CN108801444A - Array type thermoacoustic generator - Google Patents

Abstract

The invention provides an array type thermoacoustic generator, comprising at least two thermoacoustic generator units; a converging pipe with at least two input channels and an output port; and an open resonant tube; wherein each thermoacoustic generator The unit is connected to one input channel of the converging pipe, and the output ends of the input channels of the converging pipe are converging, and the output port is provided at the converging point, and the output port is connected to the open-type resonant tube, and each of the thermal-acoustic The value of the output impedance of the generator unit, the length of each input channel and the pipe diameter can make the intersection of the converging pipes form the effect of superposition of peaks and peaks, and superposition of troughs and troughs. The array type thermoacoustic generator of the present invention has high sound intensity, long action distance, and strong directivity; it can solve the problems of low sound pressure, complex devices, and poor repeatability of acoustic performance of existing low-frequency acoustic wave generators, and can be used for low-frequency long-distance noise experimental research. Industrial applications that provide basic sound sources as well as high-intensity sound sources.

Description

An Array Thermoacoustic Generator

technical field

The present invention relates to the technical field of acoustics, in particular, the present invention relates to the technical field of acoustic transducers.

Background technique

The acoustic transducers currently on the market are mainly electroacoustic transducers, including electrodynamic transducers, electromagnetic transducers, capacitive transducers, piezoelectric transducers, magnetostrictive transducers, etc. . Among them, electromagnetic transducers, capacitive transducers, piezoelectric transducers, and magnetostrictive transducers are not suitable for low-frequency playback due to their sound-generating principles. The electrodynamic transducer has a simple and firm structure, strong directivity, and high electro-acoustic efficiency, but it is generally difficult for electrodynamic transducers to obtain a large emission sound power.

In addition, there are currently some other types of acoustic transducers, such as hydrodynamic transducers, laser sound sources, and the like. Among them, the hydrodynamic sound source converts the mechanical energy of the fluid (gas or liquid) into vibration to excite the surrounding medium to generate sound waves. The hydrodynamic sound sources currently used include vibrating cavity whistle (Hartmann acoustic wave generator), Perlman acoustic wave generator, ultrasonic flute, reed whistle, single-hole or multi-hole injection rotary valve, and the like. Ultrasonic waves excited by Hartmann acoustic wave generators are widely used in plug removal in the oil extraction industry. The working frequency of this kind of hydrodynamic transducer almost falls in the kilohertz frequency band, and there is no report on low frequency research. This type of transducer uses fluid jet as a power source to excite sound waves. In the process of fluid sound generation, the flow field and sound field are coupled together, and its technology is not yet mature.

On the other hand, there is a thermoacoustic system based on the thermoacoustic effect in the field of refrigeration and power generation technology. The thermoacoustic effect refers to the thermodynamic cycle of compression, heating, expansion and heat release of compressible gas in the sound field from the solid boundary penetration depth layer, and converts heat energy into sound. As early as 1850, Sondhauss discovered that a glass ball closed at one end was connected to a hollow glass tube with an open end, and sound could be produced by heating the closed end. In 1962, Carter of the University of New Mexico in the United States and his student Feldman added a regenerator to the Sondhauss tube, which greatly enhanced the thermoacoustic effect in the tube, and developed the world's first thermoacoustic system with significant sound output. From the perspective of improving thermoacoustic conversion efficiency, increasing acoustic power, and engineering applications, thermoacoustic scholars from various countries have carried out extensive research on thermoacoustic heat engines, proposed a variety of innovative closed acoustic structures, and developed standing wave, traveling wave, etc. Type and cascade thermoacoustic heat engines to achieve the goal of gradual engineering of thermoacoustic technology. At present, the main application direction is to realize thermoacoustic conversion in a closed high-pressure thermoacoustic system, and use sound waves (mechanical waves) to realize mixed gas separation, refrigeration and power generation.

In 2010, Slaton developed an open standing wave thermoacoustic system, which only includes an open Helmholtz resonant tube, a plate stack, and heat exchangers at the hot and cold ends. The structure is simple, and the resonance frequency varies from 9Hz to 16Hz adjustable. Under the condition of input heat of 275W, the standing wave thermoacoustic generator can directly output the sound wave to the atmospheric space, and the outlet sound pressure level is 81dB. Slaton expects this type of open-type thermoacoustic system to be used as a thermoacoustic acoustic transducer in the study of low-frequency sound sources after the sound pressure level is greatly increased. The working process of the standing wave thermoacoustic generator is roughly divided into two steps: the thermal energy passes through the physical mechanism of the thermoacoustic effect, drives the gas medium to vibrate to generate sound waves, and radiates outward at the same time.

The Institute of Physical and Chemical Technology of the Chinese Academy of Sciences proposed an open-type traveling wave thermoacoustic generator (patent number: ZL201010592573.X), which uses heat to realize the conversion of heat and sound energy, which can greatly improve Slaton's open-type standing wave thermoacoustic The sound pressure level of the system. Furthermore, in 2011, Xie Xiujuan et al. successfully developed this new type of open-type traveling wave thermoacoustic generator. Under the input heat of 210W, the outlet sound pressure level can reach 133dB. The open-type thermoacoustic generator has a simple structure, low vibration temperature, and is easy to vibrate. Theoretically, it can be developed into a new type of acoustic transducer, which can play a role in the low-frequency field. However, this technology still has problems such as short radiation distance and insufficient external radiation sound intensity. There are two ways to increase the sound intensity of external radiation: one is to further match the size of key thermoacoustic components such as the regenerator, heat exchanger and resonance tube in the open thermoacoustic generator to achieve the optimal design of the sound field , so as to improve the sound power generated by itself, and at the same time reduce the sound power loss of the open-type thermoacoustic generator itself; the second is to enhance the external radiation sound intensity through the special structural design of the thermoacoustic generator. However, the above two methods can only increase the radiated sound intensity to a limited extent, usually within 10-20%, and it is still difficult to meet the requirements of long-distance and high directivity applications.

Contents of the invention

The aim of the present invention is to provide a solution that can significantly increase the output acoustic power of a thermoacoustic generator.

The invention provides an array type thermoacoustic generator, comprising at least two thermoacoustic generator units; a converging pipe with at least two input channels and an output port, and an open resonant pipe;

Wherein, each thermoacoustic generator unit is connected to one input channel of the converging pipe, the output ends of the respective input channels of the converging pipe meet, and the output port is arranged at the junction, and the output port is resonant with the opening The tube connection, the output impedance of each of the thermoacoustic generator units, the length of each of the input channels and the value of the tube diameter can make the intersection of the converging tubes form the effect of superposition of peaks and peaks, and superposition of troughs.

Wherein, the sound pressure phase difference at the intersection of the input channels of the converging pipe is less than 90 degrees.

Wherein, the output impedance of each thermoacoustic generator unit, the length and pipe diameter of each input channel are selected so that the junction of the converging pipes can meet both the pressure continuity requirement and the volume flow rate continuity requirement.

Wherein, the output impedance of each of the thermoacoustic generator units, the length of each of the input channels and the value of the pipe diameter make:

The beginning of Z _{equal-diameter tube} is the impedance at the beginning of the equal-diameter tube, which is calculated by the impedance at the opening of the sound-collecting tube, the length and cross-sectional area of the iso-diameter tube, the line type and its size parameters used for the contour of the sound-collecting tube, and the specific calculation References: Zhang Hailan, Theoretical Acoustics, Higher Education Press, 2012: 329-332. Z _xo is the terminal impedance of the xth input channel, x=1, 2, . . . , N, and N is the number of input channels of the converging pipe. The impedance at the opening of the acoustic tube can be calculated based on the radiation impedance of the circular piston on the infinite baffle, which is related to the radius of the opening and the operating frequency of the system. When the size of the acoustic tube and the operating frequency of the system are determined, the impedance at the opening is a constant value. For specific calculations, please refer to the literature: Du Gonghuan et al., Acoustic Fundamentals, Nanjing University Press, 2001: 356-362.

Among them, for any input channel x, its initial impedance _Zxi is calculated according to the following formula:

Where Z _xo is the terminal impedance of the xth input channel, Z _xC is the acoustic characteristic impedance of the xth input channel, ρ ₀ is the air density, a is the speed of sound, A _x is the cross-sectional area of the xth input channel, l _x is the length of the input channel x, and ω is the operating frequency of the corresponding thermoacoustic generator unit.

For the thermoacoustic generator unit connected to the xth input channel, the structure and design parameters of the thermoacoustic generator unit can make the output end impedance of the thermoacoustic generator unit work alone equal to or close to the calculated The input impedance of the xth input channel.

Wherein, the thermoacoustic generator unit is connected to the input channel of the multi-channel converging pipe by thread sealing, and the output port of the multi-channel converging pipe is also connected by thread sealing to the open resonance tube.

Wherein, each thermoacoustic generator unit is arranged in an equi-polygonal manner.

Wherein, the thermoacoustic generator units are arranged in an array.

Compared with the existing open-type thermoacoustic generator, the advantages of the present invention are:

1. The array type thermoacoustic generator of the present invention has high sound intensity, long working distance and strong directivity.

2. The present invention can solve the problems of low sound pressure, complex device, and poor repeatability of acoustic performance of existing low-frequency sound wave generators, and can provide basic sound sources and high-intensity sound sources for industrial application of low-frequency long-distance noise experimental research.

Description of drawings

Hereinafter, embodiments of the present invention will be described in detail in conjunction with the accompanying drawings, wherein:

Fig. 1 shows an array type thermoacoustic generator based on two coaxial open type traveling wave thermoacoustic generator units according to an embodiment of the invention;

Fig. 2 shows the A-A sectional view of the array type thermoacoustic generator of Fig. 1;

Fig. 3 shows an A-A sectional view of an open-type thermoacoustic generator array device with a triangular distribution of three thermoacoustic generator units in one embodiment of the present invention;

Fig. 4 shows an A-A sectional view of an open-type thermoacoustic generator array device with a square distribution of four thermoacoustic generator units in one embodiment of the present invention;

Figure 5 shows an A-A sectional view of an open-type thermoacoustic generator array device having five thermoacoustic generator units in an equipentagonal distribution in one embodiment of the present invention;

Figure 6 shows an A-A sectional view of an open-type thermoacoustic generator array device with six thermoacoustic generator units in an equihexagonal distribution in one embodiment of the present invention;

Fig. 7 shows an A-A sectional view of a matrix-distributed thermoacoustic generator unit array in an embodiment of the present invention.

Detailed ways

The following description and accompanying drawings will describe in detail the application examples and typical embodiments of the open-type thermoacoustic array generator of the present invention. However, various possible modifications and changes can be made to the specific implementation without departing from the principles of the present invention.

As mentioned above, the existing open-type thermoacoustic generator still has problems such as short radiation action distance and insufficient outward radiation sound intensity. There are two ways to increase the sound intensity of external radiation: one is to further match the size of key thermoacoustic components such as the regenerator, heat exchanger and resonance tube in the open thermoacoustic generator to achieve the optimal design of the sound field , so as to improve the sound power generated by itself, and at the same time reduce the sound power loss of the open-type thermoacoustic generator itself; the second is to enhance the external radiation sound intensity through the special structural design of the thermoacoustic generator. However, the above two methods can only increase the radiated sound intensity to a limited extent, usually within 10-20%, and it is still difficult to meet the requirements of long-distance and high directivity applications. The inventors proposed a brand new solution, that is, using multiple thermoacoustic generator units to form a thermoacoustic generator array, and making the sound waves from each thermoacoustic generator unit form a pressure wave over a certain transmission distance. The effect of superposition of wave crests and wave troughs, and then realize the propagation effect of multiplying the sound intensity, thus significantly enhancing the sound pressure level at the outlet of the entire thermoacoustic generating device.

Various embodiments of the present invention are described below in conjunction with the accompanying drawings.

Fig. 1 shows an array thermoacoustic generator based on two coaxial open-type traveling wave thermoacoustic generator units according to an embodiment of the present invention. Referring to FIG. 1 , the array thermoacoustic generator includes two thermoacoustic generator units 1 , a multi-channel converging pipe 2 and an open resonance pipe 3 . Wherein, the multi-channel converging pipe 2 includes two input channels respectively corresponding to two coaxial open type traveling wave thermoacoustic generator units and an output port connected with the open type resonance tube 3 .

Each coaxial open-type thermoacoustic generator unit can be regarded as an independent thermoacoustic generator, and its outlet is connected to an input channel of the multi-channel converging pipe. In one example, the thermoacoustic elements built in the resonance chamber of each thermoacoustic generator unit of the array type thermoacoustic generator include a hot end tube, a hot end heat exchanger, a regenerator, and a cold end heat exchanger in sequence. When working, the heat exchanger at the hot end and the heat exchanger at the cold end establish a temperature difference between the two ends of the regenerator. When the temperature difference is greater than the critical temperature difference of the system, the system will start to vibrate and generate sound power. The standing wave component of the sound work generated by the regenerator maintains oscillation locally, and the traveling wave component is input into the corresponding channel of the multi-channel converging pipe 2 . The internal structure of the thermoacoustic generator unit can be referred to: the literature Swift G W.Thermoacousticengines.J Acoust Soc Am,1988,84(4):1145–1180; Slaton W V.An open-air infrasonic thermoacoustic engine.Appl Acoust,2010, 71:236–240, which will not be repeated here. In this embodiment, each thermoacoustic generator unit adopts the same operating frequency (the operating frequency is the frequency at which sound work is output). Fig. 2 shows an A-A sectional view of the array thermoacoustic generator of Fig. 1 .

The multi-channel converging pipe is used to gather the sound waves from multiple thermoacoustic generator units together, and by designing specific input channel lengths and pipe diameters, the sound waves from each thermoacoustic generator unit can be transmitted over a certain distance The effect of superposition of crests and crests and superposition of troughs and troughs of pressure waves is formed, and then the propagation effect of increasing the sound intensity multiple is realized.

In order to make the sound waves from each thermoacoustic generator unit form the superimposition effect of crests and crests and troughs of pressure waves over a certain transmission distance, the multi-channel converging pipe is designed to meet the following requirements at the same time:

a) Requirements for continuity of pressure: p ₁₁ =p ₁₂ =...=p _1N ;

b) Volume flow rate continuity requirements:

Among them, ρ ₀ is the density of the working fluid, p _1x is the oscillation pressure of the working fluid at the outlet of the input channel X#, u _1x is the velocity of the working fluid at the outlet of the input channel X#, and A _x is the cross-sectional area of the input channel X#. Wherein, X represents any integer from 1 to N. The working fluid in an open-type thermoacoustic generator is usually air.

The impedances of the beginning (entry) and terminal (exit) of input channel 1# are expressed as Z _1i and Z _1o respectively, the impedances of the beginning and end of channel 2# are expressed as Z _2i and Z _2o respectively, and the beginning of channel N# and the impedances of the terminals are denoted as Z _Ni and Z _No , respectively, then

Among them, l ₁ , l ₂ ,..., l _N are the lengths of input channels 1#~N#, and ω is the design frequency of the whole system, that is, the working fluid oscillation frequency of the whole array thermoacoustic generator. The oscillation frequency is jointly determined by the structural dimensions of each thermoacoustic generator unit, and generally speaking, each thermoacoustic generator unit adopts the same operating frequency. l _x is the length of the xth channel (that is, the input channel channel x#), where x=1, 2, ..., N. In this embodiment, the length of a channel refers to the length of the central axis of the channel. The output port of each thermoacoustic generator unit is the input port of the corresponding channel. The convergence point of the central axis of each channel is regarded as the output port of each channel. For any channel, after determining its input port and output port, the length of its central axis can be determined, so as to obtain the corresponding l _x value.

In this embodiment, the open resonance tube includes an equal-diameter tube and a sound-collecting tube. Among them, the equal diameter tube is used to stabilize the frequency of the sound wave output from the converging tube and transmit the sound power to the sound converging tube. In this embodiment, the contour of the sound collecting tube adopts a linear shape that is beneficial to reduce the loss of sound power, for example, the contour of the sound collecting tube adopts a linear, exponential or hyperbolic changing linear shape. The traveling wave components output by each thermoacoustic generator unit of the array thermoacoustic generator are output to the open space along the multi-channel converging pipe 2, the isodiametric pipe 9 and the sound concentrating pipe 10 with a special line shape. The length of the equal-diameter tube is about λ/4, and its diameter is Ф10mm-Ф150mm,

The initial diameter Φ _C0 of the sound collecting tube 10 is equal to the diameter of the equal diameter tube 9 . The initial cross-sectional area A _C0 of the acoustic tube 10, the end cross-sectional area When ε=0, the line shape shows a hyperbolic change; when ε=∞, the line shape shows an exponential change; when ε=(x ₀ /h)+i(π/2), the line shape shows a conical change. For the specific design of the equal-diameter tube and the acoustic tube, please refer to: Zhang Hailan, Theoretical Acoustics, Higher Education Press, 2012.

At the opening of the sound collecting tube (that is, the end of the sound collecting tube), the impedance can be calculated according to the above; when the length and cross-sectional area of the equal diameter tube are known, the line type and size of the contour of the sound collecting tube When the parameters are also known, the impedance at the beginning of the isometric tube can be obtained by inversion. Since the equal-diameter tube is connected to the outlet of the multi-channel converging tube, the impedance at the beginning of the iso-diametric tube is the impedance of the output end of the multi-channel converging tube. According to the requirement of continuity of pressure and continuity of volume flow rate mentioned above, the impedance of the output end of each channel of the multi-channel converging pipe meeting the requirements can be obtained. which is:

The beginning of the Z _{isometric tube} is the impedance at the beginning of the isometric tube, and its calculation can refer to the above. In this paper, the channels of the converging pipes are sometimes referred to as input channels, and the converged output ports are referred to as output ports.

After the output end impedance Z _xo of each channel is obtained, the start end impedance Z _xi of each channel can be further obtained according to the relationship between the start end and the end impedance. The initial impedance of each channel corresponds to the output impedance of the corresponding thermoacoustic generator unit, that is, when designing each thermoacoustic generator unit, as long as its output impedance is equal to the calculated initial impedance of the corresponding channel, It can meet the requirements, and then make the whole system form the effect of the superposition of crests and crests of pressure waves, and the superposition of troughs and troughs, and then realize the propagation effect of multiplying the sound intensity pressure.

Of course, in terms of specific implementation, each thermoacoustic generator unit can also be designed first, and the output end impedance of the thermoacoustic generator unit can be obtained through simulation or actual measurement, and then by adjusting the diameter and diameter of each channel of the multi-channel converging tube length to obtain the desired output impedance of the channel. This reduces the difficulty of assembly and design of the individual thermoacoustic generator units. Even if the actual output impedance of the thermoacoustic generator unit deviates from the design target, the required output impedance of the converging point can be obtained by adjusting the diameter and length of each channel of the multi-channel converging pipe, thereby forming the pressure wave The effect of the superposition of peaks and peaks, and the superposition of troughs and troughs.

In this embodiment, each thermoacoustic generator unit and the multi-channel converging pipe can be connected in a threaded sealing manner, and of course other sealing connection methods can also be used. The connection between the multi-channel converging pipe and the open-type resonant pipe can also be connected in a threaded sealing manner, and of course other sealing connection methods can also be used.

Theoretically, the acoustic power output of an array thermoacoustic generator based on two identical thermoacoustic generator units can reach twice that of a single thermoacoustic generator unit. However, it is often difficult for the actual assembled array thermoacoustic generator to accurately achieve the effect of superimposing the output peaks of each thermoacoustic generator unit, and the superposition of troughs and troughs, so loss is unavoidable. As long as the phase difference of the sound pressure at the converging point of each channel (that is, the output end of each channel) is less than 90 degrees, the effect of enhancing the sound power can be achieved. Designing the pipe diameter and cross section based on the impedance formula of each channel above can well suppress the phase difference at the output end of each channel, thereby significantly improving the sound power output by the array thermoacoustic generator.

Based on the above principles, array thermoacoustic generators with other structures can also be designed. For example, Fig. 3 shows an A-A cross-sectional view of an open-type thermoacoustic generator array device with three thermoacoustic generator units in a triangular distribution in one embodiment of the present invention (the array type of this embodiment is not drawn herein The front view of the thermoacoustic generator. The A-A section here refers to the cross section of the array type thermoacoustic generator perpendicular to the axis of the isometric tube and capable of intercepting all the cross sections of the thermoacoustic generator. The same is true for Figures 4 to 7, and will not be repeated below. ). Fig. 4 shows an A-A sectional view of a square-distributed open-type thermoacoustic generator array device with four thermoacoustic generator units in one embodiment. Fig. 5 shows an A-A cross-sectional view of an open-type thermoacoustic generator array device having five thermoacoustic generator units in an equipentagonal distribution in one embodiment. Fig. 6 shows an A-A cross-sectional view of an open-type thermoacoustic generator array device with six thermoacoustic generator units in an equihexagonal distribution in one embodiment. The design principles of these modified embodiments are completely consistent with those of the first embodiment described above, so details will not be repeated here.

Fig. 7 shows an A-A section of a matrix-distributed thermoacoustic generator unit array in an embodiment of the present invention. The design principle of this embodiment is completely consistent with that of the first embodiment described above, and will not be repeated here.

To sum up, the present invention aims at the defect of insufficient radiated sound intensity of a single open-type thermoacoustic generator, and combines multiple independent open-type thermoacoustic generator units through different structural designs to form pressure over a certain transmission distance. The effect of the superposition of wave crests and wave crests, and the superposition of wave troughs, and then realize the propagation effect of increasing the sound intensity multiples.

Finally, it should be noted that the above embodiments are only used to illustrate the present invention, not to limit. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in this within the scope of the claims of the invention.

Claims (9)

1. a kind of array thermoacoustic generator, including at least two thermoacoustic generator units；With at least two input channels and The convergence pipe of one delivery outlet；And open type resonatron；

Wherein, an input channel of each thermoacoustic generator unit connection convergence pipe, each input channel of the convergence pipe Output end cross, and the delivery outlet is set in intersection, the delivery outlet is connect with the open type resonatron, Ge Gesuo Output terminal impedance, the length of each input channel and the value of caliber for stating thermoacoustic generator unit enable to convergence to manage Intersection formed wave crest be superimposed with wave crest, the effect that trough is superimposed with trough.

2. array thermoacoustic generator according to claim 1, which is characterized in that the friendship of the input channel of the convergence pipe The phase difference of acoustic pressure at remittance is less than 90 degree.

3. array thermoacoustic generator according to claim 2, which is characterized in that each thermoacoustic generator unit Output terminal impedance, the length of each input channel and the value of caliber enable to the intersection of convergence pipe while meeting pressure The continuity of power requires and the requirement of volume flow rate continuity.

4. array thermoacoustic generator according to claim 3, which is characterized in that each thermoacoustic generator unit Output terminal impedance, the length of each input channel and the value of caliber enable to：

Z_{Equal pipe beginning}For the beginning impedance of equal pipe, it is by calculating the length of poly- sound pipe opening impedance and equal pipe and cutting The profile of area and poly- sound pipe use line style and its sizecalculation obtain, Z_xoIt is hindered for the terminal of xth input channel It is anti-, x=1,2 ..., N, N be the number of the input channel of convergence pipe.

5. array thermoacoustic generator according to claim 4, which is characterized in that for any one input channel x, Beginning impedance Z_xiIt calculates according to the following formula：

Wherein Z_xoFor the terminal impedance of xth input channel, Z_xCFor the acoustic characteristic impedance of xth input channel,ρ is sky Air tightness, a are the velocity of sound, l_xFor the length of input channel x, ω is the working frequency of corresponding thermoacoustic generator unit.

For the thermoacoustic generator unit being connect with xth input channel, the structure and design of the thermoacoustic generator unit are joined Output terminal impedance when number enables to the thermoacoustic generator unit to work independently is equal or close to the calculated xth input of institute The sending-end impedance in channel.

6. array thermoacoustic generator according to claim 4, which is characterized in that poly- sound pipe opening impedance is based on opening Locate radius, system operating frequency, the radiation impedance according to circular piston on infinitely great baffle calculates.

7. array thermoacoustic generator according to claim 4, which is characterized in that the thermoacoustic generator unit with it is mostly logical It is connected by the way of thread seal between the input channel of road convergence pipe, multichannel converges the delivery outlet and open type resonance of pipe It is also connected by the way of thread seal between pipe.

8. array thermoacoustic generator according to claim 1, which is characterized in that each thermoacoustic generator unit at etc. it is polygon The mode of shape is arranged.

9. array thermoacoustic generator according to claim 1, which is characterized in that the thermoacoustic generator unit is at array Mode is arranged.