低比速离心泵半开式叶轮内流场的模拟

Numerical Simulation of Internal Flow Field of an Unshrounded Centrifugal Impeller in a Low Specific Speed Pump

本文数值模拟研究一种低比转速离心泵半开式叶轮内的三维流场,比较了不同流量时叶轮内部的流场情况。结果表明,在低流量时叶轮内较大区域中存在二次流和回流,同时由于叶轮顶端间隙处泄漏流的存在,流体在周向滑移严重,出口流动角度减小。当流量增大时,叶道中二次流及回流情况有所好转。随着流量的进一步增大至超过设计流量点时,在叶片压力侧前端可以看到分离泡,不利于叶片作功。文中详细研究了沿流道不同垂直截面内相对速度的分布和发展过程。

In this paper, a numerical study of the turbulent flows in an unshrounded centrifugal impeller for a low specific speed impeller is carried out. The three-dimensional flow features at four flowrates for the impeller are compared and analyzed. It shows that at lower flow rates, secondary and returning flows happen in a large area range of the impeller. Because of the leakage flows from the blade tip clearance, tangential slip of the flow can be observed, which reduces the flow angle at the impeller exit. Increasing the flowrate is found to be helpful for suppressing the secondary flow as well as the flow-returning. However, when the flowrate exceeds the design value, a separation bubble on the pressure side is observed near the leading edge of the blade, which may cut down the work-doing capability of the impeller. The development of the flows in the cross-sections along the impeller passage is presented and analyzed.