WO2011020988A2 - Machine à cycle de stirling - Google Patents

Machine à cycle de stirling Download PDF

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Publication number
WO2011020988A2
WO2011020988A2 PCT/GB2010/001483 GB2010001483W WO2011020988A2 WO 2011020988 A2 WO2011020988 A2 WO 2011020988A2 GB 2010001483 W GB2010001483 W GB 2010001483W WO 2011020988 A2 WO2011020988 A2 WO 2011020988A2
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WO
WIPO (PCT)
Prior art keywords
phase
electrical
piston
power
stirling cycle
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PCT/GB2010/001483
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English (en)
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WO2011020988A3 (fr
Inventor
Michael William Dadd
Original Assignee
Isis Innovation Limited
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Publication date
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Publication of WO2011020988A2 publication Critical patent/WO2011020988A2/fr
Publication of WO2011020988A3 publication Critical patent/WO2011020988A3/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
    • F02G1/00—Hot gas positive-displacement engine plants
    • F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
    • F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
    • F02G1/0435—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines the engine being of the free piston type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
    • F02G1/00—Hot gas positive-displacement engine plants
    • F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
    • F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
    • F02G1/044—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines having at least two working members, e.g. pistons, delivering power output
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
    • F02G2244/00—Machines having two pistons
    • F02G2244/50—Double acting piston machines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
    • F02G2280/00—Output delivery
    • F02G2280/10—Linear generators

Definitions

  • the present invention relates to a Stirling cycle machine, and in particular to a Stirling cycle machine which is capable of long life, zero maintenance and highly efficient operation at high speed.
  • the invention is mainly exemplified as an engine driving an electromechanical transducer so that the machine operates as an electrical power generator, the machine and the thermodynamic and electrical process within it are reversible so that it can be operated as a heat pump in response to the input of electrical power.
  • Stirling cycle machine Although there are many different configurations of Stirling cycle machine, they all basically consist of a gas filled assembly of two variable volumes Vl, V2 connected by a number of heat exchangers - i.e. a cooler 3, a regenerator 5 and a heater 7, as illustrated in Figure 1 of the accompanying drawings for example.
  • the varying volumes Vl , V2, generated by the piston and cylinder assemblies Pl , P2, 1, operate at different temperatures with a phase between them that is typically between 60 to 120 deg.
  • the volume with the retarded phase is termed the compression volume Vl and in it work is done on the gas by the piston Pl .
  • the other volume is termed the expansion volume V2 and in this case the gas does work on the piston P2.
  • the net work of the machine is the difference between the work output of the expansion volume and the work input of the input volume.
  • the expansion volume temperature Te must be higher than the compression space temperature Tc.
  • Te/Tc is made as high as possible.
  • Te and Tc are typically 1000 K and 300 K respectfully.
  • a displacer 9 is used to cause the expansion work to act directly on the gas in the compression space.
  • the “compression” piston P3 becomes subject to a gas coupled work transfer from the displacer 9 and the total work acting on it is the combined compression and expansion works.
  • the piston P3 could be appropriately termed the “net power” piston but this has been shortened to just “power” piston in common parlance. This approach is commonly used as a single piston P3 and cylinder 2 together with a displacer 9, as it can be more easily realised than a two piston arrangement.
  • Beta engines are similar in operation but are arranged so that the piston and displacer share the same cylinder with the heat exchangers forming an annulus around the cylinder. They have the advantage of a more compact arrangement.
  • the Sunpower engine schematically illustrated in Figure 3 is a good example of a Beta type engine.
  • the displacer 9 is mounted on a planar spring 1 1 while the piston P3 is connected to a linear alternator 13 which generates electrical power in response to movement of the piston P3.
  • kinematic engines that use crank mechanisms and which are oil lubricated, encompass alpha, beta and gamma types of engine.
  • crank mechanisms In kinematic engines work transfer and correct phasing is readily achieved through the use of crank mechanisms so that any of these engine types are possible.
  • Beta type engines such as the Sunpower engine of Figure 3, where the work transfer from the expansion volume to the compression volume is achieved through a displacer. In these engines the work transfer is in two stages:
  • the expansion volume face of the displacer absorbs the expansion work and mechanically transfers it to the compression space face of the displacer.
  • beta type configurations have been preferred and the power output is via a single linear generator attached to the power piston.
  • the engine is designed specifically to operate with a phase angle of 90 degrees between compression piston and expansion piston.
  • the compressor and expansion transducers are both arranged to be resonant at the operating frequency.
  • Both compressor and expander pistons are coupled to a phase lock loop oscillatory circuit. This is used to both impose the 90 degree phase difference and transfer power from the expander to the compressor.
  • phase lock loop circuit The wave form generated by the phase lock loop circuit is not sinusoidal; the output will be closer to a square wave.
  • the present invention relates to the field of linear/free piston engines designed for applications requiring long life, zero maintenance and high efficiency e.g. isolated power generators (for example solar and military applications) or space applications. These requirements generally exclude designs that have oil lubrication as these require seal replacement at regular intervals.
  • the leading example of prior art in this field is the Sunpower engine of Fig. 3 although similar designs have been produced by STC (Stirling Technology Company) and MTI (Mechanical Technology Incorporated).
  • the spring stiffness is provided by the planar spring 11. This can be increased by adding more springs but there is a limit as extra springs also add extra moving mass - ultimately the resonant frequency of the whole assembly must be lower than the resonant frequency of the springs. For a 35 W power output Sunpower have managed to attain an operating frequency of about 100Hz - this limit appears to be set by the resonance requirements. It is difficult to increase the frequency in the Sunpower design as the configuration is not suited to having additional gas springs attached to the piston.
  • the present invention provides an alpha configuration Stirling cycle machine comprising a compression piston, an expansion piston, a gas spring connected to the expansion piston or compression piston, and two electromechanical transducers, the compression piston being connected to a first of the two electromechanical transducers and the expansion piston being connected to a second of the two electromechanical transducers, and wherein at least part of the work to drive the compression piston is supplied by the electrical output from the second electromechanical transducer, said electrical output being supplied to the first electromechanical transducer via an electrical feedback circuit to set the phase of the movement of the compression piston in desired relation to the phase of the movement of the expansion piston, wherein the electrical feedback circuit establishes a phase difference between the compression and expansion pistons of 100 to 140 degrees.
  • the use of the electrical output of the second electromechanical transducer to provide at least part of the power needed to drive the compression piston, in particular by using an electrical feedback circuit allows the alpha configuration machine to enjoy the benefits of long life and zero maintenance from the use of free pistons in a mechanically simple arrangement.
  • the mechanically simple arrangement means that the spring constants and thus the resonant frequency of the vibrating assemblies can be set more flexibly, which in turn allows the operating frequency to be set more flexibly, for example increased.
  • the use of the feedback circuit allows the phase between the expansion and compression pistons to be adjusted for efficient operation at a wide variety of frequencies.
  • the electrical feedback circuit is designed to give a phase shift which is selectable as desired.
  • a phase difference can be selected which results in maximum efficiency and it has been found that for this type of Stirling engine a phase shift of 100 degrees to 140 degrees, more preferably 115 degrees to 125 degrees, for example substantially 120 degrees is appropriate. If a different balance of power and efficiency is required the phase difference can be set to a different value. This contrasts with prior art Stirling engines, for example of the Moscrip design where the phase difference is fixed at 90 degrees to provide resonance between the electrical and mechanical parts of the machine and thus cannot be altered.
  • Well-known reactive circuits based on the use of capacitors and inductors can be used to adjust the phase, but to achieve large phase shifts, for example as large as 120 degrees, without using large inductors or capacitors it can be convenient to reverse the polarity of the output from the second electrical mechanical transducer by reversing its connections, this providing effectively a 180 degree phase shift (the output being sinusoidal), which means that smaller value reactive components can achieve the remaining adjustment of 60 degrees to give a resultant phase shift of 120 degrees.
  • the configuration used also allows, for example, a gas spring to be connected to the expansion piston or compression piston, or both.
  • Gas springs can give very high spring rates with low losses and in the illustrated embodiment this allows the operating frequency to be increased to 150 Hz or greater giving much greater power without an increase in engine size.
  • the machine is in a linear configuration with the compression and expansion pistons and volumes on opposite sides of two heat exchangers and a regenerator providing fluid communication between the compression and expansion volumes, in which case gas springs can be arranged at the opposite ends of the assembly. This allows considerable flexibility because the size of the gas springs is not constrained by the other components of the machine.
  • the electrical feedback circuit may be composed of low loss passive electrical components which have low power consumption and are available at low cost.
  • the feedback circuit may be an active feedback circuit containing power converter and amplifier modules which allow control of both phase shift and amplitude.
  • a further option is for an electrical feedback circuit consisting of both passive and active circuits. Such a circuit can have the low loss of a passive circuit with sufficient control provided by the active circuit.
  • the machine can be operated as an electrical generator, with the first electromechanical transducer acting as a linear motor driving the
  • compression piston and the second electromechanical transducer as a generator driven by the expansion piston.
  • it can be operated as a heat pump or compressor.
  • the input to the first electromechanical transducer derived from the phase shifted output of the second electromechanical transducer, provides all of the work required to drive the compression piston. This means that the machine, once started, is self-sustaining.
  • the engine can be self starting but may need an initial external input to the compressor motor.
  • the feedback from the second electromechanical transducer to the first can be arranged to be insufficient to completely drive the compression piston, and a second control input provided to the second electromechanical transducer making up the balance of power required.
  • the control input to the first electromechanical transducer allows control of the amplitude of vibration and thus the power output of the machine.
  • the control input can conveniently be provided for by arranging the first electromechanical transducer as a linear motor comprising a coil with two sets of windings, one receiving the phase shifted output from the second electromechanical transducer and one receiving the control input.
  • the provision of two sets of windings is easily achieved during manufacture of the coil.
  • the second electromechanical transducer preferably also takes the form of a linear electric motor comprising a coil with two sets of windings, one for providing the output to be fed back to the first electromechanical transducer and one providing the power output of the machine. This allows, for example, one set of windings to consist of a high number of fine windings generating a high voltage, and the other a lower number of thicker windings to provide a high current.
  • the first and second electromechanical transducers can use a permanent magnet or electromagnet to provide the magnetic field, and can be of the moving coil or moving magnet type.
  • the compressor assembly may consist of a balanced compressor pair and/or the expander assembly consist of a balanced expander pair.
  • the compression and expansion transducers are not required to operate very close to resonance and the phase angle between the compressor and expander is not required to be 90 degrees.
  • the phase of the expander is determined primarily by the mechanical dynamics of the machine and transducer, not by the electrical drive. By relaxing these constraints a direct transfer of power from the expander to the compressor is possible using simple low loss components.
  • the machine is capable of being operated at a phase chosen for maximum efficiency, and the mechanical arrangement of the machine allows the provision of high spring stiffness and thus high operating frequencies giving high power.
  • the configuration is scalable and thus machines can be made to this design for a large range of power outputs from 1OW to 1OkW or even higher e.g. 10OkW.
  • the machine is applicable to electrical generators for spacecraft, e.g. using a radioactive heat source (plutonium, americium), and to power generators for military use which need to be robust, reliable and to be able to use a variety of heat sources including direct flame heating and heatpipes, and to machines using solar power as a heat source.
  • a radioactive heat source plural, americium
  • a variety of heat sources including direct flame heating and heatpipes, and to machines using solar power as a heat source.
  • FIG. 2 is a schematic illustration of a prior art gamma-configuration Stirling cycle machines
  • Figure 3 is a schematic illustration of a commercial beta-configuration Stirling cycle machine
  • Figure 4 schematically illustrates a first embodiment of the invention
  • Figure 5 is an electrical equivalent circuit diagram of the embodiment of Figure 4;
  • Figure 6 is a phasor diagram showing the signals in the circuit of Figure 5;
  • Figure 7 is an electrical equivalent circuit diagram showing an example of power factor correction for the motor
  • Figure 8 is a phasor diagram of the signals in the circuit of Figure 7;
  • Figure 9 is an electrical equivalent circuit diagram of an alternative embodiment of the invention.
  • Figure 10 is a phasor diagram of the signals in Figure 9;
  • FIG. 11 is a schematic illustration of another embodiment of the invention.
  • Figure 12 is a schematic illustration showing a general feedback circuit using active components
  • FIG. 13 is a schematic illustration of another embodiment of the invention.
  • Figure 14 is a more detailed schematic illustration of an embodiment of the active electrical feedback circuit that can be used in the invention.
  • Figure 4 illustrates a first embodiment of the invention.
  • This embodiment operates as an engine and as illustrated is in the alpha configuration with separate compression and expansion pistons Pl, P2.
  • the compression space Vl which contains working fluid is in fluid communication via a cooler 3, regenerator 5 and heater 7 with the expansion space V2 where the working fluid acts upon the expansion piston P2.
  • the compression piston Pl is driven by a first
  • electromechanical transducer 20 and the expansion piston P2 drives a second
  • the electromechanical transducer 22 which thus acts as an electrical power generator.
  • the first and second electromechanical transducers 20 and 22 are conveniently linear motors which can be of the moving coil or moving magnet type.
  • the electrical output 21 of the second electromechanical transducer 22 driven by the expansion piston P2 is supplied to an electrical circuit 24 which feeds back part 23 of the electrical power from
  • electromechanical transducer 22 to the first electromechanical transducer 20 having adjusted its amplitude and phase.
  • the remaining output power from electromechanical transducer 22 is supplied as an electrical power output 25 from the machine.
  • the proportion of power fed back from the generator 22 to the motor 20 can be fixed or can be made load-dependent.
  • the phase adjusting electrical circuit can be a low loss circuit composed of passive components or it can be a circuit comprising active components.
  • amplitude of the compressor input relative to the generator output can also be adjusted by varying the force constant of either the motor 20 or generator 22.
  • the transducer current will in general either be in phase with the generated voltage or it will be out of phase:
  • the current is out of phase with the voltage then it implies the generation of a force component that will contribute to the balance between spring and inertial forces in the system.
  • the spring and inertial forces are in anti-phase.
  • the force component from the electrical circuit can therefore either add to the spring rate or the moving mass depending on its phase.
  • Figure 5 shows one example of a feedback circuit that adjusts the phase and amplitude to give a suitable input to the compressor.
  • the motor 20 and generator 22 are generally represented by a voltage source (the transducer emf) in series with resistive and inductive components.
  • the voltage source will typically be an AC waveform with an amplitude determined by the "generator" constant and the peak transducer velocity.
  • the voltage source, internal resistance and internal inductance for the generator are denoted Vg, Rg and Lg.
  • the motor components are labelled Vm, Rm, Lm.
  • the motor 20 and generator 22 are connected together via a reactive component Z so that all the components are subject to a common current.
  • phase difference between the emfs is the same as the phase difference between the compressor and expansion pistons Pl, P2. Therefore the motor emf needs to be retarded with respect to the generator emf by an angle in the range 60 to 120 degrees. It is also desirable to keep phase angle between current and generated emfs as small as possible. In this example the motor 20 and generator 22 have the same current so the current phase angle will need to be between the phase angles of the motor and generator emfs.
  • Figure 6 shows a voltage phasor diagram for an example of this arrangement.
  • the phase angle between the generator and motor A is about 60 degrees and the current phase angle B is half this at about 30 degrees for both transducers.
  • FIG. 6 shows how the generator voltage Vg is balanced by the vector sum of the motor voltage Vm, the resistive component 1.Rt and the reactive component Vz where Rt is the total resistance in the circuit - Rt includes Rg and Rm.
  • the value and type of reactance Z needed is determined by considering the other inductances in the circuit.
  • the power transfers for the circuit are as follows:
  • phase difference between the current and motor/generator emfs also affects the mechanical dynamics as has been discussed earlier. These phase effects are not a problem as long as they can be accommodated and are accounted for in the design.
  • the basic arrangement shown in Figure 5 has some limitations. The main problem is that a phase angle of 60 deg is low for typical Stirling engine operation and does not generally give optimum power output or efficiency. However it will be clear from Figure 6 that increasing the phase angle has the effect of further reducing the power factors for the transducers and also increasing the inductive voltage component. Neither of these effects is desirable.
  • the power factors for the circuit given in Figure 5 are limited by the requirement that the motor and generator see the same current.
  • the power factors can be improved by the use of further reactive components that contribute corrective currents. This is illustrated for the motor in Figures 7 and 8.
  • the motor component of Figure 5 is shown with a capacitor Cpf connected in parallel with the motor components.
  • the voltage driving the current through the capacitor is the total voltage across the motor Vpf. This voltage has a larger amplitude then Vm and also leads by an angle D because of the effect of Lm.
  • Figure 8 shows the relationship between Vm and Vpf. It also shows how the current Iz can be formed from the vector addition of the motor current Im with the reactive component Ipf. The overall result is to allow a reduced current Im that is more in phase with Vm.
  • a similar arrangement can be used to improve the power factor of the generator.
  • the current phase is set so that there is a 30 degrees phase angle between current and voltage for both motor and generator.
  • the phase angles do not have to be equal and in practice the phase difference between current and generator voltage may be set at a lower value. It is more important that the power factor is high for the generator than for the motor. The reduction of phase angle between voltage and current will also reduce the corresponding dynamic effects on the mechanical side of the transducer.
  • phase angle As has been discussed earlier it is desirable to be able to increase the phase angle as high as 120 degrees for an optimum balance of power and efficiency in the engine.
  • FIG 10 shows how the generator voltage Vg is balanced by the vector sum of the motor voltage Vm, the resistive component I.Rt and the reactive component Vz where Rt is the total resistance in the circuit - Rt again includes Rg and Rm.
  • the extra component I. ⁇ .(Lg+Lm) is required to compensate for the opposite phase reactive components generated by the motor and generator inductances.
  • phase angles between transducer emfs and their currents is ⁇ 30 degrees giving a power factor of ⁇ 0.866.
  • the power factor can be largely corrected by the use of additional reactive components across the transducers as has already been described above.
  • Figure 5 and 9 show relatively simple phase shifting circuits.
  • Other circuits can be reactive networks very similar to those used in filters e.g. Butterworth filter. Active circuits are also possible if their losses are sufficiently low. The analysis of such circuits is well known to those skilled in the art and is greatly helped by software developed for this purpose.
  • a further aspect of the feedback design that contributes to the invention is the possibility of a fail safe engine operation.
  • the phase and amplitude of the voltage drops across the generator internal resistance and inductance is determined by the total current through the generator including the load current. If the load is lost then the feedback to the motor will be altered. This effect can be used to reduce the compressor excitation and hence automatically reduce the power under fault conditions.
  • the feedback circuit responds to loss of engine load. In some arrangements the feedback can be largely unaffected.
  • the feedback power is not sufficient to sustain engine operation.
  • a low power control input 100 is required give the compressor enough power to operate. In this way greater control can be exercised over the operation of the engine.
  • the process of combining the control input with the feedback can be done in a number of ways but one which is particularly attractive is to achieve this in motor 20 itself by having two or more windings. This approach is taken a stage further in Figure 11 by arranging for windings in both motor 20 and generator 22 to be specifically allocated to the feedback mechanism. This allows the feedback voltages to be quite different to those external to the engine and has the practical advantage of greatly widening the choice of components that can be used in the feedback loop.
  • the first set of windings provides the output 21a which is fed to the phase adjusting electrical circuit 24 and then forms the input 23 to a first set of windings in the coil of motor 20.
  • a second set of windings in the coil of generator 22 are dedicated to providing the output power 25 of the machine.
  • a second set of windings in the coil of motor 20 receive the control input 100.
  • the two sets of windings in each of the motor and generator can be designed as required, for example in the generator 22 a higher voltage can be provided by using more fine windings or a higher current by using fewer thick windings.
  • Embodiments that use just passive components are attractive as they are simple and reliable.
  • typical components such as capacitors, are not generally variable and controlling the phase shifting circuit may be limited to switching components into and out of the circuit.
  • An alternative approach is the use of active circuits that convert the power from the generator into a power source that can then be used by an amplifier to produce the required phase and amplitude for the motor.
  • the overall effect is to generate a phase shifted supply the internal process is different and it can also be regarded as a feedback circuit with phase control.
  • Active circuits generally allow much greater control of the phase adjustment. They may also occupy less space as reactive components can be smaller. For high efficiencies it is preferred that switched mode circuits are used as these avoid the use of lossy components e.g. resistors.
  • Figure 12 shows a general embodiment including an active phase shifting circuit 1200.
  • Part of the output from the generator 22 is fed into a power converter circuit 1201 which takes the generator power converts it into DC, as exemplified below, and stores it in one or more energy storage components such as capacitors,
  • the power converter circuit thus forms a controllable power supply for the amplifier 1203.
  • the energy stored is then used by the amplifier 1203 to provide a power input to the compressor motor 20.
  • a user-operable control input signal to the amplifier is provided to control the amplifier output i.e. its frequency, phase and magnitude.
  • the amplifier output will be in the form of an AC signal with the desired frequency, phase and magnitude.
  • the values of the frequency, phase and magnitude can be derived from the output of the generator 22 or they can be controlled by other parameters where available e.g. the compressor or generator position.
  • the phase can readily be set anywhere between 0 and 360 degrees without any need for reversing polarity etc.
  • the amplitude can be varied in a way that is not possible with passive circuits which adds further flexibility.
  • switched mode power supply circuits for the power converter and/or the amplifier e.g. class D PWM type amplifier or class H type which uses a class AB type with an additional Switched Mode Power Supply.
  • These circuits operate by first rectifying the input, before a switched converter (e.g. a Buck Converter) transforms the output voltage.
  • a switched converter e.g. a Buck Converter
  • Such circuits typically use MOSFET or IGBT semiconductor components for low loss switching combined with diodes and reactive components.
  • Further improvements can also include the shaping of the rectified current to provide active power factor correction in the switched mode power supply 1201. Active power factor correction eliminates the need for separate power factor correction components for the generator 22. However it does require an additional input signal to the power supply 1201 that allows the current drawn to be controlled so that it is in phase with the generator voltage.
  • the required input signal can be derived from the generator output or from expander piston position if this is available.
  • FIG. 14 An example of an active feedback embodiment with power factor correction is shown in greater detail in Figure 14.
  • the generator 22 is shown as an AC source that has a significant internal inductance Lg and a total voltage output Vl .
  • the internal resistance has been omitted as it does not significantly affect the operation.
  • the output from the generator 22 provides an input to a power converter 1201 which converts the AC power in to a DC power source. This is then used by the amplifier to provide an output for the motor 20.
  • the whole process has a number of distinct stages that are indicated by voltages Vl to V5.
  • Voltage waveforms V6 and V7 are control inputs to the converter and amplifier respectively.
  • the power converter 1201 has four main elements:
  • the rectifier circuit 1401 takes the AC input Vl and produces a DC voltage V2 ready for the convertor 1402. It may also contain filter circuits to prevent switching harmonics from travelling back into the generator.
  • the convertor 1402 uses low loss switching components in combination with diodes and reactive components, i.e. inductors and capacitors, to take power from the rectifier circuit at V2 and convert it to a power input to the storage 1403 at the desired voltage level V3.
  • the power transfer is accomplished efficiently by rapid switching between conducting and non conducting states. High frequencies are used to allow small components and high efficiencies.
  • a range of converter designs are available that allow the output voltage to be higher or lower than the DC input from the rectifier 1401 (see ref. http://en.wikipedia.org/wiki/Switched-mode power supply):
  • Booster converters are used where output voltage is higher than the input voltage.
  • the output from the converter 1402 can be filtered to reduce the switching harmonics.
  • the converter 1402 is also used to provide power factor correction by appropriate shaping of the current profile.
  • the switching components are typically low loss switching semiconductors such as MOSFETS.
  • the timing and duration of the on state is used to define the shape, phase and amplitude of the current drawn by the rectifier 1401.
  • the switching process is controlled by the input from the current controller module 1404 described below.
  • the converter 1402 also contains circuits that rectify the ac input from the controller module 1404 and converts the rectified waveform to a PMW (Pulse Width
  • the storage component 1403 consists of one or more capacitors and may also contain a low-pass filter. It takes the output from the converter 1402 at V3 and provides a smoothed output V4 ready for powering the amplifier 1203.
  • the low pass filter reduces any ripple and removes the switching harmonics.
  • the output voltage V4 is set by using V4 to the control the amplitude of the converter current in the current controller module 1404.
  • the current controller module 1404 generates an AC current waveform V6 for the converter 1402 that generally defines the shape, phase and amplitude of the current drawn by the converter 1402.
  • the amplitude of V6 is controlled so as to maintain the DC output V4 at the desired level.
  • the shape and phase of the current waveform should be the same as the generated voltage Vg.
  • a simplifying assumption that can generally be used is that the voltage waveform of Vg is sinusoidal.
  • the missing piece of the information required to define the current waveform then reduces to just the phase.
  • an initial value for the phase is assumed. This is then corrected by comparing it with a value derived from the inductance, the prescribed current and the voltage input (Vl):
  • Vg Vl - J. L ⁇ - at
  • An alternative approach that is also possible is to use the armature velocity to provide the Vg phase information - i.e. via position transducer. It is generally the case that the generator voltage Vg is closely in phase with the armature velocity.
  • an amplifier 1203 is used to generate an AC output V5 for driving the compressor motor 20.
  • the amplifier 1203 is shown as a class D switching amplifier (see ref http://en.wikipedia.org/wiki/Switching amplifier). This type of amplifier is capable of very high efficiencies ⁇ 95% and hence is very suited to this feedback application.
  • the phase and amplitude of the output V5 is controlled by the input V7 from the input generator module 1405.
  • This module 1405 uses the voltage output Vl of the generator 22 as a phase reference and allows a user input to control the frequency, amplitude and phase as required.
  • Active phase shifting circuits have the advantage of easier control but even with efficient switching mode operation they will generally be less efficient than circuits using only passive reactive components.
  • a further embodiment that is possible is to arrange for two phase shifting circuits to operate together. The first phase shifting circuit can transmit the bulk of the power using passive reactive components whilst a second active phase shifting circuit can be arranged to transmit enough to give a required range of control. In this way the losses associated with the active circuit are reduced as a proportion of the whole. With this arrangement the two circuits need only one source from the generator but they need a means of combining the power in the motor.
  • One possible approach is to use a linear motor that has two separate winding as shown in figure 11.
  • Moscrip uses a phase locking circuit where the motor and generator components are integrated with the electrical components to form a single resonant system.
  • the power transfer between the generator and motor is by AC currents flowing between motor and generator transformer components.
  • the power transfer between the transformers requires magnetic coupling in the transformers.
  • a power converter stage 1201 that takes the AC power from the generator and typically stores it (e.g. using one or more capacitors) as a DC power source. (Note: the DC does not need to be stabilised and may contain a significant AC component) 2.
  • An amplifier that uses the DC power from the power supply to generate an alternating power output for the motor.
  • inductive components may be used in both power supply and amplifier there is no general requirement for the power flow to have transformer components. Also the power supply and the amplifier will generally require identifiable control inputs for the circuit to operate. These inputs are typically used to control the amplifier output and allow power factor correction.
  • Balanced operation for a single engine can be achieved by arranging for the compression and expansion pistons to be in line with a separate balancer.
  • the balancer may be passive or active depending on the degree of balance required.
  • a preferred method for balancing two engines is to arrange for them to be an opposed configuration. If the engines are run at the same frequency and phase then there are no net forces and very good balance can be achieved.
  • FIG. 13 A further preferred embodiment that results in good inherent balance for a single engine is shown in Figure 13.
  • the single compressor and expander assemblies are replaced by twin balanced piston assemblies. Providing the pairs of assemblies are well matched, good balance is inherent and will be achieved under all circumstances without any need for external control.
  • the balanced compressor pair 1301 can work into a common compression volume Vl that is then connected to the cooler 3. Alternatively the compressors 20 can have individual compression spaces that are separately connected to a common cooler. Likewise there are similar alternatives for the balanced expander pair

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

L'invention porte sur un moteur à cycle de Stirling de configuration alpha, dans lequel le piston de détente entraîne une génératrice électrique linéaire, dont une partie de la sortie est réglée en phase et renvoyée pour alimenter un moteur électrique linéaire qui entraîne le compresseur. Le réglage de phase est assuré par des composants électriques passifs et/ou des circuits de rétroaction actifs. Les composants du moteur sont disposés dans une configuration linéaire qui permet de prévoir des ressorts pneumatiques à chaque extrémité de l'ensemble, un attaché au piston de compression et un attaché au piston de détente. La présence de ressorts pneumatiques permet un accroissement de la constante élastique et, en conséquence, un accroissement de la fréquence de fonctionnement. L'un ou l'autre du moteur et de la génératrice, ou chacun d'eux, peut comporter deux jeux d'enroulements. Dans la génératrice, l'utilisation de deux jeux d'enroulements permet à la partie renvoyée d'être séparée de l'énergie de sortie de la machine. Dans le moteur qui entraîne le compresseur, les deux jeux d'enroulements permettent de fournir une énergie d'entrée de commande.
PCT/GB2010/001483 2009-08-17 2010-08-05 Machine à cycle de stirling WO2011020988A2 (fr)

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GB0914393A GB0914393D0 (en) 2009-08-17 2009-08-17 Stirling cycle machine
GB0914393.4 2009-08-17

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WO2011020988A2 true WO2011020988A2 (fr) 2011-02-24
WO2011020988A3 WO2011020988A3 (fr) 2011-05-19

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2498378A (en) * 2012-01-12 2013-07-17 Isis Innovation Linear Stirling machine with expansion and compression pistons coupled by gas spring
WO2014079524A1 (fr) * 2012-11-26 2014-05-30 Wabco Gmbh Moteur thermique
RU2617543C2 (ru) * 2013-10-29 2017-04-25 Общество с ограниченной ответственностью "Константин Чайкин" Способ получения и накопления электрической энергии от тела человека, автономный самозаряжающийся источник питания и носимое на теле человека электронное устройство
CN109653898A (zh) * 2019-01-22 2019-04-19 中国科学院理化技术研究所 电反馈对置式自由活塞斯特林发电机
CN113047949A (zh) * 2021-03-12 2021-06-29 哈尔滨工程大学 一种基于pid闭环控制的分缸式自由活塞发电机
WO2022093093A1 (fr) * 2020-10-30 2022-05-05 Azelio Ab Moteur stirling de configuration alpha
CN115539240A (zh) * 2021-06-29 2022-12-30 中国科学院理化技术研究所 一种双对置电反馈自由活塞斯特林发电机

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US5146750A (en) 1989-10-19 1992-09-15 Gordon W. Wilkins Magnetoelectric resonance engine

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US5329768A (en) * 1991-06-18 1994-07-19 Gordon A. Wilkins, Trustee Magnoelectric resonance engine
JP2000136753A (ja) * 1998-11-02 2000-05-16 Sanyo Electric Co Ltd Ｖ型配列スターリング機器
GB0803021D0 (en) * 2008-02-19 2008-03-26 Isis Innovation Linear multi-cylinder stirling cycle machine

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US5146750A (en) 1989-10-19 1992-09-15 Gordon W. Wilkins Magnetoelectric resonance engine

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2498378A (en) * 2012-01-12 2013-07-17 Isis Innovation Linear Stirling machine with expansion and compression pistons coupled by gas spring
WO2013104894A1 (fr) * 2012-01-12 2013-07-18 Isis Innovation Limited Machines à cycle stirling
CN104114841A (zh) * 2012-01-12 2014-10-22 埃西斯创新有限公司 斯特林循环机
US9528467B2 (en) 2012-01-12 2016-12-27 Isis Innovation Limited Stirling cycle machines
WO2014079524A1 (fr) * 2012-11-26 2014-05-30 Wabco Gmbh Moteur thermique
RU2617543C2 (ru) * 2013-10-29 2017-04-25 Общество с ограниченной ответственностью "Константин Чайкин" Способ получения и накопления электрической энергии от тела человека, автономный самозаряжающийся источник питания и носимое на теле человека электронное устройство
CN109653898A (zh) * 2019-01-22 2019-04-19 中国科学院理化技术研究所 电反馈对置式自由活塞斯特林发电机
CN109653898B (zh) * 2019-01-22 2024-03-15 中国科学院理化技术研究所 电反馈对置式自由活塞斯特林发电机
WO2022093093A1 (fr) * 2020-10-30 2022-05-05 Azelio Ab Moteur stirling de configuration alpha
US12071910B2 (en) 2020-10-30 2024-08-27 EnergyIntel Services Ltd. Alpha Stirling engine
CN113047949A (zh) * 2021-03-12 2021-06-29 哈尔滨工程大学 一种基于pid闭环控制的分缸式自由活塞发电机
CN113047949B (zh) * 2021-03-12 2021-09-21 哈尔滨工程大学 一种基于pid闭环控制的分缸式自由活塞发电机
CN115539240A (zh) * 2021-06-29 2022-12-30 中国科学院理化技术研究所 一种双对置电反馈自由活塞斯特林发电机

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