Film cooling subject to bulk flow pulsations: effects of blowing ratio, freestream velocity, and pulsation frequency

Abstract Bulk flow pulsations, in the form of sinusoidal variations of static pressure and streamwise velocity, are investigated as they affect film cooling from round, simple angle holes in a turbulent boundary layer. Such pulsations are important to turbine airfoils and end walls in gas turbine engines because similar pulsations are induced by potential flow interactions and passing families of shock waves. Distributions of adiabatic film cooling effectiveness, iso-energetic Stanton number ratio, and film cooling performance parameter are presented for different pulsation frequencies, blowing ratios, freestream velocities, and hole length-to-diameter ratios. A correlation is given for the onset of protection reduction as it depends upon these parameters. The most important reductions to film cooling protection result as the pulsation frequency increases at the smallest length-to-diameter ratio and smallest blowing ratio tested.