Experimental Study on Performance Verification Test of Optimized Film Cooling Holes in a Linear Cascade

Film cooling is an essential external cooling technology in turbomachinery. In this paper, firstly, an original hole on the flat model was optimized with the RBNN surrogate model and CS optimization algorithm. The optimization variables are the laid-back angle( δ ), the expend angle( β ) and the proportion length of the cylindrical part ( Lt/d ). Subsequently, the optimized holes are arranged in a linear cascade for experimental verification. To verify the optimization method, the cooling performance of original and optimized holes on the linear cascade was investigated under different blowing ratios and positions. Compared with the original hole, the optimized one has various expand angle, laid-back angle and proportion of the expanded section. The experimental tests were performed in a linear cascade equipped with three turbine blades. The mainstream flow parameters were set with Reynolds number (inlet) values of 4.3×10 5 and Mach number (outlet) values of 0.4. The adiabatic temperature on the surface was measured by an infrared camera. As the results of the SS3 row presented, on the surface of the film hole downstream where x/d is within 5, the film cooling effectiveness ( η ) of the optimized hole is more significant than that of the original hole. In the downstream of hole rows where x/d is between 5 to 40, the η of the optimized hole is lower than that of the original hole, since the optimized hole has a larger expand angle than the original hole. In the case of the PS4 row, the η of the optimized hole is higher than original hole at any blowing ratio