冲压叶栅边界层抽吸处理分析

Numerical Investigation on the Effects of Boundary Layer Suction in a Ramrotor Cascade

关键词:  冲压叶栅  边界层抽吸  数值模拟

Key words:  Ramrotor cascade  Boundary layer suction  Numerical simulation

摘要:

为了提高冲压转子叶片的性能,通过数值模拟的方法研究了边界层抽吸技术在内压式冲压叶栅上的应用,结果表明,与未抽吸的工况相比,采取抽吸措施可以提高冲压叶栅的增压能力,且其增压能力随着抽吸流量的增加而提高。在喉口位置之前抽吸会增强抽吸缝后的激波强度；而在喉口以及喉口之后的亚声区进行抽吸可以增大叶栅扩张段的气动流通面积,这会使结尾激波向叶栅出口移动,有利于提高冲压叶栅的压比；在结尾激波之后的低能流体聚集区抽吸更有利于冲压叶栅总压恢复系数的提高。在喉口之后抽吸时,对于某一确定抽吸位置的工况,存在着使总压恢复系数最大的最佳抽吸流量；研究结果还表明,当抽吸流量固定时,在喉口位置抽吸比在其它位置抽吸更能提高冲压叶栅的增压能力。 

Abstract:

A numerical simulation on the effects of boundary layer suction was carried out in a ramrotor cascade. The results indicate that the pressure ratio of the cascade can be increased by means of the boundary layer suction. And the results show that the increase of the suction flow rate tends to increase the pressure ratio of the cascade. The suction effect trends to enhance the strength of shock waves located at downstream region of the suction slot when the boundary layer suction is performed at the upstream location of the cascade throat. The effect of boundary layer suction on cascade throat or at the subsonic region can enlarge the through flow area of the cascade. It causes the terminal shock to migrate towards the outlet of the cascade,which can benefit the enhancement of the cascade pressure ratio. The predicted results also show that the aerodynamic loss can be decreased through the adoption of a suction, which is located at high entropy area after terminal shock. In this investigation, an optimal suction flow rate can be observed for a given suction location downstream of throat, which is corresponding to a maximum value of the total pressure recovery coefficient. For a constant suction flow rate, the numerical comparison between different suction locations indicates that a higher pressure ratio of the cascade can be obtained by the suction at the cascade throat.