Optimization of airfoil's cooling passages

This chapter discusses issues related to the optimization of the cooling system of the blade of the gas turbine. Systems with both cylindrical cooling passages and with passages with any sections were considered. In the former case the optimization task consisted in finding the location and diameter of the passages; in the latter - as well as finding the location, it also involved the determination of the optimal shape of the cooling holes. To model the shape the Bezier curves, forming closed profiles of the cooling holes, were used. Additionally, in order to match the shape of the passage to the blade profile, a technique was put forward to copy and scale the profile fragments into the component, and build the contour of the passage on the grounds of them. In both cases the task was solved as a multi-objective problem with the use of the Pareto approach. Also, comparative optimization calculations for the scalar objective function were carried out and set up against the non-dominated solutions obtained in the Pareto approach. The evolutionary algorithm was used as the optimization tool, and the testing calculations were made for profile C3X available in reference literature. It was assumed that the cooling agent of the blade was either air or steam. The evaluation of individual configurations was made on the grounds of thermal-strength analyses with the use of the Finite Element Method (FEM). For comparative purposes, the optimization task was also solved by means of conjugate analyses of heat transfer (CHT). The optimization process resulted in configurations of the cooling system that allow a substantial reduction in both the temperature of the blade and its thermal stress, with decreased flow rate of the cooling agent.