开口双肋凹槽式涡轮叶顶间隙流动数值研究

Numerical Investigation of Opening Double Squealer Groove Turbine Tip Clearance Flow Character

关键词:  双肋  开口前缘  间隙泄漏  涡轮  数值研究  驱动压差  流量系数

Key words:  Double squealer  Opening leading edge  Clearance leakage flow  Turbine  Numerical investigation  Driving pressure difference  Discharge coefficient

摘要:

为研究改进的双肋凹槽叶顶结构对大折转角动叶间隙泄漏流动的影响，利用数值模拟的手段，对五种不同叶顶结构在低马赫数为0.3条件下的泄漏损失以及流动特性进行详细的研究分析。数值计算与实验测量结果进行对比校核以保证数值计算的可靠性。研究结果表明，改进的前尾缘开口的凹槽式叶顶结构使得叶栅总压损失降低7.4%，与前缘不开口的方案相比，间隙泄漏损失变化率降低23%，这对涡轮长期运行维持高效的性能有利。改进的叶顶结构对间隙内的流量分布影响明显，压力侧的泄漏流量减少26.7%，而吸力侧增加13.3%。前缘开口形式结构使得压力侧泄漏的驱动压差降低50%，并改变吸力侧泄漏流的流量系数，同样出口气流角展向分布和叶栅流道中的泄漏涡和通道涡均受到明显影响。

Abstract:

To investigate the leakage flow characteristic impacted by the modified double squealer groove tip of a large camber angle rotor blade profile，five different kinds of tip geometries with different clearance height were studied at low Mach number，i.e.，0.3 by using computational fluid dynamics (CFD). The tip leakage flow loss and flow characteristic were studied in detail. The numerical method was validated by using experiment data to ensure the reliability of numerical simulation. The results illustrate that it is beneficial to use the opening leading edge and trailing edge of the double squealer groove tip to reduce the leakage loss by 7.4% and leakage loss change rate by 23% compared with closed leading edge tip，which is beneficial to keep the good turbine performance for long time. The opening leading edge tip also have an effect on changing the mass flow across the tip squealers，the mass flow across the pressure side increases by 26.7%，while decreases by 13.3% across the suction side. The driving pressure difference of the pressure side squealer leakage flow is reduced by 50% and the discharge coefficient of the suction squealer is changed clearly with using opening leading edge tip，which also impacts the spanwise distribution of outlet flow angle，the leakage vortex and the passage vortex obviously.