Effect and optimization of backward hole parameters on film cooling performance by Taguchi method

In recent years, increasing inlet temperature of gas turbines has far exceeded the melting point of the metal materials. Film cooling technology has widely been used to protect gas turbine blades from erosion of the high-temperature gases. The film cooling performance can be improved by optimization of the hole configurations. Results show that the backward injection hole has a smaller exit momentum and a thinner velocity boundary layer near the wall compared to the forward hole. For the backward hole, high blowing ratio is beneficial to improve the film cooling effectiveness. It was found that the overall average film cooling effectiveness for the backward hole increases by 677% at a blowing ratio of 1.5 compared to that for the forward hole. In addition, the coupling effects of hole length, inclination angle and blowing ratio on the film cooling effectiveness were investigated based on the Taguchi method. A new scheme of three-factor four-level orthogonal calculations was designed. It is found that the inclination angle has the greatest effect on the film cooling effectiveness of the backward hole. When the blowing ratio is 2.0, the backward hole with a hole length of 3D and an inclination angle of 35 degrees is the optimal cooling hole configuration.