JP5434613B2 - Thermoacoustic engine - Google Patents

Description

  The present invention relates to a loop-type thermoacoustic engine, and more particularly to a thermoacoustic engine having high heat exchange efficiency.

  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. This action can be seen thermodynamically as a prime mover. A thermoacoustic engine converts energy from heat energy into mechanical energy based on this principle.

  As shown in FIG. 3, a conventional loop-type thermoacoustic engine 31 is filled with a working fluid in a hollow cylindrical tube 32 closed in a loop shape, and takes heat from outside into the working fluid. A heater 33 having fins and a cooler 34 having fins for extracting heat from the working fluid to the outside are arranged at intervals in the axial direction of the pipe 32, and the regenerator is provided between the heater 33 and the cooler 34. 35 is arranged. The heater 33, the regenerator 35, and the cooler 34 are collectively referred to as a prime mover 36.

  As shown in FIG. 4, a plurality of internal fins 37 parallel to each other are arranged inside the heater 33 of the prime mover 36 along the axis of the tube 32. The cooler 34 has a similar structure. In the prime mover 36, in the heater 33, external heat is conducted from the outer periphery of the heater 33 to the internal fins 37, and heat is released from the internal fins 37 to the working fluid. In the cooler 34, heat exchange opposite to that of the heater 33 is performed.

JP 2008-101910A JP 2003-324932 A

  In order to improve the efficiency of heat exchange with the outside in the heater 33 and the cooler 34, it is conceivable to increase the heat receiving area in contact with the outside. Specifically, in the heater 33 and the cooler 34, since the outer periphery of the pipe 32 is in contact with the outside, the outer peripheral area of the pipe 32 is increased. In order to increase the outer peripheral area, the diameter of the tube 32 is increased.

  However, in the heater 33 and the cooler 34, when the diameter of the pipe 32 is increased, the heat receiving area in contact with the outside increases, but the heat exchange efficiency in the internal fins 37 decreases. This is because, as shown in FIG. 5, in the conventional thermoacoustic engine, a plurality of internal fins 37 parallel to each other are arranged along the axis of the tube in the heater 33 (same as the cooler 34). At this time, the internal fins 37a positioned toward the end in the alignment direction have a short length in the cross-sectional width direction. On the other hand, the internal fins 37b located near the center of the arrangement direction have a long length in the cross-sectional width direction. Such long internal fins 37b have a long distance from the outer periphery of the tube 32 in the vicinity of the center in the cross-sectional width direction, so that heat is hardly conducted. The fact that heat from the outside is difficult to conduct to the internal fins 37 means that the heat exchange efficiency is lowered, and the output of the thermoacoustic engine cannot be increased or generated for a certain amount of waste heat. The waste heat that is present cannot be absorbed properly.

  In order to improve this, it is conceivable to increase the thickness of the root of the internal fin 37 (near the boundary with the pipe 32). However, in order for sound waves to pass through the gap between the internal fins 37 without resistance, Since it is necessary to make the thickness of the fin 37 as thin as possible, the measure of increasing the thickness cannot be adopted.

  Further, in the conventional thermoacoustic engine, as shown in FIG. 5, the plurality of internal fins 37 are different in length in the cross-sectional width direction. Therefore, the temperature distribution is not uniform in the same cross section because the temperature differs between the vicinity of the center in the cross-sectional width direction of the long internal fin 37b and the short internal fin 37a.

  Further, in the conventional thermoacoustic engine, if the number of the internal fins 37 is increased too much, the interval between the internal fins 37 becomes narrow, and therefore the number of the internal fins 37 is small. Since the number of the internal fins 37 is small, the total area where the working fluid contacts the internal fins 37 in the heater 33 (cooler 34) is small, and the heat exchange efficiency is not good.

  Accordingly, an object of the present invention is to solve the above problems and provide a thermoacoustic engine having high heat exchange efficiency.

  To achieve the above object, the present invention provides a hollow cylindrical inner tube, an outer tube inner wall that covers the inner tube at a distance from the inner tube in the radial direction, and a radial distance from the inner wall of the outer tube. An outer wall that covers the inner wall of the outer tube, an inner end wall that covers an end portion of the inner tube and an end of the inner wall of the outer tube, and an axial distance from the inner end wall. A closed working fluid space surrounded by the inner tube, the outer tube inner wall, the outer tube outer wall, the inner end wall, and the outer end wall by including an outer end wall covering an end portion of the outer tube outer wall. Is formed, the working fluid space is filled with the working fluid, and a plurality of internal fins are provided between the inner wall of the outer tube and the outer wall of the outer tube at a distance from the end of the inner tube in the axial direction. Are arranged radially, and the outer wall of the outer tube and the outer part are spaced apart from the heater in the axial direction. A plurality of internal fins between the outer wall in which and a regenerator formed between the cooler which is arranged radially between the heater and the cooling device.

  The cross-sectional area of the cross section perpendicular to the axis in the inner pipe may be equal to the cross-sectional area of the cross section perpendicular to the axis in the portion between the inner wall of the outer pipe and the outer wall of the outer pipe.

  A closed shielding space surrounded by the inner tube, the inner wall of the outer tube, and the inner end wall may be formed.

  The shielding space may be a vacuum.

  The present invention exhibits the following excellent effects.

  (1) High heat exchange efficiency.

It is a sectional side view of the thermoacoustic engine which shows one Embodiment of this invention. It is a cross-sectional view in the heater of the thermoacoustic engine of FIG. It is a schematic block diagram of the conventional thermoacoustic engine. It is a sectional side view in the motor | power_engine part of the conventional thermoacoustic engine. It is a cross-sectional view in the heater of the 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 hollow cylindrical inner tube 2, an outer tube inner wall 3 that covers the inner tube 2 at a radial distance from the inner tube 2, and an outer tube An outer pipe outer wall 4 covering the outer pipe inner wall 3 at a radial distance from the pipe inner wall 3, an inner end wall 5 covering between the end of the inner pipe 2 and the end of the outer pipe inner wall 3, and an inner end And an outer end wall 6 that covers the end portion of the outer pipe outer wall 4 at an axial distance from the wall 5.

  A closed working fluid space 7 surrounded by the inner tube 2, the outer tube inner wall 3, the outer tube outer wall 4, the inner end wall 5 and the outer end wall 6 is formed. The working fluid space 7 includes an inner working fluid space 7a occupying the inner side of the inner tube 2, an outer working fluid space 7b occupying between the outer tube inner wall 3 and the outer tube outer wall 4, an inner end wall 5 and an outer side. A three-dimensional circulation structure is formed by the folded working fluid spaces 7c and 7d that occupy the space between the end walls 6 and communicate the inner working fluid space 7a and the outer working fluid space 7b. The working fluid space 7 is filled with the working fluid. The working fluid is preferably a gas such as air, helium, nitrogen, or argon.

  Further, a closed shielding space 8 surrounded by the inner tube 2, the outer tube inner wall 3 and the inner end wall 5 is formed. The shielding space 8 is intended to thermally shield between the inner tube 2 and the outer tube inner wall 3. In addition to gas filling, the shielding space 8 may contain a raw fiber aggregate such as cotton or glass wool, a porous member such as sponge or gypsum board, foamed resin, granular resin, or the like. In this embodiment, the shielding space 8 is a vacuum. Although the degree of vacuum is not limited, it should be effective for thermal shielding.

  Furthermore, the thermoacoustic engine 1 according to the present invention has a plurality of internal fins 9 (see FIG. 2) between the outer tube inner wall 3 and the outer tube outer wall 4 at a position spaced in the axial direction from the end of the inner tube 2. And a plurality of internal fins 11 (see FIG. 2) between the outer tube inner wall 3 and the outer tube outer wall 4 at locations spaced axially from the heater 10. Is provided with the coolers 12 arranged radially. Between the heater and the cooler, a laminated wire mesh, porous ceramics, and the like are disposed between the outer tube inner wall 3 and the outer tube outer wall 4 to form the regenerator 13. The motor 10, the regenerator 13, and the cooler 12 constitute a prime mover 14.

  As shown in FIG. 2, when the cross section of the heater 10 is viewed, the inner working fluid space 7a, the inner tube 2, the shielding space 8, the outer tube inner wall 3, and the outer working fluid space 7b are sequentially arranged from the axial center. The outer pipe outer wall 4 is coaxially arranged. The plurality of internal fins 9 are provided along a line passing through the diameter, and are arranged at equal circumferential angle intervals in the circumferential direction. The cross-sectional structure of the cooler 12 is the same as that of the heater 10, and internal fins 11 similar to the internal fins 9 are arranged.

  Next, the function and effect of the thermoacoustic engine 1 will be described.

  When an axial temperature gradient is formed in the working fluid in the prime mover 14, the working fluid in the working fluid space 7 causes self-excited vibration, and sound waves are generated. In FIG. 1, a traveling wave of a sound wave travels as indicated by an arrow. That is, the traveling wave is folded back radially inward from the heater 10 through the outer working fluid space 7b in the folded working fluid space 7c, and radially outer in the folded working fluid space 7d through the inner working fluid space 7a. And return to the cooler 12. Standing waves also occur along this path.

  At this time, the cross section of the heater 10 of the thermoacoustic engine 1 of the present invention (FIG. 2) and the cross section of the heater 33 of the conventional thermoacoustic engine (FIG. 5) are drawn at the same scale and compared. Then, since the diameter of the outer pipe outer wall 4 is larger than the diameter of the pipe 32, the thermoacoustic engine 1 of the present invention has a larger heat receiving area in the heater 10. Similarly, the cooler 12 has a larger heat receiving area. Since the heat receiving area is large, the heat exchange efficiency is improved.

  In the thermoacoustic engine 1 of the present invention, since the internal fins 9 (11) are arranged radially, there is no such thing as the conventional internal fin 37b that is difficult to conduct heat from the outside, and the heat exchange efficiency is high. improves.

  In the thermoacoustic engine 1 of the present invention, the widths (radial lengths) of all the internal fins 9 (11) are uniform and short, so the temperature distribution in the same cross section is uniform.

  The thermoacoustic engine 1 of the present invention can reduce the thickness of the internal fins 9 (11) as a result of improved heat conduction in the internal fins 9 (11). By reducing the thickness, the sound wave can pass through the gap between the internal fins 9 (11) without resistance.

  In the thermoacoustic engine 1 according to the present invention, the internal fins 9 (11) are radially outward from the inner wall 3 of the outer tube. Therefore, even if the number of the internal fins 9 (11) is increased, the mutual spacing between the internal fins 9 (11) Can be made sufficiently wide. For example, the internal fin 9 of FIG. 2 is provided about 1.5 times the internal fin 37 of FIG. By increasing the number of the internal fins 9 (11), the total area where the working fluid and the internal fins 9 (11) are in contact with each other is increased, and the heat exchange efficiency is improved. In addition, if it is going to arrange | position an internal fin radially in the thermoacoustic engine 31 by the conventional loop tube, an internal fin will concentrate in an axial center part, and is unpreferable.

  In the thermoacoustic engine 1 of the present invention, since the heat exchange efficiency is improved, the output of the thermoacoustic engine can be increased for a certain amount of waste heat, and the generated waste heat is fully absorbed. can do.

  Since the thermoacoustic engine 1 of the present invention does not form a loop as shown in FIG. 3, it can be smaller than the conventional thermoacoustic engine 31 and can be installed in a narrow space.

  In the thermoacoustic engine 1 of the present invention, a shielding space 8 exists between the inner tube 2 and the outer tube inner wall 3. Thereby, the motor | power_engine 14 and the inner pipe 2 which consist of the heater 10, the regenerator 13, and the cooler 12 are thermally shielded. If the inner tube 2 and the outer tube inner wall 3 are in contact with each other or are not shielded, the inner tube 2 at the position where the heater 10 is located approaches the temperature of the heater 10 and the position where the cooler 12 is located. The inner pipe 2 approaches the temperature of the cooler 12, and a reverse temperature gradient is formed. This is the same as the presence of a prime mover that generates a traveling wave in the direction opposite to that shown in FIG. 1 in the inner tube 2, and reduces the output of the thermoacoustic engine. In that respect, the thermoacoustic engine 1 of the present invention has the shielding space 8, so that it is possible to prevent a reverse temperature gradient from being formed in the inner tube 2.

  In the thermoacoustic engine 1 of the present invention, since the shielding space 8 exists, the heat input to the heater 10 is difficult to escape, and the heat exchange efficiency is improved.

  By the way, in the thermoacoustic engine 1, it is desirable for the cross-sectional area of the flow path of a working fluid not to change with places. Therefore, the cross-sectional area of the cross section perpendicular to the axis in the inner pipe 2 and the cross-sectional area of the cross section perpendicular to the axis in the portion between the inner wall 3 of the outer pipe and the outer wall 4 of the outer pipe may be made equal. Thereby, the cross-sectional area of the flow path of the working fluid in the inner working fluid space 7a is the same as the cross-sectional area of the flow path of the working fluid in the outer working fluid space 7b. Further, in this embodiment, the axial center portion of the outer end wall 6 is recessed in a trumpet shape so that the cross-sectional area of the working fluid flow path does not change in the folded working fluid spaces 7c and 7d.

DESCRIPTION OF SYMBOLS 1 Thermoacoustic engine 2 Inner tube 3 Outer tube inner wall 4 Outer tube outer wall 5 Inner end wall 6 Outer end wall 7 Working fluid space 8 Shielding space 9 Internal fin 10 Heater 11 Internal fin 12 Cooler 13 Regenerator 14 Motor

Claims (4)

A hollow cylindrical inner tube;
An inner wall of an outer tube covering the inner tube at a distance in a radial direction from the inner tube;
An outer pipe outer wall covering the outer pipe inner wall at a radial distance from the outer pipe inner wall;
An inner end wall covering between the end of the inner tube and the end of the inner wall of the outer tube;
An outer end wall that covers the end of the outer wall of the outer tube at an axial distance from the inner end wall;
A closed working fluid space surrounded by the inner pipe, the outer pipe inner wall, the outer pipe outer wall, the inner end wall, and the outer end wall is formed,
The working fluid space is filled with a working fluid,
A heater in which a plurality of internal fins are arranged radially between the inner wall of the outer tube and the outer wall of the outer tube at a location spaced in the axial direction from an end of the inner tube;
A cooler in which a plurality of internal fins are radially arranged between the inner wall of the outer tube and the outer wall of the outer tube at a location spaced apart from the heater in the axial direction;
A thermoacoustic engine comprising a regenerator formed between the heater and the cooler.   The cross-sectional area of the cross section perpendicular to the axis in the inner pipe is equal to the cross-sectional area of the cross section perpendicular to the axis in a portion between the inner wall of the outer pipe and the outer wall of the outer pipe. Thermoacoustic engine.   The thermoacoustic engine according to claim 1, wherein a closed shielding space surrounded by the inner tube, the inner wall of the outer tube, and the inner end wall is formed.   The thermoacoustic engine according to claim 3, wherein the shielding space is a vacuum.

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