Blade Film Cooling by Underexpanded Transonic Jet Layers

The evolution of increasing turbine inlet temperature has led to the necessity of full-coverage film cooling for the first turbine vane and blade. A new approach using high speed wall jets for blade cooling has been proposed by the authors. In this paper a 2-D upwind-biased Navier-Stokes code is used to calculate the aerodynamic behaviour of these surface coolant jets in a linear cascade. Special emphasis is put on the investigation of the coolant flow around the leading edge. Various numerical results concerning the leading edge flow are presented in detail, showing a strong tendency of these jets to bend towards convex surfaces. Finally, Schlieren pictures taken at the Institute’s transonic cascade on a 140mm chord length blade are presented for comparison.