叶顶间隙对离心叶轮气动性能的影响规律

Analysis of Aerodynamic Performance Affected by Blade Tip Clearance in Unshroud Centrifugal Impellers

为明确半开式离心叶轮的间隙值与间隙气流对叶轮气动性能的影响,采用数值方法分析了典型叶轮叶顶相对间隙值为0~10%之间的叶轮气动性能、叶片载荷分布、间隙泄漏量的变化规律.得出:间隙对叶轮气动性能的影响基本呈线性或分段线性关系,间隙泄漏量与叶顶载荷具有相同的分布规律,表明泄漏量变化的主要控制因素是叶顶载荷;间隙仅影响流道后半段的叶顶载荷分布,原因是由于间隙进口强烈的气流加速运动,形成了间隙进口处的压力降,但这种压力降只体现于一定高度范围的间隙中;导致叶轮性能降低的主要原因还是间隙涡流与主流掺混引起的能量损失。

To estimate the blade tip clearance effects on the aerodynamic performance of unshroud impeller of centrifugal compressor,the numerical simulation method was applied to analysis the change of impeller performance parameters as efficiency and pressure ratio,blade loading distribution and tip leakage from 0 to ten percent relative tip clearances.The results indicated that the impeller efficiency and the pressure ratio were linearly decreased with the tip clearance increase,which the linear changes were different for the front and latter section in streamwise.The tip leakage was verified to be controlled by blade loading on blade tip and had same distribution trend with loading along streamwise.The reason of blade loading variation was due to the pressure drop on the gap inlet near the pressure side generated by the acceleration of tip gap flow from further down blade.