涡轮动叶倾斜肩壁凹槽状叶顶气动性能研究

Research on Aerodynamic Performance of Gas Turbine Blade Squealer Tip with Inclined Rim

基于垂直肩壁凹槽状叶顶,提出肩壁向外倾斜以实现叶顶泄漏损失的控制,并对比了3种肩壁倾斜方式(压力侧倾斜、吸力侧倾斜、压力侧和吸力侧同时倾斜)和5种肩壁倾角(10°、20°、30°、40°、50°)的涡轮动叶倾斜肩壁凹槽状叶顶结构的泄漏流动特征和动叶出口总压损失分布。结果表明:压力侧倾斜肩壁阻碍了泄漏流从压力侧进入叶顶间隙,而吸力侧倾斜肩壁对泄漏涡产生压迫,泄漏涡朝远离机匣面和吸力面的方向偏移,3种肩壁倾斜方式均减弱了叶顶间隙泄漏流在叶顶间隙内的湍流耗散。当倾角较小时,泄漏流与主流的掺混损失因速度差的提高而增大,随着倾角继续增大,泄漏量的大幅下降弥补了速度差增大带来的负面效果,泄漏损失逐渐减小。对于压力侧和吸力侧倾斜肩壁凹槽叶顶,当倾角大于40°时,主流从吸力侧进入凹槽,加剧了下游区域的泄漏流动,叶顶泄漏损失反而增大。两侧倾斜肩壁凹槽状动叶叶顶具有最低的叶顶总压损失,相比垂直肩壁凹槽状叶顶下降了13%。研究内容为提高凹槽状动叶叶顶气动性能的肩壁结构设计提供了参考。

This paper proposes a method of outward rim inclination to control the leakage losses at the blade squealer tip.The tip leakage flow characteristics and outlet total pressure loss distribution of the turbine blade squealer tip are compared with three rim inclination methods(pressure side inclination,suction side inclination,and both-side inclination)under five inclination angles(10°,20°,30°,40°,50°).The results show that the inclined pressure-side rim obstructs the tip leakage,and the momentum of the leakage flow is dissipated.The inclined suction side rim compresses the tip leakage vortex which shifts away from the casing surface and suction side surface.The three rim inclination methods all reduce the turbulent dissipation of the leakage flow in the tip clearance.When the inclination angle is small,the losses arising from mixing of the leakage flow and main flow become larger due to the increase of velocity difference.As the inclination angle continues to increase,the drop of leakage mass flow rate significantly offsets the negative effect brought by the increase of velocity difference,resulting in gradual reduction of leakage losses.However,for the blade squealer tip with rim inclination on both the pressure side and suction side,when the inclination angle is greater than 40°,the main flow enters the cavity from the suction side,which aggravates the leakage flow downstream and leads to the increase of the tip leakage losses.The blade squealer tip with rim inclined on both sides has the lowest tip total pressure loss,13%lower than the blade squealer tip with vertical rim.The study provides reference for the rim design of the blade squealer tip with improving aerodynamic performance.