对环形叶栅内非定常流动特征参数的实验研究

Research of the Unsteady-Fluid Characteristic Parameter in an Annular Cascade

通过环形叶栅实验,测出叶排后流场速度分布,捕捉叶排后流动分离的特征频率,观测气流攻角和流量的影响,分析出环形叶栅后的旋涡脱落频率及与其他气动参数之间的相互关系。在大的负攻角下,分离区范围广阔,旋涡强度也较大,分离区衰减慢,但它是收敛型的分离旋涡;在大的正攻角下也存在类似的现象,但其旋涡强度更大,是扩散型的,这意味着大的正攻角造成的分离更为危险,而叶轮机械中的不稳定流动现象(旋转失速、喘振等)又往往是由此引起;而当攻角接近设计攻角时,分离明显减小,且很快被主流区掺混而逐渐消失。在环形叶栅试验中,发现在不同测量状态下(不同攻角和流量)都存在值为723Hz左右的特征频率,然而幅值(气流分离强度)却有相应变化。

In the annular cascade test,we aim to observe the fluid field behind the annulus blades,focusing on the velocity field and the vortex shedding frequency in particular,and to investigate the effect of fluid incidence and flux on them.In comparison with the cascade with high positive incidene,the high negative incidence cascade has wider separating section,stronger vortex,and slower wake delay,but weaker vortex intensity.As the incidence approaches the designed value,it can be seen obviously that the separation diminishes and dissipates as the vortices quickly blend with the main flow. Additionally,there is a characteristic frequency valued at 723 Hz in the diverse cases.