Study On The Influence Of Fuel Injection Parameters On Performance And Emission Of Light-duty Vehicle Diesel Engine

In recent years,the fog and haze weather can be connected to the exhaust emissions from automobiles to a certain degree.In order to reduce emission and meet current stringent emission standards,more effective emission control methods are needed.The combustion and emission of diesel engine can be significantly improved by using multiple injection strategies,coupled with EGR.That is,the corresponding post-treatment technical methods are matched to meet the stringent emission standards.The effective control of fuel injection parameters and the optimization of the mixing rate of fuel and air are some of the key technologies that can be used to achieve clean combustion.Since EGR can significantly reduce NOx emission,the study of the combined effect of electronic control high pressure common rail multiple injection strategies and EGR on emission control,presents a good prospect in terms of emission reduction.In this paper,a light-duty vehicle common rail diesel engine was taken as the study object.Using both simulation and bench test,the combustion process of the diesel engine was improved by adjusting the fuel injection parameters and the EGR.Thus,a trade-off between emission and fuel consumption rate can be achieved.For the simulation process,the combustion chamber model of diesel engine was built,meshed and simulated with AVL Fire software.Afterwards,the effect of nozzle protrusion,injection timing and pilot injection parameters on the combustion and emission of the common rail diesel engine were analyzed.The results showed that,the nozzle protrusion of 3 mm within the combustion chamber,is comparatively better with regards to combustion and emission.Advancing the injection timing results in increasing peak values of the internal cylinder pressure and temperature,however,the time of attaining the peak value shortens.The delay of the injection timing can effectively reduce the NO emission.Pilot injection can increase the initial temperature in the cylinder,reduce the delay time between the main injection and combustion,and also reduce NO emissions effectively.The increase rate of pressure and temperature for pilot injection,is less than the increase rate of pressure and temperature for singleinjection.For NO and soot emission,a suitable trade-off point between the pilot injection timing and the pilot injection quantity has to be attained.With regards to the single factor variable method,the influence of injection parameters and EGR on diesel engine performance and emission were analyzed.It was found that nozzle protrusion under the injector gasket of 1.4 mm was most suitable.Also,increasing the rail pressure effectively improved the fuel atomization characteristics,the smoke and fuel consumption rate as well,nonetheless the NOx emission increased.The NOx emission effectively reduced when the main injection timing delayed.Hence,the two fuel injection parameters were used as important indexes to optimize the performance of the diesel engine.There is an optimal interval angle between main and pilot injection for a diesel engine.Increasing the quantity of pilot injection,increased the smoke and fuel consumption rate gradually,however for the NOx,an initial decreasing trend and an increasing trend afterwards were observed.When pilot injection quantity is too large or too small,combustion is not conducive.Increasing the EGR opening,decreased the NOx emissions significant,however after30% opening,the smoke began to deteriorate.The influence of fuel injection parameters and EGR on performance and emission were analyzed.Based on orthogonal test method,with regards to the test results,the primary and secondary factors that affected the test index were obtained,under comprehensive consideration,the fuel injection strategy and EGR opening under this operating condition were determined.With regards to simulation and bench testing,the key emission controls of the operating condition were calibrated and optimized,according to the engineering experience,the MAP of the related parameters were determined.To carry out the emission test,the optimized common rail diesel engine was installed in a vehicle and operated,then the emission characteristics from the vehicle were then analyzed,this provided theoretical guidance for the follow-up optimization procedures.