Multi-objective Performance Optimization Of Exhaust Gas Recirculation Diesel Engine Based On PSO Algorithm

With the rapid development of the economy and industrial technology in China,the diesel engine has become an important part of daily life.As an effective power method,the diesel engine has changed the work and lifestyle of human.At the same time,the appearance of the diesel engine has provided a strong guarantee for human beings to realize various dreams.In the background of global warming and the awakening of human environmental protection awareness,the research on the diesel engine is no longer an extreme pursuit of power,and the current research focuses more and more on energy conservation and emission reduction.As the current mainstream emission reduction technology,the exhaust gas recirculation system can greatly reduce the emission of engine NO_x.To a certain degree,EGR meets the demand of emission reduction by sacrificing the power and economy of the engine.In order to ensure the EGR emission reduction while taking into account the economy and power of the diesel engine,a multi-objective optimization algorithm is used to optimize the performance of the diesel engine.In this paper,the mathematical model of the working process of the diesel engine is used first,and the simulation model is built by Simulink software.In order to ensure the accuracy of the model,the in-cylinder pressure value of the simulation model is compared with the actual pressure value of the original machine.Then,the influence of the EGR system on the diesel engine is explored by establishing an EGR model,and it is found that with the increase of the effective flow area of the EGR valve,the NO_x emission would decrease,but at the same time,it would also have an adverse effect on power and fuel consumption.Therefore,a multi-objective optimization method is proposed for the above problems,and a multi-objective optimization function is determined with load,EGR valve effective flow area as decision variables,and power,fuel consumption,and NO_x emission as optimization goals,and optimized by PSO algorithm.On this basis,seven different optimization schemes are designed at low,medium and high speeds respectively,and the results are analyzed to determine the final optimization scheme.The simulation results show that optimizing a single objective will affect the other two objectives,especially the NO_x emission will decrease with the increase of the fuel consumption.Therefore,in order to solve the adverse effects of single-objective optimization,the distribution of weight coefficients is adjusted.It is found that when the weight coefficients of power,fuel consumption,and NO_x emission are set to 0.3,0.2,and 0.5 respectively,the NO_x emission of the diesel engine before the optimization is reduced by 42.6%on average,the fuel consumption is reduced by 1.0%on average,and the power reduction is less than2.0%.This satisfies the multi-objective optimization requirements of emission performance and economy and guarantees the power performance of the diesel engine to a certain degree.