叶顶喷气对高负荷轴流压气机性能的非定常影响机理

Mechanism of Unsteady Influence of Tip Injection on a High-Loaded Axial Compressor Performance

关键词:  轴流压气机  数值模拟  叶顶喷气  稳定裕度  非定常影响  叶顶堵塞

Key words:  Axial compressor  Numerical simulation  Tip injection  Stability margin  Unsteady influence  Tip blockage

摘要:

为了揭示叶顶喷气对高负荷压气机气动性能和稳定裕度的非定常影响机理，对一跨声速轴流压气机进行六通道三维非定常数值模拟，定量分析了两种喷嘴作用下压气机内部流场的变化。研究表明叶顶喷气提升了压气机的总压比和稳定裕度，对效率的影响不大，喷气量决定了对压气机气动性能的影响程度。喷气引起叶顶进出口流量的非同步周期性变化，当喷气流沿通道到达转子尾缘后完成对叶顶的降载作用，叶顶负荷呈周期性变化。喷嘴喉部高度不变时，27.3%和54.6%的周向覆盖比例分别获得3.3%和3.6%的裕度改进，分析可知喷气的扩稳效果取决于喷气对叶顶堵塞的抑制在通道出口产生的影响。喷气流在通道中的流动延迟使得喷气对通道出口堵塞抑制的时间大于对通道进口堵塞的抑制时间，因而较小宽度的喷嘴可以保证对叶顶堵塞的有效抑制，增加喷嘴的宽度对稳定裕度的影响不大。

Abstract:

Mechanism investigation on the unsteady influence of tip injection on a high-loaded compressor aerodynamic performance and stability margin was presented with the method of six-blade-passages three-dimensional unsteady numerical simulation in a transonic compressor. Quantitative analysis was made on the change of inner flow fields at different operating conditions with the application of two distinct injectors. The results show that tip injection is able to improve compressor total pressure ratio and stability，but it has little impact on compressor efficiency. The degree of the influence on compressor performance is determined by injected mass flow. Tip injection induces asynchronously periodic fluctuation of mass flow at compressor inlet and outlet of tip region. Blade tip loading will not be unloaded until the injected flow arrives at blade trailing edge，and blade tip loading varies periodically accordingly. The stability gain of 3.3% and 3.6%，respectively，is achieved by circumferential coverage percentage of 27.3% and 54.6%，respectively，with the identical injector throat height. It is proved that the effect on stability improvement of tip injection depends on the impact that tip injection makes at blade passage outlet by depressing tip blockage. The delay of injected flow in blade passage makes the blockage depression duration at passage outlet longer than that at passage inlet，so a small width injector is sufficient to depress tip blockage effectively and extending injector width contributes little to stability improvement.