US3346747A - Electro-fluid-dynamic generator - Google Patents

Description

TI P85 U 2 OR 5 5 45 s 7L?? Oct. 10, 1967 V J, W. LARSON 3,346,747

ELECTRO-FLUID- DYNAMI C GENERATOR Filed July '7, 1964 2 Sheets-Sheet 1 afer/Q @Jr/4W@ Oct. 1o, 1967 J. w. LARSON 3,346,747

ELECTRO-FLUID-DYNAMIC GENERATOR Filed July 7, 1964 2 sheets-sheet 2 United States Patent O 3,346,747 ELECTRO-FLUID-DYNAMIC GENERATOR John W. Larson, Phoenixville, Pa., assigner to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed July 7, 1964, Ser. No. 380,759 6 Claims. (Cl. S10-11) ABSTRACT OF THE DISCLOSURE Apparatus and method for reducing the space charge eiect in an electro-iiuid-dynamic generator wherein surfaces of constant voltage potential and the electrostatic forces normal thereto are established at an angle to the direction of fluid iiow through the generator so that the electric flux due to the space charge rnay escape the generator in a radial direction while ions pass therethrough with minimal resistance.

These surfaces of constant voltage potential are established between electrically connected and axially spaced outer and inner electrode rings of a series of axially aligned electrode assemblies which coact to dene an annular fluid passage between the inner and outer electrode rings of each electrode assembly. The electrode assemblies are electrically connected so that the potential gradient of the constant voltage potential surfaces increases in a downstream direction so that ions liberated at an inner electrode will pass across the passage and transfer its charge to an outer electrode of higher potential to thereby establish work producing electron flow between the farthest upstream and farthest downstream electrode assembly while permitting the electric llux due to the space charge to escape radially.

This invention relates to electro-fluid-dynamic generators and more particularly to apparatus and method for reducing the space charge elect therein.

An electrofluid-dynamic generator is a device which directly converts thermodynamic or fluid dynamic energy into electrical energy by carrying ions in a iluid from a region of low electric potential to a region of high electric potential, then neutralizing the charged ions at this high potential with an electron flow which provides useful electric power to a load. In the electro-fluid-dynamic generator considerable diiculty is encountered because the electric ilux due to the space charge perturbs the externally applied electrostatic iield.

It is an object of this invention to improve the performance and efficiency of an electro-fluid-dynamic generator by permitting the electric flux due to space charge to escape radially while retaining the ions within the fluid iiow region.

It is a further object of this invention to teach an electro-tluid-dynamic generator in which the electrostatic forces are established at an angle to the direction of uid flow so that the elect-ric flux due to space charge is allowed to escape radially and so that the ions are carried in the owing fluid in a downstream trajectory to a region of higher electrical potential, under the iniiuence of the drag thereon created by the fluid and the inuence of the electrostatic field attempting to move the ion to regions of higher potential.

It is a further object of this invention to teach an electro-fluid-dynamic generator in which fluid is passed through concentric cylinders made up of pairs of inner and outer electrode rings, connected by a conductor and electrically insulated from one another and established so as to be of increasing electrical potential in a downstream direction and wherein ions are released at an electrode in the low potential region and carried by the iluid to an electrode in a region of higher potential and wherein this process may be repeated several times so as to further increase the electric potential or charge on the ion or ions.

It is still a further object of this invention to teach an electrode unit for a fluid-dynamic generator comprising two concentric, axially spaced electrode rings joined by at least one conductor so as to form a truncated cone therewith.

It is still a further object of this invention t-o teach a reduction in space charge effe-ct in a thermionic converter by reducing the length of the path of the ions.

Other objects and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

FIG. 1 is a schematic representation of an electrofluid-dynamic engine or generator in its operating environment.

FIG. 2 is a cross-sectional showing through an electrofluid-dynamic engine illustrating the angular positions of the electrode rings and the electrostatic iield which they establish with respect to the axis of the engine duct and hence the direction of ow of the fluid passing therethrough.

FIG. 3 is a vectorial illustration of the effect which the iluid drag force and the electrostatic force have upon the path traveled by the ion.

FIG. 4 is a perspective showing of an electrode pair unit.

FIG. 5 illustrates the electrical connection between adjacent electrode pairs to establish each electrode pair at an equal potential and so as -to be increasing in potential in a downstream direction.

FIG. 6 is a vectorial illustration of the effect of the fluid flow, the electrostatic eld and the space charged field on the ions in the conventional electro-tluid-dynamic engine.

FIG. 7 is a vectorial illustration of the effect of the fluid ilow, the electrostatic eld and the space charged eld on the ions in my invention.

FIG. 8 is a sectional showing of a modification of the elecro-uid-dynamic engine in which contact ionization is use Referring to FIG. l, we see electro-fluid-dynamic engine 10 being fed lluid from iiuid source 12 after the fluid has passed through iluid pressure generator 14 and heat exchanger 16. The fluid used may be either a liquid or a gas or combination of both so long as it is capable of transporting ions. Air, which is dry and is therefor not an electrical conductor, could be used as the fluid. Pure water, carbon tetrachloride and acetone are also not electrical conductors and therefor could transport ions, and could not be used as the uid. The liuid pressure generator can be a conventional pressure generating device of the type fully explained in Jet Propulsion, by Hesse published in 1958 by Pitman Publishing Corp. while the heat exchanger may be of the type fully explained in Heat Transmission, by McAdams published in 1954 by McGraw-Hill Company.

Referring to FIG. 2, we see electro-fluid-dynamic engine in the form of inner cylinder 20 and outer cylinder 22 positioned concentrically about axis 24 so as to form gas passage 26 therebetween to be of annul-ar cross section and concentric about ,axis 24. Cylinders and 22 are preferably formed by a series of electrode pairs such as 30, 32 and 34, each of which includes an inner electrode ring 36, an outer electrode ring 38 and an electrical conductor 40 electrically connecting inner ring 36 and outer ring 38. Each electrode ring pair such as is electrically insulated from the adjacent electrode ring pairs by electric insulating rings such as 42 and 44 and conductors 4t) are completely surrounded by insulation.

A typical electrode ring pair 30 is shown best in FIG. 4 and includes inner electrode ring 36, outer electrode ring 38 and electrical conductors 40, with each conductor completely surrounded by electrical insulation illustrated partially at 50. Insulating ring 42 is positioned on one side of inner electrode ring 36 while a second insulating ring 52 is positioned on the other side of electrode 36. In similar fashion, electric insulating ring 44 is positioned on one side 0f outer electrode ring 38 while a similar electric insulating ring 54 is positioned on the opposite side of electrode 38. In this fashion, each of the electrode ring pairs, such as 30, is insulated from all other electrode ring pairs but the inner and outer electrode rings such as 36 and 38 of each electrode ring pair, such ,as 30, is electrically connected through electrical conductors 40 so that the electrodes of each pair will be at equal electrical potential.

Again referring to FIG. 2, it will be noted that the farthest upstream electrode ring pair 30 is electrically connected through electrical conduit 60 to the farthest downstream electrode ring pair 62 and that this electrical conduit passes through work load 64. The various electrode ring pairs are electrically connected as best shown in FIG. 5 so that they are of increasing electrical potential in a downstream direction. Heavy resistances such as 66 are electrically connected between adjacent electrode ring pairs such as 30 and 32 so as to cause the electrode rings to increase in electrical potential in a downstream direction. It will accordingly be seen that the electrode rings in each electrode ring pair are at equal potential but that the electrode rings increase in electrical potential in a downstream direction so that pair 30 is at minimum electrical potential while pair 62 is at minimum electrical potential. In operation, either positive or negative ions are generated by any method at the inner electrode ring 36 of the farthest upstream electrode pair 30. One such method is by producing ,a corona discharge in a fashion now to be described and more fully described in the publications Electrical Engineering, by Dawes, 4th edition, volume II, published by McGraw-Hill and the McGraw-Hill Encyclopedia of Science and Technology, volume 3, published in 1960.

Using the corona discharge method, ions are established and released near inner electrode rings 36 by applying a high voltage at inner electrode ring 36 and maintaining a suicient rate of increase of electrical potential between electrode pairs in the axial direction, which locally increases the electric ield intensity above the dielectric strength of the working uid at the inner electrode producing a corona electrical discharge. The geometric arrangement of concentric cylinders yields a voltage gradient which varies inversely with radius in the space between the cylindrical surfaces to satisfy the electrical potentials at these surfaces. The succession of increasing electrical potential electrode pairs in the axial direction produces this voltage gradient in the radial direction because the inner and outer electrodes of each electrode pair are at different axial positions allowing inner and outer electrodes radially opposite from each other to be at different electrical potentials. In the corona discharge method of supplying ions into the uid in the annular passage 26 an electrical eld gradient is created at the surface of the inner electrode 36 and is suiiicient in strength to cause a corona discharge. The nature of the electrical eld established between the concentric cylindrical boundaries of passage 26 is such that when the inner and outer `boundaries are at dilferent electrical potentials, the potential gradients in the annular passage are inversely proportional to the radial distance from the axis of symmetry. Thus, the potential eld, or voltage gradient, is a maximum at the surface of the inner electrode. As the Voltage difference between the inner and outer electrodes is increased, avoltage gradient is eventually achieved near the inner electrode which is at or beyond the voltage breakdown limit of the fluid (which is normally not an electrical conductor) contained in annular passage 26. The breakdown of the fluid at the inner electrode leads to current flow either outward or inward across the span in which the electrical breakdown occurred. (During electrical breakdown of the fluid, it is electrically conductive, whereas it is electrically non-conducting when not subjected to a high electrical eld.) At the outer boundary of the voltage breakdown vicinity, electrical ions are formed which drift outward through the fluid contained in the annular passage. A supply of high voltage is required to start this generation. This is but one of several methods of generating ions at the inner electrode 36.

Another method of forming ions is illustrated in FIG. 8 in which cesium is caused to ow through a heated sintered tungsten sleeve 68 so as to release ions to the inner electrode ring 36. In the FIG. 8 configuration, a contact ionization process is utilized. The inner electrode of the FIG. 8 construction is a porous sintered tungsten element through which atoms of cesium trickle. The cesium wets the outside surface of electrode 36, is ionized and then begins to drift through annular passage 26 in a fashion to be described hereinafter. Cesium is chosen in the FIG. 8 configuration because it has a low work function of ionization, that is, it ionizes at a comparatively low voltage gradient. This process of contact ionization causes a heat removal from the inner electrode which must be replaced by the fluid flowing through passage 26 so as to maintain the cesium in passage 24 at a high temperature and thereby maintain a high ionization rate. This contact ionization process is more fully described in Technical Note D-2172 entitled, Status of Electrostatic Thrusters for Space Propulsion, by Mickelsen and Kaufman and published by the National Aeronautics and Space Administration in May 1964.

The ions or ion so released at inner electrode ring 36 passes into annular passage 26 and is acted upon both the areodynamic force of the fluid passing through the passage and by the electrostatic force created by the equal potential electrodes and the increasing potential of the electrode pairs. The forces acting upon a given ion is best illustrated in FIG. 3. Under the influence of the iluid drag force and the electrostatic force, the ion at inner electrode ring 36 passes across annular passage 26 from point A on inner electrode ring 36 to point B on an outer electrode ring 72 of electrode ring pair 70, which is at a new and higher electric potential than electrode ring pair 30. The ion is neutralized by the transfer of electron charge to the outer electrode ring 72 of ring pair 70 at station B and the electron charge moves from the outer electrode 72 via conductor 40 of ring pair 70 to the inner electrode ring 74 at the new and higher potential for further ion release at the higher potential at inner electrode ring 74 for -admittance into the gas stream. This new higher potential io-n moves from point C due to forces previously described to point D which is at a still higher potential. The electron charge, at this further increased electric potential then moves from point D to point E along the connector 40 therebetween. At the inner electrode at point E a higher potential ion is released for passage to point F and so on until the charge eventually reaches point G at the outer electrode ring 80 of the farthest downstream electrode ring pair 62. The ion at electrode ring 80 is at a substantially higher electrical potential than the ion at electrode ring 36, and therefore, electrons flow through conduit 60 to perform work at load 64 and eventually pass to electrode outer ring 80 to neutralize the ion.

It will be noted that as illustrated in FIGS. 2 and 4, the outer ring such as 38 of each electrode pair such as 30 is positioned axially downstream of the inner ring 36 thereof so as to define ,a frustoconical surface of constant voltage potential therebetween in which connectors 40 lie. Lines of electrostatic force project substantially perpendicul-ar to this constant voltage potential surface or region. In this fashion, the field of electrostatic force is created at an langle to axis 24 and the direction of fluid ow through passage 26 and thereby permits the ions to pass substantially radially therethrough with greater ease than would be the case if electrode rings 36 and 38 were in axial alignment as in the conventional electro-luid-dynamic engine. While connectors 40' are shown, it will be obvious to those skilled in the art that if other means of support were provided for electrode rings 36 and 38, the rings 36 and 38 could be connected by an electrical connection external of the fluid stream.

This advantage is best viewed by examining FIGS. 6 and 7. FIG. 6 illustrates the conventional electro-fluiddynamic engine in which the ion is acted upon or dragged in an axially downstream direction by the velocity of the fluid indicated vectorially as Vp, in the opposite axial direction by the electrostatic force Ep and again in the opposite axial direction by the ion space charge force S/ Cp so as to leave a net vectorial gain acting upon the ion of the VN. By viewing FIG. 6 it will be noted that the space charge force S/ CD is in direct `axial opposition to the benecial ion force generated by the lluid velocity indicated vectorially as Vp.

By viewing FIG. 7 we see that with the equal potential lines at an angle to axis 24, as in my invention, the effect of the velocity of the fluid upon the ion, Vp, can be illustrated ina direction normal to the lines of equal potential as VpN, while the electrostatic force remains the same, Ep and the space charge force' S/Cp can be illustrated vectorially and additively to the Ep force as shown as S/CpN. It will laccordingly be seen that since the space charge force S/ Cp is atan angle to the equal potential lines in my invention, the effect thereof in impending ion movement in the all important direction normal to the lines of equal potential will be reduced.

It should be understood that the invention is not limited to the specific embodiment herein illustrated and described but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. An electro-fluid-dynamic engine comprising a duct of annular cross section and concentric about an axis, means to pass fluid through said duct, said duct including ,a plurality of 'axially aligned electrode pairs, each of said pairs comprising -axially spaced inner and outer electrode rings electrically connected together by a conductor, means to insulate each electrode ring pair from all other electrode ring pairs, means to establish a region of constant voltage potential across each electrode pair such that said regions increase in electrical potential in a downstream direction, means to electrically connect the farthest upstream electrode ring of the farthest upstream electrode pair with the farthest downstream electrode ring of the farthest downstream electrode pair, means to establish ions at said farthest upstream ring of said farthest upstream electrode pair such that said ions travel downstream in said fluid under the influence of the electrostatic force and the uid velocity force so as to pass from said farthest upstream electrode ring of said farthest upstream pair across said duct to the downstream ring of a second electrode pair of higher electrical potential from whence its charge travels by way of opposite electron motion at said higher potential to the other ring of said second electrode pair to be released as an ion therefrom into said fluid stream and to pass thereacross to the downstream electrode ring of a third electrode pair at a higher potential than said second electrode pair from whence said ion passes to the upstream electrode ring of said third electron pair and its charge is again released into said fluid stream until it eventually reaches said farthest downstream electrode ring of said farthest downstream electrode pair, thereby establishing electron ow through said electrical means connecting said farthest upstream and said farthest downstream electrode rings.

2. An electro-fluid-dynamic engine comprising a duct of annular cross section concentric about an axis, means to pass fluid through said duct so as to establish a fluid stream flowing therethrough, a plurality of axially aligned pairs of electrode rings positioned along said duct, each of said pairs including axially spaced and concentric inner and outer electrode rings electrically connected by'a conductor, means to electrically insulate all electrode ring pairs from all other electrode ring pairs and to insulate said conductors, means to establish a constant voltage potential surface across each electrode ring pair such that said surfaces are increasing in electric potential in a downstream direction, means to electrically connect the farthest upstream ring of the farthest upstream electrode pair to the farthest downstream ring with the farthest downstream electrode pair, and means to liberate ions from said farthest upstream electrode ring, said electrode ring pairs being so spaced axially that said liberated ions, under the combined effect of the forces imposed thereon by said electrostatic elds and said fluid stream will pass across said duct from the farthest upstream ring of said farthest upstream electrode pair to the farthest downstream ring of a second electrode pair to liberate ions from the farthest upstream ring of said second pair for travel across said duct until said ions eventually are neutralized on the farthest downstream ring of said farthest downstream electrode pair, thereby establishing electron ow through said electrical connecting means.

3. An electrode pair unit for an electro-Huid-dynamic engine comprising concentric and axially spaced electrode rings, one of said electrode lrings being larger than the other of said electrode rings, and electrical conductors connecting said rings and cooperating therewith to form a cone frustrum.

4. The method of reducing the space charge eifect in an electro-uid-dynamic engine having an annular uid passage defined between inner and outer walls including small ringed electrodes in the inner Wall and large ringed electrodes in the outer wall comprising positioning electrically connected pairs of small and large ringed electrodes in spaced axial relation along the passage to establish constant voltage potential regions therebetween to thereby establish the space charge eld at an angle to the electrostatic field.

5. The method according to claim 8 wherein the angle of said regions with lrespect to said engine uid flow has a greater effect in reducing the impeding space charge force than in reducing the aiding engine fluid flow velocity force.

6. The method of reducing the space charge effect in an electro-fluid-dynamic generator comprising establishing fluid flow through an annular passage defined between inner and outer walls of circular cross section and including a series of electrode assemblies positioned axially along the passage and with each electrode including a ring electrode in the inner wall electrically connected to and spaced axially from a ring electrode in the outer wall thereby establishing regions of constant voltage potential between said electrically connected electrode rings, electrically connecting said electrode assemblies so that the regions of constant voltage .potential are of increasing electric potential axially along the passag generating ions at a rst inner wall electrode ring in the region of lowest electric potential to be carried by the iluid and under the inuence of electrostatic force to a rst outer Wall electrode -ring at a region of higher electric potential Where the ion will transfer an electron charge on the rst outer wall electrode ring for electric transfer to a second inner wall electrode ring electrically connected to the first outer wall electrode ring thereby liberating an ion of higher potential at the second inner wall electrode ring to be carried by the uid and under the influence of electrostatic force to a second outer Wall electrode ring at a region of higher potential than the potential of the first outer wall electrode ring, and repeating this process to produce electrical power.

References Cited 10 MILTON O. HIRSHFIELD, Primary Examiner.

DAVID X. SLINEY, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,346,747 Octerber l0, 1967 John W. Larson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

dColumn 6, line 58, for the claim reference numeral "8" rea 4 Signed and sealed this 8th day of October 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD I. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. 4. THE METHOD OF REDUCING THE SPACE CHARGE EFFECT IN AN ELECTRO-FLUID-DYNAMIC ENGINE HAVING AN ANNULAR FLUID PASSAGE DEFINED BETWEEN INNER AND OUTER WALLS INCLUDING SMALL RINGED ELECTRODES IN THE INNER WALL AND LARGE RINGED ELECTRODES IN THE OUTER WALL COMPRISING POSITIONING ELECTRICALLY CONNECTED PAIRS OF SMALL AND LARGE RINGED ELECTRODES IN SPACED AXIAL RELATION ALONG THE PASSAGE TO ESTABLISH CONSTANT VOLTAGE POTENTIAL REGIONS THEREBETWEEN TO THEREBY ESTABLISH THE SPACED CHARGE FIELD AT AN ANGLE TO THE ELECTROSTATIC FIELD.

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