Adiabatic Film Cooling Effectiveness From Heat Transfer Measurements in Compressible, Variable-Property Flow

A variable property correction is given for turbulent boundary layers that are film-cooled using staggered rows of injection holes inclined at 35 deg. With the correction, a relation is provided between the adiabatic film cooling effectiveness for constant property flow and heat transfer coefficients for variable property flow, which are based on the difference between the freestream recovery temperature and wall temperature. The variable property correction was determined from heat transfer measurements for a range of injection parameters at different values of the nondimensional coolant temperature and from results in the literature. Because the flow is compressible, the importance of the injection mass flux ratio, momentum flux ratio, and velocity ratio are considered in the determination of effectiveness.