Numerical investigations into the effect of squealer-winglet blade tip modifications on aerodynamic and heat transfer performance

Numerical investigations have been performed to investigate the heat transfer characteristic on the squealer-winglet tip, which is also compared with the conventional squealer tip and squealer tip without pressure-side rim. The validations and verifications of the numerical methods are carried out based on the existing experimental data. At a range of winglet leading edge angles and winglet coverage percentages, the total pressure losses in the cascade, as well as the flow structures in the tip gap, are analyzed in detail. The numerical results show that, by removing the pressure side rim from the conventional squealer tip, the high heat transfer area on the tip cavity floor near leading edge has disappeared, and the total pressure loss in the cascade has been reduced. If the conventional squealer tip is modified into a full-coverage of pressure side winglet configuration, the area-averaged total pressure loss in the cascade can be reduced by 12.2%, and the area-averaged heat transfer coefficient on the tip can be reduced by about 10% (PR = 1.236). For the squealer tip configured with pressure-side winglet, the heat transfer distributions as well as the total pressure loss in the blade are not sensitive to the winglet leading edge angle. By choosing proper winglet leading edge angle and winglet coverage percentage, the area-averaged heat transfer coefficient on the tip can be reduced by 15.8%, and the area-averaged total pressure loss in the blade can be reduced by 13.8%, in contrast to the conventional squealer tip.