Aerodynamic Optimization Design Of The Nacelle For Large Bypass Ratio Turbofan Engine

The quality of the engine nacelle profiles design is directly related to the external resistance of the aircraft and the aerodynamic performance of the internal intake.In this paper,the nacelle profiles of the large bypass ratio turbofan engine are studied by using the method of combining numerical simulation with optimized design.The nacelle outer profile,the nacelle inner profile and the inlet spinner profile are parameterized by Class-ShapeTransformation function,hyperelliptic-Bezier curve and hyperelliptic curve respectively.Multi-objective optimization design platform is established,to optimize the profiles of the nacelle.The performance analysis of the threedimensional model of the optimization results is verified.Finally,a set of procedures and methods for the aerodynamic optimization design of the engine nacelle are established,and some variables design experiences of the nacelle profiles of the large bypass ratio turbofan engine are given.The research results show that the optimal nacelle profiles can be obtained by using the multi-objective optimization platform built with MATLAB.The optimization platform proposes the independent objective functions for the inner and outer profiles of the nacelle.The Latin hypercube design method is used to get optimization results,by combining with the RBF surrogate model and the NSGA-II genetic algorithm.Through the numerical verification calculation of the optimal profiles,it is confirmed that the optimal profiles can reduce the external frictional resistance of the nacelle while improving the total pressure recovery coefficient of the intake,and obtain a better nacelle aerodynamic performance.It also verifies the feasibility and effectiveness of the multi-objective optimization platform of the nacelle profiles.In addition,by comparing the performances of the different nacelle profiles,it can be known that the maximum radius of the outer line is appropriately reduced,and the outer surface of the nacelle is relatively flat,which can reduce the airflow acceleration outside the nacelle and significantly reduce the frictional resistance.And if the throat radius of the nacelle inner profile is too small,the expansion angle of the diffuser section becomes large,thereby forming a large adverse pressure gradient,finally resulting in an increase in flow loss.