An investigation on film cooling and aerodynamic performance of squealer blade tip with inclined cavity bottom

Abstract

The gas turbine blade tip poses as one of the most challenging areas for blade cooling, primarily due to its intricate three-dimensional flow characteristics, which make it one of the primary contributors to aerodynamic loss within the turbine stage. In this paper, the adiabatic film cooling effectiveness (η) distributions at five squealer tip structures (Original, PS7.5, PS15, SS7.5, SS15) with varying inclined angles of cavity bottom surface were obtained using pressure sensitive paint technique (PSP) under five coolant blowing ratios (BR = 0.4, 0.8, 1.2, 1.6, 2.0). Combined with the numerical simulations verified by the experimental data, the tip flow field details were described to reveal the cooling characteristics of the tip region. The results indicate that, at low BRs, the film hole downstream exhibits apparent cooling traces, which are most pronounced at the SS15 tip. With the increase of BR, the cooling traces gradually fade, and the area-averaged film cooling effectiveness (ηΑ-avg) rises. At low BRs (BR = 0.4, 0.8), the ηΑ-avg of the SS15 tip is 12.8 %, and 8.4 % higher than that of the Original tip, respectively. At BR = 1.6, the ηΑ-avg of the PS15 tip is the highest, 3.9 % higher than that of the Original tip. The ηΑ-avg of SS7.5 is the lowest at all BRs. In addition, the pitch-averaged η (ηavg) of PS7.5 at some BRs is higher in the front part of the tip, compared to the Original tip. At BR = 1.2, the area-averaged total pressure loss coefficient (Cpt¯)of the PS7.5 and PS15 is 1.46 % and 1.58 % higher than that of the Original tip, respectively. However, the Cpt¯ of the SS7.5 and SS15 is 1.77 % and 10.28 % lower than that of the Original tip, respectively.