Effects of rim location, rim height, and tip clearance on the tip and near tip region heat transfer of a gas turbine blade

Effects of the rim height and the tip gap clearance on the heat transfer coefficients on the blade tip and near tip regions were measured with two different rim geometries. The heat transfer coefficient distributions were measured using the transient single color capturing liquid crystals technique. Rims were located along (a) the pressure and the suction side (full-rim case) and (b) the suction side of the blade tip (suction side rim case). The rim heights were (a) 2.1%, (b) 4.2%, and (c) 6.3% and the blade tip gap clearances were (a) 1.0%, (b) 1.5%, and (c) 2.5% of the blade span. Tests were performed on a five-bladed linear cascade placed in a blowdown facility. The overall pressure ratio, inlet total pressure to exit static pressure, was 1.2, and the Reynolds number based on the exit velocity and the axial cord length was 1.1 × 106. The turbulence intensity level at the cascade inlet was 9.7%, and the inlet and exit Mach number were 0.25 and 0.59, respectively. It was found that higher rims reduce the heat transfer coefficients on the tip and shroud, but the reduction on the pressure and suction sides was not significant. The suction side rim case provided lower heat transfer coefficients on the blade tip and near tip regions than the full-rim case.