Multi-objective Optimization And Analysis Of Diesel Engine Combustion Chamber And Fuel Injection Parameters

With increasing energy shortage and environmental pollution,higher performance of the combustion and emission system of diesel engine are expected to match with.Combustion chamber and fuel injection system,integral parts of diesel engine combustion system,play a key role on fuel atomization and mixture formation,the suitable combustion chamber shape and fuel injection system parameters have a outstanding effect on improving the performance of diesel.This paper,through FLUENT,a CFD software,makes a numerical simulation analysis for combustion process of a single cylinder four-stroke diesel engine and achieves multi-objective optimization of combustion chamber structure and fuel injection parameters.The research contents are as follows:(1)Build diesel engine three-dimensional model according to the geometric parameters of diesel engine by SpaceClaim software,then,used the Design Model module of ANSYS to do the parameterization of combustion chamber shape,the variable parameters including Caliber reducing rate,Convex platform depth,Combustion chamber depth.And,at modeling time,to preparing for the Multi-objective Optimization Analysis,need ensure all models have the same compression ratio and combustion chamber space.(2)After complete the element mesh,used FLUENT do the numerical simulation for four-hole and six-hole injector diesel engine's combustion process,and comparative analysis of the dynamic performance and emission performance of them,the finding are as follow: four-hole injector have a good dynamic performance,four-hole injector have a good emission performance.(3)The shape of the six-hole injector diesel engine's combustion chamber is optimized and analyzed by Non-Dominated Sorting Genetic Algorithm-?(NSGA-?)which is based on Kriging surrogate model.Caliber reducing rate,Convex platform depth,Combustion chamber depth,Orifice diameter,Nozzle spray angle and Fuel injection advance angle are the design variables,Peak pressure,Soot emission and NO emission are the design objectives.After the optimization solution,choose one group parameters from the Pareto optimal solutions do the numerical simulation,and compare this results with the original model.(4)Two data mining methods,Analysis of Variance(ANOVA)and Self-OrganizingFeature Map(SOM),are used to analyze the influence of design variables to design objectives,it also reveals the contradictory and promotional relationship in objective functions.The finding are as follow: the larger peak pressure need lager Fuel injection advance angle,Convex platform depth and smaller Nozzle spray angle,Caliber reducing rate,but the emissions of NO is increase at the same time,and lower emissions of Soot need lager Fuel injection advance angle,smaller Caliber reducing rate and smaller Orifice diameter,that means there is a contradiction relationship between dynamic performance and emission performance,so the designer need to choose a compromise proposal about those six design variables for diesel's comprehensive performance.Besides,Combustion chamber depth has a small impact on design objectives in the optimization.The conclusion of this study on the multi-objective optimization of diesel engine combustion chamber and parameters of fuel injection system provides some reference for the selection of diesel engine combustion system parameters;a complete and feasible optimization solution devised during research will offer guidance in tackling multi-objective optimization in various fields.