Optimization of Discrete Film Hole Arrangement on a Turbine Endwall With Middle Passage Gap

For the design of modern gas turbine, cooling sources such as middle passage gap leakage flow, upstream slot leakage flow, and discrete film holes are designed to protect the blade. This research included middle passage gap leakage flow and two shapes of film holes (cylindrical holes and fan-shaped holes). First, experiment was carried out to verify the turbulence model at an inlet mainstream Reynolds number of 340,000, blowing ratio (M) of 1.0, and middle passage gap leakage mass flow ratio of 0.5%. Then, the circumferential positions of the endwall discrete film holes were optimized, and 100 samples were generated through Latin hypercube sampling (LHS) method, among which 80 samples were selected as the training data and 20 samples were selected as the verification set of radial basis function (RBF) neural network. Then particle swarm optimization (PSO) algorithm was adopted for the optimization. Finally, the flow structure, adiabatic film cooling effectiveness, and aerodynamic losses of four surrogate models were analyzed to achieve the most effective film hole arrangement on endwall. The results draw a conclusion that compared with the baseline and the best sample model, the area-averaged film cooling effectiveness of the endwall for most effective case increased by 188% and 9.6%, respectively. The area-averaged aerodynamic loss along the blade height at the endwall outlet decreased by 1.7% and 0.96%. Finally, the staggered arrangement of film holes shows the best film cooling performance.