【作者】 康钟绪；

【导师】 季振林；

【作者基本信息】 哈尔滨工程大学 ， 轮机工程， 2009， 博士

【摘要】 消声器是控制发动机进、排气噪声的有效装置,其声学性能的计算与分析是消声器设计的基础。由于能改善消声效果和气体流动特性,穿孔元件在消声器中广泛应用,为预测消声器的声学性能,首先需要确定穿孔元件的声学特性。本文针对消声器声学性能的计算方法和穿孔元件的声学特性开展系统研究。研究并发展了消声器声学性能的计算方法,包括基于平面波理论的传递矩阵法、有限元法和三维时域CFD(计算流体动力学)方法。基于平面波理论推导了考虑流速和热粘效应时典型消声元件的传递矩阵,并利用三维解析方法计算管道的末端修正系数,利用管道末端修正系数的近似公式修正了平面波理论,改善了传递矩阵法的计算精度。发展考虑流动效应时消声器声学计算的有限元法以预测穿孔管消声器的传递损失,研究有限元法计算中的数值误差,比较分析有限元法计算消声器传递损失的声波分解法和四极参数法。发展三维时域CFD方法预测消声器的传递损失,分析时域CFD方法模拟管道内声波传播的数值误差,研究时域CFD法预测消声器传递损失的脉冲法和声波分解法。通过算例分析和总结三种方法预测消声器声学性能的优缺点。以穿孔板模型为对象,采用数值方法研究穿孔元件的声学特性。无流情况下,采用有限元法研究穿孔板的声阻抗,建立穿孔板声阻抗的有限元模型,分析各种结构参数对穿孔板声学厚度修正系数的影响,并根据计算结果给出穿孔板声学厚度修正系数的近似公式；有流情况下,采用时域CFD方法研究穿孔板的声阻抗,分别建立穿孔板在通过流、掠过流下声阻抗的CFD模型,分析结构参数和气流马赫数对穿孔板声阻和声抗的影响,根据计算结果分别拟合出两种流动形式下穿孔声阻抗的近似公式。综合无流、有流情况下穿孔板声阻抗的近似公式,给出穿孔元件声阻抗新模型。应用本文获得的穿孔声阻抗新模型预测穿孔管消声器的传递损失,预测结果和实验结果吻合很好,验证了本文模型的可用性和准确性,并通过和以往声阻抗模型的比较验证了本文模型的先进性。设计、搭建消声器声学性能测量实验台,研究消声器声学性能的测量方法。在有流情况下,应用快速正弦扫频和同步时域平均技术以提高信噪比,改善测量结果的精度。应用双负载法在该实验台上测量了无流、有流情况下穿孔管消声器实验件的传递损失,实验测量结果和应用本文穿孔声阻抗新模型的预测结果吻合良好,验证了本文穿孔声阻抗新模型的可用性和准确性。应用本文穿孔声阻抗新模型预测了不同结构和气流参数下穿孔消声器的传递损失,根据预测结果分析了穿孔元件的各种结构和气流参数对消声器传递损失的影响,为实际消声器的设计提供了有意义的指导。更多还原

【Abstract】 Silencer is an efficient device to control the intake and exhaust noise of engines, and the prediction and analysis of acoustic attenuation performance is necessary for silencer design. The perforated elements are commonly used in silencers to improve the acoustic attenuation and flow characteristics. To predict the acoustic attenuation performance of silencers, the acoustic characteristics of perforated elements needs to be determined first. Therefore, the present thesis will investigate in detail the calculation methods of acoustic attenuation performance of silencers and the acoustic characteristics of perforated elements.Three kinds of methods for the prediction of silencer acoustic attenuation performance are developed, including the transfer matrix method based on the plane wave theory, finite element method and three-dimensional time domain CFD (Computational Fluid Dynamics) method. Based on the plane wave theory, the transfer matrices of several acoustic elements are derived with consideration of the flow and thermo-viscosity effect. A three-dimensional analytical approach is developed to calculate the duct end correction coefficient, and a curve-fitting expression for the end correction coefficients is obtained and used in the corrected plane wave theory to improve the accuracy of transfer matrix method. The finite element method for the prediction of silencer acoustic attenuation performance with consideration of the flow convected effect is developed to predict the transmission loss of perforated duct silencer. The numerical errors of finite element method for the acoustic computation are analyzed, and the wave decomposition method and four-pole parameter method for the calculation of silencer transmission loss by using the finite element method are discussed. The time domain CFD method is developed to predict the transmission loss of silencers. The numerical errors in the CFD simulation for sound propagation in duct are analyzed, the pulse method and wave decomposition method are combined with the time domain CFD approach to determine the transmission loss of silencers. The advantages and shortcomings of the three methods for the prediction of silencer acoustic attenuation performance are discussed.The acoustic characteristics of perforated plate are studied by using the numerical methods. For the case without flow, the acoustic impedance of perforated plate is calculated by using finite element method. The finite element model for determination of the acoustic impedance of perforation is first built, and then the effect of various structure factors on the acoustic thickness correction coefficient of perforated plate is investigated. A curve-fitting expression for the end correction coefficient is obtained based on the numerical results. For cases with flow, the acoustic impedance of perforated plate is studied with the time domain CFD method. The CFD models for the perforated plates with cross flow and grazing flow are built, and the effects of structure factors, cross flow and grazing flow on the acoustic resistance and reactance of the perforated plates are studied. Based on the numerical results, the curve-fitting expressions for the acoustic impedance of perforated plates with cross flow and grazing flow are obtained. Combining the curve-fitting expressions for the acoustic impedance of perforated plate without and with flow, the new models for acoustic impedance of perforated element without and with flow are presented. With the present models for the acoustic impedance of perforation, the transmission loss of perforated duct silencers is predicted, and the predictions are compared with measurements, and the good agreements demonstrate that the present models are suitable and accurate. The predictions with the present models are also compared with results models before, and the comparison demonstates that the present models are better.A testing bed for measuring the acoustic attenuation performance of silencer is designed and built, and the measurement method is studied. For the measurement of transmission loss of silencer with flow, the rapid sine sweep and sync time averaging techniques are used to increase the signal-to-noise ratio and improve the measurement accuracy. Using this testing bed, the transmission loss of prototype perforated duct silencers are measured with the two-load method for cases without and with flow. The measurements show good agreements with the predictions, which proves that the present models are accurate.Using the present models for the acoustic impedance of perforation, the transmission loss of perforated silencers with different structures and flow are predicted, and the effects of various structure factors and flow conditions on the transmission loss is examined, which may be used to guide the practical silencer designs.更多还原