The Simulation Of Natural Gas Engine With EGR And The Experiment Studying For National Ⅴ Stage Emission Regulation

Internal combustion engine has made a great contribution to humanity during its development of more than 100 years.With energy and environment get increasingly serious,it’s urgent to search for efficient and clean alternative energy.Natural gas is rich,cheap and good for burnt.In the meantime,natural gas engine exhausts less harmful gas: CO2,NOX,HC,compared with traditional energy engine.NG-engine is gradually used in some industries,such as city buses,taxis and harbor tractor,even it cuts power down after exchanging energy,so it’s practicable to replace part of traditional energy engine.Based on the program of “Technology development of achieving national Ⅴ stage emission regulation for NG-engine MT07”,which the Heavy Duty Truck of China cooperates with Xi-Hua university.Matching important components of natural gas control system for the engine with inside-EGR,then calibrating ignition angle and fuel/air ratio with different turbocharger for track and bus.Setting the initial and boundary conditions,and then choose appropriate combustion,ignition,and turbulence model,after selecting three-dimensional model using Pro/E and FIRE,conform the model is right finally.Study inside changes of combustion chamber be affected by the shape of combustion chamber,the ignition advance angle and fuel/air ratio with the model.Result shows that the combustion chamber with greater squeeze area,gains greater average of turbulent kinetic energy and velocity in the cylinder,which enhance urgency burning period,while be little help for slow burning period;increasing ignition advance angle and fuel/air both contribute to the forward of combustion center,increase engine power outputting,while worsen the emission of NOX because in-cylinder temperature increases.On the basis of previous studies,explore potentiality of equivalent burning combined with high inside EGR.Result shows that the technical solution is feasible to achieve the national Ⅵ stage emission regulation,when mounted TWC,in the meantime the power of engine will be increased.Based on the study of NG-engine’s technical development and its effect,a technical solution is put forward to achieve national Ⅴ stage emission regulation,which includes lean burning,intercool turbocharging,independent single-cylinder ignition with high energy,CFV NG-controller,wide area oxygen sensor,and oxidation catalyst.A experiment is designed which be used to estimate emission of transient condition through testing steady ’s.Ignition advance angle and fuel/air ratio will be changed to study its effects on power and emission character in testing emission of steady condition,and then explore the map of ignition advance angle and fuel/air ratio.Result shows that lean burn extreme of fuel/air ratio is raised at most work condition,with inside EGR working;emission of NOX increases first and then decreases with increasing of ignition angle and aways decrease with decreasing fuel/air ratio;emission of CH4 decreases first and then increases with increasing of ignition advance angle and fuel/air ratio;in order to achieve the nation emission rule of Ⅴ,power of engine in high load and full load decreases 6%,and decreases 14% in low load and middle load.