叶尖间隙对离心叶轮偏置分流叶片工作机理的影响

Effect of tip clearance on the operating mechanism of offset splitter blades in a centrifugal compressor

采用计算流体力学方法研究了不同叶尖间隙情况下偏置分流叶片提升离心叶轮性能的机理.叶尖间隙较小时,主叶片吸力面附近分离区导致主要损失,分流叶片偏向于主叶片吸力面利于削弱损失、提升叶轮性能;随着叶尖间隙的增加,泄漏流的影响增加以至损失集中于分流叶片和主叶片压力之间的通道,分流叶片宜向主叶片压力面偏置,以减少泄漏流在同一通道的聚集.叶尖间隙和分流叶片周向位置对间隙泄漏流、叶片吸力面分离形成的损失及相互关系有着耦合影响,分流叶片周向位置的改变可以调整通道的横向压力梯度、泄漏流掺混入主流的位置,改善分流叶片两侧通道的损失的分配,分流叶片最佳偏置方向随叶尖间隙的大小而发生改变.

The good circumferential position of offset splitter blades and its mechanism were studied in small centrifugal impellers, which operated with different tip clearances by the computational fluid dynamics. When the impeller worked with the small tip clearance, the main loss was attributable to the separation near the main suction surfaces, and then the offset splitter bias toward the main suction surface can suppress this loss and enhance the im- peller performance. The tip leakages increased with the tip clearance, so the loss concentrat- ed in the passage between the main pressure surface and splitter, therefore the splitters ten- ded to the main pressure surface, and then the offset splitters can reduce the concentration of the tip leakage and the loss. The tip clearance and the circumferential position of the splitter affected together the tip leakage, the separation near the suction surface and their interrela- tion. The design of the splitter circumferential position can adjust the crosswise pressure gradient in the blade passage and the location where the tip leakage mixes in the main flow, and then improve the ratio of the losses in the passages at both sides of splitter, therefore the best circumferential position of the splitter changes with the tip clearance.