扩张室压力脉动衰减器声传播的有效性

为了研究平面波截止频带内,进、出口偏置型扩张室压力脉动衰减器结构参数对其一维解析法计算精度的影响,基于面积突变处高阶模态的耗散效应,对两类偏置型扩张室一维解析法的有效性进行了分析.首先,截止频率范围内双调谐内插管扩张室一维解析法的计算结果与实验测量结果吻合良好,证明了该方法应用于液压脉动衰减器是可行的;其次,将广泛应用于气体消声系统的两类进、出口偏置型扩张室结构(结构1和结构2)引入液压系统,制成相应的压力脉动衰减器,并利用一维解析法和三维有限元法分别得到其理论计算值;最后,以扩张室腔室内部存在局部非平面波效应为背景,研究了内插管插入深度、偏心距以及偏转角对一维解析法有效性的影响.研究结果表明:结构1、2偏心距为40 mm、偏转角180°时,进、出口内插管插入深度对5 000 Hz频带内(截止频率5 469 Hz)高频区域的传递损失影响较大;而当结构1、2的内插管插入深度选定时,偏心距以及偏转角对0～4 000 Hz一维解析法计算精度的影响可忽略不计,而在4 000～5 000 Hz研究频带内,这种影响则不可忽略.

Effectiveness of Sound Propagation of Hydraulic Noise Suppressor with Expansion Chamber

In order to study the influence of structural parameters of non-coaxial expansion chambers on the accuracy of the one-dimensional (1D) analytical method within cut-off frequency, the validity of the method for two types of inlet/outlet expansion chamber is analyzed on the basis of the higher-order evanescent modes at the area discontinuities. Firstly, the calculation results of the 1D analytic method for the double-tuned extended tube chamber (DTETC) agree well with the experimental ones in the range of cut-off frequency, which proves that the method is feasible for hydraulic noise suppressors. Secondly, two types of inlet/outlet offset expansion chamber structures (configurations 1 and 2), which are widely used in gas silencing system are introduced into hydraulic system to make the corresponding pressure dampers, and their theoretical values are obtained by 1D analytical approach and three-dimensional (3D) finite element method (FEM) respectively. Finally, the effect of structural parameters such as insertion depth, eccentricity and deflection angle on the effectiveness of 1D method is explored in the case of non-planar wave effect in the expansion chamber cavity. The results show that when the eccentricity of configurations 1 and 2 is 40 mm and the deflection angle is 180°, the insertion depth of the inlet and outlet tube has a great influence on the transmission loss (TL) in the high-frequency region of 5000 Hz (cut-off frequency is 5469 Hz); When the insertion depth of configurations 1 and 2 is set, the influence of eccentricity and deflection angle on the accuracy of the 1D method in the range of 0?4000 Hz can be negligible, but it should not be ignored in the range of 4000?5000 Hz.