Numerical Simulation Of Flow Field And Combustion In A Diesel Engine Cylinder

At present,the combustion performance and emission control of diesel engine is more and more strict.The combustion process of diesel engine has a direct impact on the performance and emissions of the engine.Numerical simulation method can effectively reduce the cost,shorten the development cycle.Meantime,the amount of information is easy to be optimized and understood.Therefore,this method is widely used in the study of combustion process of diesel engine.In view of this,numerical simulation method is adopted for transient combustion process of diesel engine.Macro analysis of the in cylinder flow characteristics,emissions of soot and nitrogen oxides were studied.In this paper,Computational Fluid Dynamics(CFD)numerical analysis used Fluent,which is a solver software.Established the calculation model and parameterized the key parameters of the combustion chamber.The process of flowing state of working substance,temperature distribution,pressure distribution,velocity distribution and soot and NOx emissions in cylinder were simulated,and then formation mechanism of harmful emissions and the main reasons were analyzed.In addition,the effects of different rotational speed on the combustion process,soot and nitrogen oxide emissions of diesel engine were studied.Provide guidance for the improvement and optimization of diesel engine power and emission performance.In the shape of the combustion chamber,optimization algorithm of Hybrid Multi-objective Gradient Exploration algorithm(HMGE)is based on Kriging surrogate model for the key parameters of the combustion chamber size have been optimized and made a qualitative and quantitative analysis.The MHGE algorithm can quickly and accurately find the global optimum and get the Pareto optimal solution set,the solution set provides an effective reference and space for screening design program.The data mining result can effectively evaluate the influence degree of the interaction between the 4 design variables and their own for the four design objectives,reflecting the influence of design variables on the design goals of the law.At the same time,it also revealed that the design goals contradict each other and mutual promotion relationship.The significance of data mining is very intuitive to show the relationship between the design variables and the design goal in the high dimension data,which helped to find the main factors of affecting the objective function and improved the understand of design exploration.The optimization problem of the shape of the combustion chamber of diesel engine has been solved,and the knowledge of hiding in the data was mined.A lot of optimization experience have been accumulated in this study.The conclusions are as follows: less soot emissions need clearance is larger,lower emissions of nitrogen oxides to smaller convex platform height and smaller caliber reducing rate;there is a contradiction relationship between cylinder pressure and soot and NOx emissions,cylinder temperature and emissions of NOx and soot can get optimal simultaneously;a better power requires smaller caliber reducing rate,spray cone angle on engine power and emission had little effect;the designers can know the design variables on the size and law of the optimization influence for the design objectives,which is contributed to accumulate the design experience.