JP2007315680A - Thermoacoustic stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoacoustic Stirling engine capable of compactifying a device, and capable of efficiently providing predetermined performance. <P>SOLUTION: The thermoacoustic Stirling engine 20 is provided with an acoustic oscillation part Sg arranged in a gas column tube 21, and comprised of a stack, a high temperature side heat exchanger 26 arranged on one end of the stack, and a low temperature side heat exchanger 27 arranged on another side. First and second bulkheads 28, 29 are provided for partitioning a first closed space A including the acoustic oscillation part Sg, and another closed space B, and different types of working gas with different appropriate characteristics are sealed in each of the first closed space A and the second closed space B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermoacoustic Stirling engine, and more particularly to a thermoacoustic Stirling engine suitable for controlling the temperature of EGR gas or the like of an internal combustion engine.

  Conventionally, a thermoacoustic Stirling engine using a thermoacoustic phenomenon is known, and a refrigerator using this engine has been proposed (see, for example, Patent Document 1).

  This thermoacoustic Stirling engine has an air column tube filled with a working gas at a predetermined pressure, and a stack that is disposed inside the air column tube and is sandwiched between a high temperature side heat exchanger and a low temperature side heat exchanger. A sound wave oscillating unit comprising: The refrigerator unit includes a regenerator arranged together with the high-temperature side heat exchanger and the low-temperature side heat exchanger at asymmetric positions with the stack of the sound wave oscillating units in the same air column tube. This refrigerator unit generates a temperature gradient between both ends of the stack of the sound wave oscillating unit, thereby generating self-excited vibration of the working gas in the stack, and by the propagation of the standing wave and traveling wave obtained thereby. Cold storage is performed in the regenerator of the refrigerator unit.

  Conventionally, an apparatus for recovering waste heat of an internal combustion engine using a thermoacoustic phenomenon has been proposed (see, for example, Patent Document 2). This device includes a resonance tube connected to an exhaust gas purification catalytic converter of an internal combustion engine, a stack provided at one end of the resonance tube, and a refrigeration unit provided at the other end of the resonance tube. 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 cold heat in the freezing unit. And the cold heat obtained in a freezing part is utilized in order to cool the predetermined location of an exhaust system.

Japanese Patent No. 3015786 JP 2002-122020 A

  By the way, in order to obtain high energy conversion efficiency in a thermoacoustic Stirling engine, a condition for easily causing self-excited vibration in the sound wave oscillating portion is obtained, and a standing wave and a traveling wave obtained thereby are transmitted to other parts. Propagation needs to be done with low flow loss.

  However, in the thermoacoustic Stirling engine described in Patent Document 1, a single type of working gas is enclosed in the air column tube, and in order to obtain a certain performance, the type of the working gas and the filling pressure are compromised. It had to be set to. As a result, to obtain the desired performance, it is necessary to enlarge the entire apparatus including the diameter and length of the air column tube.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoacoustic Stirling engine capable of downsizing the apparatus and efficiently obtaining a predetermined performance.

  In order to achieve the above object, a thermoacoustic Stirling engine according to an embodiment of the present invention is disposed in an air column tube, and includes a stack, a high-temperature side heat exchanger disposed at one end of the stack, and a low-temperature disposed at the other end. A thermoacoustic Stirling engine provided with a sound wave oscillating unit comprising a side heat exchanger, wherein the first and second partitions define a first closed space including the sound wave oscillating unit and a second closed space other than the first closed space. A partition wall is provided, and the first closed space and the second closed space are filled with working gases having different appropriate characteristics.

  Here, the working gas having different characteristics is preferably a mixed gas of helium and argon having different composition ratios.

  Moreover, you may provide the abnormal condition detection means containing the vibration sensor arrange | positioned at the said air column pipe.

  Furthermore, pressure adjusting means for adjusting the pressure of the working gas in the air column tube to reduce the pressure may be provided.

  A cooling unit disposed in the air column tube and including a regenerator, a high-temperature side heat exchanger, and a low-temperature side heat exchanger; and cooling capacity improving means for improving the cooling capability of the refrigerator unit. May be.

  According to the thermoacoustic Stirling engine according to an aspect of the present invention, the first and second partition walls that partition the first closed space including the sound wave oscillating portion and the second closed space other than the first closed space are provided. Since the first closed space and the second closed space are filled with working gases having different appropriate characteristics, there is a condition for easily causing self-excited vibration in the first closed space including the sound wave oscillating portion. In addition to the above, in the other second closed space, the standing wave and traveling wave obtained by self-excited vibration are propagated to other parts with low flow loss. A thermoacoustic Stirling engine capable of efficiently obtaining performance can be obtained.

  Here, according to the embodiment in which the working gas having different characteristics is a mixed gas of helium and argon having different composition ratios, the above performance can be obtained most efficiently.

  Further, according to the embodiment provided with the abnormal state detecting means including the vibration sensor disposed in the air column tube, the operation caused by the breakage of the partition wall or the like by detecting the vibration frequency of the air column tube by the vibration sensor. The rate of change of the vibration frequency due to the change in the gas mixture ratio can be obtained, and an abnormal state such as breakage of the partition wall can be detected.

  Furthermore, according to the embodiment provided with the pressure adjusting means for reducing the working gas filling pressure in the air column tube, for example, when the above abnormal state is detected, the working gas filling pressure in the air column tube is reduced. As a result, the thermoacoustic phenomenon can be maintained.

  A cooling unit disposed in the air column tube and including a regenerator, a high-temperature side heat exchanger, and a low-temperature side heat exchanger; and cooling capacity improving means for improving the cooling capability of the refrigerator unit. According to the embodiment, for example, it is possible to compensate for the cooling performance degradation in the abnormal state described above.

  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 thermoacoustic Stirling engine 20 according to the first embodiment of the present invention. As shown in the figure, a thermoacoustic Stirling engine 20 according to the present invention is applied to, for example, an internal combustion engine 1 used as a traveling drive source of a vehicle. First, the internal combustion engine 1 to which the thermoacoustic Stirling engine 20 is applied will be briefly described. The internal combustion engine 1 burns a mixture of fuel and air inside a combustion chamber 3 formed in the cylinder block 2, The piston 4 is reciprocated in the combustion 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, an exhaust pipe L2 is connected to the exhaust manifold 6, and a catalyst device 12 is incorporated in the exhaust pipe L2. Further, an exhaust gas recirculation line (exhaust gas recirculation system) L3 is branched from the exhaust pipe L2 at a branch portion BP defined upstream of the catalyst device 12. The exhaust gas recirculation line L3 has an EGR valve 13 for adjusting the recirculation amount of exhaust gas (EGR gas) in the middle, and the tip thereof is connected to the surge tank 9 of the intake system.

  The thermoacoustic Stirling engine 20 of the present invention is used, for example, for recovering the exhaust heat of the internal combustion engine 1 as described above and cooling the EGR gas. The thermoacoustic Stirling engine 20 according to the present embodiment includes an air column tube 21 formed of stainless steel or the like so as to have a circular cross section. As shown in FIG. 1, the air column tube 21 includes a loop portion 22 formed in a loop shape and a resonance portion 23 connected to one corner portion 22 a 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.

  Further, a stack (heat storage means) 25 is disposed inside the loop portion 22 of the air column tube 21. The stack 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 stack 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 non-woven fabric in which metal fibers such as stainless steel are assembled, or the like can be used. A high temperature heat exchanger 26 is disposed adjacent to one end side of the stack 25, and a low temperature heat exchanger 27 is disposed adjacent to the other end side of the stack 25. That is, the stack 25 is disposed in a state of being sandwiched between the high-temperature heat exchanger 26 and the low-temperature heat exchanger 27, and the sound wave oscillating unit Sg is configured.

  As shown in FIG. 1, the heat transfer tubes constituting the high temperature heat exchanger 26 are incorporated in the exhaust pipe L2. Thereby, exhaust gas is supplied to the heat transfer tube of the high temperature heat exchanger 26 via the exhaust pipe L2 of the internal combustion engine 1, and the high temperature heat exchanger 26 uses the high temperature exhaust gas as a heat source. The heat transfer tubes constituting the low-temperature heat exchanger 27 are incorporated in the cooling system L4 of the internal combustion engine 1, and the low-temperature heat exchanger 27 uses the cooling water flowing through the cooling system L4 as a heat source (cold heat source). .

  Further, a thermoacoustic refrigerator portion Rg including a regenerator 250, a cold storage high temperature heat exchanger 260 and a cold storage low temperature heat exchanger 270 is disposed in the loop portion 22 of the air column tube 21. The high temperature heat exchanger for cold storage 260 is disposed adjacent to the above-described high temperature heat exchanger 26, and the heat transfer tube of the high temperature heat exchanger for cold storage 260 is incorporated in the above-described cooling system L4. The cold storage heat exchanger 270 is disposed adjacent to the low temperature heat exchanger 27 described above, and the heat transfer pipe of the cold storage heat exchanger 270 is exhaust gas so as to be located downstream of the EGR valve 13. It is incorporated in the reflux line L3. That is, the exhaust gas (EGR gas) that has flowed into the exhaust gas recirculation line L3 at the branch portion BP flows through the EGR valve 13 and the cold storage heat exchanger 270 in order.

  In the present embodiment, the air column tube 21 divides the closed space A including the sound wave oscillating portion Sg and the other closed space B (which includes the refrigerator portion Rg in the present embodiment). A first elastic film 28 and a second elastic film 29 are provided as partition walls. Further, in the closed space A and the closed space B inside the air column tube 21, any of working gas (inert gas) such as nitrogen, helium, argon, mixed gas of helium and argon can be sealed. In the present embodiment, in particular, a mixed gas of helium and argon is sealed with different composition ratios that affect their characteristics. That is, in the first closed space A including the sound wave oscillating portion Sg, as shown in FIG. 2, the composition ratio of the characteristic that the Prandtl number Pr becomes small is obtained in order to obtain an appropriate condition for causing the self-excited vibration easily. For example, a mixed gas of helium: argon = 80: 20 is enclosed. FIG. 2 is a graph showing how the Prandtl number Pr changes when the ratio (%) of argon is changed in a mixed gas of helium and argon. Here, the Prandtl number Pr is a dimensionless number in which the kinematic viscosity coefficient is gradually reduced by the temperature conductivity (thermal diffusivity), and represents the ratio of the “degree of momentum transfer” to the “degree of heat transfer” of the working gas. ing.

  Further, in the other second closed space B not including the sound wave oscillating portion Sg, as shown in FIG. 3, the composition ratio of the low flow loss characteristic capable of lowering the resonance frequency is helium: argon = 20: 80. The mixed gas is sealed. FIG. 3 is a graph showing the change of the resonance frequency when the ratio (%) of argon is changed in the mixed gas of helium and argon, as in FIG.

  In the first closed space A, a mixed gas of helium: argon = 30: 70 showing the smallest Prandtl number Pr, and in the second closed space B, only argon having the lowest resonance frequency is used (100% argon). May be enclosed. Further, in the present embodiment, the first elastic film 28 and the second elastic film 29 are used as a partition wall that partitions the above-described closed space A and the other closed space B. Instead of the resin elastic membrane, a rigid piston may be provided in the air column tube 21 so as to be slidable in the axial direction.

  The thermoacoustic Stirling engine 20 is controlled by an electronic control unit (hereinafter referred to as “ECU”) 40 that functions as control means of the internal combustion engine 1. The ECU 40 includes a ROM (read only memory), a RAM (random access memory), a CPU (microprocessor), an input port, an output port, and the like that are connected to each other via a bidirectional bus. The EGR valve 13 of the exhaust gas recirculation line L3 is connected to the output port of the ECU 40, and these are controlled by the ECU 40.

  The thermoacoustic Stirling engine 20 configured as described above operates when the internal combustion engine 1 is operated and the exhaust gas from the combustion chamber 3 passes through the high-temperature heat exchanger 26 of the thermoacoustic Stirling engine 20. Start. In this case, since the temperature of the exhaust gas reaches about 900 ° C. at the maximum, one end of the stack 25 is heated by the exhaust gas flowing through the high-temperature heat exchanger 26 to be heated. On the other hand, the low-temperature heat exchanger 27 of the thermoacoustic Stirling engine 20 is cooled at a relatively low temperature (approximately the atmospheric temperature immediately after the internal combustion engine 1 is cold started, and approximately 80 to 90 ° C. after the warm-up is completed). Since water is supplied, the other end of the stack 25 is 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 stack 25, and as a result, a thermoacoustic self-excited vibration (sound wave) of the working gas (mixed gas in which helium: argon = 80: 20) is generated. To do. The self-excited vibration of the working gas generated by the sound wave oscillating portion Sg in the first closed space A is passed through the first elastic film 28 and the second elastic film 29 and the working gas in the second closed space B. (Helium: Argon = mixed gas set to 20:80).

  When the frequency of the self-excited vibration (sound wave) of the working gas generated in this way matches the resonance frequency in the resonance part 23, a standing wave is formed in the resonance part 23, and in the loop part 22. A traveling wave traveling from the low temperature heat exchanger 27 to the high temperature heat exchanger 26 is formed. Then, due to the traveling wave created due to the temperature gradient formed between both ends of the stack 25, the high temperature heat exchanger for cold storage 260 side becomes hot between both ends of the regenerator 250 of the loop portion 22. The temperature gradient is formed so that the cold storage heat exchanger 270 side has a low temperature.

  At this time, one end of the regenerator 250 is maintained at a relatively low temperature by the regenerative high temperature heat exchanger 260 using the cooling water of the internal combustion engine 1 as a heat source. The heat exchanger 270 (its heat transfer tube) cools according to the temperature gradient. As a result, the units of the regenerator 250, the regenerator high-temperature heat exchanger 260, and the regenerator low-temperature heat exchanger 270 operate as a thermoacoustic refrigerator, and from the EGR valve 13 through the exhaust gas recirculation line L3, The EGR gas flowing through the low temperature heat exchanger 270 is cooled.

  That is, in the present embodiment, the EGR gas is cooled by the cold storage heat exchanger 270 of the thermoacoustic refrigerator unit Rg driven by the self-excited vibration of the working gas generated using the heat of the exhaust gas itself. As a result, the temperature of the EGR gas decreases (for example, 400 ° C. to 200 ° C.). Therefore, according to this thermoacoustic Stirling engine 20, it becomes possible to cool the EGR gas satisfactorily under high energy efficiency, and compared with the case where the configuration as in this embodiment is not adopted, The temperature of the EGR gas introduced into the surge tank 9 can be greatly reduced. As a result, in the internal combustion engine 1 equipped with the thermoacoustic Stirling engine 20, it becomes possible to suppress the temperature rise in each combustion chamber 3, and the NOx emission amount can be greatly reduced.

  Further, when the engine temperature (cooling water temperature) of the internal combustion engine 1 increases, the amount of heat of the exhaust gas that is waste heat of the internal combustion engine 1 increases. Therefore, the regenerator 250, the high temperature heat exchanger 260 for cold storage, and the low temperature heat exchanger for cold storage. The refrigeration output of the thermoacoustic refrigerator unit Rg constituted by 270 is also increased. The EGR gas of the internal combustion engine 1 has a higher necessity for cooling as the engine temperature is higher. Therefore, if the EGR gas of the internal combustion engine 1 is selected as the cooling target of the thermoacoustic Stirling engine 20 as in the present embodiment, the refrigerating capacity of the thermoacoustic refrigerator unit Rg and the cooling request for EGR gas are harmonized. The EGR gas can be efficiently cooled using the waste heat of the internal combustion engine 1.

  In the thermoacoustic Stirling engine 20 shown in FIG. 1, a temperature gradient is formed between both ends of the stack 25 using the exhaust gas of the internal combustion engine 1 as a heat source, and thereby the sound wave oscillating portion Sg inside the air column tube 21. The mixed gas in which helium: argon = 80: 20 as the working gas is self-excited in the first closed space A including According to the thermoacoustic Stirling engine 20 configured as described above, self-excited vibration having a predetermined frequency corresponding to the composition ratio is easily generated, and the low flow loss working gas in the second closed space B is used. Since it is propagated and resonates with a certain gas mixture of helium: argon = 20: 80, it is efficiently operated with an overall compact configuration, and the EGR gas is recovered while efficiently recovering the exhaust heat of the internal combustion engine 1. Prior to introduction into the surge tank 9, it becomes possible to cool well.

[Second Embodiment]
Hereinafter, the thermoacoustic Stirling engine 20 according to the second embodiment of the present invention will be described with reference to FIG. 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 Stirling engine 20 shown in FIG. 4 includes an abnormal state detection unit that detects an abnormal state caused by breakage of the first elastic film 28 and the second elastic film 29 that are partition walls. As this abnormal state detection means, in this embodiment, a vibration sensor 30 disposed in the air column tube 21 is used, and an output signal thereof is input to the ECU 40.

  The abnormal state detection routine in the second embodiment is executed in the ECU 40 at a predetermined cycle in accordance with, for example, the flowchart shown in FIG. Therefore, in this abnormal state detection routine, in step S501, it is determined whether or not vibration other than the predetermined frequency of the air column tube 21 is detected from the output signal from the vibration sensor 30. Here, this predetermined frequency is enclosed in the first closed space A including the working gas enclosed in the first closed space A and the second closed space B of the air column tube 21, in particular, the sound wave oscillating portion Sg. It is set corresponding to the self-excited vibration frequency of the working gas. Therefore, as a result of the determination in step S501, when the vibration of the predetermined frequency is detected, that is, when it is “No”, the abnormal state detection routine is temporarily ended, assuming that the operation is normal. On the other hand, when vibration other than the predetermined frequency is detected, that is, when “Yes”, the process proceeds to the next step S502.

  In the next step S502, it is determined whether or not the change rate of the detected frequency with respect to the predetermined frequency exceeds a predetermined range. If it does not exceed the predetermined range, the abnormal state detection routine is temporarily terminated assuming that it is within the allowable range of normal operation. By the way, if it is determined in step S502 that the rate of change of the detected frequency with respect to the predetermined frequency exceeds the predetermined range, the process proceeds to step S503 and an abnormal state is notified. Notification of this abnormal state can be appropriately performed by a warning means (not shown).

  Here, as described above, this abnormal state is caused by damage to the first elastic film 28 or the second elastic film 29, leakage of working gas when a rigid piston is used as a partition wall, or the like. It is generated by mixing the working gas sealed in the first closed space A and the second closed space B. For example, in the initial state, a mixed gas in which helium: argon = 80: 20 is sealed in the first closed space A, and a mixed gas in which helium: argon = 20: 80 is sealed in the second closed space B. When the working gas sealed in the first closed space A and the second closed space B is mixed due to the breakage of the first elastic film 28, the mixing ratio changes, for example, helium: argon = It becomes a 50:50 mixed gas. In this way, when the composition ratio of the mixed gas changes, as is apparent from the graph of FIG. 3, the oscillation or resonance frequency changes, so depending on whether the rate of change of this frequency exceeds a predetermined range, It is possible to determine whether or not there is an abnormality, in other words, whether or not the first elastic film 28 or the second elastic film 29 is damaged or whether there is a leak.

[Third Embodiment]
Next, a thermoacoustic Stirling engine 20 according to a third embodiment of the present invention will be described with reference to FIG. The same elements as those described in relation to the first and second embodiments described above are denoted by the same reference numerals, and redundant description is omitted.

  The thermoacoustic Stirling engine 20 in FIG. 6 is provided with pressure adjusting means for adjusting the filling pressure of the working gas in the air column tube 21 to the second embodiment provided with the vibration sensor 30 described above. In the present embodiment, an air communication pipe 34 having a discharge valve 32 is provided on the way as the pressure adjusting means. The discharge valve 32 can be opened and closed by an output signal from the ECU 40. Thus, even when the above-described abnormal state occurs and the thermoacoustic phenomenon stops, it is possible to maintain the thermoacoustic phenomenon by reducing the filling pressure of the working gas in the air column tube 21. .

  Therefore, the control routine in the third embodiment will be described with reference to the flowchart shown in FIG. This control routine is executed as a subroutine associated with the abnormality notification in step S503 of the abnormal state detection routine described above.

  In this control routine, in step S701, it is repeatedly determined whether or not the vibration of the air column tube 21 is stopped based on the output signal from the vibration sensor 30, and when the vibration stop is detected, the process proceeds to the next step S702. . In step S702, the discharge valve 32 is opened for a predetermined time (for example, 1 second), and in step S703, the number n of times of opening is counted up. When the release valve 32 is opened, the working gas in the air column pipe 21 is released through the atmosphere communication pipe 34, and the filling pressure in the air column pipe 21 is reduced. Therefore, the process proceeds to the next step S704, where it is determined whether or not the vibration of the air column tube 21 is detected based on the output signal from the vibration sensor 30. If no vibration is detected, the process proceeds to step S705, where it is determined whether the number n of opening operations of the discharge valve 32 is a predetermined number x (for example, five times) or more. When the number n of opening operations does not exceed the predetermined number x, the process proceeds to step S702, where the discharge valve 32 is opened again for a predetermined time, and the filling pressure in the air column tube 21 is further reduced. In step S704, it is determined again whether vibration of the air column tube 21 is detected based on the output signal from the vibration sensor 30, and here, the predetermined value of the discharge valve 32 in step S702 described above is detected until vibration is detected. The time opening operation is repeated a predetermined number of times x.

  Thus, if the filling pressure of the working gas in the air column tube 21 is lowered, even if the temperature difference in the sound wave oscillating portion Sg is the same, self-excited vibration is more likely to occur than when the filling pressure is high. The acoustic phenomenon can be recovered or maintained.

  Thus, if vibration is detected in step S704, the process proceeds to step S707, and maintenance is required. This maintenance notice is not an urgent notice but means that a certain amount of driving can be continued, and this notice can also be suitably performed by a warning means (not shown).

  Note that if no vibration is detected even after the opening operation of the discharge valve 32 is performed a predetermined number of times x (steps S704 and S705), the process proceeds to step S706 and an abnormal state is further notified. Notification of this abnormal state can be appropriately performed by a warning means (not shown) as described above.

[Fourth Embodiment]
Next, a thermoacoustic Stirling engine 20 according to a fourth embodiment of the present invention will be described with reference to FIG. The same elements as those described in relation to the first to third embodiments described above are denoted by the same reference numerals, and redundant description is omitted.

  The thermoacoustic Stirling engine 20 in FIG. 8 is obtained by adding cooling capacity improving means for improving the cooling capacity in the thermoacoustic refrigerator unit Rg to the second embodiment in which the vibration sensor 30 is provided. In the present embodiment, as the cooling capacity improving means, for example, the air-cooled secondary cooler 50 that reduces the temperature of the cooling water supplied to the cold storage high-temperature heat exchanger 260 in the thermoacoustic refrigerator unit Rg, and this A control valve 52 capable of controlling the flow of the cooling water in the secondary cooler 50 is provided. More specifically, the secondary cooler 50 is incorporated upstream of the cold storage high-temperature heat exchanger 260 in the cooling system L4, and the control valve is provided in the bypass passage L4 ′ that bypasses the secondary cooler 50. 52 is provided. The control valve 52 can be opened and closed by an output signal from the ECU 40. Thus, the temperature of the high temperature heat exchanger 260 of the cold storage heat exchanger 260 and the high temperature heat exchanger 260 of the cold storage heat exchanger 270 at both ends of the cold storage 250 is decreased, so that the temperature of the low temperature heat exchanger 270 is relatively decreased. This makes it possible to compensate for the cooling performance degradation in the abnormal state described above.

  Therefore, the control routine in the fourth embodiment will be described with reference to the flowchart shown in FIG. This control routine is executed as part of the above-described abnormal state detection routine.

  Accordingly, in step S901, as in step S501, it is determined whether or not vibration other than the predetermined frequency of the air column tube 21 is detected from the output signal from the vibration sensor 30. Here, this predetermined frequency is enclosed in the first closed space A including the working gas enclosed in the first closed space A and the second closed space B of the air column tube 21, in particular, the sound wave oscillating portion Sg. Is set in accordance with the self-excited vibration frequency of the working gas being operated, and when the vibration at the predetermined frequency is detected as a result of the determination in step S901, that is, when “No”, it operates normally. This routine is once terminated. On the other hand, when vibration other than the predetermined frequency is detected, that is, when “Yes”, the process proceeds to the next step S902, and the rate of change of the detected frequency with respect to the predetermined frequency exceeds the predetermined range as in step S502. It is determined whether or not there is. If the predetermined range is not exceeded, the routine is temporarily terminated assuming that it is within the allowable range of normal operation. By the way, if it is determined in step S902 that the rate of change of the detected frequency with respect to the predetermined frequency exceeds the predetermined range, the process proceeds to step S903, where an abnormal state is notified, and the process proceeds to step S904, where the control valve 52 is turned on. Closed.

  Here, when the control valve 52 is closed, the entire amount of the cooling water that has circulated through the bypass passage L4 ′ of the secondary cooler 50 up to this time due to the difference in flow resistance flows through the secondary cooler 50. become. Then, the temperature of the cooling water is further lowered in the secondary cooler 50 and passes through the high temperature heat exchanger 260. For example, the cooling water sent from the internal combustion engine 1 to the cooling system L4 at a temperature of 80 ° C. is further reduced to a temperature of, for example, 60 ° C. in the secondary cooler 50 and introduced into the high-temperature heat exchanger 260. Therefore, the temperature of the low-temperature heat exchanger 270 is lowered correspondingly, and the cooling performance deterioration under the abnormal condition is compensated.

  In the above-described embodiment, the EGR gas of the internal combustion engine 1 is targeted as the cooling target of the refrigerator unit Rg, but this allows the intake air of the internal combustion engine 1 to pass through the cold storage heat exchanger 270. By doing so, the intake air may be cooled. If it does in this way, it will become possible to raise the density of intake air, pumping loss can be reduced, and fuel consumption can be reduced. In addition, by disposing the cold storage heat exchanger 270 on the downstream side of the supercharger, the cooling effect of the intake air can be improved by using the cold storage heat exchanger 270 as an intercooler.

  Further, a thermoacoustic Stirling engine in which a power generation unit such as a transducer is disposed at the closed end 23b connected to the tip of the tube 23a in the resonance unit 23 of the air column tube 21 in which the sound wave oscillating unit Sg is disposed. Needless to say, the present invention can also be applied to 20.

1 is a schematic configuration diagram illustrating a thermoacoustic Stirling engine according to a first embodiment of the present invention. It is a graph which shows the mode of change of the Prandtl number Pr when changing the ratio (%) of argon in the mixed gas of helium and argon. It is a graph which shows the mode of the change of the resonant frequency when the ratio (%) of argon is changed in the mixed gas of helium and argon. It is a schematic block diagram which shows the thermoacoustic Stirling engine which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows an example of the abnormal condition detection routine in 2nd Embodiment. It is a schematic block diagram which shows the thermoacoustic Stirling engine which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows an example of the control routine in the 3rd Embodiment of this invention. It is a schematic block diagram which shows the thermoacoustic Stirling engine which concerns on the 4th Embodiment of this invention. It is a flowchart which shows an example of the control routine in the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Combustion chamber 13 EGR valve 20 Thermoacoustic Stirling engine 21 Air column pipe 22 Loop part 23 Resonance part 25 Stack (heat accumulator)
26 High Temperature Heat Exchanger 27 Low Temperature Heat Exchanger 28 First Elastic Membrane 29 Second Elastic Membrane 30 Vibration Sensor 250 Regenerator 260 High Temperature Heat Exchanger for Cold Storage 270 Low Temperature Heat Exchanger for Cold Storage 40 ECU
A 1st closed space B 2nd closed space BP Branch part L1 Intake pipe L2 Exhaust pipe L3 Exhaust gas recirculation line L4 Cooling system Sg Sound wave oscillation part Rg Refrigerator part Rg

Claims (5)

A thermoacoustic Stirling engine that is disposed in an air column pipe and includes a stack, a sound wave oscillating unit that is composed of a stack, a high temperature side heat exchanger disposed at one end of the stack, and a low temperature side heat exchanger disposed at the other end. ,
First and second partition walls that partition the first closed space including the sound wave oscillating portion and the other second closed space are provided, and the first closed space and the second closed space are provided. Is a thermoacoustic Stirling engine, each of which is filled with a working gas having different appropriate characteristics.   The thermoacoustic Stirling engine according to claim 1, wherein the working gas having different characteristics is a mixed gas of helium and argon having different composition ratios.   The thermoacoustic Stirling engine according to claim 1 or 2, further comprising an abnormal state detection means including a vibration sensor disposed in the air column tube.   The thermoacoustic Stirling engine according to claim 3, further comprising pressure adjusting means for adjusting the pressure of the working gas in the air column tube to reduce the pressure. It is provided in the air column tube, and includes a refrigerator unit comprising a regenerator, a high temperature side heat exchanger, and a low temperature side heat exchanger, and includes a cooling capacity improving means for improving the cooling capacity of the refrigerator unit. The thermoacoustic Stirling engine according to claim 3.

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