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在热声发动机系统中,谐振管用来调节系统的超振频率.通常的四分之一波长谐振管由一段谐振管后面连接一个比较大的气体容积构成,与二分之一波长谐振管相比,在相同的起振频率下前者可以有相对短的管长.锥形谐振管除了调节频率外,还可以提高热声发动机输出压力波的压比.本文通过数值计算软件Fluent6.0中的K-ε湍流模型模拟了不同长度、不同的进出口直径的一系列锥形谐振管,得出了近似四分之一波长锥形谐振管的共振频率与其长度、锥度之间的关系,并初步与实验进行了对照. 相似文献
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本文基于包含流动和传热两个方面的电路类比理论,针对一具有环路结构的气液相变热声发动机系统进行了模拟计算和分析。重点讨论了排出器、动力活塞、反馈管以及负载液柱的直径和长度对于系统谐振频率和换热器驱动温度梯度的影响。结果显示,该气液相变热声发动机的谐振频率较低(小于1 Hz),排出器和动力活塞的直径,以及反馈管的直径和长度对于谐振频率的影响较大;气液相变热声发动机所需驱动温度梯度比通常气体工质热声发动机小一到两个数量级,各主要部件的直径对气液相变热声发动机所需驱动温度梯度的影响比长度对其影响更为显著。 相似文献
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谐振管是热声热机的主要部件之一,减小声功在谐振管中的耗散对改善热声热机输出特性具有积极意义。由于近临界区流体的热物性具有特殊性,用其作为工质时将会对谐振管内的声功损耗产生重要影响。本文对声功在以近临界区CO_2为工质的谐振管中的损耗情况进行了计算和分析。结果显示,在本文的计算条件下,相较于压力较低的CO_2,采用近临界区CO_2作为工质可降低谐振管内的声功损耗,并在工作压力略低于临界压力时,谐振管内的声功损耗可达到最小值.此外,在保持谐振频率不变的情况下,采用近临界区CO_2作为工质可一定程度上缩短谐振管的长度。 相似文献
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时均流激声发动机利用流体诱导声振荡效应把自然界的风和管道气体的动能转化为声场能,可驱动热声制冷机制冷或驱动发电机和换能器发电,为风能利用提供了新思路。在国内首次搭建了正十字型时均流激声发动机实验台,以一台高压风机提供的气流模拟自然风,获得了稳定的驻波声场。在此基础上,揭示了时均流速、平均压力、斯特劳哈尔数等对时均流诱导声振荡的影响。在平均压力为106.19 kPa、时均流速为50.52 m/s、谐振管长度为0.96 m的条件下,该正十字型时均流激声发动机谐振管内的压力振幅达6.20 kPa,约为平均压力的5.80%,为时均流激声发动机驱动发电装置和热声制冷研究奠定了实验基础。 相似文献
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热声发动机的起振过程是一个产生并维持自激振荡的过程, 研究热声自激振荡机理有助于进一步了解热声效应的实质. 根据热声网络理论, 建立了驻波热声发动机的整机网络. 将热声网络比拟成电网络, 利用厄米特式计算了输入热声网络的视在功流, 功流平衡对应自激, 在角频率虚部为零的情况下计算了热声发动机的阈值温度和运行频率. 结果表明, 计算值与实验值符合得较好, 充气压力与阈值温度和运行频率的耦合关系大致相同. 所得结论有助于进一步探究热声效应机理以及热声发动机系统的优化设计. 相似文献
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Acoustic streaming in closed thermoacoustic devices. 总被引:2,自引:0,他引:2
H Bailliet V Gusev R Raspet R A Hiller 《The Journal of the Acoustical Society of America》2001,110(4):1808-1821
A derivation of acoustic streaming in a steady-state thermoacoustic device is presented in the case of zero second-order time-averaged mass flux across the resonator section (nonlooped device). This yields analytical expressions for the time-independent second-order velocity, pressure gradient, and time-averaged mass flux in a fluid supporting a temperature gradient and confined between widely to closely separated solid boundaries, both in the parallel plate and in the cylindrical tube geometries (two-dimensional problem). From this, streaming can be evaluated in a thermoacoustic stack, regenerator, pulse tube, main resonator of a thermoacoustic device, or in any closed tube that supports a mean temperature gradient, providing only that the acoustic pressure, the longitudinal derivative of the pressure, and the mean temperature variation are known. 相似文献
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Linear thermoacoustic theory is currently well accepted for simulating thermoacoustic systems, and correction is used to reduce the discrepancy between calculations and experimental results for turbulent flow. In order to calculate passive tube systems and make linear thermoacoustic theory coincide closely with experiments, a passive network model based on fluid network theory is derived. An amendment method is proposed to further correct for turbulence by amending thermal and viscous penetration depths when the ratio of the tube radius to the viscous penetration depth R/δv is large. The experiments have been done to verify the model in the acoustic amplifier, Helmholtz resonator, and inertance tube. In addition, the mechanisms of such tubes are further analyzed based on the model. 相似文献
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Thermoacoustic engines convert heat energy into high amplitude sound waves, which is used to drive thermoacoustic refrigerator or pulse tube cryocoolers by replacing the mechanical pistons such as compressors. The increasing interest in thermoacoustic technology is of its potentiality of no exotic materials, low cost and high reliability compared to vapor compression refrigeration systems. The experimental setup has been built based on the linear thermoacoustic model and some simple design parameters. The engines produce acoustic energy at the temperature difference of 325–450 K imposed along the stack of the system. This work illustrates the influence of stack parameters such as plate thickness (PT) and plate spacing (PS) with resonator length on the performance of thermoacoustic engine, which are measured in terms of onset temperature difference, resonance frequency and pressure amplitude using air as a working fluid. The results obtained from the experiments are in good agreement with the theoretical results from DeltaEc. 相似文献
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W.V. Slaton 《Applied Acoustics》2010,71(3):236-240
A low-frequency open-air thermoacoustic engine in a Helmholtz resonator has been constructed. Tests indicate that the system resonates in the Helmholtz mode for modest thermoacoustic stack temperature differences using stacks of varying type and pore size located within the neck of the Helmholtz resonator. The maximum acoustic pressure radiated from the open end of the resonator corresponds to 81 dB-SPL ref 20 μPa at a stack temperature difference of 185 K and an input electric power of 276 W. The system is well characterized by a numerical model of a representative stack. 相似文献
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Thermoacoustic oscillation is a significant problem in ducted domestic heating systems fitted with fully premixing burners as well as in combustion systems of industrial scale. This paper reports experiments using a burner closely representative of practical designs in which high-intensity free-field sound has been used to simulate the feedback which may be excited naturally in installations with different acoustic properties. This experimental approach facilitates study of the non-linear response of the burner/flame sub-system to feedback of different frequencies and direct measurement of the acoustic impedance of the burner under operational conditions. A function proportional to the Rayleigh integral has been evaluated directly from the experimental results. It is found that the head of this type of burner divides the typical installation into a quarter-wave tube and a Helmholtz resonator which must couple unstably for thermoacoustic oscillations to be autoexciting. It is further found that there is a strong interaction between the acoustic field and the mean flow which modifies significantly the behaviour of the burner as a Helmholtz resonator and thus the stability of the whole system. 相似文献
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研究了谐振管一端受活塞声源激励,另一端刚性封闭条件下,管道形状对热声发动机谐振管内部非线性声场的影响。基于流体力学基本方程建立了渐变截面谐振管内一维非线性声场的模型,考虑了黏性耗散及非线性效应的影响。利用伽辽金法数值求解了该模型的速度势方程,分析了谐振管形状、活塞振动速度及激励频率对管内声场的影响。将双曲形、指数形、锥形、正弦形等四种变截面谐振管内的非线性声场与圆柱形直管的情况进行了比较。结果反映了谐振管内声场的压力波动受活塞振动速度及谐振管形状的影响;显示了当活塞振动幅度较大时,谐振管内出现的波形畸变、频率曲线偏移、共振频率滞后等非线性现象;揭示了变截面谐振管在抑制管内的高阶谐波及提高压比等方面的优越性。 相似文献
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In this paper, an experimental study of the effect of the resonator shape on the performance of a traveling-wave thermoacoustic engine is presented. Two different resonators were tested in the thermoacoustic-Stirling heat. One resonator is an iso-diameter one, and the other is a tapered one. To have a reasonable comparison reference, we keep the same traveling-wave loop, the same resonant frequency and the same operating pressure. The experiment showed that the resonator shape has significant influence on the global performance of the thermoacoustic-Stirling heat engine. The tapered resonator gives much better performance than the iso-diameter resonator. The tapered resonator system achieved a maximum pressure ratio of about 1.3, a maximum net acoustical power output of about 450 W and a highest thermoacoustic efficiency of about 25%. 相似文献