FILM COOLING FROM TWO ROWS OF HOLES WITH OPPOSITE ORIENTATION ANGLES: INJECTANT BEHAVIORS

For film cooling from two rows of holes with opposite orientation angles, injectant trajectory behaves differently and affects film cooling performance. The inclination angle was fixed at 35°, and orientation angles were set to 45° for downstream row and -45° for upstream row. Four film cooling hole arrangements including inline and staggered configurations were investigated. The blowing ratios studied were 0.5, 1.0 and 2.0. Film cooling performance depends on the relative location of injectant center with respect to the film cooled surface and the ability of the injectant to absorb and store thermal energy. Boundary layer temperature distributions were measured to investigate these characteristics. Detailed distributions of adiabatic film cooling effectiveness were measured as well using TLC (Thermochromic Liquid Crystal). At M = 0.5, the injectant was centered near film cooled surface irrespective of hole configurations, and it showed higher film cooling effectiveness. As the blowing ratio increases, the film coolant shows different characteristics depending on hole configurations. When the blowing ratio exceeds unity, the injectant tends to lift off from the wall. With inline configuration, however, the injectant is located near the film cooled surface even at higher blowing ratios and inline configuration thus showed higher adiabatic film cooling effectiveness than staggered one.