Film cooling characteristics of trench film hole fed by the internal cross-flow

The paper describes the film cooling characteristics of the trench film hole fed by the internal cross-flow. Three internal cross-flow cases are investigated by using numerical simulations. Results show that the main flow structures of the smooth and 45° rib cases feature helical and asymmetrical, and that of the 135° rib case is straight and symmetrical. When M = 0.5, the film cooling effectiveness η of the 135° rib case is the highest at two cross-flow Reynolds numbers. As M increases to 1.0, the η of the 135° rib case at Re_c = 100,000 is the highest. When M = 2.0, interestingly, the highest η is achieved by the 45° rib case at Re_c = 100,000. The discharge coefficient and total pressure loss coefficient increase with M for the three cases. The discharge coefficient of the 135° rib case is the highest, whereas that of the 45° rib case is the lowest. And the discharge coefficient at Re_c = 100,000 is lower than that at Re_c = 50,000 because the blockage is more serious at Re_c = 100,000, while the total pressure loss coefficient at Re_c = 100,000 is higher than that at Re_c = 50,000. When Re_c = 50,000, the 135° rib case exhibits a higher heat transfer coefficient HTC than the smooth case, while the area-averaged HTC of the 45° rib case depends on the M. When Re_c = 100,000, the area-averaged HTC of the 45° rib case is always highest while that of the 135° rib case is always lowest. In addition, the net heat flux reduction (NHFR) is mainly affected by the η and is more sensitive to the cross-flow at high Re_c and low M.