JP7422402B2 - thermoacoustic silencer - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) Publication date October 26, 2020 Publication Japanese Society of Noise Control Engineers 2020 Autumn Research Presentation Collected Papers Published by Japan Society of Noise Control Engineers (published on the web)・Download URL: http://www.ince-j.or.jp/ http://www.ince-j.or.jp/20autumn_meeting_online http://www.ince-j.or.jp/journa ls_download2 ) < Materials> Research presentation overview Web page <Resources> Published presentations Research paper excerpts

The present invention relates to a thermoacoustic silencer that uses a thermoacoustic engine to attenuate sound.

Silencers used in vehicles and the like have been used to muffle noise by absorbing sound using sound-absorbing materials or by changing the shape of the muffler. In a muffler using a sound absorbing material, for example, a sound absorbing material such as glass wool is placed in the middle of a flow path, and when sound waves pass through the flow path, some of the acoustic energy is absorbed by the viscous resistance and friction generated in the sound absorbing material. It converts the energy into thermal energy and silences the sound. Silencers with different shapes include, for example, an "expanded type" in which the cross-sectional area of the flow path is expanded, and a "resonant type" in which a resonator is attached to increase the temperature by interfering with sound waves.

Conventional silencers have muted sound by utilizing viscous dissipation caused by the passage of sound waves through thin tubes. However, with this structure, the exhaust pressure of the engine is lost due to the muffling section, resulting in a pressure drop. This pressure drop also affects engine performance. Particularly in recent years, turbo engines that utilize engine exhaust pressure to increase output have been attracting attention, and it is desired to reduce the pressure loss caused by the muffling portion as much as possible.

Patent Document 1 describes a piping device that includes a sound source that inputs sound waves into piping and a thermoacoustic device provided downstream of the sound source. Patent Document 1 describes that a thermoacoustic device is used to attenuate the acoustic intensity of a supplied sound wave through a thermoacoustic effect.

Japanese Patent Application Publication No. 2004-258543

According to the piping device described in Patent Document 1, the attenuation rate of sound waves is low, and an effect of attenuating acoustic energy that can be applied to a muffler for a vehicle or the like cannot be obtained. Additionally, because the piping equipment needs to be filled with working gas, it cannot be directly connected to pipes that are an open noise source such as vehicles, and it is necessary to separate the sound waves and input them into the piping equipment. However, there is a problem in that it is a large-scale device.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermoacoustic muffler that can produce a high muffling effect while preventing pressure loss caused by the muffling portion.

One aspect of the present invention includes a flow path into which an oscillating flow of working gas is input from the upstream side and an open downstream side, and a flow path provided in the flow path, maintained in a wet state by a liquid, and formed by a thermoacoustic device. The heat storage device is a thermoacoustic muffler that has a temperature gradient formed from an upstream side to a downstream side and that attenuates the acoustic power of the working gas.

According to the present invention, by using a heat storage device that generates a thermoacoustic phenomenon, it is possible to prevent pressure loss caused by the muffling portion and attenuate acoustic power. Furthermore, according to the present invention, by keeping the heat storage device in a wet state, it is possible to amplify the effect of attenuating acoustic power using phase change.

The present invention may include a supply unit that supplies the liquid that keeps the heat storage device in a wet state.

According to the present invention, the heat storage device can always be kept in a wet state by the supply section, and the effect of attenuating acoustic power due to phase change can be maintained.

In the flow path of the present invention, a plurality of the heat storage devices may be arranged in succession.

According to the present invention, even if the acoustic power attenuation rate of each heat storage device is low, by connecting the heat storage devices in series in multiple stages, the effect of attenuating the acoustic power can be amplified.

The heat storage device of the present invention may be configured to attenuate sound waves in a predetermined band.

According to the present invention, the acoustic power of sound waves in a desired frequency band can be attenuated.

The present invention may include a plurality of the heat storage devices that attenuate sound waves in different bands.

According to the present invention, acoustic power in a wide frequency band can be attenuated.

The heat storage device of the present invention may have a plurality of thin tube channels through which the oscillating flow of the working gas flows, and the diameter of the thin tube channels may be adjusted depending on the frequency band.

According to the present invention, it is possible to form a heat storage device that attenuates acoustic power in a desired frequency band.

The boiling point of the liquid of the present invention may be adjusted to a temperature close to the temperature on the upstream side of the heat storage device.

According to the present invention, the heat on the upstream side of the heat storage device kept in a moist state can be utilized effectively to the maximum extent, and the acoustic power attenuation effect can be improved.

The temperature on the upstream side of the heat storage device of the present invention may be adjusted to a temperature near the boiling point of the liquid.

According to the present invention, it is possible to prevent the liquid that keeps the heat storage device in a wet state from volatilizing more than necessary due to the heat on the upstream side of the heat storage device, and it is possible to attenuate acoustic power while suppressing consumption of the liquid. Can be done.

According to the present invention, a high silencing effect can be produced while preventing pressure loss caused by the silencing portion.

1 is a diagram showing the configuration of a thermoacoustic silencer according to an embodiment of the present invention. It is a figure which shows the verification result of the silencing effect of a thermoacoustic silencer. FIG. 3 is a diagram showing the configuration of a thermoacoustic silencer according to Modification 1. FIG. 3 is a diagram showing the relationship between the rotation speed of an internal combustion engine and the frequency band of exhaust sound. FIG. 7 is a diagram showing the configuration of a thermoacoustic muffler according to a second modification. 7 is a diagram showing the configuration of a thermoacoustic muffler according to modification 3. FIG.

Hereinafter, a thermoacoustic silencer according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the thermoacoustic silencer 1 includes a pipe P through which an oscillating flow of working gas flows, a heat storage device 2 provided in the pipe P, and a supply section that supplies liquid to the heat storage device 2. 10. The pipe P is formed to have an arbitrary pipe length depending on the area in which it is installed. The conduit P is, for example, a waveguide formed in the shape of a circular tube with a circular cross section. The pipe P is formed so that the oscillating flow propagates in the pipe axis direction. Note that the shape of the pipe P may be tubular, and for example, the cross section may be square or triangular.

The pipe line P has a flow path R formed therein. Working gas flows through the flow path R. The pipe P is formed into a straight pipe shape. The term "straight tubular shape" is a conceptual description, and it does not necessarily have to be formed in a straight line, but a curved part or a bent part may be formed in one flow path R depending on the shape of the installation target. For example, an oscillating flow of working gas is input into the flow path R from the upstream R1 side. The downstream R2 side of the flow path R is open to the atmosphere.

For example, a sound source that generates sound waves is connected to the upstream side of the pipe P. The sound source is, for example, an internal combustion engine, and an exhaust pipe of the internal combustion engine is connected to the upstream side of the pipe P. The sound source may be connected to any source other than the internal combustion engine as long as it generates sound waves that need to be silenced. For example, exhaust gas from an internal combustion engine flows into the flow path R from the upstream side as working gas. In the flow path R, a heat storage device 2 that attenuates the acoustic power S of the working gas is provided between the upstream R1 side and the downstream R2 side.

The heat storage device 2 is a thermoacoustic prime mover. In the heat storage device 2, a thermoacoustic phenomenon occurs due to heat input, and the acoustic power S is attenuated. The heat storage device 2 may be any thermoacoustic device that utilizes an oscillating flow, for example, a thermoacoustic device that utilizes a phase-change oscillating flow or the like. A first heat exchanger 2C that supplies high-temperature heat is provided on the upstream side of the heat storage device 2, and a second heat exchanger 2D that supplies heat for cooling is provided on the downstream side.

The heat storage device 2 is formed with, for example, one to a plurality of small-diameter thin tube channels 2R through which working gas flows. The thin tube flow path 2R is provided in the heat storage device 2 in a number from one to an infinite number so as to open along the streamline direction of the working gas. The heat storage device 2 has a large number of thin tube channels 2R formed of, for example, a honeycomb structure made of ceramics or a structure in which a large number of thin stainless steel mesh plates are laminated in the streamline direction. The heat storage device 2 may be made of a material such as a glass pipe that forms a fine flow path through which the oscillating flow can pass, but is not limited to these materials.

In addition to the shape of the thin tube flow path 2R, in addition to the shape formed of foamed metal or steel wool, the shape of the thin tube flow path 2R may be filled with metal powder, or may be formed by rolling a heat-resistant thin film with unevenness. It may also be formed by combining thin plates with different shapes and thicknesses.

The thin tube flow path 2R has a cross section formed in, for example, a circular tube shape, a parallel plate shape, a polygonal shape, or a pin array shape. The thin tube channel 2R may be formed to have a plurality of randomly shaped channels by combining thin plates or the like having different channel diameters (channel widths), channel shapes, and thicknesses. The thin tube channel 2R may be formed by repeatedly forming channels in a plurality of patterns by a predetermined combination of thin plates or the like having different channel diameters (channel widths), channel shapes, and thicknesses.

When the thermoacoustic muffler 1 is applied as a muffler for an internal combustion engine, the thin tube flow path 2R is preferably formed in a straight tube shape with little resistance in order to suppress a drop in exhaust pressure. When using the thermoacoustic muffler 1 regardless of the reduction in exhaust pressure, the capillary flow path 2R may be formed in any of the above-mentioned patterns.

In the heat storage device 2, when a temperature difference occurs between one end portion 2A on the upstream side and the other end portion 2B on the downstream side along the streamline direction of the working gas, a thermoacoustic phenomenon using an oscillating flow occurs. In order to generate a temperature gradient in the heat storage device 2, the amount of heat from the heat source is input.

The heat source supplies an amount of heat that has a temperature difference with respect to room temperature as the ambient temperature. Here, normal temperature is, for example, a temperature stably obtained by the surrounding environment such as the atmosphere, seawater, river water, lake water, geothermal heat, or the like. In addition to the ambient temperature, the normal temperature may be a temperature generated from another heat source that can stably supply heat so as to create a temperature difference with the heat source.

The heat source uses, for example, unused heat that is discarded as waste heat. The heat source provides heat at a high temperature relative to room temperature. The heat source is not particularly limited as long as the amount of heat can be obtained, and for example, the amount of heat obtained from sunlight, geothermal heat, etc., or the amount of heat generated from engines, factories, various facilities, etc. can be used. For example, the amount of heat is input to the first heat exchanger 2C.

The first heat exchanger 2C is formed to exchange heat at one end 2A of the heat storage device 2 via a heat medium. The first heat exchanger 2C exchanges heat with one end portion 2A of the heat storage device 2 via a heat medium having a temperature difference from room temperature. The second heat exchanger 2D is formed to exchange heat at the other end 2B of the heat storage device 2. The second heat exchanger 2D exchanges heat with the other end 2B of the heat storage device 2 via a normal temperature heat medium.

When the thermoacoustic silencer 1 is used as a silencer for an internal combustion engine, the upstream side of the heat storage device 2 is kept at a high temperature by supplying high-temperature exhaust gas to the upstream side, and there is a gap between the heat storage device 2 and the downstream side. Since a temperature difference occurs, the first heat exchanger 2C does not necessarily need to be provided. Similarly, when the thermoacoustic muffler 1 is used as a muffler for an internal combustion engine, the heat storage device 2 may be used as a second heat exchanger if there is a temperature difference between the downstream side and the upstream side due to exposure to room temperature. The container 2D does not necessarily have to be provided. Not limited to internal combustion engines, if the heat storage device 2 is configured such that the upstream side is kept at a high temperature and a predetermined temperature difference is generated between the upstream side and the downstream side, the first heat exchanger 2C, the second heat exchanger 2, etc. The exchanger 2D does not necessarily have to be provided.

As a method of inputting the amount of heat, high temperature amount of heat is supplied to the one end 2A side of the heat storage device 2 by, for example, the first heat exchanger 2C. For example, a heat medium such as high-temperature gas or liquid is circulated through the first heat exchanger 2C. On the other hand, the other end 2B side of the heat storage device 2 is supplied with the amount of heat at room temperature by, for example, the second heat exchanger 2D. For example, a heat medium such as gas or liquid at room temperature is circulated through the second heat exchanger 2D.

In this case, a temperature gradient is generated from one end 2A of the heat storage device 2, which is the high temperature side, toward the other end 2B of the heat storage device 2, which is the normal temperature side. By the above method, when a temperature gradient (temperature difference) is generated between one end 2A and the other end 2B of the heat storage device 2, the acoustic power S of the sound wave of the working gas flowing through the flow path R in the heat storage device 2 is increased. It can be attenuated.

As described above, it has been known that when a negative temperature gradient is generated in the heat storage device 2 from the upstream side to the downstream side of the oscillating flow, the acoustic power S is attenuated. The inventors continued their intensive research and found that in a state where the temperature gradient of the heat storage device 2, which is maintained in a moist state, is negative, the acoustic power S can be reduced by using the effect of the phase change from liquid to gas. It was found that the damping effect increases. The heat storage device 2 is provided with a supply unit 10 that supplies a liquid for keeping the heat storage device 2 in a moist state, for example, in order to cause a phase change from liquid to gas.

The supply unit 10 supplies liquid to the heat storage device 2 and keeps the heat storage device 2 in a wet state with the liquid. The supply unit 10 supplies liquid in an amount that evaporates in the heat storage device 2 so as to replenish it. For example, water is used as the liquid in consideration of ease of handling and availability. Liquids other than water may be used as long as they are volatile and harmless. For example, oils and fats, alcohol, fuel, etc. may be used as the liquid. The liquid may be a highly viscous grease-like liquid as long as it is volatile. Further, liquids having different boiling points may be mixed and used.

Exhaust gas emitted from burning fuel contains water vapor. The supply unit 10 does not necessarily need to be provided as long as the water vapor of the exhaust gas is supplied to the heat storage device 2 connected to the internal combustion engine on the upstream side to maintain a moist state. Moreover, the supply unit 10 does not necessarily need to be provided as long as the humid state of the heat storage device 2 is maintained during the flow time of the working gas to be muted. For example, when a shock wave such as an explosion sound of a working gas is muffled discretely within a short period of time by the heat storage device 2 which has been kept in a moist state in advance, the moist state of the heat storage device 2 is maintained. In addition, the supply unit 10 is not necessarily provided when the environment in which the thermoacoustic silencer 1 is installed causes a large amount of liquid to exist around the heat storage device 2, and the heat storage device 2 is exposed to the liquid and maintained in a moist state. It doesn't have to be.

In the heat storage device 2, the greater the temperature difference between the upstream side and the downstream side, the greater the silencing effect, so it is desirable that the temperature on the upstream side is kept as high as possible. When the temperature of the upstream part of the heat storage device 2 is high, if a liquid with a boiling point lower than that near that temperature is selected as the liquid to keep the heat storage device 2 in a moist state, the liquid will volatilize more quickly and the liquid will be consumed more rapidly. By selecting a liquid having a boiling point close to the temperature on the upstream side of the heat storage device 2, phase change can be efficiently utilized in the heat storage device 2. That is, it is more preferable that the boiling point of the liquid is adjusted to a temperature close to the temperature on the upstream side of the heat storage device 2. For example, if the temperature on the upstream side of the heat storage device 2 is around 100° C., water may be selected as the liquid. Moreover, when the liquid that keeps the heat storage device 2 in a moist state is determined, it is more preferable that the temperature on the upstream side of the heat storage device 2 is adjusted to a temperature near the boiling point of the liquid. When the temperature on the upstream side of the heat storage device 2 fluctuates greatly, the liquid that keeps the heat storage device 2 in a moist state may be a mixture of liquids having different boiling points. By doing so, since there is a liquid that volatilizes in any temperature range upstream of the heat storage device 2, phase change can be efficiently utilized in the heat storage device 2.

The heat storage device 2 is formed to attenuate sound waves in a predetermined frequency band. In the heat storage device 2, the diameter of the capillary channel 2R is adjusted according to the frequency band of the sound wave to be silenced. The diameter of the capillary flow path 2R is formed to become smaller as the frequency band becomes higher. For example, the narrow tube flow path 2R is formed smaller in diameter when attenuating sound waves in a high frequency band than when attenuating sound waves in a low frequency band.

Next, an experiment to confirm the silencing effect of the thermoacoustic silencer 1 will be explained.

In the experiment, the upstream side of the heat storage device 2 into which the sound waves are input was set to the high temperature side, and the downstream side was set to the low temperature side. For example, the temperature on the downstream side of the heat storage device 2 was fixed at 27°C, and the temperature on the high temperature side was set in three patterns: 47°C, 67°C, and 87°C. In this state, the attenuation rate of the acoustic power S was measured when the temperature on the high temperature side of the heat storage device 2 was changed every three patterns. Further, the change in the attenuation rate with respect to frequency was measured by changing the frequency of the sound wave input to the upstream side of the flow path R in the range of 20 Hz to 160 Hz. At this time, the acoustic power S was measured on the upstream and downstream sides of the heat storage device 2, and the attenuation rate of the acoustic power S was calculated by defining downstream acoustic power/upstream acoustic power.

In the experiment, the heat storage device 2 was kept moist by adding water to the heat storage device 2. In addition, in order to confirm the effect of keeping the heat storage device 2 in a wet state, the attenuation rate of the acoustic power S of the heat storage device 2 kept in a dry state with the same specifications and the same experimental conditions was also measured, and the measurement results were compared. It was done.

FIG. 2 shows experimental results of the silencing effect of the thermoacoustic silencer 1. As shown in the figure, the horizontal axis represents the frequency, and the vertical axis represents the measurement results of the attenuation rate according to the frequency. In the figure, the measurement results of the humid state and the dry state of the heat storage device 2 are shown by the difference in the colors of the plots. In the figure, differences in the high temperature side of the heat storage device 2 are shown by differences in the shape of the plots. In the figure, the smaller the value of the attenuation rate, the greater the attenuation effect. As shown in the figure, it is shown that, over the entire frequency range, the heat storage device 2 in a wet state has a greater damping effect than the heat storage device 2 in a dry state. It is shown that, over the entire frequency range, the damping effect of the wet heat storage device 2 is greater as the temperature on the high temperature side is higher than that of the dry heat storage device 2.

When the temperature on the high temperature side is the highest at 87° C. and the frequency is 20 Hz, the attenuation rate of the heat storage device 2 in the wet state is about 0.8, while the attenuation rate of the heat storage device 2 in the wet state is about 0.8. The ratio is about 0.4. Therefore, it was confirmed that the heat storage device 2 in a wet state has about twice the attenuation effect as compared to the heat storage device 2 in a dry state. From the above results, it was confirmed that when the heat storage device 2 is kept in a moist state, the sound silencing effect is very large.

As described above, according to the thermoacoustic silencer 1, the acoustic power S can be attenuated by forming a negative temperature gradient on the upstream and downstream sides of the heat storage device 2. According to the thermoacoustic silencer 1, inside the heat storage device 2, the flow velocity of sound waves is essentially reduced without causing viscous dissipation, so that the acoustic power S is attenuated without causing pressure loss in principle. can be done.

In addition, according to the thermoacoustic silencer 1, by keeping the heat storage device 2 in a wet state, the thermoacoustic phenomenon occurring in the heat storage device 2 is accompanied by a phase change between liquid and vapor, thereby achieving a damping effect on the acoustic power S. can be made larger. According to the thermoacoustic muffler 1, it is possible to realize a muffler that can obtain a large muffling effect while simplifying the device configuration, and prevents a pressure drop in the exhaust gas that leads to a decrease in performance.

[Modification 1]
As described above, it was confirmed that the thermoacoustic silencer 1 has a greater attenuation effect on the acoustic power S by creating a temperature difference between the upstream side and the downstream side of the humid heat storage device 2. By connecting a plurality of humid heat storage devices 2 along the waveguide direction of the flow path R, further damping effect can be obtained. In the following description, the same names and symbols will be used for the same components as in the above embodiment, and overlapping descriptions will be omitted as appropriate.

As shown in FIG. 3, in the thermoacoustic silencer 1A according to the first modification, a plurality of heat storage devices 2 are connected in series in multiple stages in the flow path R. Each of the plurality of heat storage units 2 is set to have a high temperature side on the upstream side and a low temperature side on the downstream side in the input direction of the sound wave. According to the thermoacoustic silencer 1A, the acoustic power S can be attenuated every time the vibration flow generated from the sound source passes through each heat storage device 2. For example, according to the thermoacoustic silencer 1A, if the acoustic power S becomes 1/2 each time the oscillating flow passes through each heat storage device 2, then the acoustic power S after passing through the three stages of heat storage devices 2 is reduced to 1/2. It can be attenuated up to /8. At this time, the specifications and temperature settings of each heat storage device 2 do not necessarily have to be set to be the same, and the narrow tube flow path 2R is formed, and the upstream side of the input direction of the sound wave is set to the high temperature side. All you have to do is keep it. When applying the thermoacoustic silencer 1A to a vehicle, the upstream heat storage device 2 may be a catalyst device.

As described above, according to the thermoacoustic silencer 1A according to the first modification, the plurality of heat storage devices 2 are connected in series in multiple stages in the flow path R, so that the acoustic power can be attenuated in stages. can.

[Modification 2]
As shown in FIG. 4, in the internal combustion engine, the frequency band of the exhaust sound increases as the rotational speed increases. When the thermoacoustic muffler 1 is applied to a muffler for an internal combustion engine, it is necessary to have a muffling effect in a wide band.

As shown in FIG. 5, in the thermoacoustic silencer 1B according to the modified example, a plurality of heat storage devices 2 formed to attenuate sound waves in different frequency bands are connected in series in multiple stages, for example. As described above, each heat storage device 2 is formed so as to attenuate acoustic power in different predetermined frequency bands A, B, and C (see FIG. 4) by adjusting the diameter of the thin tube flow path 2R. The numbers of frequency bands A, B, and C are merely examples, and may be increased or decreased. The frequency bands of each heat storage device 2 may overlap each other (see FIG. 4). In order to enhance the silencing effect according to each frequency band A, B, and C, one or more heat accumulators 2 may be connected in series in multiple stages as in Modification 1. The arrangement order of each heat storage device 2 is an example, and is not limited to this.

As described above, according to the thermoacoustic silencer 1B according to the second modification, the plurality of heat storage units 2 formed to attenuate sound waves in different frequency bands are connected in series in multiple stages, so that the sound source It is possible to obtain a silencing effect in a wide frequency band for internal combustion engines.

[Modification 3]
In Modification 2, the plurality of heat storage units 2 are connected in series in multiple stages. Although it is possible to obtain a high silencing effect in a wide frequency band by connecting a plurality of heat storage units 2 in series in multiple stages, there is a risk that resistance will occur when sound waves pass through the narrow tube flow path 2R, and the overall exhaust resistance will increase. There is.

As shown in FIG. 6, in the thermoacoustic silencer 1C, for example, channels RA, RB, and RC each having a plurality of heat storage devices 2 connected in series in multiple stages are arranged downstream of the channel R depending on the frequency band. It is formed by branching on the sides. Valves 20A, 20B, and 20C, which can open and close their openings, are provided downstream of the flow paths RA, RB, and RC, respectively. In the thermoacoustic silencer 1C, the valves 20A, 20B, and 20C are adjusted to the open state in the respective frequency bands to be muted, and are adjusted to the closed state in the other frequency bands. That is, the valves 20A, 20B, and 20C are opened and closed according to the rotational speed of the internal combustion engine, and attenuate acoustic power in a wide frequency band. The valves 20A, 20B, and 20C may be provided upstream of the flow paths RA, RB, and RC.

As described above, according to the thermoacoustic silencer 1C, the channels RA, RB, and RC each having a plurality of heat storage devices 2 connected in series in multiple stages are branched to the downstream side of the channel R depending on the frequency band. By being formed as such, it is possible to attenuate acoustic power in a wide frequency band and prevent an increase in exhaust resistance.

The thermoacoustic silencer according to the embodiment described above may be installed in a muffler section of an automobile or a ship. In addition, thermoacoustic silencers can be installed if a duct, a heat storage device, or a porous body are installed to create a temperature gradient, so they can be installed in industrial facilities and equipment such as boilers and exhaust ducts. It can also be used for sound deadening. As long as the requirements for installing a duct, a heat storage device, a porous body, and creating a temperature gradient are satisfied, it can be used not only for the above-mentioned purposes. Furthermore, thermoacoustic silencers are applicable regardless of the following parameters present as design factors:
・Type of working gas, average pressure ・Type of liquid to be added ・Porous body to be installed ・Flow path diameter, length, material of heat storage ・Size, length, shape of duct (circular pipe, rectangular pipe, etc.)
・Changes in the cross-sectional area of heat storage units and ducts ・Number of heat storage units ・Number and shape of acoustic power generation sources

1, 1A, 1B, 1C Thermoacoustic silencer 2 Heat storage device 2A One end 2B Other end 2C First heat exchanger 2D Second heat exchanger 2R Capillary flow path 10 Supply section 20A, 20B, 20C Valve P Pipe line R Channel R1 Upstream R2 Downstream RA, RB, RC Channel S Sound power

Claims (8)

A flow path into which an oscillating flow of working gas is input from the upstream side and is open on the downstream side;
a heat storage device provided in the flow path, kept in a wet state by a liquid, and formed by a thermoacoustic device;
The heat storage device has a temperature gradient formed from an upstream side to a downstream side, and attenuates the acoustic power of the working gas.
Thermoacoustic silencer. comprising a supply unit that supplies the liquid that keeps the heat storage device in a wet state;
Thermoacoustic silencer according to claim 1. In the flow path, a plurality of the heat storage devices are connected in series,
The thermoacoustic silencer according to claim 1 or 2. The heat storage device attenuates sound waves in a predetermined frequency band.
The thermoacoustic silencer according to any one of claims 1 to 3. comprising a plurality of the heat storage devices that attenuate sound waves in different frequency bands;
The thermoacoustic silencer according to claim 4. The heat storage device is formed with a plurality of capillary channels through which the oscillating flow of the working gas flows, and the diameter of the capillary channels is adjusted according to the frequency band.
Thermoacoustic silencer according to claim 5. The liquid has a boiling point adjusted to a temperature close to the temperature on the upstream side of the heat storage device.
The thermoacoustic silencer according to any one of claims 1 to 6. The temperature on the upstream side of the heat storage device is adjusted to a temperature near the boiling point of the liquid.
The thermoacoustic silencer according to any one of claims 1 to 6.

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