Effect of shelf squealer tip configuration on aerothermal performance of gas turbine blade

The tip leakage flow between rotating turbine blades and the stationary turbine casing causes aerodynamic losses and high thermal loads. Numerous novel tip geometries have been proposed for reducing both of these effects, one of them is a shelf squealer tip. The objective of this study is to investigate the aerothermal performance of three squealer blade tip configurations: conventional, vertical shelf and inclined shelf. Heat transfer was measured to analyze heat transfer features on the blade tip using transient IR thermography method. Also, computational fluid dynamics simulation and particle image velocimetry were conducted to visualize the flow characteristics around the blade tip. The experiment was conducted under conditions of a Reynolds number of 140,000 which was based on the inlet velocity in a wind tunnel. Thermal loads with vertical and inclined shelf squealer tip configurations are lower than with the conventional squealer tip. Due to the recessed pressure side rim of the vertical shelf squealer tip, the tip leakage flow was less reattached comparing to conventional squealer tips. This resulted in reduced thermal load on the tip surface and a larger tip leakage vortex around the blade suction side, which increased aerodynamic losses. Especially in the inclined shelf squealer tip, a separation bubble was generated on its inclined pressure side rim, which reduced the tip leakage flow due to the vena contracta effect. Consequentially, the reduced tip leakage flow decreased both heat loads and aerodynamic losses for the inclined shelf squealer tip. Therefore, the inclined shelf squealer tip demonstrated a good performance with respect to both aerodynamic loss and heat transfer.