Influence of turbine blade leading edge shape on film cooling with cylindrical holes

Influence of turbine blade leading edge shape, gill film, and coolant-to-mainstream density ratio and blowing ratio on film cooling with cylindrical holes has been experimentally studied using pressure sensitive paint (PSP) technique. Three leading edge models are selected including a semi cylinder of radius R = 38.1 mm, elliptical leading edges of major radius 1.5R & 2.0R with an after body. Each leading edge model has three rows of film cooling holes with 15 holes each at fixed pitch of 4 hole-diameter and located along the stagnation line (0°) and at ±30°, respectively. Additional two rows of gill holes are located at ±60° (measured from inside surface). Internal impingement cooling geometry has been used while keeping the impingement hole plate at fixed distance of 31.7 mm from the stagnation line in all three leading edge models. Two configurations, with gill film holes ON and OFF are tested separately and the effects of coolant-to-mainstream density ratios (DR = 1.0, 1.5 and 2.0) with three different blowing ratios (M = 0.5, 1.0 and 1.5) are investigated. Experiments were conducted in a suction type low-speed wind-tunnel facility at Reynolds number of 102,446 based on the mainstream velocity and leading edge diameter. The mainstream turbulence intensity near the leading edge model is about 7%. Results indicate that 1.5R leading edge model has relatively better performance over others and gill film holes benefit to achieve improved coverage with higher overall film effectiveness. Additionally, to understand the flow physics, computational simulations for 1.0R leading edge model for DR = 1.5 and 2.0 at M = 1.0 are also performed using realizable k-ɛ turbulence model for both gill film holes ON and OFF.