An automatic design algorithm for parametric shape optimization of three-dimensional cooling passages inside axial gas turbine blades has been developed. Smooth serpentine passage configurations were considered. The geometry of the blade and the internal serpentine cooling passages were parameterized using surface patch analytic formulation, which provides very high degree of flexibility, second order smoothness and a minimum number of parameters. The design variable set defines the geometry of the turbine blade coolant passage including blade wall thickness distribution and blade internal strut configurations. A parallel three-dimensional thermoelasticity finite element analysis (FEA) code from the ADVENTURE project at the University of Tokyo was used to perform automatic thermal and stress analysis of different blade configurations. The same code can also analyze nonlinear (large/plastic deformation) thermoelasticity problems for complex 3-D configurations. Convective boundary conditions were used for the heat conduction analysis to approximate the presence of internal and external fluid flow. The objective of the optimization was to make stresses throughout the blade as uniform as possible. Constraints were that the maximum temperature and stress at any point in the blade were less than the maximum allowable values. A robust semi-stochastic constrained optimizer and a parallel genetic algorithm were used to solve this problem while running on an inexpensive distributed memory parallel computer.

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