中比转速离心泵小流量工况下压力脉动特性

Pressure Fluctuation Characteristics of Centrifugal Pump with Medium Specific Speed at Low Flow Operation

采用Navier-Stokes方程和RNG k-ε湍流模型,对不同流量工况下离心泵内部非定常流动进行了数值计算,计算得到的离心泵外特性与试验结果吻合较好。数值模拟结果表明,不同流量工况下叶轮内压力脉动具有明显的周期性变化,压力脉动强度随着流量的减小而增强,叶片压力面脉动强度更加剧烈,叶轮旋转频率始终占主导作用。由叶轮进口至出口,叶片压力面和吸力面压力脉动最大幅值均渐渐增大。相同监测点的压力脉动最大幅值在30%设计流量工况时最大,约为设计流量工况下3~4倍。随时间叶轮流道内存有旋涡的产生、发展、脱落的周期性变化过程,这是造成离心泵运行效率低、压力脉动副值增大、脉动波形紊乱的主因。

The unsteady flows for different operating conditions in centrifugal pump are numerically investigated by using Navier-Stokes equations and RNG k-e turbulence model. The calculation results of external characteristic are in good agreement with experimental data. The pressure fluctuation in impeller has obvious periodic property under different flow conditions, the intensity of pressure fluctuation increases with the decrease of flow rate. The influence of low flow condition on impeller suction side is the most obvious. The dominant frequencies of pressure fluctuation on blade surface are the impeller rotating frequency. The amplitudes of pressure fluctuation increase gradually from impeller inlet to outlet. The maximum amplitude of pressure fluctuation appears in the condition of 30% design flow and the value is about 3 - 4 times of that under design flow condition. The vortex in impeller is also periodically generated, developed and shed, which is the main cause of low operating efficiency, large pressure fluctuation and disturbed fluctuation waveform of centrifugal pump.