端壁组合射流对高速扩压叶栅损失特性的影响

Loss Reduction of a High Speed Compressor Cascade

关键词:  扩压叶栅  流动损失  端区流动  组合射流

Key words:  Compressor cascade  Flow losses  End-wall flow  Combined-jets

摘要:

提出了一种端壁组合射流技术以控制进口马赫数0.67的高速扩压叶栅端区流动。通过前缘射流旋涡可以增强端壁附面层与主流间的流体交换，阻碍横向二次流动，减小角区低能流体堆积；而采用角区射流注入能量能够进一步减弱吸力面侧流动分离。以上组合控制方法可较单独采用前缘或角区射流更有效减小栅内损失，提高其气动性能。当角区射流位于近吸力面侧的分离起始位置附近时，其改善栅内流动的效果最佳；远离吸力面的端壁射流则可抑制端区低能流体横向迁移及其与分离区流体间的相互作用，但其减小损失的效果弱于近吸力面侧的射流。随着射流总压比的增加，组合射流减小损失的效果先增加后减小；过大的总压比会加剧射流与来流间的掺混损失，使得叶栅气动性能恶化。当射流总压比为1.2时，损失减小最大可达12.6%，而射流流量仅相当于叶栅进口流量的0.64%。

Abstract:

A new method using combined-jets is proposed to control the end-wall secondary flow in a high speed compressor cascade with inlet Mach number of 0.67. The end-wall vortex generator jet (VGJ) near the leading edge could enhance the fluid exchange between the end-wall boundary layer and the mainstream，thus suppressing the cross flow and reducing the low energy fluid accumulation in the corner region. The injection of high energy fluid by the corner jet(CJ) could further delay the separation on the rear part of the suction side. Therefore，a more significant loss reduction and better cascade performance could be obtained with the combination of VGJ and CJ. With the location of the VGJ fixed，the best benefit is gained by the end-wall CJ applied near the suction side at the initiation of flow separation. Additionally，the jet with a certain distance from the suction side also shows a potential to reduce losses，which is caused by constraining the end-wall cross flow and weakening the low energy fluid accumulation in the corner region. With the increase of the jet-to-inflow total pressure ratio for the combined-jets，the total loss is decreased firstly and then increased. An excessive jet total pressure would strengthen the mixing losses of the jet and the inflow，thus deteriorating the cascade performance. A maximum loss reduction up to 12.6% is obtained with a jet-to-inflow total pressure ratio of 1.2，where the jet mass rate is only 0.64% of the inflow.