Aerodynamic Analysis of Film Cooling Jet Under Different Main Stream Pressure Gradient

Streamwise pressure gradient is an important characteristic of the turbine flow and compound angle film cooling is a sufficient way to improve cooling performance. Both experimental and numerical studies are carried out to investigate the effect of streamwise pressure gradient and film cooling hole compound angle on aerodynamic loss of film cooling. Stronger mainstream favorable pressure gradient leads to a larger discharge coefficient. The effect of momentum supplement of the coolant jet with large blowing ratios is significant when pressure loss coefficient is investigated. Kinetic loss coefficient considering the kinetic energy of the coolant jet is used to investigate the overall aerodynamic loss of film cooling. The kinetic loss coefficient increases with blowing ratio. Favorable pressure gradient decreases the loss coefficient. The boundary layer is quite thick for adverse and moderate favorable pressure gradient case that the coolant jet remains within the boundary layer which increases the mixing loss. The kinetic loss coefficient of compound angle film cooling is about 40% higher than the axial hole. This is due to the dissipation of the momentum component in the spanwise direction and the stronger shearing between the single large vortex formed by the compound angle injection with the main flow.