Progress of experimental research on axial turbine tip leakage flow

Based on the public literature and experimental results obtained by our group, the experimental research for the axial turbine tip leakage flow is summarized, and the future development is also prospected. The analysis shows that most researches are still based on the linear turbine cascade, and there are few measurements on the tip leakage flow under rotating conditions. As for the measurement methods, steady-state, quantitative and qualitative measurements which focus on the outlet flow field are still dominant, while non-intrusive and transient measurements inside the tip gap are relatively deficient. As for the measurement conditions, many studies are conducted at low speed condition, but only few studies are conducted under transonic and supersonic condition. Meanwhile, most analyses focus on the effect of the leakage flow on the turbine performance, but the unsteady flow mechanism of the tip leakage vortex and its breakdown is not fully revealed. In the future, based on the turbine rotor test rig, using the end-wall dynamic pressure measurement array, endoscopic PIV, and LDV to measure the unsteady leakage flow inside and near the tip clearance is an important direction that needs to be studied urgently.