叶轮出口宽度对离心泵噪声辐射影响的分析与试验

为研究叶轮出口宽度对离心泵在水动力激励下泵壳振动辐射噪声的影响，该文以一台单级单吸离心泵为研究对象，保持泵体和叶轮其他几何参数不变，运用FEM\BEM（finite element method\boundary element method）声振耦合计算和试验测量方法进行了叶轮出口宽度分别为10、8和12 mm的噪声辐射分析。采用大涡模拟方法对离心泵内部瞬态流场进行计算，得到蜗壳壁面偶极子声源。在对泵壳体结构进行模态分析的基础上，利用LMS Virtual Lab的间接边界元IBEM声振耦合模块计算非定常流动引起的离心泵内部噪声，并进行了试验验证，在此基础上，对离心泵外场噪声及其声辐射进行计算，并研究了叶轮出口宽度对离心泵外场噪声辐射的影响。结果表明，离心泵叶片通过频率处的辐射声功率随着叶轮出口宽度的增大而增大；叶轮出口宽度存在一个合适的取值范围，使得各流量工况下外场噪声声压级较小；综合考虑离心泵能量性能与外场噪声，叶轮出口宽度为10 mm时，离心泵综合性能较优。研究结果可为低振动低噪声离心泵的水力优化设计提供参考。

Analysis and experimental of centrifugal pump noise based on outlet width of impeller

Abstract: In order to better understand the effects of impeller outlet width on the flow-induced vibration and noise of centrifugal pumps, a single grade end suction centrifugal pump was chosen as research object. The impeller outlet width was varied from 8mm to 10mm and 12mm, while the volute and other geometric parameters were kept constant. The flow-induced noise of centrifugal pumps was studied experimentally and numerically. A FEM\BEM acoustic-vibration-coupling method was developed to study the effect of impeller outlet width on the centrifugal pump noise caused by the hydrodynamic forces. The developed method was validated and verified through experimental results. For the internal flow of pumps characterized by a small Mach number, the sound analysis of fluid was separated into the following two steps. The first step was a hydrodynamic analysis, which is a CFD simulation to be performed to obtain noise-generating fluid forces; in this step, the large eddy simulation method was used to solve the transient flow field of the pump, and a time series for the pressure fluctuations at the fluid-wall interface was obtained. The second step was hydroacoustic-vibration coupling analysis, which considers the solution of an inhomogeneous wave equation. The fluid pressure fluctuations obtained at the first step are fed to the pump case structure causing vibration of the outer casing surface vibrating, based on the elastic-wave propagation of the structure,the vibration velocities on the outer casing surface was simulated. And the acoustical simulation of noise emission to the environment was performed by FEM\BEM methods, in which the feedback influences of environmental noise on the structure and of structural vibration on the fluid were considered. In the second step, the modal of the pump casing structure was analyzed using the finite element method (FEM), and the acoustic noise caused by the unsteady flow of the pump was calculated by the acoustic-vibro coupling module of the Virtual Lab software. First, the interior noise fields were calculated and compared with experimental results, showing that the validation of the LES combined with the FEM\BEM methods for centrifugal pump noise computation was verified, and the FEM\BEM coupling methods was more accurate than the BEM uncoupling methods. On this basis, the outer sound fields were investigated, and the effect of impeller outlet width to outer sound fields was studied. The results show that the sound power at the blade passing frequency becomes larger as the impeller outlet width increases. In order to investigate the sound spatial distribution around pump, 36 monitoring points were arranged each 1 meter farther from the center of impeller, and noise directivity distribution was obtained by using FEM\BEM calculations. The noise directivity results show that the sound pressure level at the blade passing frequency becomes larger as the impeller outlet width increases, and the growth amplitude of the sound pressure level increases as the impeller outlet width increases. Considering the energy performance of the pump and the outer sound field, there exists a suitable impeller outlet width to ensure a better comprehensive performance of the pump. The research results are helpful for hydraulic optimization design of low vibration and low noise centrifugal pumps.