Mechanism And Optimization Methods Of Gas Turbine Cooling Structures

Gas turbine is an essential power equipment for aero propulsion and efficientutilization of fossil energy. Cooling design is one of the key technologies of gas turbineengineering. The aim of the dissertation is to develop the design optimization methodfor the cooling structures of advanced gas turbine. Based on the optimization platformof turbine cooling design built in this work, the mechanism of several typical coolingstructures is studied numerically and experimentally. And a group of optimizationmethods is developed and validated regarding the different aspects of cooling design.The automated mesh generation method is studied accommodating therequirements of3D conjugate heat transfer (CHT) simulations of turbine complexcooling structures. Subsequently an automated mesh generation tool named Coolmesh iscomposed. The optimization platform of turbine cooling structure/system is built basedon Coolmesh and numerical methods experimentally validated. A mechanism study anda optimization search are preformed for the classical cooling channels with repeated ribs,which proved the capability of the platform and the validity of optimization results.For the impingement cooling in turbine vanes with strong crossflows, anAnti-Crossflows (ACF) structure is developed and studied using CFD and TLCexperiments. The ACF structure can weaken the negative interactions between the jetsand crossflows, reducing the pressure loss of the impingement structure. Asingle-objective optimization strategy with cooling flow constrains added bypunishment functions is developed and tested in the CHT optimization of the coolingsystem of the2ndstage turbine vane of GE E3. The optimization strategy has a goodperformance when the thermal load of is comparatively lower. Then the ACF structureis applied in the cooling system of the vane and optimized under a higher thermal load,using an improved optimization strategy based on a metamodel. The cooling systemwithACF structure can provide a more uniform temperature on the vane surface.In order to achieve good film cooling performance with low-cost cylindrical holes,a tripod film hole with cylindrical branches is initiated and studied. The tripod film holecan weaken the kidney vortices, suppressing the lift-off and mixing of coolant jets. PSPexperiments show that an optimized tripod hole can achieve the same film cooling effectiveness as a well-designed shaped hole. On the other hand, a two-leveloptimization strategy together with a metamodel is developed and proved through theoptimization study of the exit shaping of shaped holes. Besides, a semi-inverse designoptimization method is invented for the of film cooling arrangement on turbine vanes.This optimization method is tested through the film cooling design for the nozzle of aheavy-duty gas turbine, which proved that the optimized film cooling arrangement usesalmost equivalent coolant while improving the temperature distribution on vane surface.The nozzles of advanced gas turbines often work under strong radiation and inletswirl. These effects were added to the physical model of semi-inverse designoptimization method, which is validated through the cooling system optimization for thenozzle of GE E3. The effects of radiation, inlet temperature distortion and inlet swirl onthe cooling performance of nozzles are numerically studied, indicating that inlet swirlexerts stronger influence on the wall temperature than inlet temperature distortion whenfilm cooling is predominant. Based on the optimization methods developed, theinfluence of various design conditions on optimal cooling scheme and coolant amount isquantitively investigated. It is concluded that improving film cooling is the mosteffective approach to increase the temperature level of gas turbine.This dissertation lays the foundation for applying3D optimization methods in thecooling design of advanced gas turbines.