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.