叶顶泄漏流对半开式离心泵叶轮流动结构的影响

为研究不同叶顶间隙下叶顶泄漏流对半开式叶轮离心泵流动结构的影响,设计5种不同尺寸叶顶间隙方案,采用SSTk-ω湍流模型,对半开式叶轮离心泵进行全流道三维数值计算,分析半开式叶轮叶顶间隙内部流动结构并进行可视化实验验证.结果表明:随着叶顶间隙的减小,离心泵的扬程和效率明显上升,间隙值减小到0.7 mm时,进一步减小叶顶间隙,泵的效率不再有明显变化;叶顶间隙选取最佳值对泄漏涡发展有一定的抑制作用.利用Q准则对涡进行判别发现:随着间隙的减小,主泄漏涡强度减弱,二次泄漏涡逐渐消失,对主流的影响减小;当间隙减小到0.7 mm时,二次泄漏涡完全消失,主泄漏涡强度最弱;叶顶间隙泄漏流对流场的干涉程度受流量影响,小流量工况时,通过减小叶顶间隙可以提高叶片区流动抗干扰能力.

Effect of tip leakage flow on flow structure of semi-open centrifugal pump impeller

In order to study the effect of the tip leakage flow under different tip clearances on the flow structure of the semi-open impeller centrifugal pump, five different tip clearance size schemes were designed. The SST k-ω turbulence model was used to calculate the whole flow field of the semi-open impeller centrifugal pump. The internal flow structure of the semi-open impeller tip clearance under different working conditions was analyzed and verified by visualization experiment.The results show that with the decrease of the tip clearance, the head and efficiency of the centrifugal pump significantly increase, but when the clearance value is reduced to 0.7 mm, the pump efficiency no longer changes significantly with further decrease of the tip clearance. Choosing the optimum value of the tip clearance has a certain inhibition effect on the development of leakage vortex. It can be found by using the Q criterion to discriminate vortex, as the clearance decreases, the strength of the main tip leakage vortex weakens, the secondary tip leakage vortex in the mainstream channel gradually disappears, and the disturbance to the mainstream decreases. When the clearance is reduced to 0.7mm, the secondary leakage vortex completely disappears, and the strength of the main leakage vortex is the weakest. The degree of interference of the leakage flow at the blade tip on the flow field is affected by the flow rate. At low flow condition, by reducing the tip clearance, the anti-interference ability of flow in the blade region can be improved.