Experimental and Numerical Investigations Into the Blade Tip Phantom Cooling Performance

In the gas turbines, the blade tip is difficult to be cooled down due to the complex flow and the intense heat transfer process here. Phantom cooling has been considered a kind of second-order cooling effect to help protect the tip using upstream spent cooling air. In this work, the blade tip phantom cooling performance of four different tip configurations (the flat tip (FT), the squealer tip with suction-side rim (SSRST), the squealer tip with pressure-side rim (PSRST), and the squealer tip with double-side rims (DSRST)) was compared under four different cooling air blowing ratios (M), with two different tip gaps (τ = 1.32% C (chord), and 3.22% C). Pressure sensitive paint technique was adopted to obtain the cooling effectiveness contours. The turbulence-validated computational predictions were performed to help analyze the flow characteristics near the tip. Results indicated that the FT case presents the best phantom cooling performance than others, and phantom cooling traces can be detected on most portions of the tip. The η values of the SSRST case are a little bit lower than the FT case, and the PSRST and DSRST cases perform the worst for almost no phantom cooling traces can be observed on the cavity surface. Additionally, a bigger tip gap would reduce the tip phantom cooling effectiveness for any tip configuration. Moreover, from the computational results (τ = 1.32% C, M = 1.5), relatively lower aerodynamic losses are obtained in SSRST and DSRST cases, while the PSRST case shows the highest loss.