旋转失速条件下离心泵叶轮压力脉动特性研究

Investigation of Pressure Fluctuation in Centrifugal Pump Impeller under Rotating Stall Conditions

离心泵发生旋转失速时,失速团周期性地生成和脱落往往会诱发低频压力脉动,严重影响水泵的安全稳定运行。为研究离心泵旋转失速对压力脉动的影响,采用动态混合非线性SGS模型对一离心泵叶轮进行了大涡模拟,得到了叶轮内部流场和叶片上的压力脉动特性。对不同旋转时刻的内部流动进行分析,可以看到旋转失速团产生于叶片吸力面头部附近,沿圆周方向向叶片压力面运动,并逐渐衰减。对叶片上的压力脉动进行分析,发现当旋转失速发生以后,叶片上的压力脉动幅值远大于非失速工况。失速团对叶轮中的压力脉动有很大影响,叶片上的压力脉动频率以失速频率为主;叶片吸力面头部压力脉动幅值最大,并沿着水流方向,叶片上的压力脉动幅值依次减小。随着流量进一步减小,叶轮进入深失速工况,压力脉动主频幅值有所降低,而失速频率逐渐增大。

Under the rotating stall condition the periodic generation and shedding of stall cells always induce the low frequency pressure fluctuation,which has severe influence on the safety and stability of pumps. In order to reveal the role of the rotating stall cells in the pressure fluctuations,a centrifugal pump impeller was chosen as the research object to investigate by numerical simulation. A number of reference locations were arranged in the entrance of the passages for recording the pressure fluctuation.A developed large eddy simulation named dynamic mixed nonlinear model（ DMNM） was applied to the numerical simulation and the simulation results showed good agreement with the experimental results. The internal flow field and pressure fluctuation characteristics under different stall operation conditions were also obtained. The simulation results showed that the stall cells first occurred in the suction side of the blade,and then moved to the pressure side with continuous decay. When the rotating stall occurred,the amplitude of pressure fluctuation was much higher than that at unstalled point. The propagation of stall cells had significant effect on the pressure fluctuations in the impeller. The dominant frequency of pressure fluctuation at blades was rotating stall frequency. The maximum amplitude of pressure fluctuation was located at the leading edge of blade,and it decreased gradually along the flow direction. As the flow rate was further reduced, the amplitude of dominant frequency decreased but the stall frequency increased. This research can provide useful reference for the secure and stable operation of centrifugal pumps.