Numerical Study of Double-Jet Film Cooling on a Semi-Cylindrical Leading Edge

A numerical investigation is performed for double-jet film cooling (DJFC) on a semi-cylindrical leading edge under four momentum flux ratios. Three rows of film cooling holes are distributed on the leading edge, wherein DJFC units are applied at ± 30 deg lines and the film cooling holes at the stagnation line remain in cylindrical shape in the baseline case. Totally, nine cases of DJFC units are designed by altering the spanwise spacing, streamwise spacing, and streamwise injection angle, while keeping the spanwise injection angle unchanged. The results show that proper layout of DJFC unit produces a “branched” spreading feature of jet trajectories, attributed to the formation of the anti-kidney vortex pair. Evaluated in the spatially averaged results on the semi-cylindrical leading-edge surface, DJFC could increase the adiabatic film cooling effectiveness up 20% at I = 1.3 with respect to the baseline case. Among the current geometric parameters in the DJFC unit, the spanwise spacing is an important parameter affecting the jet spreading feature. In relative to the spanwise spacing, the streamwise injection angle shows a weaker influence on vortical structures in the downstream flowfield. A larger spanwise spacing produces a greater adiabatic film cooling effectiveness but also a little bigger heat transfer coefficient. A similar trend is also demonstrated for the streamwise injection angle. The streamwise spacing has nearly no influence on the spatially averaged heat transfer coefficient. A smaller streamwise spacing is more promising for increasing adiabatic film cooling effectiveness.