叶顶间隙对低比转数半开式离心泵性能的影响

为研究叶顶间隙对低比转数半开式高速离心泵内部流动及性能的影响,基于雷诺时均Navier-Stokes方程和Spalart-Amaras湍流模型,在叶顶间隙分别为0.5,1.1和2.5 mm时对一台比转数为19.3的半开式高速离心泵内部流动进行三维紊流数值计算,并进行外特性试验验证.研究结果表明：叶顶间隙可以改善叶轮内部的流动情况,但较大间隙的叶轮内部的循环流动引起的水力损失大于较小间隙内的循环流动和回流引起的水力损失;因此随着叶顶间隙的增大,离心泵扬程及效率均减小;而且在叶片中部和尾部的叶顶间隙层内,相对速度和静压随着叶顶间隙的增大而减小,且相对速度受叶顶间隙的影响尤为明显,静压沿着叶轮半径近似呈线性增加;叶轮流道内沿轴向分布的切向速度和径向速度随着叶顶间隙的增大分别减小,但切向速度较为均匀,减小量相对较小;数值模拟与试验得到的外特性曲线变化趋势一致.

Effect of tip clearance on performance of low specific speed centrifugal pump with semi-open impeller

In order to analyze the effects of tip clearance on the flow and performance of low specific speed high-speed centrifugal pump with a semi-open impeller, the inner flow field in a pump with the specific speed ns = 19.3 was numerically simulated based on the Navier- Stokes equations and the Spalart - Allmaras turbulence model at the tip clearances 0.5, 1.1 and 2.5 mm. The performance of the centrifugal pump was measured as well. The results show that the flow in the impeller is improved with a bigger clearance, but the hydraulic loss caused from the circular flow in the impeller at a relatively big clearance is larger than that at a more tight clearance, so the head and efficiency were decreased with increasing tip clearance. Also, the relative velocity and static pressure of fluid in the clearance were reduced at the middle and trailing edge of blade with increasing tip clearance, especially the relative velocity. The static pressure shows a nearly linear relation to radius. The tangential and radial velocity along the axial direction in the impeller passages were lowered with increasing clearance. Comparison of the results simu- lated with the experimental data suggests CFD method is quite able to simulate a change in the perfor- mance due to varying tip clearance.