Influence of inlet flow condition on turbine blade showerhead film cooling

Abstract

This study focuses on the influence of the internal flow condition on turbine blade showerhead region film cooling. The elliptical leading edge model has five rows of film cooling holes with 15 holes each at fixed hole-to-hole spacing of 4-diameter and located along the stagnation line (0o), at ±30o and at ±60o measured from the stagnation line. Two inlet flow conditions, channel flow, and impinging flow are investigated separately, and the effects of coolant-to-mainstream density ratios (DR = 1.0, 1.5 and 2.0) with three different coolant-to-mainstream blowing ratios (M = 0.5, 1.0 and 1.5) are tested using pressure sensitive paint measurement technique. Experiments were conducted in a suction type low-speed wind-tunnel facility at a flow Reynolds number around 100,000 based on the oncoming mainstream velocity and leading edge diameter. The mainstream turbulence intensity near the leading edge model is about 7%. Results indicate that overall the impingement inlet configuration provides better film effectiveness for all the DRs. However, the difference is found to be minimum at M = 0.5 and 1.0 for heavier density coolant (DR = 2.0). Additionally, computational simulations have been performed to understand the flow physics of these two inlet flow configurations using a realizable k-epsilon turbulence model.