离心泵作透平水动力噪声特性研究

Hydrodynamic Noise Characteristics Research in Centrifugal Pump as Turbine

为研究离心泵作透平在水动力载荷激励作用下的噪声特性,以某单级离心泵反转作透平为研究对象,基于雷诺时均法获得透平内部非定常流场,进而运用直接边界元法求解叶轮和壳体壁面偶极子源引致的噪声,并借助水听器对透平出口水动力噪声进行试验测量.在对计算获得的水动力噪声试验验证的基础上,对比了各过流部件压力脉动特性以及不同性质噪声源的辐射声压特性.研究结果表明,450Hz以内的低频段内,壳体声源作用的水动力噪声能够体现多声源的共同作用,最优和大流量工况下计算与试验频谱曲线吻合较好,叶频及其倍频下平均误差仅为4.35%.蜗壳内压力脉动主频为叶频,叶轮流道内除次主频叶频外存在1个主频轴频,进水管和尾水管内压力脉动主要为蜗壳内压力脉动传播所致,而叶轮内部形成的低频压力脉动传播现象不明显.轴频处,叶轮旋转偶极子作用下的声压较强;而在叶频及其倍频处,壳体偶极子是主要声源.

To investigate the noise characteristics under hydrodynamic fluid load in centrifugal pump as turbine( PAT),a single-stage centrifugal pump in reverse operation was chosen as research object. The unsteady flow was obtained based on Reynolds-averaged Navier-stokes method( RANS),the Direct Boundary Element Method( DBEM) was subsequently used to solve hydrodynamic noise caused by impeller and casing dipole sources. Experimental measurement was performed through the hydrophone to validate calculation accuracy. Then,the pressure fluctuation characteristics in various components and radiated sound pressure characteristics of different noise sources were compared. Results show that the hydrodynamic noise due to casing dipole source can reflect joint action of multiple sources in low-frequency band below 450 Hz.The calculated spectrum curves agree well with experimental results under optimal and larger flow conditions. The average error is only 4. 35% at Blade Passing Frequency( BPF) and its harmonics. The unsteady flow in volute is characterized by periodic fluctuation with BPF as dominant frequency. While,apart from the secondary BPF,shaft frequency dominates the pressure fluctuation in impeller. The pressure fluctuations in inlet pipe and draft tube are mainly caused by the transmission of pressure fluctuation in casing,not low-frequency pressure fluctuation formed in the impeller. At shaft frequency,the sound pressure due to impeller rotating dipole is stronger. While at BPF,the casing dipole is main source.