涡轮叶尖间隙泄漏涡不稳定性分析

Unsteadiness of tip clearance vortex in turbine

关键词:  叶尖间隙高度+  叶尖间隙泄漏涡+  不稳定性  数值仿真

Key words:  Tip clearance height+  Tip leakage vortex+  Instability  Numerical simulation

摘要:

结合Rains间隙泄漏涡模型和长波不稳定性理论,应用高雷诺数k-ε湍流模型加壁面函数,基于压力修正的三维计算流体力学程序,对某一轴流涡轮平面叶栅叶尖间隙流场进行仿真,通过将叶尖间隙泄漏涡与其在机匣表面镜像形成的虚拟泄漏涡组合成一对泄漏涡,对涡轮叶尖间隙泄漏涡的不稳定性进行了分析,并计算了五个不同叶尖间隙高度下泄漏涡的最不稳定的波长及对应的频率。结果表明,利用长波不稳定性理论可以预测叶尖泄漏涡的不稳定性和最不稳定的波长及对应的频率,从而为采用合成射流控制方法去控制涡轮叶尖泄漏涡提供理论基础。

Abstract:

A pressure-correction based 3D Reynolds-averaged Navier-Stokes equations with high Reynolds-Number k-ε turbulence model and wall function CFD code was used to simulate the tip leakage flow filed in a linear turbine cascade.Based on the Rains model of tip clearance vortex and long wave instability theory,regarding the tip leakage flow and its dummy vortex imaged by the casing wall as a couple of vortex,the instablity of tip leakage vortex was analyzed.The most unstable wavelength and its frequency of tip leakage vortexs under five different tip clearance heights are calculated.The results show that the long wave instablity theory can predict the instablity and the most unstable wavelength and its frequency of tip leakage vortex,which can lay a theoretic foundation for synthetic jet to control the tip leakage vortex.