Experimental Study On Characteristics Of Ultrafine Particulate Emissions From Compression Ignition Engines

High-density fine particle is a vital factor causing hazy and low-transparencyweather which is also harmful to people’s health. Vehicle exhaust, especially dieselengine emission, is one of the most predominant resources of particle emissions.Exploring the particle formation mechanism, clarifying the physical and chemicalproperties of diesel particular could lay a better foundation for the particle emissioncontrol. In this paper the effect of engine operating conditions and fuel properties onthe particle formation were investigated by employing multistage diluter on asupercharged, cooling, and high-pressure common-rail diesel engine, and the physicaland chemical properties of particulates were also analyzed using several apparatus.Diesel engine test bench suitable for the research was established firstly. Themultistage diluter was set up and the dilute parameters could be controlled in arelatively wide range. Besides, the collected particle parameters from engine exhaustalso met the specifications of measuring instruments.The effect of engine load on the particle density distribution under the operatingcondition of1400r/min and2200r/min was measured on the test engine fueled bydiesel, and the influence of speeds on the particle density distribution under theoperating condition of BMEP (Brake Mean Effective Pressure)=0.08Mpa andBMEP=1.0Mpa was also analyzed. After that, mixture fuel of diesel blended with20%v/v biodiesel was compared and analyzed under the same conditions to explorethe effect of operating conditions on the engine particle distributions.The effect of oxygen contents on the relationship between particle densitydistribution and particle size distribution was farther studied. The results are:1) Underthe same operating condition, the oxygen content in fuel could reduce particle massemission significantly, and can also reduce the quantity density in a certain range,however, the relationship is not linear, especially under the condition of low-speedand high-load.2) Particle emission is related to fuel properties. dimethoxym ethane and methyl carbonate are excellent additive for the reduction of engine particularemission.Finally, the physical and chemical properties of engine particle emissions by fivedifferent fuels were investigated. In this study, Raman spectrum was used to study thecrystalline structure of particles, FIRE analysis was employed to research the surfaceoxygen-contained groups, OCEC analyzer was used to investigate the organic andinorganic elemental carbon proportion, and thermal gravity analysis was employed toexplore high-temperature oxidation of particles. The results are:1) The crystallinesize increases and its internal structure becomes more stable with the increase ofoxygen content.2) The oxidized property becomes stronger with the increment ofsurface oxygen-contained groups.3) The increase of the ratio of organic carbon/inorganic carbon exerts positive effect on the particle characteristics of captured andoxidized.This study is helpful for the diesel particular control and atmosphereenvironment protection.