Effect of Compound and Forward Diffusion Angles on Film Cooling Effectiveness of Flat Plate Surface

Abstract

The pivotal role of film cooling to protect gas-turbine blades from high temperatures and hence high thermal stresses. Improvements have been made to the shaping of the cooling hole to provide higher heat transfer effectiveness. The main factors affecting the effectiveness of cooling are blowing ratio, streamwise injection angle, compound injection angle, forward diffusion angle, lateral diffusion angle, hole diameter, spanwise pitch,…etc.) The present work investigates the effect of increases the forward diffusion angle (�) and varying compound injection angle ( �) on film cooling effectiveness on the adiabatic wall flat plate. The forward diffusion angle is varied from 0° to 10° with a step of 5°, while the compound injection angle is varied from 90° to 0° with a step of 30°. Streamwise injection angle ( �) is kept constant at 35°. Four blowing ratios have been tested at 0.25, 0.5, 0.75 and 1 while the density ratio is kept constant at 1.14. Solving using CFD ANSYS FLUENT® 13 packages and choosing the standard k-� model, it was concluded that increasing the forward diffusion angle enhances film cooling effectiveness and reduces coolant penetration into the mainstream. Furthermore, varying the compound injection angle enhances film cooling effectiveness in lateral direction. Increasing blowing ratio affected effectiveness negatively due to the lift-off effect. Nomenclature