JP2011149670A - Thermoacoustic engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoacoustic engine having an optimal number and positions of bent parts of a loop pipe. <P>SOLUTION: In the thermoacoustic engine 1, a motor 7 composed of a heater 4, a regenerator 5, and a cooler 6 aligned in series is installed to the loop pipe 3 composed of a cylindrical pipe 2 closed in a loop shape. The bent parts 8a, 8b of the cylindrical pipe 2 are formed at only two positions on the loop pipe 3. The bent angle at the respective bent parts 8a, 8b is 180°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermoacoustic engine in which a prime mover is provided in a loop tube, and relates to a thermoacoustic engine having an optimal number and position of bent portions of the loop tube.

  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 thermoacoustic engine 31 includes a prime mover 37 in which a heater 34, a regenerator 35, and a cooler 36 are sequentially arranged in a loop tube 33 formed by closing a cylindrical tube 32 in a loop shape. Is installed.

Japanese Patent No. 3050543 JP 2006-145176 A

  By the way, the conventional thermoacoustic engine 31 is configured by combining the loop tube 33 with four straight portions and four bent portions. That is, bent portions 39a and 39d bent by 90 ° with an appropriate bending radius such as a minimum bending radius are provided at both ends of the long side linear portion 38a where the prime mover 37 is installed. 38b and 38d are connected to each other and the motor 37 is connected to the long-side straight line portion 38c on the opposite side via the bent portions 39b and 39c. When viewed macroscopically, the loop tube 33 is closed by being bent into a quadrangle (rectangle).

  However, in general, in a thermoacoustic engine, if there is a bent portion, an antinode of flow velocity (= node of sound pressure) tends to occur there. For this reason, in the thermoacoustic engine 31 having the four bent portions 39a to 39d, four sound pressure nodes are easily formed.

  On the other hand, in general, in a thermoacoustic engine, there are two optimal sound pressure nodes in order to improve heat exchange efficiency. On the other hand, in the conventional thermoacoustic engine 31, since four nodes of the sound pressure are formed, the heat exchange efficiency is lowered, and the output of the acoustic energy is smaller than the input of the same thermal energy.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a thermoacoustic engine having an optimal number and position of bent portions of a loop tube.

  To achieve the above object, the present invention provides a thermoacoustic engine in which a prime mover in which a heater, a regenerator, and a cooler are arranged in order is installed in a loop tube formed by closing a cylindrical tube in a loop shape. Only two bent portions of the tube are formed in the loop tube, and the bending angle at each bent portion is 180 °.

  The two bent portions may be provided at positions of 30 to 35% and 80 to 85% of the entire length of the loop pipe in the direction from the prime mover to the heater.

  The present invention exhibits the following excellent effects.

  (1) A thermoacoustic engine having an optimal number and position of bent portions of a loop tube is provided.

(A) is the block diagram of the thermoacoustic engine which shows one Embodiment of this invention, (b) is the arrangement | positioning division figure which expanded and showed the loop pipe | tube. (A)-(d) is an enlarged view of the bending part by embodiment of this invention. It is a block diagram 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, in a thermoacoustic engine 1 according to the present invention, a heater 4, a regenerator 5, and a cooler 6 are arranged in order on a loop tube 3 formed by closing a cylindrical tube 2 in a loop shape. A thermoacoustic engine 1 in which a prime mover 7 is installed. In this thermoacoustic engine 1, the bent portions 8a and 8b of the cylindrical tube 2 are formed in only two places on the loop tube 3, and the bending angle at each of the bent portions 8a and 8b is 180 °.

  The loop tube 3 is configured by combining two straight portions 9a and 9b and two bent portions 8a and 8b. That is, the bent portions 8a and 8b bent by 180 ° are provided at both ends of the straight portion 9a where the prime mover 7 is installed, and the straight portions 9b opposite to the prime mover 7 are connected to the bent portions 8a and 8b. Thus, the cylindrical tube 2 is closed in a loop shape.

  The inside of the loop tube 3 is filled with a working fluid. The working fluid is preferably a gas such as air, helium, nitrogen, or argon.

  In the heater 4, a plurality of internal fins (not shown) are arranged inside the cylindrical tube 2, and a plurality of external fins (not shown) are arranged around the cylindrical tube 2. A cooler 6 is provided at a location separated from the heater 4 by an appropriate distance in the axial direction. Like the heater 4, the cooler 6 includes a plurality of internal fins disposed inside the cylindrical tube 2 and a plurality of external fins disposed around the cylindrical tube 2. Between the heater 4 and the cooler 6, a regenerator 5 made of a plurality of metal meshes laminated in the axial direction or porous ceramics is provided.

  The effects of the thermoacoustic engine of the present invention will be described.

  As already explained, in general, in a thermoacoustic engine, if there is a bending portion, an antinode of a flow velocity (= node of sound pressure) is likely to occur there. For this reason, in the thermoacoustic engine 1 of the present invention having only two bent portions 8a and 8b, only two sound pressure nodes are formed.

  On the other hand, as already explained, in a thermoacoustic engine, in general, there are two optimal sound pressure nodes in order to improve heat exchange efficiency. In the thermoacoustic engine 1 of the present invention, since only two sound pressure nodes are formed, the heat exchange efficiency is improved, and the output of the acoustic energy is increased with respect to the same heat energy input as compared with the conventional case.

  In order to further improve the above-described effects, the present inventors have decided where to place the bent portions 8a and 8b.

  For this purpose, 20 sections are defined by dividing the loop length into 20 parts with the center of the prime mover 7 (the center of the regenerator 5) as a reference. The oscillation temperature difference (the temperature difference between the heater and the cooler that is the minimum necessary for the generation of acoustic vibrations) is determined in what number and what section when viewed from the prime mover 7 the two bent portions 8a and 8b are arranged. We investigated by. A section having a small oscillation temperature difference is a preferable section for the arrangement of the bent portions 8a and 8b. If two sections having the smallest oscillation temperature difference are found, this indicates an optimum arrangement. The positions of the bent portions 8a and 8b are represented by the center position of the bent portion.

  As a result of the investigation, as shown in FIG. 1 (b), the bent portion 8a is arranged at a position of 30 to 35% of the total length of the loop tube 3 from the section A1 (6/20 to 7/20), that is, from the reference, It turned out that it is optimal to arrange | position the bending part 8b in section A2 (16 / 20-17 / 20), ie, the position of 80 to 85% of the full length of the loop pipe | tube 3 from a reference | standard.

  By disposing the bent portion 8a in the section A1 and arranging the bent portion 8b in the section A2, sound pressure nodes are formed in the sections A1 and A2. Therefore, the antinode of the sound pressure is formed at the exact center between the sections A1 and A2. Therefore, the antinode of the sound pressure is formed at a position away from the prime mover 7. In the thermoacoustic engine 31 of FIG. 3, the antinode of the sound pressure (= node of the flow velocity) is formed at the position of the prime mover 37. However, since the fluid displacement is small at the antinode of the sound pressure, large heat exchange can be performed. The heat exchange efficiency is low. On the other hand, in the thermoacoustic engine 1 of the present invention, since the nodes of the sound pressure are formed at the two bent portions 8a and 8b, the antinode of the sound pressure is formed at a position away from the prime mover 7. Therefore, the fluid displacement of an appropriate magnitude | size can be ensured in the heat exchanger (the heater 4 and the cooler 6) of the motor | power_engine 7, and heat exchange efficiency improves.

  Next, the definition and embodiment of the bending part will be described.

  The bent portions 8a and 8b in the present invention are formed by bending the cylindrical tube 2 by 180 °, and various forms are conceivable.

  The bent portion 21 in FIG. 2A is bent with a minimum radius of curvature from the start to the end of bending, the radius of curvature inside the bend is almost 0, and the radius of curvature outside the bend is the cylindrical tube 2. Is approximately equal to the diameter of Thereby, the linear part 9a and the linear part 9b contact | connect.

  The bent portion 22 in FIG. 2B is bent with an appropriate radius of curvature from the start to the end of bending. The radius of curvature outside the bend is larger by the diameter of the cylindrical tube 2 than the radius of curvature inside the bend. The straight line portion 9a and the straight line portion 9b are separated from each other.

  The bending portion 23 in FIG. 2 (c) is obtained by connecting the cylindrical tubes 2 cut at an angle of 45 ° with respect to the axis, and has a right-angle portion on both the outside of the bend and the inside of the bend. There is a very short straight line portion between the straight line portion 9a and the straight line portion 9b.

  The bending portion 24 in FIG. 2D maintains an appropriate radius of curvature from the start to the end of bending inside the bending, and the linear portion 9a and the linear portion 9b are separated from each other. On the outside of the bend, there are a rounded portion and a straight portion.

  In the present invention, a bending of a total of 180 ° is included in a range sufficiently short with respect to the loop length, for example, in a range corresponding to one of the 20 equal sections shown in FIG. For example, it is defined as being bent 180 ° at one place. Therefore, all shown in FIGS. 2A to 2D are included in the bent portion of the present invention. For example, the bending portion 22 in FIG. 2B and the bending portion 23 in FIG. 2C are included in a range A corresponding to one section from the start to the end of bending.

  As described above, according to the present invention, since the bent portions 8a and 8b having a bending angle of 180 ° are formed only in two places of the loop tube 3, the number of sound pressure nodes is two, and heat exchange is performed. Efficiency is improved.

  Further, according to the present invention, since the two bent portions 8a and 8b are provided in the direction from the prime mover 7 to the heater 4 at positions 30 to 35% and 80 to 85% of the total length of the loop tube 3. As a result, the energy conversion efficiency is improved and the oscillation start temperature is lowered as compared with the conventional case. Conventionally, for example, if the cooler 36 is at room temperature in the motor 37, the heater 34 having a temperature considerably higher than the room temperature is required. A heater 4 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.

  Further, according to the present invention, the energy conversion efficiency is improved. Therefore, when a refrigeration unit and a cooling unit are incorporated in the loop pipe 3 as a passive unit to form a refrigeration unit and a cooling unit, refrigeration / cooling is performed as compared with the conventional case. Performance can be improved dramatically.

  In addition, according to the present invention, the energy conversion efficiency is improved. Therefore, when a power generator is incorporated in the loop pipe 3 as a passive machine to generate power, the power generation amount can be dramatically improved as compared with the conventional case.

DESCRIPTION OF SYMBOLS 1 Thermoacoustic engine 2 Cylindrical tube 3 Loop tube 4 Heater 5 Regenerator 6 Cooler 7 Motor | generator 8a, 8b Bending part 9a, 9b Straight part

Claims (2)

In a thermoacoustic engine in which a prime mover in which a heater, a regenerator, and a cooler are arranged in order is installed in a loop tube formed by closing a cylindrical tube in a loop shape,
The thermoacoustic engine, wherein the bent portion of the cylindrical tube is formed in only two places on the loop tube, and the bending angle at each bent portion is 180 °.   2. The heat according to claim 1, wherein the two bent portions are provided in positions of 30 to 35% and 80 to 85% of the total length of the loop pipe in the direction from the motor to the heater. Acoustic engine.

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