Simulation Investigation On Optimization Of Combustion System Of 170 Marine Diesel Engine

A reasonable match between the marine diesel engine intake system,the fuel injection system and the shape of the combustion chamber helps to improve the combustion process within the cylinder,thereby reducing pollutant emissions and fuel consumption.In order to meet increasingly strict emission regulations and improve fuel economy,this paper carries out an optimization simulation investigation of the combustion system of 170 turbocharged marine diesel engine.Based on the combustion chamber geometry of the original engine,the compression ratio is guaranteed to be constant,this paper designs three combustion chamber geometrys and the simulation models of the combustion system are established in the AVL Fire software,in order to study the effect of the combustion chamber geometry on the combustion and emission of the diesel engine at full power point.The results show that the wave combustion chamber,the?type double-layer diverging combustion chamber and the?type double-layer diverging combustion chamber all contribute to the improvement of fuel economy,the IMEP is increased by 3.01%,2.68%,1.59%compared with the original engine;the NO_x emission of the wave combustion chamber is reduced by 5.0%compared with the original engine;the soot emission of the?type double-layer diverging combustion chamber and the wave combustion chamber are reduced,which is 7.6%and 2.8%lower than the original engine.Using the orthogonal design method and considering the interaction between parameters,this paper designs a multi-parameter matching scheme of the diesel engine combustion system,parameters include the intake vortex ratio,injection angle,nozzle penetration height,fuel injection duration,orifice diameter and combustion chamber geometry.Select NO_x emission,soot emission and indicated work as optimization targets,and use multi-objective optimization function to study the combined impact of different parameter matching schemes on fuel economy and emission under multiple operating conditions of marine diesel engine E3cycle.In this paper,the variance analysis method is used to obtain the optimal combustion system scheme at each power point and the parameters of combustion system that have a significant impact on the comprehensive performance of the diesel engine.Based on the optimization simulation analysis of the combustion system at four single power points,the better combustion system of the marine diesel engine working under multiple operating conditions is obtained.The results show that the?type double-layer diverging combustion chamber matches the longer injection duration and the larger orifice diameter,which can achieve better comprehensive performance than the original combustion system.The optimal scheme is better than the original engine's combustion system.Compared with the original engine,the indicated work is unchanged at 100%power point,the NO_x emission is reduced by 54.0%,the soot emission is increased by 2.3%;the indicated work is increased by 1.4%at75%power point,NO_x emission is decreased by 52.4%,soot emission is decreased by 11.0%;the indicated work is increased by 1.1%at 50%power point,the NO_x emission is reduced by49.5%,the soot emission is decreased by 23.1%;the indicated work is unchanged at 25%power point,the NO_x emission is reduced by 56.8%,the soot emission is decreased by 15.5%.