JP5434680B2 - Thermoacoustic engine - Google Patents

Description

  The present invention relates to a thermoacoustic engine that prevents a decrease in output due to an increase in reflected waves.

  In order to extract energy from waste heat, research and development of Stirling engines have been actively conducted. Stirling engine types include α type, β type, γ type, and free piston type. On the other hand, in recent years, research and development of thermoacoustic engines that have a simple structure and do not have moving parts composed of pistons and cranks have been actively conducted in the United States and the like.

  The thermoacoustic engine maintains a temperature gradient between the heater and the cooler in the axial direction of the tube, a heater that exchanges heat with the high-temperature heat source, a cooler that exchanges heat with the low-temperature heat source, and the like. A regenerator is arranged. When the working fluid in the tube is locally heated in one place and cooled in another, a part of the heat energy is converted into acoustic energy, which is mechanical energy, and the working fluid in the tube undergoes self-excited vibration, Acoustic vibration, that is, sound waves are generated in the tube.

  As shown in FIG. 3, in a conventional thermoacoustic engine 51, a working fluid is filled in a loop tube 52 formed by closing a cylindrical tube in a loop shape, and heat from outside is taken into the loop fluid 52. A heater 53 having fins for cooling and a cooler 55 having fins for extracting heat from the working fluid to the outside are disposed at intervals in the longitudinal direction of the cylindrical tube, and between the heater 53 and the cooler 55. A regenerator 54 is arranged. A prime mover (prime mover) 56 is configured by sequentially arranging the heater 53, the regenerator 54, and the cooler 55.

JP 2008-101910A Japanese Patent No. 3050543 JP 2001-207909 A

  In the conventional thermoacoustic engine 51, the flow passage cross-sectional area of the working fluid is not uniform over the entire length of the loop, and the flow passage cross-sectional area is reduced at the prime mover 56.

  As shown in detail in FIG. 4, the heater 53 has a heater cylindrical tube 71 having the same shape and dimensions as the cross-sectional contour with respect to the loop tube 52 and open at both ends, and the inside of the heater cylindrical tube 71. Are arranged with a plurality of internal fins 72 parallel to the flow path, and a plurality of external fins 73 are provided on the outer periphery of the heater cylindrical tube 71. Similarly, the cooler 55 has a cooler cylindrical tube 74 having the same shape and dimensions as the cross-sectional contour with respect to the loop tube 52 and open at both ends, and the cooler cylindrical tube 74 is parallel to the flow path. A plurality of internal fins 75 are arranged, and a plurality of external fins 76 are provided on the outer periphery of the cooler cylindrical tube. The regenerator 54 has a regenerator cylindrical tube 77 having the same cross-sectional outline shape and dimensions as the loop tube 52 and open at both ends, and a plurality of wire meshes traversing the flow path inside the regenerator cylindrical tube 77. 78 are stacked in the longitudinal direction. As a result, the loop tube 52 on one side communicates with the heater cylindrical tube 71, the regenerator cylindrical tube 77, the cooler cylindrical tube 74, and the loop tube 52 on the opposite side with the same cross-sectional outline and shape.

  In the prime mover 56, in the heater 53, external heat is absorbed by the external fins 73, the heat is conducted to the internal fins 72, and heat is released from the internal fins 72 to the working fluid. In the cooler 55, heat exchange opposite to that of the heater 53 is performed.

  In the prime mover 56, neither the heater 53 nor the cooler 55 can reduce the thickness of the internal fins 72, 75 so as to ensure the heat transfer performance of the internal fins 72, 75. On the other hand, the presence of the internal fins 72 and 75 in the heater cylindrical tube 71 or the cooler cylindrical tube 74 having the same size as the loop tube 52 allows the working fluid in the heater cylindrical tube 71 or the cooler cylindrical tube 74 to flow. The cross-sectional area of the flow path is smaller than the cross-sectional area of the working fluid in the loop pipe 52. When the thickness of the internal fins 72 and 75 is increased, the flow path cross-sectional area in the heater cylindrical tube 71 or the cooler cylindrical tube 74 is further reduced. Also in the regenerator 54, since the wire mesh 78 exists in the regenerator cylindrical pipe 77, the flow path cross-sectional area becomes smaller than the flow path cross-sectional area in the loop pipe 52.

  Incidentally, in general, in a thermoacoustic engine, it is desirable to reduce reflection of generated sound waves. When reflection of a sound wave occurs, a standing wave is excited from a traveling wave. Since the thermodynamic cycle of the thermoacoustic engine is realized by traveling waves, it is desirable to make the proportion of the traveling wave component higher than the proportion of the standing wave component. Therefore, suppressing reflection of sound waves is a necessary issue for improving the output of the thermoacoustic engine.

  The reflection of the sound wave occurs at a place where the cross-sectional area of the working fluid flow path changes. Conversely, reducing the change in the cross-sectional area of the working fluid flow path as much as possible is effective in suppressing reflection of sound waves.

  In the prime mover 56, the thermoacoustic engine 51 of FIG. 3 has a markedly reduced flow path cross-sectional area, so that the reflection of sound waves is significant, causing the output of the thermoacoustic engine 51 to decrease.

  Accordingly, an object of the present invention is to provide a thermoacoustic engine that solves the above-described problems and prevents a decrease in output due to an increase in reflected waves.

  In order to achieve the above object, the present invention provides a heat exchanger in which a prime mover comprising a heater having internal fins, a regenerator containing a wire mesh, and a cooler having internal fins is installed in a loop tube filled with a working fluid. In the acoustic engine, the cross-sectional area of the working fluid in the prime mover is the same as the cross-sectional area of the working fluid in the loop pipe.

  The present invention exhibits the following excellent effects.

  (1) A decrease in output due to an increase in reflected waves can be prevented.

It is a block diagram of the thermoacoustic engine which shows one Embodiment of this invention. FIG. 2 is a side cross-sectional view and flow path cross-sectional area distribution diagram in the vicinity of a prime mover of the thermoacoustic engine of FIG. 1. It is a block diagram of the thermoacoustic engine provided with the conventional motor | power_engine. It is a side sectional view and a flow path sectional area distribution map in the vicinity of a prime mover of a conventional thermoacoustic engine.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, a thermoacoustic engine 1 according to the present invention includes a loop tube 2 filled with a working fluid, a heater 3 having internal fins, a regenerator 4 containing a wire mesh, and a cooling having internal fins. In the thermoacoustic engine 1 in which the prime mover 6 composed of the vessel 5 is installed, the cross-sectional area of the working fluid in the prime mover 6 is the same as or slightly larger than the cross-sectional area of the working fluid in the loop tube 2.

  The loop tube 2 is a cylindrical tube closed in a loop shape, and is filled with a working fluid. The working fluid is preferably a gas such as air, helium, nitrogen, or argon.

  As shown in detail in FIG. 2, the heater 3 includes a heater cylindrical tube 21 having both ends that are larger than the loop tube 2 and open at both ends, and the heater cylindrical tube 21 is parallel to the flow path. A plurality of internal fins 22 are arranged, and a plurality of external fins 23 are provided on the outer periphery of the heater cylindrical tube 21. Similarly, the cooler 5 has a cooler cylindrical tube 24 whose both ends are larger than the loop tube, and a plurality of internal fins 22 parallel to the flow path are arranged inside the cooler cylindrical tube 24. A plurality of external fins 23 are provided on the outer periphery of the cooler cylindrical tube 24. The regenerator 4 has a regenerator cylindrical tube 25 whose both ends are larger than the loop tube 2, and a plurality of wire meshes 26 that cross the flow path are laminated in the longitudinal direction inside the regenerator cylindrical tube 25. The

  As a result, the dimension (inner diameter) increases or decreases stepwise at the boundary between the loop tube 2 on one side and the heater cylindrical tube 21 and the boundary between the loop tube 2 on the opposite side of the cooler cylindrical tube 24.

  On the other hand, the flow path cross-sectional area in the heater 3 is obtained by subtracting the total cross-sectional area of the internal fins 22 from the cross-sectional area of the heater cylindrical tube 21. Looking at the distribution of the cross-sectional area of the flow path, the cross-sectional area of the flow path in the heater 3 is the same as the cross-sectional area of the flow path in the loop pipe 2 as indicated by the broken line or in the loop pipe 2 as indicated by the solid line. It is larger than the channel cross-sectional area. Similarly, the channel cross-sectional area in the cooler 5 is equal to or larger than the channel cross-sectional area in the loop pipe 2. The flow path cross-sectional area in the regenerator 4 is obtained by subtracting the total cross-sectional area of the skeleton portion of the wire mesh 26 from the cross-sectional area of the regenerator cylindrical tube 25. The flow path cross-sectional area in the regenerator 4 is the same as the flow path cross-sectional area in the loop pipe 2 as shown by a broken line or larger than the flow path cross-sectional area in the loop pipe 2 as shown by a solid line, Here, the flow path cross-sectional area in the heater 3 and the cooler 5 is larger.

  Hereinafter, the operation of the thermoacoustic engine 1 of the present invention will be described.

  In the thermoacoustic engine 1 of the present invention, the cross-sectional area of the working fluid in the prime mover 6 is equal to or larger than the cross-sectional area of the working fluid in the loop pipe 2.

  When the cross-sectional area of the working fluid in the prime mover 6 is the same as the cross-sectional area of the working fluid in the loop pipe 2, the flow path breaks over the entire loop length of the thermoacoustic engine 1 (the combined length of the loop pipe 2 and the prime mover 6). Since there is no change in the area, there is no reflection of sound waves at the change location of the channel cross-sectional area. As a result, more traveling waves are obtained as compared to standing waves, output reduction due to an increase in reflected waves can be prevented, and the output of the thermoacoustic engine 1 can be increased.

  When the cross-sectional area of the working fluid in the prime mover 6 is larger than the cross-sectional area of the working fluid in the loop pipe 2, the resistance of the flow passage in the prime mover 6 is reduced, so that sound wave attenuation is suppressed.

  As described above, according to the present invention, in the thermoacoustic engine 1 in which the prime mover 6 is installed, the cross-sectional area of the working fluid in the prime mover 6 is the same as the cross-sectional area of the working fluid in the loop pipe 2. As a result, the energy conversion efficiency is improved, so that the effect of lowering the oscillation start temperature (temperature difference between the heater 3 and the cooler 5 necessary for oscillation) can be obtained compared to the conventional case. Conventionally, for example, when the cooler 5 in the prime mover 6 is at a normal temperature, the heater 3 having a temperature considerably higher than the normal temperature is required. A heater 3 with a low temperature can be used.

  In addition, according to the present invention, the energy conversion efficiency is improved, so that a greater acoustic intensity can be obtained than before.

  In addition, according to the present invention, since the energy conversion efficiency is improved, it is possible to oscillate with a smaller amount of input energy than before.

  In addition, according to the present invention, it is possible to oscillate with a small amount of input energy, and thus it is possible to reduce the size. By miniaturization, the volume of the thermoacoustic engine 1 can be made smaller than before.

1 Thermoacoustic Engine 2 Loop Tube 3 Heater 4 Regenerator 5 Cooler 6 Motor

Claims (1)

In a thermoacoustic engine in which a prime mover comprising a heater having internal fins, a regenerator containing a wire mesh, and a cooler having internal fins is installed in a loop tube filled with a working fluid,
The thermoacoustic engine, wherein a cross-sectional area of a working fluid in the prime mover is the same as a cross-sectional area of the working fluid in the loop pipe.

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