Research On Matching Optimization Of Ventilation Mechanism And Ventilation System Of Opposed Two-stroke Diesel Engine

As the progress and development of The Times,energy and environment problem more and more national attention,in order to deal with energy and environmental crisis,reduce automobile fuel consumption of the energy problem,automobile exhaust pollution to the environment,the researchers on the one hand,committed to the traditional four stroke diesel engine of technology improvement and upgrading,such as high pressure injection system,exhaust gas aftertreatment systems,etc.;On the other hand,it is to break out of the limitations of the traditional four-stroke and develop new power modes to meet the increasingly stringent performance and emission targets.Under this background,OP2 S diesel engines have attracted more and more attention due to its high power density and high thermal efficiency.However,due to the lack of special valve mechanism,the two-stroke internal combustion engine has a short air change time,and the intake and exhaust processes are carried out at the same time,which will lead to the mixing of fresh charge and exhaust gas,the large residual exhaust gas coefficient in the cylinder,the poor scavenging quality and other problems,which will affect the further improvement of the performance of opposed-piston diesel engine.Therefore,this paper takes opposed-two-stroke diesel engine as the research object and aims to improve its air exchange performance.Based on one-dimensional and three-dimensional co-simulation,optimization analysis and research are carried out.The main research contents are as follows:(1)The establishment of one-dimensional simulation.A one-dimensional simulation model of OP2 S diesel engine was established by using GT-POWER software.The influences of inlet/exhaust height and inlet/exhaust width circumference ratio on the Power performance and ventilation performance of OP2 S diesel engine were studied.The evaluation parameters of ventilation performance were determined as the air feed ratio,scavenging efficiency and average indicating pressure.(2)Optimization of OP2 S diesel engine port structure by Taguchi algorithm.Taguchi method can be applied to OP2 S diesel engine intake structure optimization,and can directly show the level of influence of parameters on the properties of ventilation accounted,on the basis of the basic parameters of diesel engine in this paper,when the inlet height is 25 mm,vent height is 33 mm,into circular vent width ratio 0.75,can keep the cylinder structure stiffness,and can achieve good ventilation performance,at this point,the OP2 S diesel to gas ratio: 0.7142,the scavenging efficiency is: 0.6836,the mean indicated pressure was: 0.7773.(3)Establishment of 3D model.OP2 S diesel engine was established based on AVL-the Fire of the 3 d simulation model,to determine the boundary conditions of 3 d model building,when OP2 S to 3500 r/min speed diesel engine power,inlet pressure is 0.13 MPa,outlet pressure is 0.1 MPa,into the exhaust pressure difference is 0.03 MPa,when using Ⅱ port shape,can achieve good ventilation performance,proved the sleek port shape to improve the ventilation performance of OP2 S diesel engine has a certain influence.(4)Established a set of optimized match way,into the exhaust outlet width circumference ratio 0.75,inlet height is 25 mm height is 33 mm,vent,air inlet shape using Ⅱ scheme,into the exhaust pressure difference is 0.03 MPa,the single chamber structure of double row set,more conducive to improve the ventilation performance of OP2 S diesel engine,the ventilation performance compared with the initial model by about 32%.