Research On Numerical Simulation And Emission Control Of 1E40F Two-stroke Engine Scavenging Process Based On CFD

Two-stroke gasoline engine has many advantages,such as good dynamic performance,small size,light weight,low vibration noise,easy to start and low cost.It is widely used in motorcycle,rowing and garden machinery.The scavenging process of two-stroke gasoline engine largely affects the charge and air flow of the fresh working fluid and pollutant emission in the cylinder,and then affects the performance index of the power,fuel economy and emissions.In this paper,the modeling,simulation and experimental study on the scavenging process of a 1E40F two stroke gasoline engine are carried out.Based on the comprehensive analysis and research,the reasonable structure parameters of two-stroke gasoline engine scavenging system are obtained to lay a good foundation for the application of low emission of two stroke gasoline engine.The main research works are below:1 On the bench test,the dynamic parameters and emission characteristics of the two stroke gasoline engine with the original scavenging parameters are obtained.Then the influence of excess air coefficient on the emission is analyzed,and the calculation method of the air port parameter is calculated.2 The parametric modeling of the flow field in the prototype was carried out by using three-dimensional modeling software CATIA(After the optimization of the reference theory of air inlet parameters).Firstly,the 0 degree model,the 8 degree model and the 15 degree model are established for the elevation angle of the scavenging port.Secondly,according to the shape of piston top,the circular convex model and the pit step model are established.Thirdly,a semi closed airway model is established for the main scavenging structure.Finally,the 20 degree model is established for the elevation angle of the main scavenging port.Using ICEM CFD,each model is divided into grid and boundary treatment.3 The application of computational fluid dynamics(CFD)method,which is based on CFD software Fluent,set the same boundary conditions and initial conditions,the scavenging process of the established model were obtained in numerical simulation,flow pressure diagram,temperature diagram,velocity vector diagram and sweep the exhaust mass flow.Makeanalysis of the parameters of the model through the simulation of the conclusions,in order to obtain a more reasonable structure of the internal flow of advice.In addition,the numerical simulation of spatial stratified scavenging scheme is also presented.Through the experimental analysis,as for the 1E40F two stroke engine,the fuel consumption is lower than that of the low speed operation at higher speed(greater than 4500r/min).When the engine load is from 0.2Mpa to 0.3Mpa,the emission index of NOX,CO and CH is reasonable.Through the fluid simulation analysis,At high speed,increasing the engine scavenging angle,changing the engine piston shape is changed,the ladder shaped pits is a semi enclosed engine inlet port channel and appropriate to increase the main channel angle,have great impact on airflow and engine exhaust condition.When the elevation angle is 8 degree,it is more advantageous to sweep and exhaust the exhaust gas from other angles.When the piston top is changed into pit ladder type,at the beginning of scavenging,the scavenging of the upper left corner of the cylinder is not enough.lt is more reasonable to improve the scavenging flow organization in the later period of scavenging.The gas flow near the wall increases,and the scavenging effect is enhanced.The results of the model show that the velocity vector of the exhaust port on the middle surface is obviously reduced after the main clearance is semi closed,which means that the short circuit loss of fresh mixturegas is much reduced.It is found that the scavenging effect of the latter is better than that of the original one,but the short-circuit loss is serious.The numerical simulation results show that the short circuit loss of fresh gas is greatly reduced.