Aerodynamic Optimization Design Method Of Turbine Blade And Exhaust System

Exhaust system is of great importance to the overall performance of the steam turbine. However, the present exhaust hoods do not work very well because of the separated designs of both the last stage turbine and exhaust system, in spite of the former research having revealed the interactions between the last stage turbine and the exhaust system and the suggestion of designing the two parts together.This dissertation is a first step and a preparation of the united design approach of last stage turbine and exhaust system. It presents an optimization method and procedure capable of adopting Design Of Experiment (DOE), Response Surface Methodology (RSM) and Optimization Toolbox together with the parameterization code and NS solver to optimize 3D blade and exhaust hood.The main contents of the dissertation are as following:Parameterization methods of 2D and 3D turbine blade, meridional end-walls and the exhaust hoods mainly by the polynomial curves are developed. An AutoLISP code is also developed based on AutoCAD to rebuild blades or exhaust hoods automatically by simply inputting several parameters.A combination of DOE, RSM and Optimization Toolbox forms the core methodology of optimization procedure. DOE is used to analyze the influences of the parameters on the optimization object and RSM is for building the surrogate model to reduce the number of CFD simulation and to predict the object value. Codes from MATLAB Optimization Toolbox are used for searching the optimal point in Response Surface.Based on the parameterization codes and optimization procedure, stacking line of a stator are optimized, which on one hand proves the validation of the optimization procedure developed and on the other hand searches for the best stacking design in terms of minimum total pressure loss from blade inlet to outlet.Optimization of an "axial-radial exhaust hood is carried out with two different inflow conditions-clean inflow and inflow with non-zero tangential angle and non-uniform radial total pressure distribution. The relationships between the geometry parameters and exhaust performance are analyzed, and the influences of inflow conditions on the optimization result are compared. In the condition of clean inflow, and in terms of maximum static pressure recovery of the exhaust hood, the optimum angle of outer guide vane at diffuser inlet should be valued around 14°and the lean angle of hood back be around 8°, while in the inflow condition with non-zero tangential angle and non-uniform radial total pressure distribution the optimum exhaust system is quite different from the former one. A new design of axial-radial diffuser is proved to be of high pressure recovery coefficient by taking the diffuser area expansion rate as a direct-input parameter and by designing the arc-type hood back.