基于大涡模拟的离心泵水动力噪声数值模拟

Numerical Simulation of Hydrodynamic Noise in Centrifugal Pump Based on LES

运用计算流体力学(Computational fluid dynamics,CFD)技术及Lighthill声类比理论研究离心泵3个流量下由蜗壳及叶片表面偶极子声源产生的水动力噪声。离心泵内部瞬态流场由大涡模拟方法(Large-eddy simulation,LES)模拟得到,流场计算结果显示,各流量下隔舌处压力脉动在叶片通过频率BPF处有明显峰值,说明叶轮和隔舌之间的相互作用是引起离心泵隔舌处压力脉动的主要原因。以离心泵内表面作为边界元模型,考虑蜗壳的散射效果。采用直接边界元法求解离心泵内声场,声场计算结果与试验结果吻合良好,验证基于LES和Lighthill理论的流动噪声数值模拟方法的可行性。结果表明,轴频点的声压峰值在设计工况下最小,叶频及其谐频处的声压峰值随流量的增加而升高;通过计算叶片偶极子声源噪声,可以定量预测叶频及其谐频点的噪声;蜗壳偶极子噪声的计算值与试验结果趋势一致,小流量工况下误差较大。

The computational fluid dynamies（CFD） technique combined with the Lighthill acoustic analogy theory are applied to study the hyodynamic noise caused by the volute surface dipole and the blade rotating dipole in a centrifugal pump. The large eddy simulation method is employed to solve the transient flow field of the pump. The fiuid fields show that obvious peak of pressure fluctuations near the tongue is observed at blade passing frequency under different flow conditions, indicating that the interaction between the impeller and the tongue is the main cause of pressure fluctuation near the tongue. The interior boundary element method（BEM） model of pump is constructed, and the sound scattering effect of the volute easing is considered. The direct BEM is applied to solve the interior sound field of the pump. The computational results show good agreements with experimental ones. The validation of the LES combined with the Lighthill method for the hydrodynamic noise computation is verified. The results show that the sound pressure level at the shaft frequency under the design point is lowest, and the level of noise at the blade frequency and its harmonics becomes higher as the flow rate increases. The noise level at the blade frequency and its harmonics can be predicted quantitatively by calculating the blade rotating dipole source. The trend of the noise eansed by the volute surface dipole is identical with the experimental trend. Comparing with the design and higher flow rates, the error between simulation and experiment is bigger at partial flow rate.