机匣喷气位置对涡轮间隙流动控制的影响

Effects of casing air injection position on controlling tip clearance flow in axial turbines

关键词:  航空发动机  涡轮  涡轮效率  二次流  流动特性

Key words:  Aircraft engine  Turbine  Turbine effectiveness  Secondary flow  Flow characteristic

摘要:

采用数值模拟方法对利用机匣喷气方式控制涡轮间隙流动进行了研究。结果显示,采用机匣喷气方法能降低通过间隙的流量,推迟间隙涡形成,减小通道内二次流分布区域,使得涡区相对总压增大。采取适当的喷气位置,可以提高涡轮效率。不同轴向位置喷气提高涡轮效率的原理不同,30%轴向弦长位置喷气主要是减小上通道涡损失,而60%轴向弦长位置喷气主要是减小间隙涡损失。最大效率出现在30%轴向弦长位置喷气1%主流流量时,效率可以提高0.3341%。

Abstract:

This paper presents a numerical investigation of a novel method for tip desensitization based on casing air injection.The detailed three-dimensional flow structure was revealed inside the tip clearance.The effects of different injection position on turbine performance were compared with the baseline case without injection.The results show that casing air injection can reduce tip clearance massflow effectively,and delay the inception of tip clearance vortex axially.Moreover,sizes of both tip clearance vortex and tip passage vortex decrease.Thus turbine isotropic efficiency can be improved with appropriate injection position.The 30% axial chord injection case yields the largest reduction of loss in regions occupied by the tip passage vortex,but injection at the 60% axial chord has more effect on the tip leakage vortex.In the current study,the optimum isotropic efficiency occurs when 1% passage massflow is injected at 30% axial chord,which is improved by 0.3341 percent points.