Research On Some Problems In Applying Adjoint Method For Aerodynamic Shape Optimization Of Turbomachinery

The fine design based on adjoint optimization method is the trend of aerodynamic design of turbomachinery,therefore,it is one of the most important research directions in the field of turbomachinery to develop the optimization system,to explore the fine design and to master the application specification.In the early stage of the research group,the adjoint optimization system of turbomachinery was developed,but the problems of local solution,blade parameterization,inverse problem and optimization strategy were encountered in the engineering application.In order to solve these problems,and explore the new technology of turbomachinery based on the adjoint optimization method,in this paper,the related theories and numerical studies are carried out.Firstly,this paper analyzes the local solution of the application of the adjoint method during turbomachinery design process,and summarizes three kinds of performance of the local optimization method with local issues: the choice of different parameters(parametric problem),the direction selective of optimal path in the case of multi polar value and the drift of working condition.Among them,the drift of the working condition is the most harmful to the engineering application and the most urgent need to be solved.Taking this as the breakthrough point,the paper puts forward the measures of applying the static pressure and the air flow angle constraint,from the angle of inheriting the traditional turbine design system,make the adjoint optimization has a certain global.The results of related application case show that during the optimization cycle,the static pressure between row interface deviates from the initial design is very small,avoid the tip of the static pressure substantial growth with the increase of cycle number of the optimization,effectively avoid the drift of working condition.Secondly,it is pointed out that the integration of blended blade end-wall is the development trend of three dimensional complex blade passage.Based on the previous work,in addition to the blade surface parameterization,the paper puts forward a new scheme of blade thickness,radial flow path geometry parameters,to further expand the turbomachinery optimization parameterization space.The results of blade thickness parameterization show that although the follow-up still need to consider the strength effect,the blade thickness on the aerodynamic performance is significantly affected by weaken the intensity of shock waves and reasonable load distribution,the adiabatic efficiency increased by 1 percentage points,and the pressure and the mass flow rate changes a little,the margin maintains at least not fall.The flat casing Rotor67 rotor case study shows that the casing contraction has the best angle about 11 degrees,improve its aerodynamic performance significantly,which adiabatic efficiency increased by 1.5 percentage points,while the pressure ratio and mass flow rate change is very small.Thirdly,this paper points out the fundamental limitation of the three dimensional inverse problem and the basic method of the adjoint method applied to the inverse problem design.Using VB language composed multi-row and multi-section blade surface target pressure adjustment tool,and with the original optimization system constitute the inverse problem blade design system based on adjoint method,the inverse design of blade based on adjoint method is realized.Then,a comparative study of the adjoint method is based on the inverse problem of combined optimization design strategy,the results show that compared with the single direct problem and inverse problem,joint optimization of direct and inverse problems has the potential to further improve performance.Due to some blindness currently in inverse problem of target pressure distribution adjustment,direct?inverse optimization strategy is difficult to bear fruit;while inverse?direct optimization strategy can further enhance the aerodynamic the performance,the improvement is slightly larger than the single direct optimization problem.Finally,this paper puts forward with the optimization method to realize full three-dimensional centrifugal impeller,the exit boundary conditions for the adjoint field of centrifugal impeller are derived,by using multi-section parametric to relieve straight generatrix constraint,take Krain centrifugal impeller as an example,the results indicate that with the pressure ratio,mass flow and outlet flow angle keep constant,gain a full three-dimensional centrifugal impeller,improve the overall thermal efficiency of about 0.4 percentage points.It is pointed out that reducing the shock in super/transonic turbine must be optimized by computer,and the adjoint method is the best choice.Take Russia's three typical super/transonic turbine cascade as example,optimized in different back pressure,the calculated results show that,based on the adjoint method,the reduced shock blading technique can greatly improve the performance of the cascade.The TTM super/transonic turbine case results show that the suction surface curvature after throat of the reduced shock blade growth rapidly,appears the after loading characteristics,effectively reduce the intensity of shock waves,and almost the whole condition in significant performance improvement.Full three-dimensional centrifugal impeller,super/transonic turbine reduced shock blading technology based on adjoint method,relieve straight generatrix constraint,overcome the reduced shock blading technology is difficult to quantify only qualitative rules,make full three-dimensional centrifugal impeller and turbine reduced shock blading technology to be specific,engineering,can further improve the aerodynamic performance of centrifugal compressor and super/transonic turbine.