Numerical Research Of Gas Turbine Cooling Structure Design With Aerodynamic Thermal Mechanical Conjugate Methods

Increase the turbine inlet temperature was the important way which could improv the efficiency and thrust to weight ratio. At present, the inlet temperature has exceeded the turbine material sustainable limit. It was necessary to adopt effective cooling techniques which made the turbine run well. The most effective turbine cooling methods were film cooling , impingement cooling, turbulent ribs, trailing edge slot and so on. Compound cooling methods should be employed to fulfill the demand of modern gas turbine. With the rapid development of CFD technique, numerical simulation became powerful tools of turbine cooling structure design. Predict the blade temperature and stress status exactly was the foundation to improve the turbine cycle life and reliability. The main work of the dissertation investigated several rows of turbine blades using conjugate and thermal mechanical methods. The cooling efficiency which influenced by corresponding factors was studied through numerical analysis. After that, the CFD results was transferd to FEA mesh nodes and blade stress status and total deformation were presented. Finally, cooling structure was designed for four rows of gas turbine blades. The initial cooling configuration was improved according to the practical cooling effect.Geometry modeling and mesh generation was the key step of numerical simulation. In order to protect the blade, muiltple cooling mehthods were employed which made the whole cooling configuration comlicated. The dissertation compared two types of modeling methods which one was non parameterized methods and another was parameterized methods. The detailed modeling process was introduced. The non parameterized modeling methods was flexible to set cooling configuration at any area and many types of cooling holes, such as compound holes, laid back diffuse holes could be arranged based on the blade local flow character. Therefore, long time consumption, fussy operation and easy to make mistakes were the disadvantages of non parameterized modeling methods. The accuracy of the non parameterized modeling method was also limited. Compara to the non parameterized modeling methods, the blade profile became function format when parameterized methods was employed. This format avoid the drawbacks of interplotion error which result form less control points, non reasonable distance, location deviation and maintain high precision in the modeling process. When the blade was parameterized, it could esay to generate new geometry through control parameters and short the design period.The cooling efficiency was influenced by many factors,this dissertation studied the influence of different main flow turbulent intensity and cooling air mass flow rate. It was concluded that the main flow turbulent intensity has much more influence on blade surface temperature rather than Cp and Cu. The higher cooling efficiency was appeared in low turbulent intensity case at the leading edge. Low turbulent intensity reduce the mix of cooling air and main flow which result to high cooling efficiency. At the middle and rear of the blade , the accelerated mainflow made the cooling air close to the surface. Therefore, the cooling efficiency was little higher in high turbulent intensity case. Because of the film cooling air dissipatation, the cooling efficiency became identical at the rear of the blade in both two cases. The pressure side film cooling benefited from the high cooling flow injection. On the suction side, the average cooling efficiency was lower in that case. The high injection momtum just improved the situation at leading edge aera and the cooling efficiency in low turbulent intensity case was higher at the rest of areas.Initial cooling configuration design was implemented for four rows of gas turbine blade and the cooling effect was testified. Low cooling efficiency area was improved base on the calculation. In the cooling configuration design process, typical turbine blade cooling structure was adopted such as, full film cooling, impingement cooling, trailing edge turbulent ribs, rib roughed serpentine passage, smooth serpentine passage. The initial cooling configuration was testified using conjugate method and local cooling structure was modified. The new model was generated through parameterized blade which save much more time.