium or argon at lower than atmospheric pressure, so that attachment/recombination losses are not excessive, enters the generator from the primary heat source at the left, as shown in the figure by an arrow 64. In an illustrative example, the compromising temperature, taking cognizance of material limitations and good cycle efliciency, of the gas is chosen about 1645 K. (2500 F.) and for the sake of tolerable fractional pressure drop, its speed subsonic, at about 1000 meters/ second.
The gas first passes an unobstructing primary crossed field electron gun region 66, between a cathode assembly, comprising an electron emitter 68, a Wehnelt electrode 102 and control grid 63 and an accelerator electrode of the electron gun which is shown as a short type crossed field electron gun. The primary crossed field electron gun controls the gas ionization by means of controlled electron beam injection and periodic ionizing electric field pulses as previously described so as to minimize excess ionization within it by application of proper ionizing pulse duration and repetition rate and electric gradient at the cathode aperture, to minimize recombination energy loss.
With reference to FIGS. 4 and 4a through 4e, that the anodes (shown shorted to the emitting soles, for longitudinal coupling) actually perform dual functions. That is, the anode accommodates not only the output power (terminals) and shorted transverse voltage and current (shorting straps), but also independently the pulsed ionizing voltage, with respect to the emitting soles; identically with that applied between the accelerator and cathode of the primary crossed field electron gun.
To avoid interference between these two functions, the anodes are structurally composite and independent or,
alternately, blocking or chokes are inserted in the output terminals and shorting straps so as to not only prevent the flow of pulse current through these circuits, but to prevent shunting of the pulse voltage that is applied between each anode and sole pairs.
The composite anode may comprise one set of interdisposed and connected elements for the pulse voltage, and the other set for the output power and shorted transverse voltage and currents. In the alternate means involving blocking or chokes, these can be inserted in the output terminals and shorting straps so that the subject pulsing voltage applied to the anodes behaves as though the output terminal and shorting straps are absent, yet does not interfere with their individual functions.
Thereby, use of appropriate pulse voltage duration (to prevent excess gas ionization and hence sparking and arcing), appropriate pulse voltage amplitude (to raise the electron temperature in appropriate increments), and appropriate pulse voltage repetition rate (to compensate for the ionization decay rate), provides encouragement for achieving a uniform, continuous and adequate gas ionization throughout the effective interaction space.
The subject pulsed electric field gas ionization means supplements that achieved by means of the electron beam. Thus, the two non-equilibrium gas ionization means working together provide promise of attaining the desired range of electrical gas conductivity and other benefits previously mentioned.
Furthermore, working at high Hall parameter enables a corresponding high output (power) impedance so that the cathode current density is very low.
Furthermore, use of secondary electron emitting soles with high secondary electron yield eliminates electron emission problems. These emitters take advantage of the back bombardment characteristic of crossed field operation of emitters.
Various type crossed field electron guns, as illustrated by FIGS. 6 and l720 in accordance with the principles of this invention, can be substituted for the type of gun shown. It should be noted that although FIGS. 6 and 17 illustrate primary cathode heaters, this is not necessary since the hot gas is at adequate temperature for the cathodes contemplated, especially since the nonthermal electron emission properties of the cathode are emphasized.
The electron gun in FIG. 4 employs crossed periodic pulsed ionizing electric field and direct current magnetic fields, the periodic pulsed ionizing electric field being provided by means of a source (i.e., MHD generator) of electric potential represented arbitrarily by a keyed battery, 72, connected between the accelerator, 70, and the cathode assembly 68, 63, 102. This cathode assembly with or without the control grid, 63, and Wehnelt electrode, Hi2, may comprise (not shown) the emitting soles, 78, 84, 91 if desired.
The magnetic field can be provided by one or more conventional or superconducting solenoids (or by one or more permanent magnets, not shown, which are not likely to be practical due to the high MMF requirements of Hall generators). The magnetic field distribution is generally substantially uniform throughout the MHD interaction space and the electron gun regions of the MHD generator (and MHD motor). However, certain situations may indicate modified (non-uniform) magnetic field distribution at the ends of the electrodes along the flow so as to increase the local charge density. The magnetic field is indicated by an arrow, 74, shown perpendicular to the paper.
The applied electric field in the electron gun region is governed by Paschens and crossed field laws. The effects of the former law are mitigated (by utilizing pulse durations of the order of a nanosecond at typical nonequilibrium MHD conditions) and controlled so as to increase the gas conductivity beyond the limit of electron beam injection alone by utilization of periodic pulsed ionizing electric field at appropriate pulse duration (e.g., order of decimicrosecond as previously discussed), and at a repetition rate to mitigate ionization decay rate and for the sake of full (100%) duty operation, and to avoid the deleterious eifects of gas discharge and consequent non-uniform gas ionization. Furthermore, the relative intensities of the electric and magnetic fields can be such that only insignificant electron current flows to the accelerator, 70, and consequently quite modest electron current need by demand of the illustrative periodic pulser, 72, in energizing the electron gun. Provision against reverse electron current can also be made by means common to the state of the gas discharge art.
A control grid electrode, 63, is incorporated for alternating current operation. It is used with a Wehnelt electrode, 102, as shown in conjunction with the cathode, 68, the electrode, 63, being appropriately biased, (i.e., with intermittent (pulsed) or alternating potential) with respect to the cathode, by means of a biasing source represented arbitrarily in the figure by modulator 65. The purpose of the electrode, 63, is to control the electron beam. Although separate sources for the electron gun are illustrated, these very low power sources of potential are energized by the MHD generator. The cathode, 68, is a non-thermal and thermal type electron emitter, in the latter case deriving its heat from the hot gas flow in which it is in contact.
Electrons emitted from the cathode, 68, are drawn away toward the accelerating electrode, 70, under the influence of the periodic pulsed electric field and direct current magnetic field, by application of appropriate sources mentioned-In addition, modulation of the grid for alternating current operation can be included. Thereupon the electrons, except for any captured by the accelerator electrode, are immediately constrained to move in magnetron paths, due to the combined eflfect of the orthogonal crossed electric and magnetic fields.
The pulsed electric and continuous magnetic field intensities are preferably adjusted so that the paths of the electrons in the gas starting at the extreme left of the cathode will just barely graze the accelerator plate and will not be substantially collected thereby but will be further constrained to continue substantially parallel to the accelerator plate in accordance with crossed field constraints, before, at, and after passing the throat of the electron gun. The result is substantially a smooth electron flow forming a stream of electrons emerging from the throat of the electron gun, in magnetron paths, all substantially along the plane of the electrodes.
FIGURE 4 shows schematically the electron stream from the primary crossed field electron gun, 66, as it is injected into the gaseous stream in the interaction space of the generator. In the interaction space, the moving gas passes between a series of electrode pairs anode, 76, cathode, 78, anode, S2, cathode, 84, anode, 88, cathode, 90, etc. of parallel electrodes separated by insulating spaces without plates. The upper plate in each pair, as shown in the figure serves as an anode while the lower plate of each pair serves as a crossed field cathode similar to that of the electron gun and is referred to as electron emitting sole. The emitting soles are non-thermal and thermal or thermionic type (i.e., cermet or dispenser) type-deriving their optimum operating temperature for the thermal or thermionic portion for electron emission from the flowing hot gas with which they are in contact. They can also be, as the cathode of the primary electron gun, indirectly heated to meet any additional heat requirement on account of any inadequacy on the part of the hot gas. The emitting soles are preferably highly productive of secondary as well as primary electrons.
A succession of many short electrodes is employed instead of long continuous electrodes in order to break up the longitudinal circuit and so prevent large axial or longitudinal surface currents which would otherwise flow in the electrodes, due to the Hall effect which is made dominant for the purposes of this invention, a circumstance which would cause large ohmic losses. Furthermore, since at high magnetic fields or high Hall effect parameter, the current density tends to peak at the trailing edges of the electrodes, appropriate design considera tions have been applied to minimize erosion thereat.
The emitting soles 78, 84, 90, etc. supply the electrons to the gas or plasma in the interaction space as required to make up for electron loss and those passing to the :load. To short circuit the electrodes of each electrode pair, electrical conducting straps, 80, 86, 92, etc., are provided outside the interaction space between the anode and the emitting sole. The axial or longitudinal current, voltage and power are taken otf through a load circuit, 94, connected between the first and last pairs of electrode pairs, as shown. The magnetic field, both in the electron gun and in the interaction space is in the same direction but not necessarily the same magnitude and perpendicular to the plane of the paper and that of the ionized gas fiow and electron beam flow. Both the applied magnetic field and the injected electron beam are made as substantially uniform as possible throughout the interaction regions between facing pairs of electrodes. However, there may be an advantage in controlling the magnetic field distribution in the interaction space with respect to the vicinity of the edges of the electrodes to take advantage of the increase in local density of charges thereat and so increase the power output from the MHD generator.
The use of the electrical ionization via electron beam injection, supplemented by periodic pulsed ionizing electric field means as previously discussed for maintaining adequate and uniformly as possible ionization of the flowing gas so that the desired electrical gas conductivity is achieved in the interaction spaces of the MHD generator (and the MHD motor), renders the system as a whole self-exciting and self-starting, as in the case of an electromagnetic machine or self-excited thermionic oscilator. With the gaseous stream forced through the duct, ionization is established immediately upon entering the primary crossed field electron gun portion of the duct. Full MHD generator (or MHD motor) action begins immediately upon the establishment of adequate ionization in the flowing gas, which requires continual and uni form ionization throughout the volume of the duct.
Requirement for continual uniform ionization arises on account of the rapid rate of decay of ionization, due primarily to recombination/ attachment loss, which is characteristic of the behavior of the gas. The distribution and energy of the electron stream can be adjusted to accomplish this desired result while at the same time its energy is virtually entirely absorbed in the gas upon reaching the far end of the interaction space and an electron collector and heat regenerator, 98, which is provided at that point.
The energy required to maintain the desired degree of gas conductivity by electrical ionization, namely conductivity in the order of mho/m. or more, is moderate; it being of the order of a base percentage the useful power output of the generator. It is known in the art and as has been pointed out previously that the electric power generated is less than a percent of the total energy associated with the gas. That is, the total energy is equivalent to a small fraction of an electron volt at typical MHD conditions. Since the ionization potential of ordinary gases are relatively high, only a few percent of the atoms at the most would be ionized under ideal conditions of the available energy extracted and utilized. Nevertheless, the electrical conductivity of the gas when ionized to the extent of a small fraction of a percent is substantially as high as for the completely ionized gas.
A supplemental means for ionizing the gas with crossed field electron beam periodic pulsed ionizing electric field means, at the expense of .a small fraction of the power output of the MHD generator, is also utilized, as previ- 18 ously discussed to achieve the desired electrical gas conductivity.
Only a few of the required representative electrode pairs in the generating portion of the generator, 50, are shown for illustration in FIG. 4.
The pair of electrodes nearest the electron gun comprises the anode, 76, and the electron emitting sole electrode, 78, connected together outside the gas duct by the electrical conductive strap, 80, which is of negligible resistance. The opposing faces of the electrodes of each pair are parallel to the direction of the magnetic field. An intermediate electrode pair comprises the anode, 82, and the electron emitting sole, 84, connected by a like strap, 86. The pair of electrodes farthest from the electron gun comprises the anode, 88, and the electron emitting sole, 90, connected by a like strap, 92. The output terminals of the generator, 50, comprise the electrode pair, 76, 78, and strap, 80, which constitute the generator terminal conventionally called the negative terminal, for direct current operation, and the electrode pair, 88, 90, and strap 92, which constitute the positive terminal. The electrical load connected to the generator terminals is represented in the figure by the impedance, 94.
Electrons emitted by the cathode, 68, follow, in the simplest case, halt cycloidal paths in the region between the cathode and the accelerator. The gun forms an electron beam which substantially permeates uniforrnally the entire interaction region of the gas duct as previously discussed. The electron beam moves to the right as shown in the figure, while ionizing the flowing gas, moving in the same direction, with the aid of the applied periodic pulsed ionizing electric field between cathode and anode or accelerator. In the interaction portion of the generator, the plasma is subjected to a strong Hall eifeet, which induces both transverse and axial or longitudinal current and voltage in the plasma. The transverse currents serve to provide the necessary physical resistance to flow. The load, 94, is coupled through the longitudinal currents and voltages. Thereby, desired high rather than low impedance output characteristics are realized.
The electron beam injection and applied pulse duration, amplitude and repetition rate of the ionizing electric field can be controlled so that the ionization effect of the electron beam and pulsed electric field is substantially uniform and limited to the desired interaction region of the gas duct. After traversing the interaction region the plasma deionizes very rapidly as previously discussed, due primarily to recombination/ attachment losses. Residual charges are collected at the ion collection/regenerator 98, which in a very simple form can comprise one or more plates arranged edgewise to the gaseous stream. The ion collector/regenerator, 98, primarily serves the purpose of absorbing residual heat energy from the exhaust gas. The neutral gas leaving the ion collector/regenerator, 98, is in turn exhausted toward the right in the figure as indicated by the arrow, 100.
To adapt the MHD generator for alternating current component operation, an alternating voltage, represented by a modulator 69, is impressed between the control electrode, 63, and the cathode, 68, as shown schematically in FIG. 4. The action of the electron gun is the same as described previously, except that the electron flow is modulated instead of steady. For direct current operation the periodic pulsed non-ionizing electric field bias voltage, 65, can be applied, but is optional. Its pulse duration is so short (order of a nanosecond) that no significant gas ionization occurs on its account. The alternating voltage from modulator, 69, can be superimposed on this for alternating current power output from the MHD generator. As a result, there is a controlled variation of the degree of gas ionization and, hence, of the electrical gas conductivity in the MHD generator. This in turn causes a corresponding modulation of the power output of the MHD generator. The modulation of the power output of the MHD generator is attributable to the fact that the ions of the gas recombine extremely rapidly in the absence of an effective process of continual ionization so that significant variation of the electron output of the electron gun and periodic pulsed ionizing electric field is reflected in corresponding variations of the electrical gas conductivity and hence power output of the generator.
A switch, 67, is shown whereby the modulator, 69, can be included in the circuit or not, depending upon whether direct current or alternating current component operation is desired. It will be evident that the modulated or alternating current output from the MHD generator obtainable by use of the modulator can be converted by means of a transformer in conventional manner and that all known intermittent or pulsed or alternating current te hniques can be employed in the utilization of the power output of the generator. Direct current operation especially at commercial voltages, is applicable in practice. Alternating current operation could also be obtained, in principle at least, alternatively by modulating the current in the solenoids producing the impressed magnetic field (especially in the case of a superconducting solenoid) but with much more drive required (except in the case of superconducting solenoids) and much less economy compared to low drive voltage modulation of the control electrodes of the primary cross field electron gun and secondary crossed field emitting soles.
Double-walled duct embodiment FIGS. 6, 8 and 11 show an illustrative embodiment of coaxial ducts, primary crossed field electron guns and electrode structures for use in an MHD generator (or MHD motor) according to the invention. The emitting soles thereof can be replicas of the primary cathode assembly or can be simpler, as discussed previously. The coaxial duct is built on the Dewar principle with two spaced walls and thermal insulating space between the walls to minimize heat loss from the inner duct. The inner duct wall is a suitable dielectric (e.g., ceramic) with matching metal (e.g., tantolium, etc.) inserts on the inside to form the electrodes and joining members of sections. Those electrodes that are cathodes and emitting soles can be directly heated (via the hot flowing gas) or indirectly heated (via an auxiliary heater) thermionic and non-thermal electron emitter, as previously described. They can have a coating or a layer or comprise a body of electron emissive material such as a dispenser or cermet type.
Suitable dielectric (or ceramic) spacers are provided between the inner and outer walls at intervals along the duct for the purpose of isolating and supporting the inner duct in the outer one. The outer duct wall is of suitable metal (e.g., stainless steel) with suitable dielectric (or ceramic) inserts at locations where electrical connection is made to an electrode inside the duct. The ducts can be made in demountable setcions which can be welded (e.g., heli-arc) together to make up any required length, and separated (e.g., by grinding off the welds) a number of times and rescaled as before as desired.
FIG. shows in three-dimensional diagrammatical form a general convergent-divergent duct or nozzle which involves consideration of the Joule-Thomson (Ioule-KeL vin) effect. Such nozzle can be used in practice for converting the random motions of the gas into more axially directed motion within the electron gun and interaction spaces in the gas duct in an MHD converter. In the near vertical wall of the divergent portion of the duct are shown schematically the crossed field electron gun cathode 68 the first sole electrode 78 in the interaction space, for simplicity a few intermediate sole electrodes, and the last electron emitting sole electrode, 90. Usually in practice, a much larger number of intermediate emitting sole and anode electrodes will be required, depending upon design requirements. In the far vertical wall of the divergent portion of the duct are shown schematically the electron gun accelerator electrode 70, the first anode electrode 76 in the interaction space, a few intermediate anode electrodes, and the last anode electrode, 88. The sole electrode of each opposing pair of electrodes in the interaction space in shown strapped to the respective anode electrode of the pair, the first strap and the last strap 92 constitute respectively, the negative terminal and the positive terminal for the load impedance 94 for direct current operation. The relative directions of the gas velocity, v and the magnetic field intensity, B, are shown by arrows in the figure.
FIG. 6 shows a longitudinal or axial cross section of a simple MHD generator. The coaxial ducts therefore, in a central plane perpendicular to the magnetic field. This plane is also perpendicular to the planes of the opposed electrodes. FIGS. 7 and 8 show external appearance at side and one end, respectively. Although a conventional straight duct system is illustrated, in practice, the inner duct may be tapered, for example as illustrated in FIG. 5, so that where C and /gf denote cross section dimension and final gas velocity, respectively. The dielectric (or ceramic) inner duct wall that is uppermost in the figure is designated, 200, and the lower inner duct wall is designated, 202. The upper metal duct outer wall is designated, 204, and the lower, 206.
The electron cathode assembly of a simpler illustrative type of crossed field short electron gun suitable for direct current operation is shown generally at 208. The cathode of the gun need not have an indirect heater assembly since the hot flowing gas is at adequate gas temperature for optimum thermionic operation. Other electron guns (e.g., those disclosed in FIGS. 17 through 22) for alternating current operation can be substituted for the electron gun shown. A simplified cathode 210 is shown comprising electron emissive material either coated upon a suitable base metal or comprising a cermet or dispenser type unit. The cathode 210 can operate by virtue of heat of the hot (e.g., 2500 F.) inert gas or its own accord, thermionically by means of a suitable integral electrical heat source. It can also be primarily a non-thermal type of emission cathode.
The indirectly heated (optional) cathode 210 is shown in the form of an inverted metal box separated on all sides from the main portion of the inner wall 202 by a gap 212. Inside the cathode, 210, are located a plurality of electrically heated heater elements indicated schematically at 214. All the heater elements 214 are connected in parallel in conventional manner and brought out through an insulating tube 220 to a pair of heater connections 222. The heaters are held in place by a cover plate assembly 224 through which the tube, 220, projects.
A Wehnelt electrode, 226, generally surrounds the sides of the cathode 210. The electrode 226 comprises a sheet of metal inserted into the wall 202 to the left of the cathode, folded downward over the edge of the wall 202 at the gap, 212, passing under the cathode and back up opposite the cathode at the right of the cathode to fasten to the wall 202 at the right of the gap 212. A suitable dielectric (or ceramic) spacer ring 228 permits the cathode to be insulated and supported by the control electrode. An access side duct 230 for cathode connections is inserted in the lower outer wall 206. The duct 230 is provided with a suitable cover plate 232 and a suitable dielectric (or ceramic) electrode base press 234, sealing a hole in the plate 232, through which the heater connections 222, a cathode connection 236 and a control electrode connection 238 are brought out. The modulator 69 and the biasing voltage 65 can be inserted when required between the cathode connection 236 and the control electrode connection 238 in a manner similar to that shown in FIG. 4 between the electrodes 68 and 63 of that figure.
The accelerator for the elementary short electron gun is shown generally at 240. The accelerator plate 242 is a metal (e.g., tantalum) plate inserted (i.e., brazed) in the upper inner duct wall 200. The plate 242 extends opposite the control electrode 226 and the cathode 210. Electrical connection is made to the plate 242 by way of a metallic pin 244, which can be integral with the plate, the upper end of which makes a suitable engagement with a nut 246. An access hole in the upper outer wall 204 opposite the nut 246 is sealed by a metal-dielectric (e.g., metal-ceramic) plug assembly 248, which can be sealed (e.g., heli-arc welded) to a metallic collar 250. Through the plug assembly 248 extends a shouldered metallic pin 252, the lower end of which makes a (e.g., set screw) locked engagement with a nut 254 to permit angular orientation of the nut 254.
Hairpin type electrically conducting wires 256 are inserted into holes in, or otherwise secured to the peripheries of the nuts 246 and 254.A set screw (not shown) is provided in the nut 254 for securing the nut in correct angular position on the pin 252 so as to align the placements or holes for the wires 256. A plan view of the nut 246, hairpin wires 256 and without the set screw is shown in FIG. 9. The shouldered end of the pin 252 is provided with suitable means for engaging an external electrical connector 260.
The metal and ceramic parts are joined in vacuum-tight manner as known in the art, so that the space between the inner duct and the other casing can be evacuated by known means and operated under high vacuum to reduce heat transmission from the inner duct to the outer casing and the ambient medium.
A sole electrode for the electron gun is shown at 262. It can be an electron emitter or not, depending upon the application. In any event, its construction can be simple for direct thermionic electron emission by means of the hot gas or it can be primarily a non-thermal electron emitter independent of the hot gas. Its form can be generally similar to that shown for the accelerator electrode 240.
An auxiliary anode electrode for the electron gun is shown generally at 264. The construction of the auxiliary anode electrode can be substantially the same as for the accelerator 240. The auxiliary anode electrode is flush with the upper wall of the duct as shown.
An anode electrode, for either an MHD generator or an MHD motor with an electrical connection external to the duct, is shown generally at 266. The construction of this anode electrode can be substantially the same as shown for the electrode 240, except for current capacity and because at the high Hall parameter or magnetic field characteristic of the Hall generator (FIG. 1C) the trailing edge of the anodes (and cathodes) with respect to the gas flow must be made more erosion resistant due to the concentration of electric current there. The anode electrodes are inserted into the upper wall of the duct. In an MHD generator, the external electrical termination of anode electrode 266 is used only at the two generator terminals that are to be connected to the electrical load of the generator.
The first of these, from left to right, is the negative terminal of the generator for direct current operation. It is the first anode electrode to the right of the primary electron gun. The second terminal is the positive terminal of the generator and is the last anode electrode shown generally at 268 at the extreme right hand end of the interaction space of the generator, the construction of which is substantially the same as shown for the other anode electrodes that have external electrical connections. In an MHD motor, all the anode electrodes and emitting soles may require external electrical connections.
The electron emitters of the cathode of the electron gun and sole in the MHD generator can be operated either as a non-thermal thermionic emitters, actuated by the passing hot gas stream, or as indirectly heated emitters, actuated by impressed external heat source, shown in the drawings only for the cathode of the primary electron gun.
The magnetic field can be readily supplied by permanent magnets, however, because of the high mmf. requirements it may be desirable to generate the magnetic field by means of electromagnets, conventional or superconducting.
The non-therrnal thermionic electron emitters can be refractory dispenser or cermet types, having an operating temperature of about the ambient gas temperature (or 2500 F.). Operating these emitters at their optimum temperature insures long operating life.
An anode electrode that has no electrical connection through the outer duct wall is shown generally at 278. The structure comprises a metallic plate 272 inserted in the upper inner duct wall 200. A metallic pin 274 which can be integral with the plate 272 makes electrical contact with the plate 272 on the upper face thereof and extends upwardly to the upper surface of the wall 200 into a strap groove 302 (FIG. 12) for connection to a strap 288, as will be explained presently with reference to FIG. 11.
An electron emitting sole electrode that has no electrical connection through the outer wall of the duct is shown generally at 276 (FIG. 6). The structure comprises a composite metallic plate 278 inserted in the inner lower wall 202 of the duct. The upper surface of the composite plate 278 can be impregnated or coated with a thermionic or secondary electron emissive material to promote copious emission of electron as required. The strap 288 lying in a strap groove 302 (FIG. 12) is connected to the plates 278 and 272 as shown in FIGS. 11 and 6.
An anode electrode having no electrical connection through the outer wall of the duct and having a thermal and electrical isolator and spacer spanning the region between the inner and outer walls of the duct, is shown as an example at 286. The structure is generally similar to that shown for the anode electrode 270, except that a pin corresponding to the pin 274 extends sufficiently beyond the upper surface of the wall 208 to form a support or axle for a thermal spacer such as a wheel 282. The rim of the wheel 282 is displaced laterally from the axle to such an extent that the rim bears against the inside surface of the upper outer wall 204, while the axle bears against the outer surface of the upper inner wall 268. The spacer or wheel 282 can have a plurality of spokes which extend diagonally between the axle and the rim.
An electron emitting sole electrode, similar in size to the anode electrode 280, is shown generally at 284. This electrode is inserted into the lower inner wall 202 of the duct and the thermal spacer or wheel 286 corresponding to the spacer or wheel 282 spans the region between the outer surface of the inner lower wall 202 and the inner surface of the outer lower wall 2%.
FIG. 11 shows a cross section of the duct through the anode electrode structure 286 and the electron emitting sole electrode structure 234. The view ShOWs the inner and outer walls of the duct in cross-section, together with the thermal and electrical isolators and spacers shown as the wheels 282, 286. The view further shows the short-circuiting strap 288, which corresponds generally to any one of the straps 80, 86, 92 shown schematically in FIG. 4 for connecting an anode electrode to an opposing electron emitting sole electrode by an electrical conductive path outside the inner wall of the duct; specifically over the outer surface of the inner wall of the duct. The anode end of the strap 288 is electrically connected to a metallic pin 290 that forms the support for the isolator and spacer wheeel 282. The strap 288 lies in a groove in the outer surface of the inner wall 260' of the duct, extending upwardly as shown in FIG. 11 and over the top outer surface of the inner wall, and thence downwardly to an electrical connection with the metallic pin 292 that forms the support for the isolator and spacer wheel 286.

Claims (1)

1. IN A PLASMA ENERGY CONVERTER, APPARATUS FOR GENERATING IONS COMPRISING MEANS FOR GUIDING PLASMA ALONG A PREDETERMINED PATH, SAID CONDUIT MEANS INCLUDING A GAS INPUT MEANS AND A GAS OUTPUT MEANS, A SOURCE OF HEATED NEUTRAL GAS, MEANS FOR CONNECTING SAID SOURCE OF HEATED GAS TO SAID GAS INPUT MEANS SO THAT THE HEATED GAS FLOWS THROUGH SAID CONDUIT MEANS, MEANS FOR INJECTING AN ELECTRON BEAM INTO A GIVEN REGION WITHIN SAID CONDUIT MEANS, MEANS FOR APPLYING A MAGNETIC FIELD TO AT LEAST SAID REGION WITHIN SAID CONDUIT MEANS, SAID MAGNETIC FIELD HAVING A DIRECTION SUBSTANTIALLY PERPENDICULAR TO SAID PREDETERMINED PATH, MEANS FOR APPLYING A PULSED ELECTRIC FIELD TO SAID REGION, SAID PULSED ELECTRIC FIELD HAVING A DIRECTION SUBSTANTIALLY PERPENDICULAR TO BOTH THE DIRECTION OF SAID MAGNETIC FIELD AND SAID PREDETERMINED PATH, SAID PULSED ELECTRIC FIELD HAVING A PULSE DURATION OF LESS THAN TEN NANOSECONDS TO FIELD IONIZE SAID NEUTRAL GAS WITHOUT BREAKDOWN WHEREBY THE NEUTRAL GAS IS IONIZED PARTLY BY THE INJECTED ELECTRON BEAM AND PARTLY BY THE FIELD IONIZATION RESULTING FROM THE PULSED ELECTRIC FIELD.
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US3585422A (en) * 1968-12-06 1971-06-15 Alsthom Cgee Homopolar dynamoelectric motor utilizing a moving, conductive fluid
US3708704A (en) * 1971-09-09 1973-01-02 Gen Electric Thermionic cathodes for mhd generators
US3736447A (en) * 1971-09-27 1973-05-29 Gen Electric Uniform ionization means for mhd generators
US4016438A (en) * 1975-05-27 1977-04-05 The United States Of America As Represented By The Secretary Of The Air Force Enthalpy augmentation to MHD generation
EP0018822A2 (en) * 1979-05-04 1980-11-12 Ben-Gurion University Of The Negev Research And Development Authority A closed-circuit magnetohydrodynamic (MHD) system for producing electrical power and a method for producing electrical power by means of a magnetohydrodynamic (MHD) generator
US4516043A (en) * 1980-10-16 1985-05-07 The Regents Of The University Of California Method and apparatus for generating electrical energy from a heated gas containing carbon particles
US20040195503A1 (en) * 2003-04-04 2004-10-07 Taeman Kim Ion guide for mass spectrometers
US20110011728A1 (en) * 2009-07-15 2011-01-20 Sackinger William M System and method for conversion of molecular weights of fluids
US20110011727A1 (en) * 2009-07-15 2011-01-20 Sackinger William M System and method for conversion of molecular weights of fluids
US20110241477A1 (en) * 2010-12-30 2011-10-06 David Mitchell Boie Hall Effect Power Generator
US20120001517A1 (en) * 2009-02-20 2012-01-05 Japan Science And Technology Agency Transportation of micrometer-sized object and extraction of mechanical work by constant electric field
US20120153772A1 (en) * 2008-08-28 2012-06-21 Landa Labs (2012) Ltd. Method and device for generating electricity and method of fabrication thereof
US20220190747A1 (en) * 2019-08-20 2022-06-16 Calagen, Inc. Circuit for producing electrical energy
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US3524086A (en) * 1966-04-28 1970-08-11 Parsons & Co Ltd C A Magnetohydrodynamic apparatus
US3505550A (en) * 1966-07-19 1970-04-07 Thiokol Chemical Corp Plasma energy system and method
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US3736447A (en) * 1971-09-27 1973-05-29 Gen Electric Uniform ionization means for mhd generators
US4016438A (en) * 1975-05-27 1977-04-05 The United States Of America As Represented By The Secretary Of The Air Force Enthalpy augmentation to MHD generation
EP0018822A2 (en) * 1979-05-04 1980-11-12 Ben-Gurion University Of The Negev Research And Development Authority A closed-circuit magnetohydrodynamic (MHD) system for producing electrical power and a method for producing electrical power by means of a magnetohydrodynamic (MHD) generator
EP0018822A3 (en) * 1979-05-04 1980-12-10 Ben Gurion University Of The Negev Research And Development Authority A method for producing electrical power and magnetohydrodynamic apparatus for carrying out the method
US4516043A (en) * 1980-10-16 1985-05-07 The Regents Of The University Of California Method and apparatus for generating electrical energy from a heated gas containing carbon particles
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US20120153772A1 (en) * 2008-08-28 2012-06-21 Landa Labs (2012) Ltd. Method and device for generating electricity and method of fabrication thereof
US9126198B2 (en) * 2009-02-20 2015-09-08 Japan Science And Technology Agency Transportation of micrometer-sized object and extraction of mechanical work by constant electric field
US20120001517A1 (en) * 2009-02-20 2012-01-05 Japan Science And Technology Agency Transportation of micrometer-sized object and extraction of mechanical work by constant electric field
US20110011727A1 (en) * 2009-07-15 2011-01-20 Sackinger William M System and method for conversion of molecular weights of fluids
US20110011728A1 (en) * 2009-07-15 2011-01-20 Sackinger William M System and method for conversion of molecular weights of fluids
US20110241477A1 (en) * 2010-12-30 2011-10-06 David Mitchell Boie Hall Effect Power Generator
US8519594B2 (en) * 2010-12-30 2013-08-27 David Mitchell Boie Hall effect power generator
RU2783405C2 (en) * 2018-09-11 2022-11-14 Ионек Лимитед Energy accumulation and conversion
RU2783405C9 (en) * 2018-09-11 2023-03-14 Ионек Лимитед Energy accumulation and conversion
US20220190747A1 (en) * 2019-08-20 2022-06-16 Calagen, Inc. Circuit for producing electrical energy
US11671033B2 (en) 2019-08-20 2023-06-06 Calagen, Inc. Cooling module using electrical pulses
US11677338B2 (en) 2019-08-20 2023-06-13 Calagen, Inc. Producing electrical energy using an etalon
US20230318491A1 (en) * 2019-08-20 2023-10-05 Calagen, Inc. Cooling module using electrical pulses
US11863090B2 (en) * 2019-08-20 2024-01-02 Calagen, Inc. Circuit for producing electrical energy

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