Experimental and numerical investigations on double-jet film-cooling with different mainstream incidence angles

The present work focuses on the effects of the mainstream incidence angle (i) on the double jet film-cooling (DJFC) structure, with cooling effectiveness measured by pressure sensitive paint (PSP) and flow field obtained by RANS simulations. Seven incidence angle conditions ranged from -30 degrees to +30 degrees are studied. The relative angle between the two DJFC holes is a constant of 90 degrees. The film holes have a diameter (d) of 5 mm and incline 35 degrees to the surface. The spanwise distance (p/d) and the streamwise distance (s/d) are kept as 1.0 and 3.0, respectively. Two blowing ratios (M = 0.5 and 1.5) and two density ratios (DR = 1.0 and 2.5) are considered. Results show that the mainstream incidence angle has a significant effect on the performances of double-jet film-cooling, while the affecting trend varies with operation conditions. The high effectiveness of the double jet film-cooling is caused by the anti-kidney vortex and this flow structure is directly influenced by the mainstream incidence angle. Consequently, a proper incidence angle leads to beneficial anti-kidney vortex effects and thus high film-cooling effectiveness, while for other incidence angle cases the cooling performance deteriorates.