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Development, Trial Manufacture an Evaluation of Acoustic Compressor

声压机的开发、试制及评价

基本信息

批准号：
12555045
负责人：
KAWAHASHI Masaaki
金额：
$ 8.13万
依托单位：
SAITAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

Finite amplitude wave motion in closed tubes are classic but interesting research field for the applications in recent advanced technology. When the gas column in a closed tube is driven by a piston at one end at the resonant frequency, large amplitude standing wave is induced in the tube. The mode of the standing wave, the pressure waveform and its amplitude at the closed end strongly depend on the geometry of the tube shape. In the case of cylindrical tube, the amplitude of the waveform is restricted due to the nonlinear effect in propagating shock-wave generation by the steepenig of wave front. Acoustic saturation comes quickly because the energy supplied to generate standing wave at exiting frequency mode is dissipated to higher harmonics instead of increasing the amplitude of the pressure waveform. On the other hand, in varying cross-sectional area tube, a large amplitude standing wave can be achieved and shock waves disappear with the wave motion. This large amplitude pressure fl … More uctuation has a practical application in the development of acoustic compressor which can consist an oil-less compression system of gases. The large amplitude standing wave in closed tube also induces non zero mean pressure distribution along the tube axis, steady circulating streaming at every 1/4 wave length section, and thermoacoustic effect of cooling at the node of pressure fluctuation and heating at the loop. The coupling of acoustic streaming with unstable convection not only transforms it into stable convection with cellular structure characterized by the wavelength of the sound wave but also increases the velocity of the convection current. Thermoacoustic effect induced by the air column oscillation can be applied to design thermoacoustic engine and refrigerator.The geometry of the tube shape is conical, exponential or half cosine function cross-sectional area contraction towards the closed end. The cylindrical tube is used as reference tube. The length of each tube is same. All the tubes area symmetric with regards to axis of the tube. The finite amplitude wave motion is induced in tube by sinusoidal oscillation of piston at big end of each tube. Linear and nonlinear theories have been derived by using the basic fluid dynamics equation. By the linear theory, the resonant frequency can be evaluated for different shaped tubes with different area contraction ratios. And it can be used to estimate the node position which is necessary to place the stack plate in tubes to design thermoacoustic engine and refrigerator. The nonlinear theory based on Chester' theory reveals that changing the shape of the tube can reduce the discontinuity of the waveform appeared in closed cylindrical tube. The result obtained by the nonlinear calculation agrees well with previous investigation.Finite difference MacCormack scheme keeping accuracy with second order in time and fourth order in space was used for numerical simulation of wave motion in closed tube. One-dimensional fluid dynamic equations are solved taking viscous and frictional dissipation into considerations. The limit of cross-sectional area contraction ratio to which shock wave appears, the effect of tube lengths, and effect of gas properties is investigated by numerical simulation. Numerical result revealed the possibility of getting shockless high amplitude pressure waveform by changing cross-sectional area of the tube.An experimental setup was made to investigate the characteristics of wave motion in different tube geometries. Conical, exponential and half cosine area contraction tube was used to compare the hardening, hysteresis and frequency shift in each tube geometries. Experiments were conducted for different piston acceleration and results are compared with the results obtained by numerical simulation.The finite amplitude standing wave in closed area change tubes was studied theoretically, numerically and by experiment. Experimental result agrees well with the numerical and theoretical result. The high amplitude shockless pressure waveform as well as high compression ratio in closed area change tube was developed. And the characteristic of the compressor mode operation for each shaped tube has been investigated for different gases.As the results, it has been revealed that the geometry of the tube shape is the most important factor in determining shock free high amplitude pressure waveform and obtaining the stability of the resonant frequency. And the half cosine shaped area change tube is the best tube shape to design acoustic compressor in this investigation. Less

闭合管内的有限振幅波动是现代先进技术应用的经典而有趣的研究领域。当封闭管内的气柱被一端的活塞以谐振频率驱动时，管内会产生很大幅度的驻波。驻波的模式、闭口处的压力波形及其幅值强烈地依赖于管子的几何形状。在圆柱管的情况下，由于波前陡峭在传播激波过程中的非线性效应，使波形的幅度受到限制。声饱和来得很快，因为在出射频率模式下产生驻波的能量被耗散到更高的谐波中，而不是增加压力波形的幅度。另一方面，在变截面圆管中，可以获得较大幅度的驻波，激波随波的运动而消失。这种大幅值压力fl…声学压缩机是一种无油压缩系统，在声学压缩机的研制中具有实际应用价值。闭合管内的大振幅驻波还会引起沿管轴的非零平均压力分布，在每1/4波长截面处产生稳定的循环流动，以及在压力脉动节点处冷却和在环路处加热的热声效应。声流与不稳定对流的耦合不仅使其转化为具有以声波波长为特征的蜂窝状结构的稳定对流，而且增加了对流的速度。空气柱振荡产生的热声效应可应用于热声发动机和制冷机的设计，管子的几何形状呈圆锥形、指数形或半余弦函数形，截面面积向封闭端收缩。采用圆柱管作为参照管。每根管子的长度都是一样的。所有的管子相对于管子的轴线面积对称。每根管子大端活塞的正弦振动引起管子内的有限振幅波动。从流体动力学基本方程出发，导出了线性和非线性理论。根据线性理论，可以计算出不同形状、不同面积收缩比的圆管的共振频率。它可以用来估算在设计热声发动机和制冷机时将堆栈板放入管内所需的节点位置。基于切斯特理论的非线性理论表明，改变圆管的形状可以减少闭合圆柱管中出现的波形的不连续性。非线性计算结果与前人的研究结果吻合较好。采用时间精度为二阶、空间精度为四阶的有限差分MacCormack格式对闭合管内的波动进行了数值模拟。求解了考虑粘性和摩擦耗散的一维流体动力学方程。通过数值模拟，研究了产生冲击波的截面收缩比的极限、管长的影响以及气体性质的影响。数值计算结果表明，通过改变管子的横截面面积可以获得无激波的高幅压力波形，并利用实验装置研究了不同管子几何形状下的波动特性。用圆锥形、指数形和半余弦面积收缩管比较了不同几何形状下的硬化、滞后和频移。对不同活塞加速度下的驻波进行了实验研究，并与数值模拟结果进行了比较。从理论、数值和实验三个方面对封闭变截面管内有限幅驻波进行了研究。实验结果与数值计算和理论计算结果吻合较好。研制了高幅值、无激波、高压缩比的闭合变截面管内压力波形。结果表明，管型的几何形状是决定无激波高幅值压力波形和获得谐振频率稳定性的重要因素。半余弦变截面管型是本研究中设计声压机的最佳管型。较少