Optimization of the film cooling hole for minimizing stress concentration factor based on surrogate model

Abstract

Film cooling is a typical cooling technology in gas turbines that can lower heat load by spreading coolant on the blade's surface. However, it faces the problem of stress concentration. The present work focuses on optimizing the film cooling hole for minimizing the stress concentration factor based on the surrogate model. The stress concentration factor is the ratio of the maximum stress in a plate with a film hole subjected to frictionless support constraints in the sidewalls at a homogeneous temperature to the average sidewall stress. An optimization platform is built to implement the optimization, which contains a finite element parallel computation module, a support vector regression surrogate model, and a two-layer optimization module for adding sample points around the candidate optimal point. After 50 rounds of optimization process, the optimization results converge. The lowest stress concentration factor obtained is about 1.79, 71.5 % lower than that of the traditional cylinder film hole. Considering that the reduction of the stress concentration factor should not be accompanied by the reduction of the film cooling effectiveness, this work tests the film effectiveness of four candidate holes by means of pressure-sensitive paint experiments. Geo4 has the lowest stress concentration factor and the maximum film effectiveness when both factors are considered.