管道及消声器声学计算的时域脉冲法应用研究

发布时间：2018-05-07 21:03

本文选题：管道 + 消声器　；参考：《哈尔滨工程大学》2014年博士论文

【摘要】：消声器广泛应用于降低管道内传播的噪声,其声衰减性能的计算方法可分为两种:频域法和时域法。频域法的优点是计算速度快,其主要缺点是不能很好地考虑介质流动和粘性对声传播及衰减的影响。时域方法直接求解质量、动量和能量守恒方程,并且保留了方程中的非线性项,可以较好地处理复杂气流流动、介质粘性和热传导效应对消声器内声传播及管口声辐射的影响。为此,本文采用时域方法研究消声器和管路系统的声学特性。将时域脉冲法应用于计算无流时简单膨胀腔消声器、外插进出口管膨胀腔消声器、双级膨胀腔消声器、直通穿孔管消声器、横流穿孔管消声器和混合膨胀腔消声器的传递损失,并与实验测量结果、有限元法计算结果进行了比较。结果表明,时域脉冲法能够精确预测抗性消声器的声衰减性能。有限元计算中使用穿孔阻抗表述穿孔结构的声学特性,穿孔阻抗经验公式的准确性和适用性直接影响消声器传递损失的计算精度。而时域法对于穿孔进行实体建模,在计算中可以考虑穿孔附近的非线性效应,提高了计算结果的精度。此外,时域计算中使用多孔介质模拟吸声材料,粘、惯性阻力系数的推导和多孔介质处网格质量的高低决定了时域法的预测精度。以穿孔管消声器为例,使用时域脉冲法研究了气流流动和温度对于消声器声衰减性能的影响。通过对比分析可知,时域法预测结果与实验测量结果吻合较好,且优于FEM计算结果。数值计算结果表明气流速度和温度会影响穿孔管消声器的声学性能。随着流速的增加,在多数频率范围内穿孔管消声器的传递损失增大。气流温度升高时,消声器的传递损失曲线向高频方向移动,共振峰值有所降低。使用实验室现有实验台在无流和有流条件下测量了双级膨胀腔消声器的传递损失,并与时域脉冲法计算结果进行了对比。在考虑的频率范围内,测量结果和预测结果整体吻合较好,但测量曲线中有锯齿形波动,且随着马赫数的增加测量精度降低。为此,对原实验台进行局部改动,使用快速正弦扫频信号和同步时域平均技术以提高声源信号的信噪比。通过对比分析可知,直通穿孔管消声器传递损失的测量结果不仅与时域脉冲法的预测结果吻合较好,而且测量曲线的波动减小了。将时域脉冲法应用于研究无流和有流条件下圆形管道的反射系数幅值,并与实验结果、边界元法(BEM)计算结果进行了比较。由对比分析可知,无流条件下时域法可以准确地预测管口的声学特性,考虑气体流动时时域法的预测结果在亥姆霍兹数较小的区域存在计算误差,原因是计算模型的出口使用的是有反射边界条件。气流流动和管道出口角度对于管口的声学特性有一定的影响。有气流流动时,反射系数幅值随着亥姆霍兹数的增加先升高后降低;随着气流马赫数的增加,反射系数的幅值增大,曲线中峰值对应的亥姆霍兹数也增大。相比于直切口管道而言,斜切口会降低管口的反射系数,且夹角越小,反射系数下降的越快。通过用户自定义函数(UDF)补充水密度的计算程序将时域脉冲法扩展用于水管路消声器的声衰减性能研究。无流时分别使用时域脉冲法和FEM计算了简单膨胀腔消声器、外插进出口管膨胀腔消声器、双级膨胀腔消声器、直通穿孔管消声器和横流穿孔管消声器的传递损失,两种数值结果基本吻合,峰值频率有细微偏差,原因可以归结为FEM计算中没有考虑介质粘性和可压缩性,导致FEM计算中的声速与时域计算中稍有不同。鉴于有限元法难于准确模拟消声器内部水流流动对其声学性能的影响,仅仅使用时域脉冲法预测了有流时穿孔管消声器的传递损失。随着流速的增加,多数频率下消声器的传递损失有所增大。
[Abstract]:The muffler is widely used to reduce the noise propagating in the pipeline. The calculation method of acoustic attenuation performance can be divided into two kinds: frequency domain method and time domain method. The advantage of frequency domain method is that the advantages of frequency domain method are fast calculation speed, and its main disadvantage is that the effect of medium flow and viscosity on sound propagation and attenuation can not be considered well. Time domain method directly solves mass, momentum and energy. The equation of conservation of quantity and the nonlinear term in the equation are retained, which can deal with the influence of the complex flow, the viscosity of the medium and the heat conduction effect on the sound propagation in the muffler and the sound radiation of the tube. In this paper, the time domain method is used to study the acoustic characteristics of the muffler and the pipeline system. The time domain pulse method is applied to the calculation of the flow free time. The simple expansion cavity muffler, outside the inlet and outlet tube expansion chamber muffler, the double stage expansion chamber muffler, the perforated perforated tube muffler, the cross flow perforated tube muffler and the mixed expansion chamber muffler, is compared with the experimental results and the finite element method. The results show that the time domain pulse method can accurately predict the resistance elimination. Acoustic attenuation performance of an acoustic device. The finite element calculation uses the perforation impedance to express the acoustic characteristics of the perforated structure. The accuracy and applicability of the empirical formula of the perforation impedance directly affect the calculation accuracy of the transmission loss of the muffler. The time domain method is used to model the perforation, and the nonlinear effect near the perforation can be considered in the calculation. In addition, the prediction accuracy of the time domain method is determined by the use of porous media to simulate the sound absorption material in porous media, the derivation of the viscosity, the inertia resistance coefficient and the quality of the meshes at the porous medium. The time domain pulse method is used to study the acoustic attenuation performance of the flow and temperature of the muffler. The results of the time domain method are in good agreement with the experimental results, and it is better than the FEM results. The numerical results show that the velocity and temperature of the air flow can affect the acoustic performance of the perforated tube muffler. The transmission loss curve of the muffler moves to the high frequency direction and the resonance peak is reduced. The transmission loss of the double stage chamber muffler is measured under the current laboratory test bench under the condition of no flow and flow, and the results are compared with the time domain pulse method. The overall agreement is good, but the measurement curve has the zigzag fluctuation and the measurement precision decreases with the increase of the Maher number. Therefore, a local change is made to the original experimental platform. The signal to noise ratio of the sound source signal is improved by the fast sinusoidal sweep frequency signal and the synchronization time domain average technique. Through the contrast analysis, the direct through perforated tube muffler transfer the loss. The measurement results are not only in good agreement with the prediction results of the time domain pulse method, but also reduce the fluctuation of the measurement curves. The time domain pulse method is applied to the study of the amplitude of the reflection coefficient of a circular pipe under the condition of flow without flow and flow. The results are compared with the experimental results, and the results of the boundary element method (BEM) are compared. The method can accurately predict the acoustic characteristics of the pipe mouth, considering the prediction results of the gas flow time domain method in the smaller area of Helmholtz. The reason is that the calculation model has reflected boundary conditions. The air flow and the outlet angle of the pipe have a certain influence on the acoustic characteristics of the pipe mouth. When the Helmholtz number increases, the amplitude of the reflection coefficient increases and then decreases with the increase of the number of Helmholtz. With the increase of the Maher number of the airflow, the amplitude of the reflection coefficient increases, and the number of Helmholtz corresponding to the peak in the curve is also increased. The oblique incision will reduce the anti ejection coefficient of the pipe, and the smaller the angle, the faster the reflection coefficient decreases. The time domain pulse method is extended to study the sound attenuation performance of water pipe silencers by using the user defined function (UDF) to supplement the water density. Time domain pulse method and FEM are used to calculate the simple expansion cavity muffler, external plug and import tube expansion chamber muffler, double expansion chamber muffler, straight through perforated tube muffler. The transmission loss of the perforated perforated tube muffler is basically consistent with the two numerical results, and the peak frequency has a slight deviation. The reason can be attributed to the fact that the FEM calculation does not consider the viscosity and compressibility of the medium. The sound velocity in the FEM calculation is slightly different from the time domain calculation. In view of the difficulty of the finite element method, it is difficult to accurately simulate the flow of flow inside the muffler. With the effect of acoustic performance, the transmission loss of the perforated tube muffler is predicted by the time domain pulse method only. With the increase of flow velocity, the transmission loss of the muffler at most frequency increases.

【学位授予单位】：哈尔滨工程大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB535.2

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