扩压叶栅叶尖非定常流动的涡动力学机理

Vortex-dynamics mechanism of tip-region unsteady flow in compressor cascade

为了揭示压气机叶尖区旋涡结构与流动非定常性之间的关联,采用URANS对一亚声速平面扩压叶栅在不同攻角下的流场进行了求解,并借助Q判据提取了叶尖瞬态涡系结构。结果表明:泄漏涡的破碎现象能够通过诱导新的涡结构间接作用于相邻通道的叶尖流动,是导致叶尖流场失稳的关键因素。在-0.3°和+0.7°攻角下,叶尖泄漏涡发生了螺旋破碎,并伴随有非定常诱导涡的出现,诱导涡对相邻叶片载荷的影响使得叶尖泄漏涡发生周期性摆动;在+1.7°攻角下,泄漏涡破碎会导致反流涡的形成,反流涡的输运会给叶片载荷和来流攻角带来非定常扰动,反过来又会作用于泄漏涡的破碎和反流涡的生成,最终表现为一种自维持的非定常流动现象。

To reveal the relation between vortex structures and flow unsteadiness in the tip region of compressors,we calculated the flow fields in a subsonic compressor cascade at different incidences by solving URANS equations and extracted the tip-region vortex structures based on the Q-criterion.The results show that unsteady breakdown of the tip leakage vortex can indirectly influence the tip-region flow by inducing the formation of new vortex structures and therefore is the key factor leading to the instability of the tip-region flow.At incidences of-0.3°and+0.7°,the spiral-type breakdown of the tip leakage vortex occurs,accompanied by the unsteady induced vortex.The effect of induced vortexes on the loading of the adjacent blade leads to the periodic fluctuation of the tip leakage vortex trajectory.At an incidence of+1.7°,the breakdown of the tip leakage vortex results in the formation of backflow vortexes.The transportation of backflow vortexes gives rise to the perturbations of blade loading and incidences,both of which,in turn,act on the vortex breakdown and backflow vortex formation.This periodic process leads to the self-sustained unsteady flow phenomenon.