Analysis of Vortex Evolution in Turbine Rotor Tip Region Based on Liutex Method

In turbine rotor tip region, vortex structures are complex and aerodynamic loss is large. The double-cavity tip is expected to reduce the aerodynamic loss in this region. In this paper, influence of the double-cavity tip on the flow field in the tip region is numerically studied. The evolution characteristics of vortex structures are analyzed by using the Liutex method, and control effects of different double-cavity tip geometries on tip-leakage flow and leakage loss are discussed. The results show that the double-cavity tip can form multiple aero-labyrinth liked sealing effect and effectively control the leakage flow. The double-cavity tip with small pressure side cavity has better control effect, which can improve the turbine stage efficiency by more than 0.16%. Increasing the cavity depth of the double-cavity tip will enhance the squealer rib corner vortex, but the comprehensive control effect on leakage flow is not obvious. The inclined pressure side rib of double-cavity tip can provide larger space for scraping vortex by inhibiting the pressure side squealer rib corner vortex, which is beneficial to controlling the leakage flow. However, the inclination of the middle rib will cause the open separation at the top of the pressure side rib, which has a negative impact on the control of the leakage flow.