JP2005180294A - Thermoacoustic engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal acoustic engine capable of excellently securing silence and reliability. <P>SOLUTION: This thermal acoustic engine 20 has a columnar gas pipe 21 sealed with a working fluid, and a heat accumulator 25 arranged in the columnar gas pipe 21, and generates thermal acoustic self-excited vibration of the working fluid, by forming a temperature gradient between both end parts of the heat accumulator 25. The thermal acoustic engine 20 has a working fluid pipe L4, an opening-closing valve 28, a pump 29, a working fluid storage tank 30, a moving pipe 31 and an actuator 32 for changing pressure amplitude of the thermal acoustic self-excited vibration. The opening-closing valve 28, the pump 29 and the actuator 32 are controlled so that the pressure amplitude is kept in an allowable range by an ECU 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoacoustic engine that forms a temperature gradient between both ends of a heat storage means arranged in an air column tube and generates thermoacoustic self-excited vibration of a working fluid in the air column tube.

  Conventionally, a refrigerator utilizing a thermoacoustic phenomenon has been proposed (see, for example, Patent Document 1). This refrigerator includes a pipe filled with gas, a stack disposed inside the pipe and sandwiched between a high temperature side heat exchanger and a low temperature side heat exchanger, and a high temperature side at a position asymmetric with the stack. And a regenerator arranged together with the heat exchanger and the low temperature side heat exchanger. This refrigerator generates a self-excited vibration of gas in the stack by forming a temperature gradient between both ends of the stack, and stores it in the regenerator by propagation of standing waves and traveling waves obtained thereby. It is.

  Conventionally, an apparatus for recovering exhaust heat of an internal combustion engine using a thermoacoustic phenomenon has been proposed (see, for example, Patent Document 2). This device includes a resonance pipe connected to an exhaust gas purification catalytic converter of an internal combustion engine, a stack provided at one end of the resonance pipe, and a transducer provided at the other end of the resonance pipe. In this apparatus, one end of the stack is heated by heat generated from the catalytic converter, and a temperature gradient is applied between both ends of the stack. Thereby, sound waves are generated in the stack, and the energy of the sound waves is converted into electric energy by the transducer.

Japanese Patent No. 3015786 JP 2002-122020 A

  As described above, by using the thermoacoustic phenomenon, it is possible to obtain cold without using a compressor, chlorofluorocarbon or the like, or to recover exhaust heat (waste heat) of the internal combustion engine. However, there are many problems to be solved in putting a device using a thermoacoustic phenomenon into practical use, and sufficient silence and reliability are obtained when generating acoustic output by generating thermoacoustic self-excited vibration of the working fluid. It is necessary to secure.

  Accordingly, an object of the present invention is to provide a thermoacoustic engine that can ensure good silence and reliability.

  The thermoacoustic engine according to the present invention has an air column tube in which a working fluid is enclosed, and heat storage means disposed inside the air column tube, and operates by forming a temperature gradient between both ends of the heat storage unit. In a thermoacoustic engine that generates thermoacoustic self-excited vibration of a fluid, pressure amplitude detecting means for detecting the pressure amplitude of the thermoacoustic self-excited vibration, pressure amplitude setting means capable of changing the pressure amplitude, and pressure amplitude detecting means Determination means for determining whether or not the detected value exceeds a predetermined threshold, and control means for controlling the pressure amplitude setting means so that the pressure amplitude is maintained within an allowable range based on the determination result of the determination means. It is characterized by providing.

  In this thermoacoustic engine, the pressure amplitude of the self-excited vibration of the working fluid generated in the air column tube is detected by the pressure amplitude detection means, and whether the detection value of the pressure amplitude detection means exceeds a predetermined threshold value by the determination means It is determined whether or not. Then, the pressure amplitude setting means is controlled by the control means according to the determination result of the determination means, whereby the pressure amplitude of the thermoacoustic self-excited vibration is kept within the allowable range. As a result, in this thermoacoustic engine, it is possible to suppress the pressure amplitude of the self-excited vibration from becoming excessively large. Therefore, the noise when generating the acoustic output by generating the thermoacoustic self-excited vibration of the working fluid. In addition, it is possible to improve durability by reducing the pressure-resistant burden of various components including the air column tube.

  In this case, the threshold is preferably determined based on at least one of noise caused by thermoacoustic self-excited vibration and a pressure limit of the air column tube.

  The pressure amplitude setting means includes means for changing the average pressure of the working fluid, means for changing the frequency of the thermoacoustic self-excited vibration, means for changing the temperature gradient formed between both ends of the heat storage means, and the thermoacoustic engine. It is preferable that any one of the means for changing the load or a combination of these means.

  That is, by changing at least one of the average pressure of the working fluid, the frequency of self-excited vibration, the temperature gradient formed between both ends of the heat storage means, and the load of the thermoacoustic engine, The pressure amplitude can be easily and reliably kept within the allowable range.

  For example, the pressure amplitude setting unit includes a working fluid storage unit that stores the working fluid, and moves the working fluid between the working fluid storage unit and the air column tube to change the average pressure of the working fluid in the air column tube. It is good that it is a means to make. Further, the pressure amplitude setting means may include a resonator and a means for changing the pipe length of the resonator. Further, when the working fluid is a mixed fluid in which a plurality of fluids are mixed, the pressure amplitude setting means collects the working fluid in the air column tube and separates it into a plurality of fluids. Means that can be individually re-supplied inside the tube may be employed.

  And the thermoacoustic engine by this invention is further provided with the high temperature heat exchanger arrange | positioned at the one end side of a thermal storage means, and it is preferable that this high temperature heat exchanger uses exhaust gas of an internal combustion engine as a heat source. As a result, the exhaust heat of the internal combustion engine can be efficiently recovered using the thermoacoustic engine.

  According to the present invention, it is possible to realize a thermoacoustic engine that can ensure quietness and reliability.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a schematic configuration diagram showing a first embodiment of a thermoacoustic engine according to the present invention. As shown in the figure, the thermoacoustic engine 20 is applied to, for example, an internal combustion engine 1 used as a travel drive source of a vehicle. First, the internal combustion engine 1 to which the thermoacoustic engine 20 is applied will be briefly described. The internal combustion engine 1 burns a mixture of fuel and air in a combustion chamber 3 formed in the cylinder block 2 and burns it. The piston 4 is reciprocated in the chamber 3 to generate power.

  The intake port of the combustion chamber 3 is connected to the intake manifold 5, and the exhaust port of the combustion chamber 3 is connected to the exhaust manifold 6. In addition, an intake valve Vi that opens and closes an intake port, an exhaust valve Ve that opens and closes an exhaust port, a spark plug 7, and an injector 8 are disposed for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. The intake manifold 5 is connected to a surge tank 9, and an air supply pipe L <b> 1 is connected to the surge tank 9. The air supply pipe L1 is connected to an air intake port (not shown) via the air cleaner 10. Further, a throttle valve 11 is incorporated in the middle of the supply pipe L1 (between the surge tank 9 and the air cleaner 10). On the other hand, the exhaust manifold 6 is connected to an exhaust pipe L2, and a front-stage catalyst device 12a and a rear-stage catalyst device 12b are incorporated in the exhaust pipe L2.

  The thermoacoustic engine 20 of the present invention is used to recover the exhaust heat of the internal combustion engine 1 as described above. The thermoacoustic engine 20 has an air column tube 21 formed of stainless steel or the like so as to have a circular cross section, and inside the air column tube 21 is an operation such as nitrogen, helium, argon, a mixed gas of helium and argon. A fluid (inert gas) is enclosed. As shown in FIG. 1, the air column tube 21 includes a loop portion 22 formed in a substantially rectangular loop shape and a resonance portion 23 connected to one corner portion of the loop portion 22. The resonance part 23 includes a tube part 23a having a circular cross section approximately the same diameter as the loop part 22, and a closed end part 23b connected to the tip of the tube part 23a, and functions as a resonator. The diameter of the closed end portion 23b is gradually increased from the distal end of the tube portion 23a toward the closed end. (Sound / electrical conversion means) 24 is arranged. The transducer TD is connected to the power generation amount controller 24, and the power generation amount of the transducer TD is set by the power generation amount controller 24.

  A heat accumulator (heat storage means) 25 is disposed inside the loop portion 22 of the air column tube 21. The heat accumulator 25 has a plurality of narrow flow paths extending in parallel with the axial direction of the air column tube 21 at the arrangement location. As the heat accumulator 25, a honeycomb structure made of ceramic or the like, a thin mesh made of stainless steel or the like arranged at a minute interval, a nonwoven fabric in which metal fibers such as stainless steel are gathered, or the like can be used. A high temperature heat exchanger 26 is disposed adjacent to one end side of the heat accumulator 25, and a low temperature heat exchanger 27 is disposed adjacent to the other end side of the heat accumulator 25. That is, the heat accumulator 25 is arranged in a state of being sandwiched between the high temperature heat exchanger 26 and the low temperature heat exchanger 27.

  Exhaust gas flowing through the exhaust pipe L2 of the internal combustion engine 1 is supplied to the heat transfer tubes constituting the high temperature heat exchanger 26, and the high temperature heat exchanger 26 uses the exhaust gas of the internal combustion engine 1 as a heat source. In the present embodiment, the high-temperature heat exchanger (its heat transfer pipe) 26 is incorporated in the exhaust pipe L2 between the front-stage catalyst apparatus 12a and the rear-stage catalyst apparatus 12b. The heat transfer tubes constituting the low-temperature heat exchanger 27 are incorporated in the cooling system L3 of the internal combustion engine 1, and the low-temperature heat exchanger 27 serves as a heat source (cold heat source) for cooling water flowing through the cooling system L3. . The cooling system L3 includes a refrigerant introduction valve 14 that is an on-off valve or a flow rate adjustment valve. By controlling the refrigerant introduction valve 14, cooling water for the low-temperature heat exchanger (the heat transfer pipe) 27 is provided. It is possible to change the supply amount and the like.

  In addition, the air column pipe 21 (the pipe portion 23a in the present embodiment) of the thermoacoustic engine 20 is provided with a working fluid storage tank (through a working fluid pipe L4 having an on-off valve (normally closed) 28 and a pump 29 in the middle. Working fluid storage means) 30 is connected. The working fluid storage tank 30 stores the same fluid as the working fluid sealed in the air column tube 21 under a predetermined pressure. Therefore, by opening the on-off valve 28 and operating the pump 29, the working fluid in the working fluid storage tank 30 is introduced into the air column tube 21, and the pressure of the working fluid in the air column tube 21 (average) Pressure) can be increased. Further, when the pressure (average pressure) of the working fluid in the air column tube 21 is high to some extent, the working fluid is returned from the air column tube 21 to the working fluid storage tank 30 by opening the on-off valve 28, and the air column tube The pressure (average pressure) of the working fluid in 21 can be reduced. That is, the working fluid pipe L4, the on-off valve 28, the pump 29, and the working fluid storage tank 30 function as means for changing the average pressure of the working fluid in the air column pipe 21.

  Furthermore, a movable tube 31 having an outer diameter smaller than the inner diameter of the tube portion 23a is slidably disposed inside the distal end of the tube portion 23a of the resonance portion 23. An actuator (fluid pressure cylinder) 32 for moving the moving tube 31 in parallel with the tube portion 23a is disposed inside the closed end portion 23b. The actuator 32 is connected to a fluid source (not shown) via the on-off valve 33. By operating the on-off valve 33 to operate the actuator 32, the pipe length of the resonance unit 23 can be changed. Accordingly, the movable tube 31 and the actuator 32 function as means for changing the resonance frequency of the working fluid in the air column tube 21.

  The thermoacoustic engine 20 includes an electronic control unit (hereinafter referred to as “ECU”) 40 that functions as control means. The ECU 40 includes a CPU, a ROM, a RAM, an input / output port, a storage device, etc., all not shown. The refrigerant introduction valve 14 of the cooling system L3, the on-off valve 28 of the working fluid pipe L4 and the pump 29, the on-off valve 33 for the actuator 32, the power generation amount controller 24 of the transducer TD, etc. are connected to the input / output ports of the ECU 40, respectively. These are controlled by the ECU 40. In addition, a pressure sensor 34 is installed in the air column tube 21 of the thermoacoustic engine 20 in the vicinity of a connection portion between the loop portion 22 and the resonance portion 23. The pressure sensor 34 is also connected to the ECU 40, and the sensor 34 detects the pressure of the working fluid in the air column tube 21 and gives a signal indicating the detected value to the ECU 40.

  In the thermoacoustic engine 20 configured as described above, after the internal combustion engine 1 is operated and the exhaust gas from the combustion chamber 3 passes through the pre-catalyst device 12a, it passes through the high-temperature heat exchanger 26 of the thermoacoustic engine 20. When it comes to start operation. In this case, since the temperature of the exhaust gas that has passed through the pre-stage catalyst device 12a reaches about 900 ° C. at the maximum, one end of the heat accumulator 25 is heated by the exhaust gas flowing through the high-temperature heat exchanger 26. Raise the temperature. On the other hand, the low temperature heat exchanger 27 of the thermoacoustic engine 20 is supplied with cooling water (approximately 80 to 100 ° C.) that flows through the cooling system L3. Cooled by the cooling water flowing through the low-temperature heat exchanger 27. As a result, a large temperature gradient is formed between both ends of the heat accumulator 25, and as a result, thermoacoustic self-excited vibration (sound wave) of the working fluid is generated.

  When the frequency of the self-excited vibration (sound wave) of the working fluid generated in this way matches the resonance frequency in the resonance part 23, a standing wave is formed in the resonance part 23. Further, a traveling wave traveling from the low temperature heat exchanger 27 to the high temperature heat exchanger 26 is formed in the loop portion 22. And the vibration part of the transducer TD arrange | positioned at the closed end part 23b is vibrated by the standing wave formed in the resonance part 23. FIG. The transducer TD converts standing wave energy (acoustic energy) in the resonance unit 23 into electric energy, and the obtained electric energy is supplied to a predetermined electric load via the power generation amount controller 24. Thereby, according to the thermoacoustic engine 20 of this invention, the exhaust heat of the internal combustion engine 1 can be collect | recovered efficiently, and the electric power for predetermined | prescribed electric loads can be obtained. In place of arranging the transducer TD in the resonance unit 23, units of a heat accumulator, a high temperature heat exchanger, and a low temperature heat exchanger are arranged in the loop unit 22, and the exhaust heat energy recovered by the thermoacoustic engine 20 is used. Then, the unit may be operated as a refrigerator.

  Now, it is possible to recover exhaust heat (waste heat) of the internal combustion engine 1 satisfactorily by using the thermoacoustic phenomenon as described above. It is necessary to sufficiently ensure the quietness and reliability when generating the acoustic output by generating the thermoacoustic self-excited vibration of the fluid. In other words, if the pressure amplitude of the self-excited vibration of the working fluid becomes excessive when obtaining the acoustic output from the thermoacoustic engine, noise problems and the pressure of the working fluid will approach the pressure limit of the air column tube, etc. There may be a problem that the durability of the column tube or the like is lowered. Therefore, in the thermoacoustic engine 20 of the present embodiment, the pressure amplitude control routine shown in FIG. 2 is executed in order to keep the pressure amplitude of the self-excited vibration of the working fluid within the allowable range.

The pressure amplitude control routine shown in FIG. 2 is repeatedly executed by the ECU 40 every predetermined time. When it is time to execute the pressure amplitude control routine, the ECU 40 calculates the pressure amplitude P ₀ of the working fluid that self-oscillates in the air column tube 21 based on the signal sent from the pressure sensor 34 (S10, S12). In this case, the ECU 40 acquires the maximum pressure and the minimum pressure of the working fluid that self-oscillates in the air column tube 21 based on the signal from the pressure sensor 34 in S10, and these maximum pressures in S12. Then, the pressure amplitude P ₀ of the working fluid in the air column tube 21 is obtained from the minimum pressure.

When determining the pressure amplitude _{P 0} of the working fluid Kihashirakan in 21, ECU 40 determines whether the pressure amplitude _{P 0} is permitted pressure amplitude _{P A} more than is predetermined (S14). Allowable pressure amplitude P _A used herein, the breakdown voltage limit noise tolerance or Kihashirakan 21 due to thermoacoustic self-excited vibration, or determined based on both of them, it is stored in advance in the storage device . Then, ECU 40 is, S14 in the case where the pressure amplitude P ₀ is determined that the allowable pressure amplitude P _A more than is predetermined, the pressure amplitude decreases to reduce the pressure amplitude P ₀ of the working fluid Kihashirakan 21 Processing is executed (S16). In the present embodiment, any one or more of the following processes (1) to (4) are executed as the pressure amplitude reduction process of S16.

(1) Average Pressure Reduction Process This average pressure reduction process is to reduce the pressure amplitude P ₀ of the working fluid that vibrates by itself by reducing the average pressure of the working fluid in the air column tube 21. In this case, ECU 40, when the pressure amplitude P ₀ is determined to be allowable pressure amplitudes P _A or more is predetermined at S14, the opening and closing valve 28 of the hydraulic fluid conduit L4 to a predetermined time or pressure amplitude P ₀ allowable pressure It is opened for a time corresponding to the deviation between the amplitude _{P a} (S16). As a result, the working fluid in the air column tube 21 is returned to the working fluid storage tank 30 via the working fluid tube L4, so that the pressure (average pressure) of the working fluid in the air column tube 21 is reduced. .

Here, the average pressure Pm (the average value of the pressure of the self-excited working fluid, that is, the average of the maximum pressure and the minimum pressure) and the pressure amplitude P ₀ are shown in FIG. If the average pressure Pm decreases, the pressure amplitude P ₀ also decreases accordingly. Therefore, the pressure amplitude P ₀ of the self-excited working fluid is reduced by returning the working fluid in the air column tube 21 to the working fluid storage tank 30 and lowering the average pressure of the working fluid in the air column tube 21. It becomes possible to make it.

(2) Resonance Frequency Change Process This resonance frequency change process is to reduce the pressure amplitude P ₀ of the self-excited working fluid by increasing the resonance frequency of the working fluid in the air column tube 21. In this case, ECU 40, when the pressure amplitude P ₀ is determined to be allowable pressure amplitudes P _A or more is predetermined at S14, as the moving tube 31 is moved by a predetermined amount toward the loop portion 22 actuator 32 Is operated (S16). As a result, the pipe length of the resonator constituted by the tube portion 23a and the closed end portion 23b is shortened, and the resonance frequency of the working fluid in the air column tube 21 is increased. so that the pressure amplitude P ₀ of the fluid is reduced.

(3) Temperature gradient change process This temperature gradient change process is self-excited by reducing the temperature gradient formed between both ends of the heat accumulator 25 by the high temperature heat exchanger 26 and the low temperature heat exchanger 27. The pressure amplitude P ₀ of the working fluid is decreased. In this case, ECU 40, when the pressure amplitude P ₀ is determined to be allowable pressure amplitudes P _A or more is predetermined at S14, the control to the low-temperature heat exchange refrigerant introduction valve 14 provided in the cooling system L3 The supply of the cooling water to the heater (its heat transfer tube) 27 is stopped or the supply amount of the cooling water is decreased. As a result, the cooling capacity of the heat accumulator 25 by the low-temperature heat exchanger 27 is reduced, so that the temperature gradient formed between both ends of the heat accumulator 25 is reduced. which in turn reduces the pressure amplitude P _0.

(4) Acoustic load changing process This acoustic load changing process increases the power generation amount of the transducer TD (if a thermoacoustic refrigerator is arranged in the loop portion 22 or the like, the amount of cold heat generated by the refrigerator). it is intended to reduce the pressure amplitude P ₀ of the working fluid self-excited vibration. In this case, ECU 40, when the pressure amplitude P ₀ is determined to be allowable pressure amplitudes P _A or more is predetermined at S14, predetermined so as to increase the power generation amount of the transducer TD against power generation controller 24 Is given (S16). As described above, it is possible to reduce the pressure amplitude P ₀ of the working fluid that vibrates by itself by increasing the load of the thermoacoustic engine 20.

Thus, the thermoacoustic engine 20, at the unacceptably pressure amplitude P _A of the pressure amplitude P ₀ are predetermined, in order to reduce the pressure amplitude P ₀ of the working fluid self-excited oscillation, (1) Average Any one or more of a pressure drop process, (2) resonance frequency change process, (3) temperature gradient change process, and (4) acoustic load change process are executed. As a result, the pressure amplitude of the thermoacoustic self-excited vibration is always kept within the allowable range, and the pressure amplitude of the self-excited vibration can be suppressed from becoming excessively large. Therefore, in the thermoacoustic engine 20, while suppressing the noise at the time of obtaining the acoustic output by generating the thermoacoustic self-excited vibration of the working fluid, the pressure-resistant burden of various components including the air column tube 21 is reduced. Durability can be improved.

  In order to change the resonance frequency of the working fluid, the resonance portion of the air column tube 21 may be configured as shown in FIG. 4 includes a tube portion 23a, a closed end portion 23b connected to the tube portion 23a, and a movable chamber 23c disposed in the closed end portion 23b. The movable chamber 23c is rotatably supported inside the closed end 23b and has one opening 23d. Thereby, the inside of the movable chamber 23c and the flow path defined between the inner surface of the closed end 23b and the outer surface of the movable chamber 23c communicate with each other through the opening 23d of the movable chamber 23c. The movable chamber 23c is rotated in the forward and reverse directions inside the closed end portion 23b by driving means (not shown) via a rack and pinion RP composed of a rack R and a pinion P.

Under such a configuration, the movable chamber 23c is rotated inside the closed end portion 23b to change the position of the opening 23d, whereby the tube portion 23a, the closed end portion 23b, and the movable chamber 23c are configured. The pipe length of the resonator can be changed. Therefore, even with a resonance portion 23A of FIG. 8, to increase the resonance frequency of the working fluid Kihashirakan 21, it becomes possible to reduce the pressure amplitude P ₀ of the working fluid self-excited vibration.

[Second Embodiment]
Hereinafter, the thermoacoustic engine of the internal combustion engine according to the second embodiment of the present invention will be described with reference to FIGS. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  The thermoacoustic engine 20 </ b> A shown in FIG. 5 has basically the same configuration as the thermoacoustic engine 20 of the first embodiment, and a mixture of fuel and air inside the combustion chamber 3 formed in the cylinder block 2. Is applied to the internal combustion engine 1 that generates power by reciprocating the piston 4 in the combustion chamber 3. In the thermoacoustic engine 20A, a mixed gas of helium and argon is used as a working fluid. And thermoacoustic engine 20A is comprised so that the mixing ratio of helium and argon in the working fluid which is a mixed gas of helium and argon can be changed.

  That is, a pump 35 and a working fluid introduction valve (open / close valve) 36 that can suck out the working fluid in the air column pipe 21 are provided in the air column pipe 21 (the pipe portion 23a in this embodiment) of the thermoacoustic engine 20. A fluid separation device 50 is connected via a working fluid recovery pipe L5. The fluid separation device 50 includes a container 51 that can store a fluid therein, and a separation membrane 52 that partitions the internal space of the container 51 into two fluid storage chambers 51A and 51H.

  The working fluid recovery pipe L5 described above is connected to one fluid storage chamber 51A of the container 51. The fluid storage chamber 51 </ b> A is connected to the air column pipe 21 (in this embodiment, the pipe portion 23 a) via a fluid introduction pipe L <b> 6 having a first supply valve (open / close valve) 53. The other fluid storage chamber 51H of the container 51 is connected to the air column tube 21 (in this embodiment, the tube portion 23a) via a fluid introduction tube L7 having a second supply valve (open / close valve) 54. . The pump 35, the working fluid introduction valve 36, and the first and second supply valves 53 and 54 are respectively connected to the input / output ports of the ECU 40, and these are controlled by the ECU 40. The pump 35, the working fluid introduction valve 36, the working fluid recovery pipe L5, the fluid separation device 50, the first and second supply valves 53 and 54, and the fluid introduction pipes L6 and L7 are operated in the air column pipe 21. It functions as a means for changing the mixing ratio of helium and argon in the fluid.

  In addition, the separation membrane 52 that partitions the inside of the container 51 can pass only helium in the working fluid and separate it from argon. In the present embodiment, a porous membrane formed of polyimide, cellulose acetate, polynullphen, polyamide, polyetherimide, or the like is employed as the separation membrane 52. The separation membrane 52 formed of any of these materials regulates the passage of argon (molecular weight 40) having a relatively high molecular weight, while allowing the passage of helium (molecular weight 4) having a molecular weight smaller than that of argon. As the separation membrane 52, a porous glass hollow fiber membrane having a large number of minute pores of about 0.3 to 1.0 nm and capable of concentrating helium to about 500 times that of nitrogen may be employed. .

Also in the thermoacoustic engine 20A configured as described above, the pressure amplitude control routine of FIG. 2 described in relation to the first embodiment by the ECU 40 in order to keep the pressure amplitude of the self-excited vibration of the working fluid within an allowable range. Is executed. Then, the thermoacoustic engine 20A, when the pressure amplitude P ₀ of the working fluid self-excited vibration in Kihashirakan within 21 is determined to be allowable pressure amplitudes P _A more than is predetermined, the pressure amplitude P ₀ As the pressure amplitude reduction process for reducing the ratio, the mixture ratio change process shown in FIG. 6 can be executed.

The mixing ratio changing process shown in FIG. 6 is to reduce the pressure amplitude P ₀ of the self-excited working fluid by changing the mixing ratio of helium and argon in the working fluid in the air column tube 21. . In this case, ECU 40, at S14 when the pressure amplitude _{P 0} is determined to be allowable pressure amplitudes _{P A} more than is predetermined, with opening the working fluid inlet valve 36 of the hydraulic fluid recovery pipe L5 (S20), The pump 35 of the working fluid recovery pipe L5 is operated for a predetermined time (S22). When the pump 35 is operated for a predetermined time, the ECU 40 connects the first supply valve (Ar supply valve) of the fluid introduction pipe L6 that connects the pipe portion 23a of the air column pipe 21 and the fluid storage chamber 51A for storing argon. 53 is closed (maintained in a closed state), and the second supply valve (He supply valve) 54 of the fluid introduction pipe L7 that connects the pipe portion 23a of the air column pipe 21 and the fluid storage chamber 51H that stores helium is provided. It is opened by time corresponding to the pressure amplitude _{P 0} obtained at a predetermined time or S12 (S24).

Here, a correlation as shown in FIG. 7 is recognized between the ratio of argon in the working fluid and the resonant frequency of the self-excited working fluid, and the more the ratio of argon in the working fluid decreases. The resonance frequency of the working fluid in the air column tube 21 is increased. Accordingly, by introducing a predetermined amount of helium (only) from the fluid separation device 50 (fluid storage chamber 51H) into the air column tube 21 through the fluid introduction pipe L6 by the mixing ratio changing process (S24) of FIG. The resonance frequency of the working fluid in the air column tube 21 can be increased to reduce the pressure amplitude P ₀ of the working fluid that vibrates by itself.

  As a result, the thermoacoustic engine 20A according to the second embodiment also maintains the pressure amplitude of the thermoacoustic self-excited vibration within the allowable range at all times, and suppresses the pressure amplitude of the self-excited vibration from becoming excessively large. be able to. Therefore, also in the thermoacoustic engine 20A, the thermoacoustic self-excited vibration of the working fluid is generated to suppress the noise when obtaining the acoustic output, and the pressure-resistant burden of various components including the air column tube 21 is reduced. Thus, durability can be improved. Needless to say, in the thermoacoustic engine 20A according to the second embodiment, the temperature gradient changing process and the acoustic load changing process described in relation to the first embodiment can be executed.

1 is a schematic configuration diagram showing a first embodiment of a thermoacoustic engine according to the present invention. 2 is a flowchart for explaining a procedure for controlling a pressure amplitude of a working fluid in the thermoacoustic engine of FIG. 1. It is a graph which illustrates the correlation with the average pressure and pressure amplitude of the working fluid which self-oscillates in an air column pipe. It is a schematic diagram which illustrates the other structure for changing the resonant frequency of the working fluid in an air column pipe. It is a schematic block diagram which shows 2nd Embodiment of the thermoacoustic engine by this invention. 6 is a flowchart for explaining a procedure for changing the mixing ratio of the working fluid in the thermoacoustic engine of FIG. 5. It is a graph which illustrates the correlation with the ratio of the argon in the working fluid in an air column tube, and the resonant frequency of a working fluid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 14 Refrigerant introduction valve 20, 20A Thermoacoustic engine 21 Air column pipe 22 Loop part 23, 23A Resonance part 23a Pipe part 23b Closed end part 23c Movable chamber 23d Opening part 24 Power generation amount controller 25 Heat accumulator 26 High temperature heat exchange Unit 27 Low-temperature heat exchanger 28, 33 On-off valve 29, 35 Pump 30 Working fluid storage tank 31 Moving pipe 32 Actuator 34 Pressure sensor 36 Working fluid introduction valve 50 Fluid separator 51 Container 51A, 51H Fluid storage chamber 52 Separation membrane 53 1 supply valve 54 2nd supply valve L1 supply pipe L2 exhaust pipe L3 cooling system L4 working fluid pipe L5 working fluid recovery pipe L6, L7 fluid introduction pipe RP rack and pinion TD transducer

Claims (4)

An air column tube in which the working fluid is sealed, and heat storage means disposed inside the air column tube, and a temperature gradient is formed between both end portions of the heat storage unit so that the thermoacoustic self-excitation of the working fluid is performed. In a thermoacoustic engine that generates vibration,
Pressure amplitude detecting means for detecting the pressure amplitude of the thermoacoustic self-excited vibration;
Pressure amplitude setting means capable of changing the pressure amplitude;
Determination means for determining whether or not a detection value of the pressure amplitude detection means exceeds a predetermined threshold;
A thermoacoustic engine comprising: control means for controlling the pressure amplitude setting means so that the pressure amplitude is maintained within an allowable range based on a determination result of the determination means.   The thermoacoustic engine according to claim 1, wherein the threshold is determined based on at least one of noise caused by the thermoacoustic self-excited vibration and a pressure limit of the air column tube.   The pressure amplitude setting means includes means for changing an average pressure of the working fluid, means for changing the frequency of the thermoacoustic self-excited vibration, means for changing a temperature gradient formed between both ends of the heat storage means, and heat. The thermoacoustic engine according to claim 1 or 2, wherein any one of the means for changing the load of the acoustic engine or a combination of these means is used. The high-temperature heat exchanger disposed on one end side of the heat storage means is further provided, and the high-temperature heat exchanger uses exhaust gas from the internal combustion engine as a heat source. Thermoacoustic engine.

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