Development And Research Of Discrete Adjoint Optimization System For Turbimachinery Aerodynamic Shape Design

The fine design has become the development trend of the current aviation turbine design,while the adjoint optimization system is an important tool basis for realizing the fine design.Considering the importance of independent development of aviation turbine CFD and optimization technology,and in the face of domestic rarely self-developed based on unstructured grid based turbine flow field solving program,has not independently developed multi-row turbomachinery discrete adjoint optimization system,and the lack of which is difficult to support the development of the original technology of the turbomachinery.In this paper,a discrete adjoint optimization system including unstructured grids generation,flow solver,discrete adjoint solver,sensitivity solver,mesh deformation and optimization method on the unstructured grids is developed.This paper explores and evaluates the potential of the three-dimensional integration of the internal flow channel.The main work includes the following aspects:(1)With the aid of the method in which the hexahedron elements are divided into tetrahedron elements,the unstructured grid generation and blade parameterization software TurboPara&Gen based on the multiblock structured grids is developed.TurboPara&Gen has now been able to generate many types of grids including single row/multistage grids,single channel/multi channel grids in 2D or 3D format used in inviscid and viscous flow calculation and TurboPara&Gen has also the ability to handle endwall clearance,clearance between rows,rounded end/chamfer and so on.Now,the unstructured grid can be generated quickly based on the multiblock structured meshes with O+H topology.(2)Considering the versatility and the requirements in the following aeroelastic area,The CFD solver on unstructured grid the for turbomachinery named TurboSim(un)is developed using the arbitrary Lagrange-Euler RANS equation which are closed by SA turbulence model.The solver adopts the node-centered finite volume method,and in the solver the Roe flux difference splitting scheme and for unsteady-state flow the dual time step with 1-4 order Backward Differentiation Formulae scheme is selected.Besides,several convergence acceleration techniques such as multigrid,local time-stepping and so on are implemented.Four basic benchmark cases that are inviscid shock tube flow,laminar plate flow,turbulent plate flow and unsteady flow around a cylinder are selected to verify the correctness and accuracy of the numerical scheme used in TurboSim(un).Furthermore,three turbomachinery cases that are Goldman cascade,Rotor67 transonic rotor and Stage35 transonic compressor stage are chose to verify the correctness of the boundary conditions such as the inlet,outlet and the periodic boundary conditions,to verify the non-inertial terms added in non-inertial environment and importantly to verify the accuracy of predicting the steady flow in turbomachinery.(3)The adjoint equation and the equation are derived based on the unstructured grid deformation.The adjoint equation solver with SA turbulent model named TurboAdjD in which the linear system is solved using GMRES method is developed using time stepping method.Combined with unstructured mesh generation software TurboPara&Gen,flow solver TurboSim(un),geometric parameterization tool,optimization algorithm,sensitivity calculation program,mesh deformation module,the discrete adjoint optimization system named TurboOpt is established.In the system,objective functions based on the linear superposition of the sub objective function are implemented for the adjoint optimization of turbomachinery.The sub objective functions used in the paper involve the total pressure,total temperature,entropy,efficiency and pressure distribution.The Hicks-Henne function is adopted as the basis function in the parametric module.Basically,this discrete adjoint optimization system avoid two problems that emerged in former continuous adjoint in-house code: one problem is that the turbulent viscous adjoint equation is not fully deduced,and the other problem is that the objective function chose is less.With the simple external flow around ONERA M6 wing,preliminary validation of adjoint solver and the whole optimization system is confirmed.Moreover,three turbomachinery flow cases that are Goldman cascade,Rotor67 transonic rotor and Stage35 transonic compressor stage are chose to verify optimization ability and reliability in turbomachinery from the direct optimization application problem and inverse redesign application problem respectively.(4)Facing the contradiction between the three-dimensional and the design idea of the strong space of the current blade surface,the contradiction between the means and the quasi-three-dimensional is still pointed out,and the trend of the whole three-dimensional integration of the impeller channel is pointed out.The three dimensional integration optimization of channel composed of blade and endwall is proposed and the potential of the integrated design with the aid of adjoint method is evaluated.Through three cases that are nozzle,Goldman cascade and NACA65 cascade,the potential of the integrated design is confirmed to some extent,this may provide the basic idea in integrated adjoint optimization parameterization method used in the future for turbomachinery.In the paper discrete adjoint optimization system for turbomachinery aerodynamic shape design is developed and the three dimensional integration optimization of channel composed of blade and endwall is evaluated,this is meaningful under the background of national development of "aviation engines and gas turbines".