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Progresses in conjugate heat transfer simulation method provide a new approach for turbine blade cooling design. The procedure of air-cooled blade design introduced in this paper consists of two levels, a schematic design using 1D flow network calculation method, and a detailed design based on CFX conjugate heat transfer simulation. The program platform for the design method was developed, including an air-cooled blade design program, a 1D cooling structure flow network solver, and conjugate mesh generation tools for air-cooled blade. The design platform contains parametric methods for blade profile, cooling channel, and various cooling structures. The key parametric algorithm named Element Design Method was invented and introduced, which brings about parametric design for complex cooling channel, and accelerates the calculation model generation during the schematic design and detailed design. The flow network solver for schematic design consists of a pressure solving program, a temperature solving program, and a film cooling solving program. The pressure solving program uses linear method to solve the momentum equation, so higher stability of the flow network solver can be achieved. In detailed design, CFD pre-treatment using the commercial software is time-consuming. The mesh generation tools, combined with parametric design programs, can automatically create hexahedron/mixed mesh for turbine cascade and cooling structures with considerable speed and quality, which significantly reduces the difficulty of pre-treatment during detailed design.

The cooling system design for air-cooled turbines is a critical issue in modern gas turbine engineering. Advances in the computational fluid dynamics (CFD) technology and optimization methodology are providing new prospects for turbine cooling system design, in the sense that the optimum cooling system of the vanes and blades could be designed automatically by the optimization search coupled with the full three-dimensional conjugate heat transfer (CHT) analysis. An optimization platform for air-cooled turbines, which consists of the genetic algorithm (GA), a mesh generation tool (Coolmesh), and a CHT solver is presented in this paper. The optimization study was aimed at finding the optimum cooling structure for a 2nd stage vane with, simultaneously, an acceptable metal temperature distribution and limited amount of coolant. The vane was installed with an impingement and pin-fin cooling structure. The optimization search involved the design of the critical parameters of the cooling system, including the size of the impingement tube, diameter and distribution of impingement holes, and the size and distribution of the pin-fin near trailing edge. The design optimization was carried out under two engine operating conditions in order to explore the effects of different boundary conditions. A constant pressure drop was assumed within the cooling system during each optimization. To make the problem computationally faster, the simulations were approached for the interior only (solid and coolant). A weighted function of the temperature distribution and coolant mass flow was used as the objective of the single objective genetic algorithm (SOGA). The result showed that the optimal cooling system configuration with considerable cooling performance could be designed through the SOGA optimization without human interference.

Shaped film holes can achieve higher film cooling effectiveness compared with the simple cylindrical film holes. According to former studies, the geometry of the shaped film holes has significant influence on the cooling performance. In order to maximize the film cooling effectiveness of the shaped holes, a two-level design optimization methodology of the hole exit shaping is developed in the present study. The optimization methodology consists of a parametric design and CFD mesh generation tool called Coolmesh, a RANS CFD solver, a database of film cooling effectiveness distributions, a metamodel, and a genetic algorithm (GA) for evolutionary optimization. A binary parametric representation of the 2D hole exit shaping is initiated based on the B-spline methods. The metamodel can efficiently predict the detailed distribution of film cooling effectiveness using the CFD results in the database, which is continuously updated for higher accuracy. In each first-level iteration, a second-level GA optimization search is carried out coupled with the metamodel, and then the optimal geometry is evaluated using CFD methods and added to the database. An anisotropic turbulence model is applied to the CFD solver for higher accuracy according to a detailed experimental validation using PSP measurements. In the present study, three design optimizations of the shaped holes without and with compound angles are carried out on a flat plate. The optimization methodology can efficiently find the optimal geometries of shaped holes using only hundreds of CFD runs. For the shaped holes with compound angle, the optimized geometry can generate a back flow vortex which interacts with the shear vortex and weakens the mixing of coolant and hot gas, resulting in a higher film cooling effectiveness on the plate.