基于跨声速高压涡轮凹槽叶顶间隙模型的大涡模拟研究

Large Eddy Simulation on Transonic High-Pressure Turbine Cavity Tip Gap Model

关键词:  跨声速高压涡轮  凹槽叶顶  叶顶泄漏流动  大涡模拟  非定常流动

Key words:  Transonic high-pressure turbine  Cavity tip  Tip leakage flow  Large eddy simulation  Unsteady flow

摘要:

为研究跨声速高压涡轮叶顶间隙非定常流动特性及流场结构，基于跨声速高压涡轮凹槽叶顶间隙的几何特征，建立了可行的简化数值模型，并通过大涡模拟对叶顶凹槽间隙内部的非定常流动进行了数值计算，探讨了凹槽叶顶几何参数对流动稳定性和气动性能的影响。研究结果表明，当跨声速泄漏流动流经凹槽叶顶时，在凹槽入口处形成激波，同时凹槽前分离泡发生周期性膨胀并产生间隙脱落涡，脱落涡与激波相互作用使得凹槽内的激波呈现明显的非定常性；凹槽深度从1.0mm增加至1.5mm后，间隙脱落涡尺寸明显减小，其产生周期缩短20%，涡量拟能展向分量平均占比从40%升高至49%，同时间隙脱落涡的扩张、破碎过程及其与回流区的掺混受到抑制，使得泄漏流动的非定常性明显下降。

Abstract:

To investigate the unsteady flow character and flow field structure of transonic high-pressure turbine tip gap， a feasible idealized model constructed from the size based on the HP turbine cavity tip was solved by LES. The effects of cavity tip geometry on the flow stability and aerodynamic performance were researched. Results show that when the transonic leakage flow passes the cavity tip， a shockwave forms at the entrance of the cavity. Meanwhile， a separation bubble at the front of cavity expands and a shedding vortex generates periodically， interaction between shedding vortex and shockwave cause the shockwave to appear its unsteadiness. After the cavity depth increases from 1.0mm to 1.5mm， size of the gap shedding vortex significantly is reduced， its shedding period decreases by 20%， the average spanwise component of the enstrophy increases from 40% to 49%. Expansion and breakdown of gap shedding vortex are suppressed. Mixing between the backflow and the vortex is also restrained. Thus， unsteadiness of leakage flow is significantly reduced.