Study On Optimization Method Of High Speed Gasoline Engine Based On NSGA-Ⅱ

Study of engine performance optimization is the topic of engine researchers,however,the performance optimization of the engine is a multi-objective,multivariable nonlinear optimization problem.There are a lot of parameters on the modern engines,it will cost a lot of time and resource to optimize engine performance if we use traditional ways.Therefore,it’s significantly important to study one new optimization method for improving engine performance and optimization efficiency.This paper took a high speed gasoline engine as the research object,the simulation model of the engine was established in GT-Power,and the accuracy of the model was verified by the test data.The influence of the structural parameters of the intake and exhaust system on the performance of the engine was calculated and analyzed by GT-Power.Using the DOE module in GT-Power,the 1000 groups of test points of different inlet and exhaust system structure parameters were produced.Through the sensitivity analysis of the performance of the engine,the length and diameter of intake pipe,length of the exhaust pipe and the volume of the air filter were determined as the key parameters affecting the performance of the engine.Aiming at traditional engine optimization method was not efficient for multi-objective optimization,the method combined NSGA-II and GT-Power model was proposed.The adaptive penalty function method was proposed to solve the nonlinear constraint conditions.Through the comparison with static penalty function,this method can get the optimization parameters faster.To build a coupling optimization simulation platform,the engine 5500 rpm and 7000 rpm torque for multi-objective optimization.According to the results of the optimization calculation,the three optimization schemes were selected to carry out the performance adaptability analysis of the engine under transient conditions.A set of intake and exhaust system is determined,and the experiment was carried out.The results show that the optimized torque is increased by 4.6%(7000rpm)and the maximum power is increased by 4.1%(5500rpm),but the BSFC is not significantly improved.Using the simulation platform again,the engine’s ignition angle and the air fuel ratio were used to optimize the torque and effective fuel consumption,The optimization results are compared with the simulation results,and the BSFC can be reduced by 7%(3000rpm,4000rpm).Simulation and experimental results show that the method of combination NSGA-II & GT-Power can be used to optimize the performance of engine,and a good optimization effect can be obtained by using this optimization method.