Experimental investigation on film cooling of expanded hole at both inlet and outlet with various injection angles

To study the film cooling characteristics of expanded holes,heat transfer coefficient ratios and film cooling effectiveness was investigated downstream of a row of holes with inclination angles of 20° 45° and 90° as well as three varying hole diameters.Momentum flux ratios vary in the range of 1 to 4.The discussion was focused on the effect of momentum flux ratios and inclination angles on heat transfer coefficient ratios and film cooling effectiveness in the presence of mainstream zero pressure gradient.The experimental results show that the increasing momentum flux ratios leads to the increasing heat transfer coefficient ratios and film cooling effectiveness.The effect of momentum flux ratios on cooling effectiveness becomes weaker with the increase of angles.The angles have complex influence on heat transfer coefficient ratios.The increasing angles lead to the decreased cooling effectiveness.Film cooling effectiveness of inclination angle of 20° is bigger than those of 45° and 90°.