轴流泵轮缘间隙非定常流动的大涡模拟

Large Eddy Simulation of Unsteady Flow in Tip Region of Axial-flow Pump

为了揭示轴流泵叶顶间隙流动特征,采用LES方法和滑移网格技术,对一低比转数轴流泵的内部湍流进行了数值计算,分析了5种不同工况下轮缘间隙泄漏涡形态及叶片近轮缘区压力脉动特性。结果表明:不同工况下,轮缘间隙主泄漏涡均发展至相邻叶片正面,其起始位置随流量增加沿流向逐渐上移;主泄漏涡与叶片夹角随流量增加逐渐减小,0.7Qd和1.2Qd工况下分别为20°和14°;叶片表面近轮缘侧压力脉动幅值均随偏离设计工况程度的增大而增加,压力面增幅尤为显著;受轮缘泄漏涡影响,0.7Qd工况下,叶片正面进口边近轮缘侧监测点PP3处压力脉动幅值为设计工况下的8.5倍,脉动频率以高频为主,流量大于1.0Qd时,该监测点压力脉动主频为叶轮转频。

To discover the characteristic of tip clearance flow,the large eddy simulation( LES) method with sliding mesh technique was used for analyzing the unsteady flow in a low-specific-speed axial-flow pump under five different operating conditions.The tip-leakage vortices and pressure pulsations of neartip zone on the blades were examined.It was found that the dominant tip-leakage vortex extended to the pressure side of the neighboring blade for all five investigated flow rates.As the flow rate increased from0.7Qd to 1.2Qd,the angle between the dominant tip-leakage vortex and the blade reduced from 20° to 14°.The results also showed that the amplitude of pressure fluctuation in the near-tip zone on the blades became higher when the flow rate was farer from the design flow rate,especially on the pressure side of the blade.At the 0.7Qd condition,the pressure fluctuation amplitude of the monitoring point PP3( at the near-tip zone on the pressure side of the blade close to the blade leading edge) was 8.5 times of the one at design flow rate,and the high-frequency pulsation occurred due to tip-leakage vortices.When the flow rate was more than 1.0Qd,the pressure fluctuations of PP3 was dominated by the rotation frequency.