JP2006145176A - Thermoacoustic engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve output efficiency by specifying a component such as a stack more precisely. <P>SOLUTION: The thermoacoustic engine is provided with a looped piping 1 sealing predetermined gas, the columnar stack 2 arranged in the looped piping 1, a high temperature side heat source 3 provided on one end of the stack 2, and a low temperature side heat source 4 provided on another end of the stack. A length Lh of the stack 2 is set at a length of 20mm or more, and such that a temperature gradient of an interior of the stack 2 becomes 4K/mm or more. The looped piping 1 includes a vertically arranged erected part 1a, the stack 2 is vertically arranged in the erected part 1a, the high temperature side heat source 3 is provided on the lower end of the stack 2, and the low temperature side heat source 4 is provided on the upper end of the stack 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoacoustic engine that generates a sound wave by causing pressure vibration by a thermoacoustic phenomenon in a looped pipe filled with a predetermined gas (working gas).

  Conventionally, as a “thermoacoustic phenomenon”, there is a phenomenon in which sound waves are generated by installing a stack in which thin plates or thin tubes are bundled in a pipe and applying a temperature difference to the stack by heat exchangers provided at both ends thereof. On the contrary, there is a phenomenon in which a temperature difference is generated between both ends of a heat accumulator sandwiched between heat exchangers by applying a sound wave to one end of a pipe. By utilizing such a thermoacoustic phenomenon, energy exchange between sound and heat can be realized using sound waves instead of moving parts such as pistons and valves. A new engine based on such a thermoacoustic phenomenon is referred to as a “thermoacoustic engine”.

  Patent Documents 1 and 2 below describe this type of thermoacoustic engine. In Patent Document 1, a stack sandwiched between a high-temperature side heat exchanger and a low-temperature side heat exchanger is inserted into a loop-shaped pipe filled with gas, and a regenerator is placed at a position asymmetric with the stack. And a loop tube air column acoustic wave refrigerator that is arranged with a low temperature side heat exchanger to form a circuit. In this refrigerator, standing waves and traveling waves generated from the gas sealed in the stack are propagated to the regenerator through the pipe so that the regenerator cools and freezes, and at the same time, performs smooth heat dissipation. It has become.

  In Patent Document 2, in a thermoacoustic engine that generates a traveling wave in a loop pipe formed by enclosing a working gas, the loop pipe is formed in a state having a rising pipe at least partially, and the rising pipe portion is formed in the rising pipe portion. It is described that a high-temperature side heat absorber, a heat accumulator (stack), and a low-temperature side radiator are arranged in order from the top, and a second radiator is arranged in the upper part of the high-temperature side heat absorber. In this thermoacoustic engine, the working gas heated by the high-temperature side heat absorber rises in convection, so that the thermoacoustic self-excited vibration easily occurs in the stack, and the thermoacoustic self-excited vibration is generated even with a small temperature gradient. It is like that.

No. 2000-88378 Japanese Patent Publication No. 2002-31423

  However, Patent Documents 1 and 2 have no description regarding the length of the stack, and the efficient stack length is unknown in design. Further, Patent Document 2 does not describe anything about disposing the high-temperature side heat absorber in the lower portion of the stack from the viewpoint of improving the output efficiency. Further, Patent Document 1 describes at which position of the loop pipe the stack is arranged, but from the viewpoint of improving the output efficiency, no strict examination of the position of the stack has been made.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermoacoustic engine capable of improving output efficiency by strictly specifying components such as a stack. is there.

  In order to achieve the above object, the invention described in claim 1 is provided at a loop-shaped pipe filled with a predetermined gas, a columnar stack disposed in the loop-shaped pipe, and one end of the stack. In a thermoacoustic engine provided with a high temperature side heat source and a low temperature side heat source provided at the other end of the stack, the length of the stack is 20 mm or more and the temperature gradient inside the stack is 4 K / mm or more. The purpose is to do so.

  According to the configuration of the invention, a standing wave and a traveling wave are self-excited from a gas enclosed in the stack by a thermoacoustic phenomenon by giving a temperature difference to both ends of the stack by the high temperature side heat source and the low temperature side heat source. The sound wave which consists of is generated. This sound wave propagates to the refrigerator, for example, so that the refrigerator cools and freezes. Here, in order for sound waves to form a thermal cycle, a certain length is required for the stack, and a certain temperature gradient is required inside the stack. Therefore, the length of the stack is set to 20 mm or more, and the temperature gradient inside the stack is set to 4 K / mm or more, so that the conversion efficiency from heat to sound waves is improved.

  In order to achieve the above object, the invention according to claim 2 is the invention according to claim 1, wherein a plurality of prime movers configured as a set of the stack, the high temperature side heat source and the low temperature side heat source are arranged in parallel. Intended to be

  According to the configuration of the invention described above, in addition to the operation of the invention according to claim 1, since a plurality of prime movers are arranged in parallel, the conversion efficiency from heat to sound waves is increased without unnecessarily increasing the length of the stack. improves.

  In order to achieve the above object, the invention described in claim 3 is provided in a loop-shaped pipe filled with a predetermined gas, a columnar stack arranged in the loop-shaped pipe, and one end of the stack. In a thermoacoustic engine having a high temperature side heat source and a low temperature side heat source provided at the other end of the stack, the loop-shaped pipe includes an upright portion arranged vertically, and the stack is arranged vertically on the upright portion. And the high temperature side heat source is provided at the lower end of the stack, and the low temperature side heat source is provided at the upper end of the stack.

  According to the configuration of the invention, a standing wave and a traveling wave are self-excited from a gas enclosed in the stack by a thermoacoustic phenomenon by giving a temperature difference to both ends of the stack by the high temperature side heat source and the low temperature side heat source. The sound wave which consists of is generated. This sound wave propagates to the refrigerator, for example, so that the refrigerator cools and freezes. Here, the stack is arranged vertically in the upright portion arranged vertically of the loop-shaped pipe, the high temperature side heat source is provided at the lower end of the stack, and the low temperature side heat source is provided at the upper end of the stack. An ascending airflow is generated from the provided high temperature side heat source, and the heat transfer by the ascending airflow effectively acts on the generation of sound waves.

  In order to achieve the above-mentioned object, the invention described in claim 4 is provided at a loop-shaped pipe filled with a predetermined gas, a columnar stack disposed in the loop-shaped pipe, and one end of the stack. In a thermoacoustic engine including a high temperature side heat source and a low temperature side heat source provided at the other end of the stack, the loop-shaped pipe includes a first corner, a second corner, a third corner, and a fourth corner; The purpose of the present invention is to arrange the center of the stack between the second corner and a position that is 23% of the total length of the looped pipe from the first corner.

  According to the configuration of the invention, a standing wave and a traveling wave are self-excited from a gas enclosed in the stack by a thermoacoustic phenomenon by giving a temperature difference to both ends of the stack by the high temperature side heat source and the low temperature side heat source. The sound wave which consists of is generated. This sound wave propagates to the refrigerator, for example, so that the refrigerator cools and freezes. Here, since the center of the stack is arranged between the first corner of the loop-shaped pipe and the second corner from the position where it is 23% of the entire length of the loop-shaped pipe, the flow velocity characteristic in the loop-shaped pipe is the refrigeration output. It becomes the characteristic that is easy to generate.

  In order to achieve the above object, the invention described in claim 5 is the invention described in claim 4, wherein a plurality of prime movers configured as a set of a stack, a high temperature side heat source and a low temperature side heat source are arranged in parallel. Intended to be

  According to the configuration of the invention, in addition to the operation of the invention according to claim 4, since a plurality of prime movers are arranged in parallel, the conversion efficiency from heat to sound waves can be improved without increasing the length of the stack more than necessary. improves.

  According to the first aspect of the present invention, the output efficiency of the thermoacoustic engine can be improved by strictly specifying the stack length.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the conversion efficiency from heat to sound waves is improved without increasing the length of the stack constituting each prime mover more than necessary. It is possible to make the stack the required length.

  According to the third aspect of the present invention, the output efficiency of the thermoacoustic engine can be further improved by strictly specifying the arrangement of the high temperature side heat source and the low temperature side heat source with respect to the stack.

  According to invention of Claim 4, the output efficiency as a thermoacoustic engine can be further improved by specifying the arrangement | positioning of the stack | stuck in loop-shaped piping further strictly.

  According to the invention described in claim 5, in addition to the effect of the invention described in claim 4, the conversion efficiency from heat to sound wave is improved without increasing the length of the stack constituting each prime mover more than necessary. It is possible to make the stack the required length.

[First Embodiment]
Hereinafter, a first embodiment of a thermoacoustic engine according to the present invention will be described in detail with reference to the drawings.

  The thermoacoustic engine of this embodiment is mounted and used, for example in a motor vehicle. In this case, the thermoacoustic engine can be driven using the exhaust heat discharged from the engine of the automobile as a heat source. By driving the refrigerator using this thermoacoustic engine, various coolers mounted on the automobile can be functioned. Applicable objects include a cooler for cooling a passenger compartment, an oil cooler, a cooler for cooling a canister, and the like.

  FIG. 1 shows a schematic configuration diagram of a thermoacoustic engine. The thermoacoustic engine includes a loop-shaped pipe 1 filled with a predetermined gas (working gas), a column-shaped stack 2 disposed in the pipe 1, and a high-temperature side heat source 3 provided at one end of the stack 2. And a low temperature side heat source 4 provided at the other end of the stack 2. In this embodiment, the loop-like pipe 1 forms a closed loop and includes a first upright portion 1a and a second upright portion 1b arranged vertically, and the stack 2 is arranged vertically on the first upright portion 1a. . Here, the high temperature side heat source 3 is provided at the lower end of the stack 2, and the low temperature side heat source 4 is provided at the upper end of the stack 2. The stack 2, the high temperature side heat source 3, and the low temperature side heat source 4 constitute a set of prime movers 5. In such a configuration, a temperature difference is given to both ends of the stack 2 by the high temperature side heat source 3 and the low temperature side heat source 4, so that the standing wave and A sound wave composed of a traveling wave is generated. Here, in this embodiment, the length (stack length) Lh of the stack 2 is set to a length that is 20 mm or more and the temperature gradient inside the stack 2 is 4 K / mm or more. In this embodiment, specifically, the stack length Lh is set to “60 mm”.

  Conventionally, when producing a thermoacoustic engine under certain conditions, it has not been clear how much the efficiency of conversion from heat into sound waves by the prime mover is maximized by the length of the prime mover stack. Therefore, in this embodiment, the optimum stack length Lh was experimentally confirmed by measuring the pressure behavior in the looped pipe 2 using the stack length Lh as a parameter.

  FIG. 2 shows a cross-sectional view of the structure of the thermoacoustic engine used in the experiment. In this embodiment, the loop-shaped pipe 1 has an inner diameter of “φ55 mm”. The loop pipe 1 is configured by connecting a plurality of curved pipes 6 and a plurality of straight pipes 7 in combination. In this embodiment, the gas enclosed in the loop-shaped pipe 1 is air. The prime mover 5 includes a low temperature side heat exchanger 11 as the low temperature side heat source 4, a honeycomb ceramic 12 as the stack 2, a sheath heater 13 as the high temperature side heat source 3, and a power supply block 14 that supplies power to the sheath heater 13. including. The power supply block 14 includes a heater holder 15 that protrudes toward the sheath heater 13. In FIG. 3, the principal part of the motor | power_engine 5 is shown with an exploded sectional view. As shown in FIG. 3, the sheath heater 13 is connected to the lower end of the honeycomb ceramic 12 through two heat transfer meshes 16. The low temperature side heat exchanger 11 is also connected to the upper end of the honeycomb ceramic 12 through two heat transfer meshes 16. Here, since the low temperature side heat exchanger 11 is held between the curved pipe 6 and the straight pipe 7, the sheath heater 13, the heat transfer mesh 16, the honeycomb ceramic 12 and the heat transfer mesh are directed toward the heat exchanger 11. 16 are pressed by the heater holder 15 and connected to each other.

  As shown in FIG. 2, a pressure / flow velocity measuring device 17 is provided at a position asymmetric with respect to the prime mover 5 in the second upright portion 1b. The measuring device 17 measures the gas pressure and flow velocity.

  FIG. 4 shows a plan view of the end face of the honeycomb ceramic 12. FIG. 5 shows a front view of the honeycomb ceramic 12. FIG. 6 shows an enlarged part of FIG. The honeycomb ceramic 12 is formed of a porous cell having a cylindrical shape and having a mesh shape in plan view. As shown in FIG. 6, in this embodiment, the thickness of the porous partition wall 12a is “0.102 mm”, and the width of each square cell 12b is “0.936 mm”.

  FIG. 7 is a plan view showing the sheath heater 13. FIG. 8 is a front view of the sheath heater 13. The sheath heater 13 is formed in a substantially spiral shape with a wire, and both ends of the wire are electrodes 13a and 13b. Gas is allowed to flow through the gaps between the wires configured in a substantially spiral shape.

  FIG. 9 is a front view of the low temperature side heat exchanger 11. FIG. 10 is a right side view of FIG. The heat exchanger 11 includes a main body 11a made of a hexagonal thick metal plate, and a pair of pipe joints 18 and 19 serving as water inlets and outlets are provided on the right side surface of the main body 11a. As shown in FIG. 3, a water passage 11b is formed inside the main body 11a. A plurality of slits 11c for allowing gas to pass through are formed in the center of the main body 11a.

  FIG. 11 is a table showing various conditions related to the thermoacoustic engine used in the experiment of the present embodiment. As can be seen from this table, the half (honeycomb cell radius) r of the cell 12b of the honeycomb ceramic 12 is “0.47 mm”. The input power to the sheath heater 13 is “180 W”. The pipe height LV in FIGS. 1 and 2 is “940 mm”. Similarly, the pipe line width LH in FIGS. 1 and 2 is “460 mm”. The pipe length (full length) L of the loop-shaped pipe 1 is “2800 mm”. The position (prime mover honeycomb position) Ls of the honeycomb ceramic 12 in the prime mover 5 is “770 mm”. The honeycomb position Ls means a distance from the lower side of the first upright portion 1a to the center position of the stack 2 (honeycomb ceramic 12). The pressure in the looped pipe 1 (pressure in the pipe line) is “1 atm”. The position of the pressure / flow velocity measuring machine 17, that is, the pressure / flow velocity measuring position is “0.55 × L from the prime mover”, that is, the position of “55%” of the pipe length L from the prime mover 5. That is, the point is “1540 mm” counterclockwise from the center of the stack 2 (honeycomb ceramic 12). In this experiment, under various conditions as described above, the stack length (the length of the honeycomb ceramic 12) Lh was changed to “20 mm”, “60 mm”, and “100 mm”, and the pressure and flow velocity measuring device 17 was used to change the pressure and flow rate. The flow rate was measured.

  FIG. 12 is a graph showing the pressure measurement result. As is apparent from this graph, the pressure amplitude is greatest when the stack length Lh is set to “60 mm”. The flow rate was similar, although not shown. In general, the energy of sound waves can be evaluated by the product of pressure and flow velocity. In this case, it can be said that the output efficiency of the prime mover 5 is the best when the stack length Lh is set to “60 mm”. This is because if the stack length Lh is too short, the heat cycle for converting heat into sound waves in the stack 2 (honeycomb ceramic 12) is inhibited, and if the stack length Lh is too long, the same amount of heat is given. In this case, it is considered that the temperature difference (corresponding to the temperature gradient in the stack 2) of the thermal cycle is reduced, and the thermal efficiency is reduced, so that the efficiency is reduced. Therefore, the lower limit of the stack length Lh is about “20 mm”, and the upper limit of the stack length Lh is such that the temperature gradient is larger than the temperature gradient in the stack 2 (honeycomb ceramic 12) in the case of “60 mm”. That's all you need to do. In addition, when the heat input per unit area is constant, for example, when the exhaust heat of an automobile becomes heat input, if a prime mover with a large stack length Lh is used, there may be cases where the heat input does not fall within the above range. In such a case, as shown in FIG. 13, it is effective to arrange a plurality of prime movers 5 in parallel so that the stack 2 has the above length.

  In FIG. 14, the structure of the thermoacoustic refrigeration apparatus which applied the thermoacoustic engine is shown with sectional drawing. In this thermoacoustic refrigeration apparatus, a refrigerator 20 is incorporated in a loop-shaped pipe 1. The configuration shown in FIG. 14 is obtained by replacing the pressure / flow velocity measuring device 17 shown in FIG. 2 with a refrigerator 20, and the configuration other than the refrigerator 20 is the same as FIG. 2. The refrigerator 20 is disposed in the second upright portion 1b at a position asymmetric with the prime mover 5.

  In FIG. 15, the principal part of the refrigerator 20 is shown in an exploded sectional view. The refrigerator 20 shown in FIG. 15 is shown upside down with the refrigerator 20 shown in FIG. As shown in FIG. 15, the refrigerator 20 functions as a water-cooled low-temperature side heat exchanger 21 (having the same configuration as the low-temperature side heat exchanger 11 of the prime mover 5), a honeycomb ceramic 22, and a refrigeration unit. And an endothermic plate 23. The low temperature side heat exchanger 21 includes a main body 21a, and a water passage 21b is formed in the main body 21a. A plurality of slits 21c for allowing gas to pass are formed in the center of the main body 21a. The low temperature side heat exchanger 21 is connected to one end of the honeycomb ceramic 22 through two heat transfer meshes 24. A first temperature sensor 25 is provided between the heat exchanger 21 and the heat transfer mesh 24. The heat absorbing plate 23 is also connected to the other end of the honeycomb ceramic 22 through two heat transfer meshes 24. A second temperature sensor 26 is provided between the heat absorbing plate 23 and the heat transfer mesh 24. Here, the refrigerator 20 is sandwiched and held between the curved pipe 6 and the straight pipe 7, whereby the members 21 to 26 are pressed and connected to each other. FIG. 16 is a front view of the heat absorbing plate 23. FIG. 17 is a right side view of FIG. The endothermic plate 23 is formed of a circular metal thick plate material, and a plurality of slits 23 a for allowing gas to pass through are formed in the center of the endothermic plate 23.

  As described above, according to the thermoacoustic engine of this embodiment, in FIG. 1, the temperature difference is given to both ends of the stack 2 by the high temperature side heat source 3 and the low temperature side heat source 4, so A sound wave composed of a standing wave and a traveling wave is generated from the gas enclosed in 2 in a self-excited manner. In FIG. 2, a temperature difference is given to both ends of the honeycomb ceramic 12 by the sheath heater 13 and the low temperature side heat exchanger 11, so that a standing wave is self-excited from the gas enclosed in the ceramic 12 due to a thermoacoustic phenomenon. And a sound wave consisting of a traveling wave is generated. Therefore, as shown in FIG. 14, in the thermoacoustic refrigeration apparatus to which this thermoacoustic engine is applied, the chiller 20 cools and refrigerates when sound waves from the prime mover 5 propagate to the refrigerator 20. The refrigerator 20 can exhibit a required refrigeration function.

  Here, in order for sound waves to form a heat cycle, a certain length is required for the stack 2 (honeycomb ceramic 12), and a certain temperature gradient is required inside the stack 2 (honeycomb ceramic 12). In this embodiment, the stack length Lh is 20 mm or more, and the temperature gradient inside the stack 2 (honeycomb ceramic 12) is 4 K / mm or more, so the conversion efficiency from heat to sound waves is improved. To do. For this reason, the intensity | strength (pressure and flow velocity) of the sound wave in the pipe line of the loop-shaped piping 1 can be enlarged. As described above, by strictly specifying the stack length Lh, the output efficiency of the thermoacoustic engine can be improved. For this reason, according to the thermoacoustic refrigeration apparatus shown in FIG. 14, the refrigeration output by the refrigerator 20 can be improved.

  Further, as shown in FIG. 13, in a thermoacoustic engine in which a plurality of prime movers 5 are arranged in parallel, the conversion efficiency from heat to sound waves without increasing the stack length Lh of the stacks 2 constituting each prime mover 5 more than necessary. Will improve. Therefore, when the heat input per unit area to the stack 2 is constant, for example, when the exhaust heat of the automobile becomes the heat input to the stack 2 of the prime mover 5, if the relatively long stack 2 is used, the stack length There is a case where Lh is not in the range of 20 mm or more as described above, and the temperature gradient inside the stack 2 is 4 K / mm or more. In such a case, it is effective that the stack length Lh can be set within the specific range by arranging a plurality of prime movers 5 in parallel as shown in FIG.

[Second Embodiment]
Next, a second embodiment that embodies the thermoacoustic engine of the present invention will be described in detail with reference to the drawings.

  In each embodiment described below (including this embodiment), the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The explanation is centered.

  In the above-mentioned Patent Document 2, a high-temperature side heat absorber, a heat accumulator (stack), and a low-temperature side radiator are arranged in order from the top in a riser portion formed in a part of a loop pipe line, so that heat is converted into sound waves. It is described that the conversion efficiency is improved. However, Patent Document 2 has not been evaluated numerically as an example, and has room for improvement. Therefore, in this embodiment, the arrangement of the high temperature side heat source 3 and the low temperature side heat source 4 with respect to the stack 2 is opposite to the configuration described in Patent Document 2, that is, the high temperature side heat source 3 is at the lower end of the stack 2 4 is provided at the upper end of the stack 2. And the difference in the pressure behavior in the loop-shaped piping 1 by the difference in arrangement | positioning of these heat sources 3 and 4 was confirmed experimentally.

  In this experiment, a thermoacoustic engine having a configuration similar to the thermoacoustic engine of FIG. 2 was used. However, in order to eliminate the effect of the position of the prime mover 5, the prime mover 5 is arranged so that the center of the prime mover 5 is located at the center of the first upright portion 1 a in the looped pipe 1.

  FIG. 18 shows various conditions regarding the thermoacoustic engine used in the experiment of the present embodiment. As can be seen from this table, the honeycomb cell radius r is “0.47 mm”. The input power to the sheath heater 13 is “180 W”. The pipeline height LV in FIGS. 1 and 2 is “1140 mm”. Similarly, the pipe line width LH in FIGS. 1 and 2 is “460 mm”. The pipe length (full length) L of the loop-shaped pipe 1 is “3200 mm”. The prime mover honeycomb position Ls is “570 mm”. The pressure of the looped pipe 1 (pressure in the pipe line) is “1 atm”. The pressure / flow velocity measurement position is “0.55 × L in the traveling direction of the sound wave from the prime mover”, that is, the position of “55%” of the pipe length L in the traveling direction of the sound wave from the prime mover 5. Here, since the sound wave generated in the loop-shaped pipe 1 travels in the opposite direction to the heat flow in the prime mover 5, the measurement position of the pressure / velocity in the pipe is the progression of the sound wave from the center of the prime mover 5. It is set to “0.55 × L” in the direction. Therefore, when the high temperature side heat source 3 (sheath heater 13) is disposed below the prime mover 5, that is, at the lower end of the stack 2 (honeycomb ceramic 12), the stack 2 ( When measurement is performed at a point “1760 mm” from the center of the honeycomb ceramic 12) and a high-temperature side heat source is arranged on the upper side of the prime mover, that is, at the upper end of the stack, the stack 2 of the prime mover 5 is clockwise in FIGS. Measurement was performed at a point of “1760 mm” from the center of (honeycomb ceramic 12).

  FIG. 19 is a graph showing the pressure measurement result. As is clear from this graph, when the high-temperature side heat source 3 is disposed on the lower side, that is, the sheath heater 13 is disposed on the lower side (under the heater), the pressure is higher than when the sheath heater 13 is disposed on the upper side (on the heater). It can be seen that the amplitude is large. The flow rate was similar, although not shown. Moreover, it was not possible to observe that the generated sound wave disappeared or fluctuated greatly under any condition. As described above, the energy of the sound wave can be evaluated by the product of the pressure and the flow velocity. In this case, unlike the thermoacoustic engine described in Patent Document 2, by heating the lower side of the prime mover 5, It can be said that the output efficiency is good. This is because the heat transfer of the air passing through the stack 2 (honeycomb ceramic 12) and the stack 2 (honeycomb ceramic 12) is promoted by the rising airflow generated by heating the lower side of the prime mover 5, and the degree of energy conversion is increased. This is thought to be due to improvement.

  As described above, according to the thermoacoustic engine of this embodiment, the stack 2 (honeycomb ceramic 12) is arranged vertically on the first upright portion 1a arranged vertically of the loop-shaped pipe 1, and the stack 2 ( The high temperature side heat source 3 (sheath heater 13) is provided at the lower end of the honeycomb ceramic 12), and the low temperature side heat source 4 (low temperature side heat exchanger 11) is provided at the upper end of the stack 2 (honeycomb ceramic 12). Ascending airflow is generated from the high temperature side heat source 3 (sheath heater 13) provided at the lower end of the ceramic 12), and the heat transfer by the ascending airflow effectively acts on the generation of sound waves. In this sense, in the thermoacoustic engine, the conversion efficiency from heat to sound waves can be further improved, and the intensity (pressure / flow velocity) of sound waves in the pipe line of the looped pipe 1 can be further increased. For this reason, output as a thermoacoustic engine is specified by strictly specifying the arrangement of the high temperature side heat source 3 (sheath heater 13) and the low temperature side heat source (low temperature side heat exchanger 11) with respect to the stack 2 (honeycomb ceramic 12). Efficiency can be further improved.

[Third Embodiment]
Next, a third embodiment of the thermoacoustic engine of the present invention will be described in detail with reference to the drawings.

  Patent Document 1 described above describes in which position of the stack the stack is arranged, but from the viewpoint of improving the output efficiency, strict examination of the position of the stack has not been made. Therefore, in this embodiment, the arrangement of the prime mover 5 and the characteristics of the sound wave in the pipe line were experimentally confirmed under the condition that the aspect ratio of the loop pipe 1 is greatly different.

  FIG. 20 shows a schematic configuration diagram of a thermoacoustic engine. In this embodiment, as shown in FIG. 20, the loop-shaped pipe 1 includes a first corner C1, a second corner C2, a third corner C3, and a fourth corner C4. The center P1 of the stack 2 is disposed between the second corner C2 and a position that is 23% of the entire length of the loop-shaped pipe 1 from the first corner C1. Here, the direction from the first corner C1 to the second corner C2 is the traveling direction of the sound wave generated from the prime mover 5 (the direction from the normal temperature side of the prime mover 5 toward the high temperature side where the heater is heated). In this experiment, as shown in FIG. 21, a thermoacoustic engine having a structure similar to the thermoacoustic engine of FIG. 2 was used.

  In FIG. 22, various conditions regarding the thermoacoustic engine used in the experiment of this embodiment are shown in a table. As can be seen from this table, the honeycomb cell radius r is “0.47 mm”. The honeycomb length (stack length) Lh is “60 mm”. The input power to the sheath heater 13 is “180 W”. The pipe line height LV in FIG. 20 is “1140 mm”. Similarly, the pipe line width LH in FIG. 20 is “260 mm”. The pipe length (full length) L of the loop-shaped pipe 1 is “2800 mm”. The pressure in the looped pipe 1 (pressure in the pipe line) is “1 atm”. The pressure / velocity measurement position is “0.55 × L from prime mover”, that is, “55%” of the pipe length L from prime mover 5.

  FIG. 23 is a graph comparing the flow velocity waveforms depending on the distance X (ratio to the pipe length L) X from the first corner C1 to the center of the stack 2 (honeycomb ceramic 12). Here, the flow velocity waveform is compared between “X = 0.154L”, “X = 0.236L”, and “X = 0.296L”. In this graph, the negative flow velocity on the vertical axis means that the flow direction changes due to the oscillating flow. As is apparent from FIG. 23, it can be seen that the waveform is different between “X = 0.296L” and other cases. In FIG. 24, as shown in FIG. 14, the refrigerator 20 is arranged at the pressure / flow velocity measurement position, and the measurement results of the temperature difference between both end faces of the honeycomb ceramic 22 in the refrigerator 20 are compared and shown. As is apparent from FIG. 24, in the case of “X = 0.296L”, it is understood that the temperature difference is small and the refrigerating capacity is inferior compared to the other cases. When the aspect ratio of the pipe is changed in the direction in which the pipe width LH is increased, the value of the distance X at which the refrigeration capacity becomes inferior is slightly increased. In this case, the range described in Patent Document 1 is used. Exclude on reason. Therefore, the upper limit of the distance X can be considered to be about “X = 0.236L”. Also, from the results shown in FIG. 24, it can be seen that the lower limit of the distance X is near the corner. Under the conditions shown in the table of FIG. 22, “X = 0.154L” was obtained, and it was found that the refrigerating capacity could be obtained even if the range described in Patent Document 1 was not satisfied.

  As described above, according to the thermoacoustic engine of this embodiment, the center of the stack 2 (honeycomb ceramic 12) is a position where the center of the looped pipe 1 is 23% of the total length of the looped pipe 1 from the first corner C1. Since it is arrange | positioned between 2nd corners C2, the flow velocity characteristic in the loop-shaped piping 1 becomes a characteristic which is easy to generate | occur | produce a refrigeration output. For this reason, by specifying the arrangement of the stack 2 (honeycomb ceramic 12) in the looped pipe 1 more strictly in this way, the output efficiency as the thermoacoustic engine can be further improved, and the refrigeration output is further improved. be able to.

  The present invention is not limited to the above-described embodiments, and can be implemented as follows without departing from the spirit of the invention.

  For example, in the third embodiment, one prime mover 5 is provided in the loop-shaped pipe 1, but a plurality of prime movers may be arranged in parallel in the loop-shaped pipe as shown in FIG. In this case, the conversion efficiency from heat to sound waves is improved without increasing the length of the stack constituting each prime mover more than necessary. For this reason, it is effective to make the stack the required length.

The schematic block diagram which shows a thermoacoustic engine. Sectional drawing which shows the structure of the thermoacoustic engine used for experiment. The exploded sectional view showing the principal part of a motor. The top view which shows the end surface of a honeycomb ceramic. The front view which shows a honeycomb ceramic. The enlarged view which shows a part of FIG. The top view which shows a sheath heater. The front view which shows a sheath heater. The front view which shows a low temperature side heat exchanger. The right view of FIG. The table | surface which shows various conditions regarding the thermoacoustic engine used in experiment. The graph which shows an experimental result. The schematic block diagram which shows a thermoacoustic engine. Sectional drawing which shows the structure of a thermoacoustic refrigeration apparatus. The exploded sectional view showing a refrigerator. The front view which shows an endothermic board. The right view of FIG. The table | surface which shows various conditions regarding the thermoacoustic engine used in experiment. The graph which shows an experimental result. The schematic block diagram which shows a thermoacoustic engine. Sectional drawing which shows the structure of the thermoacoustic engine used for experiment. The table | surface which shows various conditions regarding the thermoacoustic engine used in experiment. The graph which shows an experimental result. The graph which shows an experimental result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Loop-shaped piping 1a 1st upright part 1b 2nd upright part 2 Stack 3 High temperature side heat source 4 Low temperature side heat source 5 Engine 11 Low temperature side heat exchanger 12 Honeycomb ceramic 13 Sheath heater Lh Stack length L Pipe length C1 1st Corner C2 Second Corner C3 Third Corner C4 Fourth Corner

Claims (5)

A looped pipe filled with a predetermined gas;
A columnar stack arranged in the loop-shaped pipe;
In a thermoacoustic engine comprising a high temperature side heat source provided at one end of the stack and a low temperature side heat source provided at the other end of the stack,
A thermoacoustic engine characterized in that a length of the stack is 20 mm or more and a temperature gradient inside the stack is 4 K / mm or more. 2. The thermoacoustic engine according to claim 1, wherein a plurality of prime movers configured by combining the stack, the high temperature side heat source, and the low temperature side heat source are arranged in parallel. A looped pipe filled with a predetermined gas;
A columnar stack arranged in the loop-shaped pipe;
In a thermoacoustic engine comprising a high temperature side heat source provided at one end of the stack and a low temperature side heat source provided at the other end of the stack,
The loop-shaped pipe includes an upright portion arranged vertically, and the stack is arranged vertically in the upright portion;
The thermoacoustic engine, wherein the high temperature side heat source is provided at a lower end of the stack, and the low temperature side heat source is provided at an upper end of the stack. A looped pipe filled with a predetermined gas;
A columnar stack arranged in the loop-shaped pipe;
In a thermoacoustic engine comprising a high temperature side heat source provided at one end of the stack and a low temperature side heat source provided at the other end of the stack,
The loop-shaped pipe includes a first corner, a second corner, a third corner, and a fourth corner;
A thermoacoustic engine comprising: the center of the stack being disposed between a position that is 23% of the total length of the loop-shaped pipe from the first corner and the second corner. 5. The thermoacoustic engine according to claim 4, wherein a plurality of prime movers configured by combining the stack, the high temperature side heat source, and the low temperature side heat source are arranged in parallel.

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