Aerodynamic loss characteristics of a turbine blade with trailing edge coolant ejection: Part 2 : External aerodynamics, total pressure losses and predictions

Investigation of the internal fluid mechanic losses for a turbine blade with trailing edge coolant ejection was presented in Uzol, Camci and Glezer (2000). The current study is a detailed experimental investigation of the external subsonic flowfield near the trailing edge and the investigation of the external aerodynamic loss characteristics of the turbine blade with trailing edge coolant ejection system. Particle Image Velocimetry experiments and total pressure surveys in the near wake of the blade are conducted for two different Reynolds Numbers and four different ejection rates. Two different trailing edge configurations with different cut-back lengths are also investigated. Numerical simulations of the flowfield are also performed for qualitative flow visualization purposes. Two dimensional, incompressible and steady solutions of Reynolds Averaged Navier Stokes equations are obtained. A two equation standard k-e turbulence model coupled with an Algebraic Reynolds Stress Model is used for the simulation of the turbulent flowfield. The results show that the aerodynamic penalty levels in the wake region near the trailing edge are increased due to the mixing of the coolant and main stream flows for 0 to 3% ejection rates. However after a threshold level (5% ejection rate), the ejected coolant flow has enough momentum to fill the wake of the blade which in turn results in a decrease in the aerodynamic penalty levels.