Investigation Of The Coupling Effect Of Air Oxygen And Oxygen Fuel On The Emission Characteristics Of The Diesel Engine

In order to relieve the energy shortage crisis and environmental deterioration,countries are paying more and more attention to search for alternative fuels.Oxygenated fuels can significantly improve the emission of diesel engines and become the focus of current alternative fuel research.N-butanol is considered as a new generation of oxygenated fuel due to its superior combustion performance and abundant sources.Based on a single-cylinder diesel engine modified by a 4-cylinder turbocharged intercooled high-pressure common-rail diesel engine,the effect of coupling of gaseous oxygen and oxygenated fuels on the emission characteristic is studied.Firstly,the influence of the coupling effect of air oxygen and oxygenated fuel on the emission characteristics of the diesel engine is studied.The results show that with the decrease of oxygen concentration,oxygen concentration of the intake gas and combustion temperature are the main factors affecting soot,NOx,HC and CO emissions.When considering the soot emissions and NOX emissions under the same oxygen concentrations,the soot emissions decrease,NOx emissions increase,and fuel oxygen and the ignition delay are the main causes;HC emissions increase,the combustion temperature and the combustion duration are the major factors in its change;The increase in CO emissions,fuel oxygen and combustion duration are the main reasons for its change.Secondly,the cetane number improver 2-ethylhexyl nitrate(EHN)is added to the B20 fuel to investigate the influence of the oxygen content of the fuel and the ignition delay on the emission characteristics.Results are shown as follow,when the ignition delay is fixed,the influence of fuel oxygen content on soot emissions increases first and then decreases as the decrease of oxygen concentration.The influence of fuel oxygen and EHN on NOx emission is weaker first and then became intensive.The effects of fuel oxygen and latent heat of vaporization on HC emissions is weaker first and then became intensive.Fuel oxygen has a weaker influence on CO emissions.When the fuel oxygen is fixed,the impact of ignition delay on soot emissions increases first and then decreases as the oxygen concentration decreases.The impact of the ignition delay on NOx emissions is maintained at a certain level and then weakened.The effect of combustion duration on HC emissions is weaker and then increases.The impact of the ignition delay on CO emissions gradually diminishes.Finally,the differences in the emissions of different fuels under different intake pressures are compared to investigate the effects of oxygen and ignition delay on the emission characteristics.Results are shown that,when the ignition delay is fixed,with the decrease of the intake pressure,the influence of fuel oxygen on the soot emissions will diminished.The influence of fuel oxygen and EHN on NOx emissions is weakened;The effect of the latent heat of vaporization and EHN on HC emissions are enhanced;The latent heat of vaporization and fuel oxygen has an increased influence on CO emissions.When the oxygen content of the fuel is fixed,as the intake pressure decreases,the influence of the ignition delay on the soot emissions gradually decreases.The coupling effect of ignition delay and combustion duration on the HC emissions gradually increased.The combustion duration has an increasing impact on CO emissions.When the oxygen concentration is fixed between 20.9% and 16%,the effect of the ignition delay on the NOx emission changes from the promotion to inhibition.When the oxygen concentration is lower than 16%,the effect of the ignition delay on the NOx emission is still weak.