Patent Grant
8443599
The present invention relates to an apparatus for conducting energy conversion between thermal energy and acoustic energy through the use of thermoacoustic effect. In particular, it relates to, for example, a thermoacoustic apparatus in which energy conversion and energy exchange, temperature control, acoustic control, and the like are conducted efficiently through the use of thermoacoustic effect.
Previously, thermoacoustic apparatuses have been known as apparatuses for conducting energy conversion between thermal energy and acoustic energy. For example, apparatuses shown in Patent Document 1 and Patent Document 2, as described below, have been known.
A thermoacoustic apparatus shown in this Patent Document 1 will be described. As shown in
Furthermore, regarding such a thermoacoustic apparatus, an apparatus for improving the energy conversion efficiency has also been proposed. For example, in Patent Document 2 described below, as shown in
Incidentally, in the case where a relatively long narrow portion as shown in Patent Document 2 described above is disposed, the transfer of heat is reduced and the energy conversion efficiency can be improved after the acoustic wave is generated, but the energy conversion cannot be conducted until the standing wave and the traveling wave are generated in the loop tube. At this time, if rapid generation of acoustic wave through self excitation in the thermoacoustic apparatus, as shown in
Accordingly, the present invention has been made in consideration of the above-described issues. It is an object of the present invention to provide a thermoacoustic apparatus capable of reducing the time elapsed until an acoustic wave is generated and improving the energy conversion efficiency significantly.
That is, in order to solve the above-described issues, a thermoacoustic apparatus according to the present invention is provided with an acoustic wave generator for generating an acoustic wave, an acoustic heat exchanger including a pair of heat exchangers set on the high temperature side and on the low temperature side and a stack having a plurality of transmission paths in the inside, and a hollow member including the above-described acoustic wave generator and the acoustic heat exchanger, the thermoacoustic apparatus converting acoustic energy generated in the hollow member to thermal energy by using the above-described acoustic heat exchanger, wherein a particle velocity acceleration portion for forcedly accelerating the particle velocity of the acoustic wave by reducing the inner diameter of the hollow member is disposed at a midpoint position between the acoustic wave generator and the acoustic heat exchanger in the hollow member or/and a particle velocity reduction portion for forcedly reducing the particle velocity of the acoustic wave generated in the hollow member is disposed in the vicinity of the acoustic heat exchanger in the hollow member.
Preferably, the hollow member is formed from a loop tube.
Consequently, in the case where the particle velocity acceleration portion is disposed, the particle velocity at that point can be made relatively larger than the particle velocities at other points, and the position of a node of the sound pressure (antinode of particle velocity) can be set forcedly so that a stable acoustic wave can be generated rapidly. Alternatively, in the case where the particle velocity reduction portion for reducing the particle velocity is disposed, the position thereof can be forcedly set at an antinode of the sound pressure (node of particle velocity). Consequently, a stable acoustic wave can be generated rapidly. Incidentally, the “position at which the particle velocity is a maximum” or the “position at which the particle velocity is a minimum” here refers to not only the position at which the particle velocity is strictly the maximum or the minimum” but also positions at a distance within the range of λ/4 from the center position at which the particle velocity is the maximum or the minimum, where λ represents a maximum wavelength of the acoustic wave generated in the hollow member.
In such an invention, the particle velocity acceleration portion is configured to be slidable along the inside of the hollow member.
Furthermore, the particle velocity reduction portion is formed from an opening portion of a branch tube connected to the hollow member.
Consequently, the inner diameter of the connection portion of the hollow member and the opening portion increases and, thereby, the particle velocity becomes small relatively. This position can be forcedly set at the position of an antinode of the sound pressure.
Then, in the case where this branch tube is connected, the length of this branch tube is specified to be a length suitable for generating, in the branch tube, the same wavelength as an integral multiple of the one-quarter wavelength of the acoustic wave generated in the hollow member.
Consequently, the wavelength of the acoustic wave generated in the hollow member can be made an integral multiple of the one-quarter wavelength of the acoustic wave generated in the branch tube, and a stable acoustic wave can be generated rapidly in the hollow member through the use of a resonance phenomenon.
Alternatively, in the case where the particle velocity reduction portion is disposed, a transmission path blocking portion for blocking transmission of the working fluid is disposed with respect to the stack. Here, in the case where the transmission path blocking portion is disposed with respect to the stack, it may be disposed in the stack or be disposed at an end portion of the stack.
In this case as well, the energy conversion efficiency can be improved by forcedly setting the position of the sound pressure.
Alternatively, in the case where the particle velocity reduction portion is disposed, a blocking component for blocking the hollow portion of the hollow member is disposed in the hollow member. Here, the blocking component may be a tabular member for blocking the hollow portion or be a film member in the shape of a thin film.
In such a case as well, the position of the blocking member can be forcedly set at the position at which the particle velocity is a minimum, and a stable acoustic wave is generated rapidly, so that the energy conversion efficiency can be improved.
According to the present invention, the particle velocity acceleration portion is disposed and, thereby, the particle velocity at that position can be made relatively larger than the particle velocities of other positions. Consequently, the position of the node of the sound pressure (antinode of particle velocity) can be forcedly set, so that a stable acoustic wave can be generated rapidly. Alternatively, the particle velocity reduction portion for forcedly reducing the particle velocity is disposed and, thereby, the position thereof can be forcedly set at the position of the antinode of the sound pressure (node of the particle velocity). Consequently, a stable acoustic wave can be generated rapidly.
A thermoacoustic apparatus 1 according to a first embodiment of the present invention will be described below with reference to drawings.
As shown in
The loop tube 2 constituting the thermoacoustic apparatus 1 is configured to include a pair of linear tube portions 2a disposed in the vertical direction relative to the ground, arm portions 2c disposed at upper and lower corner portions of the linear tube portions 2a, and connection tube portions 2b connected to the linear tube portions 2a with the arm portions 2c therebetween, each being composed of a hollow metal pipe or the like. These linear tube portions 2a, arm portions 2c, and connection tube portions 2b have nearly equal inner diameters except the narrow portion 21 having the reduced inner diameter and are connected to each other through flanges or the like, although not shown in the drawing. On the other hand, the narrow portion 21 has a narrow path 22 having an inner diameter relatively smaller than those of other sections and is set to be a node of the sound pressure of the acoustic wave generated in the loop tube 2 by increasing the particle velocity in the narrow path 22. It is favorable that such a narrow portion 21 is disposed nearly in the vicinity of the midpoint position between the acoustic wave generator 3 and the acoustic heat exchanger 4. In the case where the narrow portion 21 is disposed at such a position, a standing wave composed of one wave component in which antinodes of sound pressure are the position of the acoustic wave generator 3 and the position of the acoustic heat exchanger 4 can be generated easily. This state is explained with reference to
Incidentally, this narrow portion 21 may cause fluctuations in the energy conversion efficiency significantly depending on the position of disposition. Therefore, in the present embodiment, the position in the loop tube 2 is made changeable. As for a method for changing the position of the narrow portion 21 in the loop tube 2, for example, a method is conceived, in which an elastic resin or the like is wounded around the peripheral portion of the narrow portion 21 formed into a cylindrical shape, and the narrow portion 21 is inserted into the loop tube 2 by being pushed while the elastic resin is shrunk. Consequently, the narrow portion 21 is pushed in up to an optimum position and can be fixed at an appropriate position. In this regard, in the case where the position of the narrow portion 21 is pushed in, it is necessary that the position is changed by a pushing operation inside the loop tube 2. However, this position change can also be conducted through an operation outside the loop tube 2. In an example of such a method, as shown in
In this regard, the case where the cylindrical narrow portion 21 is attached is explained with reference to
The acoustic wave generator 3 generates a standing wave and a traveling wave in the loop tube 2 and is configured to include a first high-temperature-side heat exchanger 31 and a first low-temperature-side heat exchanger 33 and a first stack 32 sandwiched therebetween in order to generate an acoustic wave through self excitation in the present embodiment. On the other hand, the acoustic heat exchanger 4 converts the acoustic energy based on the acoustic wave generated in the loop tube 2 to thermal energy and is configured to include the second high-temperature-side heat exchanger 41 and the second low-temperature-side heat exchanger 43 and a second stack 42 sandwiched therebetween similarly to the acoustic wave generator 3.
Among them, the first high-temperature-side heat exchanger 31, the first low-temperature-side heat exchanger 33, the second high-temperature-side heat exchanger 41, and the second low-temperature-side heat exchanger 43 are formed from metal members and inside surfaces thereof are provided with transmission paths which are a plurality of holes for transmitting the standing wave and the traveling wave. Among these heat exchangers, the first high-temperature-side heat exchanger 31 is set at, for example, about 30° C. to 700° C. through heating by inputting an electric power, waste heat, or the like from the outside. On the other hand, the first low-temperature-side heat exchanger 33 is set at a temperature of, for example, 18° C. to 20° C. relatively lower than that of the first high-temperature-side heat exchanger 31 by circulating water in the surroundings.
The first stack 32 and the second stack 42 take on cylindrical shapes having outer diameters which touch the inner wall of the loop tube 2 and are formed from a raw material containing ceramic, sintered metal, gauze, nonwoven metal fabric, or nonmetallic fibers. Furthermore, a plurality of transmission paths 34 and 44 penetrating in the axis direction of the loop tube 2 are disposed in the inside. The transmission paths 34 and 44 may be paths linearly formed from honeycomb-like or grid-like multiholes or be meandering paths which looks as if cotton or the like is compressed.
The acoustic wave generator 3 having the above-described configuration is disposed below the center of the linear tube portion 2a while the first high-temperature-side heat exchanger 31 is disposed on the upper side. The acoustic wave generator 3 is disposed below the center of the linear tube portion 2a on the grounds that an acoustic wave is generated rapidly through the use of an updraft generated when the first high-temperature-side heat exchanger 31 is heated and that a warm working fluid generated when the first high-temperature-side heat exchanger 31 is heated is prevented from entering the first stack 32. A large temperature gradient is formed in the first stack 32 by preventing the warm working fluid from entering the first stack 32, as described above.
On the other hand, the acoustic heat exchanger 4 is disposed at a distance of about L/2 from the acoustic wave generator 3, where the total circuit length of the loop tube 2 is assumed to be L. In attachment of this acoustic heat exchanger 4 to the loop tube 2, the second high-temperature-side heat exchanger 41, around which water is circulated, is disposed on the upper side and, in addition, the second low-temperature-side heat exchanger 43 for outputting low-temperature heat to the outside is disposed on the lower side. Then, as shown in
The operation of the thermoacoustic apparatus 1 having the above-described configuration will be described below.
In the case where high heat is applied to the first high-temperature-side heat exchanger 31 on the acoustic wave generator 3 side and, in addition, the first low-temperature-side heat exchanger 33 is set at low temperatures by circulating water in the surroundings, a temperature gradient is formed between the first high-temperature-side heat exchanger 31 and the first low-temperature-side heat exchanger 33. Then, as shown in
The thus generated acoustic wave is propagated in the loop tube 2 and vibrates particles of the working fluid. At this time, regarding the narrow portion 21, the inner diameter is relatively smaller than the inner diameter of the surrounding loop tube 2 and, therefore, the particle velocity of the working fluid is larger than those of the other portions. Consequently, the position of this narrow portion 21 can be forcedly set at the position of the antinode of the particle velocity, and among acoustic waves with various wavelengths, an acoustic wave having the antinode of the particle velocity at this position can be generated rapidly.
The thus generated standing wave and traveling wave are transferred as acoustic energy to the acoustic heat exchanger 4 side.
On the acoustic heat exchanger 4 side, the working fluid in the second stack 42 is expanded and compressed on the basis of the standing wave and the traveling wave propagated along the loop tube 2. In the transmission paths 44 of the second stack 42, as shown in
In this manner, according to the above-described embodiment, since the narrow portion 21 is disposed at the midpoint position between the acoustic wave generator 3 and the acoustic heat exchanger 4, the particle velocity at that portion can be increased, that portion is forcedly set at the antinode of the particle velocity in the standing wave, and an acoustic wave can be generated rapidly. Furthermore, in the case where an acoustic wave is generated through self excitation, the acoustic wave can also be generated rapidly even when a temperature difference between the first high-temperature-side heat exchanger 31 and the first low-temperature-side heat exchanger 33 is reduced, and the energy conversion efficiency can be improved by significantly lowering an amount of input heat and an input temperature.
Incidentally, in the above-described first embodiment, the acoustic wave generator 3 and the acoustic heat exchanger 4 are disposed in the loop tube 2. However, the tube is not necessarily in a looped shape, and as shown in
Moreover, in the above-described embodiment, the acoustic wave generator 3 for generating an acoustic wave through self excitation is disposed, although not limited to the acoustic wave generator 3 through self excitation. For example, a speaker or the like which forcedly generates an acoustic wave may be employed.
Furthermore, in the above-described embodiment, the narrow portion 21 is disposed at a midpoint position between the acoustic wave generator 3 and the acoustic heat exchanger 4, although not limited to this. The narrow portion 21 may be disposed in the vicinity of an antinode of the particle velocity of the standing wave desired to be generated in the loop tube 2.
In addition, in the above-described embodiment, each of the acoustic wave generator 3 and the acoustic heat exchanger 4 is disposed at one place. However, the number of the unit is not necessarily one, and a plurality of units may be disposed. Alternatively, a plurality of narrow portions 21 may be disposed in a hollow member.
A second embodiment according to the present invention will be described below with reference to
Regarding the thermoacoustic apparatus 1 according to the second embodiment, a branch tube 2e is connected to a loop tube 2 including the acoustic wave generator 3 and the acoustic heat exchanger 4, an acoustic wave of an integral multiple of the one-quarter wavelength of the standing wave generated in the loop tube 2 is generated in the branch tube 2e, an acoustic wave is generated rapidly through the use of a resonance phenomenon and, in addition, it is made possible to set an opening portion 2d of the connection portion at the position of the antinode of the sound pressure. The configuration of the thermoacoustic apparatus 1 in the second embodiment will be described below in detail.
As in the first embodiment, the loop tube 2 is configured to include linear tube portions 2a, arm portions 2c, and connection tube portions 2b. Furthermore, the branch tube 2e is connected to the linear tube portion 2a. These linear tube portions 2a, arm portions 2c, connection tube portions 2b, and branch tube 2e have nearly equal inner diameters, and the narrow portion 21 and the like are not disposed in the configuration. The acoustic wave generator 3 is disposed in the loop tube 2 and, in addition, the acoustic heat exchanger 4 is attached in the branch tube 2e. These acoustic wave generator 3 and acoustic heat exchanger 4 are attached with a distance of about L/2. In the present embodiment, the acoustic heat exchanger 4 is attached in the vicinity of the opening portion 2d on the branch tube 2e side, but may be attached on the linear tube portion 2a side, as shown in
Then, as a feature of the present embodiment, the branch tube 2e is connected to the loop tube 2 in the vicinity of the acoustic heat exchanger 4 by disposing the opening portion 2d, and a standing wave with the same wavelength as that of the standing wave generated in the loop tube 2 is generated in the inside thereof. An end portion 25 opposite to the opening portion 2d of the branch tube 2e may be in a closed state, or be in an opened state. In the case where the branch tube 2e with the opposite-side end portion 25 being in the closed state is connected, as shown in an upper drawing in
The branch tube 2e connected to the loop tube 2 may be in a bent state or be in a linear state. In the case where the tube is linear, reflection at the bent portion and the like are eliminated and, therefore, an acoustic wave can be generated rapidly. On the other hand, in the case where the branch tube 2e in a bent shape is used, a main linear tube portion is made parallel to the linear tube portion 2a of the loop tube 2 and, thereby, the thermoacoustic apparatus 1 itself can be made compact. Furthermore, in the case where a bent branch tube 2e is connected, the branch tube 2e can also be connected from the outside of the loop tube 2. However, if such a configuration is employed, the thermoacoustic apparatus 1 becomes large. Therefore, as shown in
In the above-described embodiment, the branch tube 2e is attached and, thereby, the position at which the particle velocity becomes a minimum is set. However, the position at which the particle velocity becomes a minimum can be forcedly set by devising the configurations of the first stack 32 and the second stack 42. This configuration will be described with reference to the second stack 42 as an exemplification and
Furthermore, in
According to the above-described second embodiment, the branch tube 2e having the opening portion 2d for reducing the particle velocity is connected and, thereby, the position of the opening portion 2d can be forcedly set at the position of the antinode portion of the sound pressure. Consequently, a standing wave can be generated rapidly. Furthermore, in the present embodiment as well, in the case where an acoustic wave is generated through self excitation, the acoustic wave can be generated rapidly even when a temperature difference between the first high-temperature-side heat exchanger 31 and the first low-temperature-side heat exchanger 33 is reduced, and the energy conversion efficiency can be improved by reducing an amount of input heat.
In the above-described two embodiments, the first embodiment having the configuration in which the narrow portion 21 is disposed and the second embodiment in which the branch tube 2e is disposed are explained separately. However, these configurations can be used at the same time. Moreover, the second stack 42 including the transmission path blocking portion 45 may be used together with them.
In the above-described embodiment, high-temperature heat is input into the first high-temperature-side heat exchanger 31, and low-temperature heat is output from the second low-temperature-side heat exchanger 43. However, low-temperature heat may be input from the first low-temperature-side heat exchanger 33, and high-temperature heat may be output from the second high-temperature-side heat exchanger 41, conversely.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-238378 | Sep 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/053155 | 2/21/2007 | WO | 00 | 10/16/2009 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/029521 | 3/13/2008 | WO | A |
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| 4114380 | Ceperley | Sep 1978 | A |
| 4355517 | Ceperley | Oct 1982 | A |
| 5996345 | Hofler | Dec 1999 | A |
| 6032464 | Swift et al. | Mar 2000 | A |
| 6164073 | Swift et al. | Dec 2000 | A |
| 6658862 | Swift et al. | Dec 2003 | B2 |
| 20060185370 | Watanabe et al. | Aug 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 11-344266 | Dec 1999 | JP |
| 2000-088378 | Mar 2000 | JP |
| 2005-188846 | Jul 2005 | JP |
| 2006-105009 | Apr 2006 | JP |
| 2006-189219 | Jul 2006 | JP |
| Entry |
|---|
| International Search Report of PCT/JP2007/053155; Mailing Date of Apr. 17, 2007. |
| Number | Date | Country | |
|---|---|---|---|
| 20100064680 A1 | Mar 2010 | US |
