亚声速半开式离心叶轮叶顶间隙的流动特征

针对半开式离心叶轮的间隙泄漏和间隙气流对气动性能的影响,采用数值方法分析了3种叶顶间隙值下叶轮的气动性能、设计工况下的叶片载荷分布、间隙流动气流角以及泄漏涡的分布特征.结果表明:叶轮叶片表面的压力分布规律不受叶顶间隙的影响,但叶片载荷在叶片的中后部有不同程度的减小;间隙处的内泄漏流动本身引起的流动损失较小;与零间隙相比,间隙处的内泄漏气流对流道前半段主流的影响甚微,但在流道中部以后,间隙流扰乱了主气流方向,并在叶顶吸力面附近形成涡流聚集区,造成明显的熵增,带来不可忽视的能量损失.希望所得结果能为建立半开式离心叶轮的间隙气动模型提供参考.

Nature of tip clearance flow in subsonic unshroud impeller of centrifugal compressor

The tip clearance seriously affects the aerodynamic performance of unshroud centrifugal impeller.The flow field in impeller with three tip clearances was investigated using the numerical simulation method,and then the effect of tip clearance on the aerodynamic performance of impeller,blade loading,flow angle across the tip clearance and the motion of leakage vortex was analyzed in detail.The results indicate different tip clearances have little effect on the blade loading profile,but a value reduction of static pressure from the middle to the trailing age of blade.The flow loss on tip clearance is hardly generated by leakage flow itself.The main flow is disturbed by leakage flow in the second half of the flow channel rather than in the first half.There exist amounts of vortexes near the shroud which cause significant entropy increase which leads to energy loss.The results are hoped to help to develop the aerodynamic model of tip clearance in unshroud centrifugal impeller.