带翼型围带涡轮叶栅冲角适应性的实验与数值研究

Experimental and Numerical Investigation of the Adaptability to Incidence Variation of a Turbine Cascade With Winglet-Shroud

针对一新型翼型围带结构,通过数值计算验证其相对于全周小翼结构在改善涡轮叶栅气动性能的优势。在此基础上,结合实验与数值模拟分析了带此翼型围带涡轮叶栅的冲角适应能力。结果表明,翼型围带可在全周小翼基础上进一步削弱泄漏涡与通道涡强度,使涡轮叶栅下游流场更为均匀;冲角变化主要影响叶片表面前半部分的静压系数,冲角增加,中径与近叶顶区域的横向压差增大,导致通道涡强度增加;由于冲角变化对泄漏涡生成发展的通道后部区域的静压改变不大,所以泄漏涡对冲角的敏感性不强;基于负冲角可改善涡轮叶栅气动性能的结果,文章最后对多组大负冲角下的叶栅性能做了数值研究,发现冲角小于一定值时,压力面流体分离严重,导致-80°冲角的总压损失甚至高于+10°冲角。

Numerical simulations are carried out to verify the advantages of a new winglet-shroud blade tip structure with respect to the pure winglet structure in improving the aerodynamic performance of a turbine cascade.Based on this result,experiments and numerical simulations are further conducted to investigate the adaptability to incidence variation of the turbine cascade with winglet-shroud.Results indicate that relative to the pure winglet,the winglet-shroud further weakens the leakage vortex and the passage vortex intensity.This leads to the downstream flow field of the turbine cascade being more uniform.The variation of incidence mainly affects the static pressure coefficient distribution in the front part of the blade surface.The lateral pressure difference at the midspan and near blade tip increases with the increase of incidence,which leads to the increase of the passage vortex intensity.Incidence has little effect on static pressure in the rear part of passage which can alter the development and generation of leakage vortex.Based on those results,it is demonstrated that negative incidences can improve the aerodynamic performance.The aerodynamic performance of the cascade at other conditions of large negative incidences is further studied.It is found that fluid separation on the pressure surface is serious when the incidence is less than a certain value,i.e.—80°at which the total pressure loss is even higher than that of ＋10°.