Conjugate heat transfer analysis for laminated cooling effectiveness, part b: Effects of film hole incline angle

The laminated cooling or multi-layered impingementeffusion cooling, which originates from combustion liner cooling, is believed to be an advanced and promising gas turbine blade cooling technique. Previous authors' works have found that surface curvatures have different influences on overall cooling effectiveness of laminated cooling. To determine the optimal configuration of laminated cooling for various surface curvatures respectively, the conjugate heat transfer approach that has been validated by the experimental data was employed to study numerically the effects of streamwise incline angles (including 15, which was 20 degree for flat plate and concave surface, 30, 60 and 90 degree) on overall cooling effectiveness with different surface curvatures. The results show that the shallower film holes restrain the liftoff of the coolant ejection, and lead to a higher overall cooling effectiveness. However, shallower injection angle causes higher pressure loss. The relationship between injection angle and overall cooling effectiveness for different curvature is illustrated in the paper. The results indicate that shallower injection angle provides more than 10% improvement of cooling effectiveness compared to that of 90° injection angle for flat plate, concave surface and convex surface with smaller curvature at high blowing ratio. But for convex surface with large curvature, blowing ratio of 0.7 to 0.9 is better for overall cooling effectiveness, and shallower injection angle has little effect on cooling effectiveness. Moreover, additional pressure loss occurs to shallower injection angle because of the serious flow separation.