Lightweight Optimization Of Stiffened Casing Structures With Cutout In Aero-engines

Aero-engine has a direct impact on the performance of aero-aircraft.Weight requirement is a basic requirement of aero-engine research and development.Reducing weight can significantly improve the thrust-weight ratio of the engine,which is beneficial to the performance,economy and environmental protection of the aircraft.As the skeleton of an aero-engine,the casing is connected with combustion chamber,oil pipeline,exhaust pipe,cooling pipe and other components.It is a common thin-walled stiffened structure in the engine.The lightweight design of the casing structure is one of the effective ways to improve the thrust-weight ratio of the engine.However,due to the installation of equipment,pipe laying,heat dissipation,such as demand,cutouts often appear in the machine box structure,which has seriously affected the structure stiffness and strength,and casing complex geometry structure,special-shaped surface for the space,or complicated curved surface of geogrid reinforced,these all greatly increased the difficulty of optimization design.Therefore,it is necessary to study the optimal design of stiffened casing with cutout.In this paper,an optimal design framework is established for the casing structure with cutout in aircraft engine,and a reasonable lightweight design of the casing structure with cutout is obtained based on this framework,which is of practical value and guiding significance to practical engineering problems.The main research contents of this paper are as follows:(1)For the open casing structure,this paper proposes a size-topology hybrid optimization design method.Due to the functional requirements,cutouts often exist in aircraft engine structure.The existing design method is to determine the optimal global stiffeners layout first,then on this basis,the area around the opening was optimized.However,this design method does not fully consider the coupling relationship between the effect of global bar layout and local bar layout on the structural performance of openings.In this paper,by using MATLAB program and combining size optimization and topology optimization,a hybrid optimization design method is proposed,which can cooperatively consider the global stiffener layout and local stiffener layout around the cutout,which has certain guiding significance for engineering practice.(2)The large structural size and complex geometry of aero-engine casing increase the computational complexity and difficulty of optimization solution.In this paper,MATLAB program is adopted to realize the automatic flow of the traditional optimization method for the open casing structure,and the flow is improved.In the optimization solution part of global stiffener layout of traditional design method,the non-matched mesh is proposed to conduct discrete and finite element analysis of the structure.(3)In this paper,the above two flows are used to optimize the design of a stiffened casing structure with cutout.To improve the efficiency of finite element analysis,unmatched meshes are used to analyze the structure in the optimization design of global stiffener layout of the traditional optimization;in the hybrid optimization design of the casing structure with cutout,the local strain energy was proposed as the optimization objective of the topology optimization problem around the cutout,so as to further improve the performance around cutout.On the basis of satisfying the requirements of the structure performance,the configuration of the lightweight design is given in the two examples,and good results are obtained.