Design And Optimization Of Rapid Mixing Combustion System Of 320 Marine Diesel Engine

With the increasing worldwide energy problems and environmental problems,and increasingly stringent regulations on marine diesel emissions,people pay more and more attention to the economic and emissions performance of marine diesel engines.The Tier III standard,which has been implemented,is reduced by more than 80% relative to the current Tier II standard NOX emissions in marine diesel engine emission standards established by the International Maritime Organization(IMO).So how to improve the economy while reducing nitrogen oxides(NOX)and particulate matter has become the most important research of marine diesel engines.In this paper,three-dimensional CFD simulation and optimization of L6-320 diesel engine are carried out using the AVL FIRE Suite.Using the three-dimensional simulation software to simulate the combustion and emission of the diesel engine,we can explore the performance trend of the whole combustion and emission,and provide a reliable data foundation for the subsequent experiments.In this paper,the automatic optimization method can be used to quickly and accurately give the combustion chamber size parameters and fuel injection parameters on the combustion and emission performance of the impact,and can achieve the mutual matching between the various parameters.The specific works are as follows:(1)At first using the FIRE ESE Diesel software establish the three-dimensional calculation model of L6-320 diesel engine,and this software can automatically divide the grid.And adjusts the calculation parameters in the simulation process,and completes the match with the original cylinder pressure curve.The distribution of fuel ratio,temperature,NOX and soot in the cylinder is given.(2)According to the relevant design criterion of the combustion chamber line,four combustion chambers were designed on the basis of the original combustion chamber,and the three-dimensional simulation was carried out.The results of IMEP,NOX and soot of four new combustion chambers and the original engine were compared and analyzed,and the influencing factors of combustion and emission performance were analyzed.The NOX emission results of the original engine are the best,but the IMEP performance is the worst,the IMEP performance of the ? type combustion chamber is the best,which is 6.64% higher than that of the original engine,but the NOX emission result is the worst,which is 119.33% higher than that of the original engine.Considering all the factors,choosing the original engine and ? type combustion chamber(IMEP increased by 2.65%,NOX and soot relative increase in the smaller range)as the object of next step to optimize the calculate.And then verified the feasibility of the optimization of the combustion chamber under partial load.(3)The original engine and ? type combustion chamber were optimized for the size parameter of the profile.Five parameters were selected and optimized for 250 cases,and the optimization results were obtained.Select the original engine RUNID = 206 and type ? combustion chamber RUNID = 215 as the second step optimization object.Five fuel injection parameters were selected to optimization calculate of the above objects for 250 cases.In the final optimization results,NOX decreased by 17.8%,soot decreased by 27.40% and IMEP increased by 0.15% compared with the original machine.In the final optimization results of the ? type combustion chamber,NOX were reduced by 9.09%,soot decreased by 34.60% and IMEP increased by 1.87% compared with the original machine.