叶片正弯曲对间隙流动损失的影响

对具有2.3%相对顶部间隙的常规直叶栅和正弯叶栅的流道及间隙内的气动参数进行了详细测量,实验结果发现:顶部间隙的存在对叶栅的气动性能有较大影响,使叶栅上半翼展损失明显增高;叶片正弯曲减小了叶顶后部的横向压力梯度,削弱了泄漏流与端壁横流的相互作用,降低相对漏气量的同时也降低了叶栅的流动损失,明显改善了叶栅的出口流场。 

EFFECTS OF BLADE CURVING ON CLEARANCE FLOW LOSSES

Detailed experimental investigations of the flows in the cascades of conventional straight blades and positively curved ones,both with 2.3% tip clearance,were carried out in a low speed wind tunnel.The measuring planes were arranged as 4 before,11 in 4 after the cascades and 1 in the middle of the tip clearance.Flows inside the clearance were searched in great detail with a micro five-hole pitot tube of 1mm head size and another of 5 mm head size in the passage.The quite detailed information about the tip leakage flows and the flows in the cascades has been obtained,such as flow vectors,pressure and loss distributions throughout the clearance and in the passage.In comparison with the conventional straight blades,positive blade curving decreases the flow vectors within the tip clearance and also reduces the strength of the leakage vortex.As a result,the mass flux crossing the tip clearance decreased,the interaction between leakage vortex and passage vortex in the curved cascade also decreased.Thereby,the total flow losses downstream of the curved blade have been cut down by 8%.