变转速工况下离心泵蜗舌处压力波动的试验研究

Experimental Study of the Pressure Fluctuation Around the Volute Tongue of a Centrifugal Pump At Variable Rotating Speed

对某一单吸离心泵在变转速工况下蜗舌处的压力波动进行了测量与分析。该离心泵的叶轮为半开式叶轮并具有背叶片,它由原叶轮车削后得到,从而使得叶轮出口离蜗舌距离较大。结果显示:随着转速的提高,离心泵的流量及效率线性增大,而扬程以二次曲线形式增加。该离心泵蜗舌附近的压力波动频谱以叶轮转动频率整数倍的离散分量为主,特别是叶片通过频率及其二次谐波。最大波动分量的幅度占参考动压ρv22/2(v2为叶轮出口周向速度)的0.5%左右。随着转速的增大,压力波动的增加速度比转速提高速度快,且宽频波动幅度的提高比离散分量显著。另外,频谱分量中存在叶轮转动频率非整数倍的离散分量,以及与转速无关而取决于流体系统固有振动特性的离散分量。

In this paper,the characteristics of the pressure fluctuations around the volute tongue of a centrifugal pump running at variable speed was studied. The pump under study has a single suction and a single volute casing. The impeller is unshrouded,and has five backswept main blades in the front side and small back blades. It was machined from an original impeller causing large clearance between the blade tip and casing. The results show that the flow rate and efficiency vary linearly with the rotational speed,while the water head is a quadratic function of the rotational speed. In the pressure fluctuation spectra,the discrete components related to the impeller rotation are outstanding,especially the blade passing frequency（ BPF） and its second harmonic; the maximum amplitude of pressure fluctuation is approximately 0. 5% of the reference dynamic pressure 0. 5ρv22where v2 is the circumferential velocity at the impeller outlet. With the pump speed increasing,the intensity of pressure fluctuations increases more rapidly,and the broadband pressure fluctuations increase more noticeably than the discrete components. Some discrete components have frequency not exactly integral multiples of the rotational speed. They may be related to the natural frequencies of the fluid system.