Film cooling effectiveness and net heat flux reduction of advanced cooling schemes using thermochromic liquid crystal

Abstract

Abstract An experimental investigation of the film cooling effectiveness and net heat flux reduction performances for the hybrid and the louver schemes using Thermochromic Liquid Crystal technique is presented in this paper. The two film cooling schemes were designed to reduce the secondary flow jet lift off hence reducing the secondary flow penetration into the main flow. The hybrid scheme includes two consecutive film hole configurations with interior bending to direct the secondary flow in the streamwise direction. While the secondary flow inside the louver scheme passes through a bend and impinges with the blade material causing impingement effect, then exits to the outer surface of the aerofoil through the film cooling hole. The cooling performance for the hybrid and the louver schemes has been investigated experimentally for a density ratio of 0.94 and blowing ratio of 0.5, 1.0 and 1.5. The results showed that the hybrid and the louver schemes provided a high local and average film cooling effectiveness performance and enhanced more at high blowing ratios. The two schemes provided a wide spreading of the secondary flow extensively over the outer surface, thus the lateral film cooling performance enhanced over the downstream surface area. Moreover, the hybrid and the louver schemes produced a positive net heat flux reduction values without having the possibility of creating hot spot over the entire surface area. As a result, the two advanced schemes are able to protect the airfoil surfaces consequently the gas turbine inlet temperature can be increased and hence increasing the overall gas engine efficiency.