Study Of Aerodynamic Optimization Of Multi-stage Axial-flow Turbine Flow Path

Energy is the foundation for ensuring economic growth and socialdevelopment, and promotes the development of modern civilization. With therapid economic growth, irrational exploitation and utilization of energy sourcesalso occurs, which brings about ecological and environmental deterioration,resource depletion and other issues. Turbomachinery has been widely used invarious fields of national economy as a very significant part of energyconversion. Cascades play a crucial role within turbomachinery; it is the mainworking unit to implement the energy conversion.Since the blade surface lossand end wall secondary flow loss of the flow path loss account for a large sharein the total losses.studieshave been thoroughly focused on reducingflow pathlosses,improvingthe energyconversion efficiency of theturbomachinery, andachieving sustainable development.To be prepared for the optimization design of the multi-stage axial-flowturbine flow path, an in-depth study has been implemented in the first place onthe details of the internal flow. The occurrence and development of thesecondary flow are thoroughly analyzed in such feature locations as the staticblades, interface between blade rows, and rotor blades. Results indicate that theloss of work due to the secondary flow occupies a large share in the flow pathtotal loss, leading to negative influence on the turbomachinery efficiency. Thispaper aims to reduce the secondary flow loss and to improve the performance ofthe turbine.Based on the aerodynamic optimization system which hasbeen alreadydeveloped by the CFD group, this paper modifies the flow path geometricprofiling method and the form of optimization parameters, to further reducethedesign variables and to enhancethe system stability of the optimization design.The system consists of three parts:(a) a three-dimensional cascade through-flowparametric geometric profiling system to extract design variables;(b) a cascadethrough-flow profiling aerodynamic performance evaluation system to completenumerical simulation of the flow field and to obtain aerodynamic performanceparameter as the objective function of the optimization design;(c) reasonable optimization strategy to search the design space and to acquire the bladethrough-flow geometric profiling with thehighest aerodynamic performance.Trigonometric functions and NURBS curve have been adopted forparametric profiling of the turbine blade, the endwall and the stacking line. Athree-dimensional control module is integrated into the aerodynamicoptimization platform based on the iSIGHTsoftware, and simulated annealingalgorithm is used for three-dimensional aerodynamic optimization design of atwo-stage axial-flow high pressure turbine blades.Numerical simulation resultshave shown that the established non-axisymmetric endwall and bowed bladejoint profiling method can effectively optimize the pressure distribution nearthe end wall and reduce the tranverse flow, thus weakening the passage vortexwhile reducing the secondary flow loss. The total pressure loss coefficient isremarkably reduced, with the blade efficiency enhanced by0.48%.