共查询到18条相似文献,搜索用时 126 毫秒
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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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采用计算流体力学软件Fluent模拟研究了11种不同形状参数的指数型热声谐振管内二维非线性声场特性,分析了驱动频率和驱动强度对管内声压演化过程及固有频率的影响,并探索了指数管的固有频率与理论计算谐频之间的关系.研究发现:当驱动频率偏离谐振管固有频率时,管内将出现明显的"拍"现象;指数管的固有频率随驱动强度的增加而增加,呈现硬弹簧效应,但驱动强度对固有频率的影响较小并且在任何驱动下指数管的固有频率均小于理论计算谐频.针对所研究的指数型管,获得了其固有频率与理论计算谐频之间的关系式.结果表明,相同驱动下,形状参数m值约等于2.8的指数管所能获得的压力幅值及压比最大,且m=2.8指数管的固有频率与理论计算谐频之间的关系式与其他管型略有不同. 相似文献
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为了扩展谐振管内非线性驻波在工程中的应用, 以及克服现有数值计算方法仅局限于求解直圆柱形和指数形谐振管内非线性驻波的问题. 根据变截面的非稳态可压缩热黏性流体Navier-Stokes方程和空间守恒方程, 并基于求解压力速度耦合方程的半隐式算法和交错网格技术, 构建一种能够计算任意形状轴对称谐振管受活塞驱动时内部非线性驻波的有限体积算法. 分别对圆柱形、指数形和圆锥形谐振管内的非线性驻波进行仿真计算. 通过与现有试验结果以及数值仿真结果的对比, 验证了该方法的正确性.并获得除驻波声压之外的另外一些新的物理结果, 包括速度、密度、温度的瞬时变化.在直圆柱形谐振管内产生冲击声压波, 速度波形中出现钉状结构.而在指数形和圆锥形谐振管内产生高声压幅值的驻波, 没有出现冲击波, 速度波形中均未发现钉状结构. 计算结果表明谐振管内非线性驻波的物理属性与谐振管形状之间有密切关系. 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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The influence of the resonator shape on nonlinear acoustic field in a thermoacoustic engine is studied.The resonator of themoacoustic engine is boundary driving by a piston at one end,and the other end of it is rigid closed.A one-dimensional wave equation that accounts for gas dynamic nonlinearities and viscous dissipation in the resonator is established based on the governing equations of viscous hydromechanics.The nonlinear wave equation is solved using approximate Galerkin method.The nonlinear acoustic field in four different types of shaped resonators including hyperbolical,exponential,conical and sinusoidal are obtained and compared with that of a cylindrical resonator.It is found that the amplitude and waveform of the pressure are strongly affected by the resonator shape,the driving amplitude and the oscillation frequency of the piston.Waveform distortion,resonance frequency shift and hysteresis are observed,when the piston oscillation amplitude is large enough.The advantages of shaped resonator for thermoacoustic engine lie in inhibition of higher order harmonics and improvement of pressure ratio,etc. 相似文献
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《声学学报:英文版》2017,(3)
The two-dimensional nonlinear acoustic field of eleven exponential shaped resonators was simulated with a computational fluid dynamics software Fluent.The influence of driving frequency and driving intensity on pressure in resonator as well as its natural frequency was investigated.The relationship between natural frequency and theoretical calculation resonance frequency was also explored.It is found that beating phenomena can be observed in the resonator when the driving frequency deviates from the natural frequency.Moreover,the natural frequency of resonator increases with the increasing of driving intensity,which shows a hard spring effect.However,the driving intensity plays little effect on natural frequency and the natural frequencies are smaller than the theoretical calculation values in any driving intensity.Meanwhile,a formula between the natural frequency and its first-order resonance frequency from theoretical calculation was obtained by linear fitting for all these exponential shaped resonators under consideration.It is also found that the highest pressure amplitude and highest pressure ratio can be obtained from the exponential shaped resonator of m=2.8 under the same driving intensity.Moreover,the relation between natural frequency and the theoretical resonance frequency for m=2.8-tube is slightly different from other tubes in consideration. 相似文献
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An investigation of the effect of resonator dimensions on nonlinear standing waves in shaped resonators is conducted. Simple forms of the shear viscosity term in the momentum equations are developed for an axisymmetric (2D) resonator and a low aspect ratio rectangular (3D) resonator. The cross sections of the resonators are exponentially expanded and the one-dimensional wave equations are solved by using the Galerkin's method. The quality factors, pressure waveforms, compression ratios, and resonance frequencies are calculated for different dimensionless cross sections and lengths of the resonators. The results show that, apart from the resonator length, the ratio of the cross-section dimension to the length of the resonator is an important parameter. If the ratio is greater than 0.04, the characteristics of the shaped resonator are not affected significantly. However, when the ratio is less than 0.01, the resonance becomes weak, the compression ratio drops substantially, and the frequency response changes as well. 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
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磁致伸缩换能器辐射板形状对声场分布的影响 总被引:1,自引:0,他引:1
磁致伸缩换能器可作为热声制冷机的声源装置,辐射板的形状直接影响声压输出效率,从而影响制冷效果。为提高换能器工作效率、减小换能器体积,辐射板需在Terfenol-D棒的激励下产生大振幅、高频率的活塞振型。针对这一问题,应用ATILA软件分析了磁致伸缩换能器辐射板形状对谐振腔振动幅频特性的影响以及对谐振腔内声场分布的影响。结果表明:相同激励条件下,凹球面辐射板出现活塞振型时振幅最大,对应谐振腔中声压幅值最高;谐振腔端面形状为凹球面时,具有聚焦声压幅值的作用;端面形状为凹发射端-凸反射端组合的谐振腔内声压幅值最高。以上结论为合理设计辐射板、谐振腔两端面组合形状提供了参考。 相似文献
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A Helmholtz resonator is placed in a room with distinct acoustic modes, and is tuned to one of the corresponding resonant frequencies. The optimal resonator damping ratio is investigated, as a goal-dependent value. For example, minimizing reverberation time requires a different damping ratio from minimizing the sound pressure level. The optimum damping values for a Helmholtz resonator are analytically computed, and then verified by means of experimentation. Furthermore, a construction is introduced which allows for a fine adjustable setting for the eigenfrequency and the damping ratio of the resonator. 相似文献
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In order to raise the sensitivity of microwave electron-paramagnetic-resonance (EPR) spectrometers, it is proposed to use a piece of ferroelectric material as an additional resonator. The method has been tested using the RE-1307 microwave EPR spectrometer and a pulsed microwave spectrometer. The possibility of raising the signal-to-noise ratio when using ferroelectric resonators of rectangular-parallelepiped and spherical shape has been considered. For a potassium-tantalate ferroelectric resonator of rectangular-parallelepiped shape, the signal-to-noise ratio has been raised by a factor of 16 at 331 K and by a factor of 10 at 292 K. In the pulse experiment, the presence of the ferroelectric resonator permits a reduction in microwave power, required for sample saturation, by a factor of 50 at 50 K. 相似文献