Research On Transient Conditions Of Diesel Engine With1D/3D Simulation Platform

With the developing of economy and technology, more and more vechiles areproduced to meet people daily needs. Emissions regulations become s increasingly strict,especially in PM and NOx emissions of diesel. Additionally, there are obviously differencesbetween transient conditions and steady conditions and many new transient emissionregulations are created, such as EPA (USA) and ETS (Europe). Therefore, more researcherstransfer their study on transient conditions.Establishment of1D/3D simulation platform for diesel engineIn this study, a new simulation platform combining1-D and3-D models wasestablished for diesel combustion process and emissions formation research. In the newsimulation platform,3-D model is used in combustion simulation and1-D model is used inother parts. Compared with traditional1D simulation, the improved model can predict heatrelease rate, A/F ratio, combustion pressure and emissions more accurately. The changingtrends of simulation results are similar with the experiment results. Compared withtraditional CFD simulation, the improved simulation saved70%times in the simulation oftransient conditions.Investigation of transient conditions on simulation platformIn the sutdy, based on the improved simulation platform, combustion and emissions ofsteady conditions and transient conditions are calculted and finally some conclusions aredrawn.(1) Compared with steady conditions, there are delays in output torque andturbocharger of transient conditions, and delays become larger as transient rate increasing.The reason is compressibility of gas and interance of turbocharge.(2) Compared withsteady conidtions, air inflow decreases; fuel consumption increases; temperature peak valueincreases; pressure peak value decreases. Additionally, these phenomenons become moreobviously as transient rate increasing.(3) There are some differences of emissions betweentrasient and steady conditions. More Soot are produced in transient conditions andincreaseing as transient rate being higher.The reason is: in the same output torqueconditions, there are more fuels in transient conditions which means more fules would beinjected into the area of lack oxygen and air flow. Based on this, more Soot are produced;Fewer NOx are produced in transient conditions. In low load conditions, low temperatureof chamber will absorb heat which causes combustion temperature decreases; In hig loadconditions, the average temperature are higher than1600K which means temperatr has littleeffect on NOx production. Then, there is less oxygen in chamber in transient conditions.Based on these, fewer NOx are produce in transient conditions.