| With the number of motor vehicles sustainable growth,and the exhaust emissions resulted from motor vehicles have serious effects on the environment and human life.Nanoparticles with high specific surface area and thermal conductivity,as additives,can improve fuel energy density,promote more complete combustion of the fuel and improve engine power output,at the same time,adding nano-additives can reduce the emission of pollutants such as soot and NO_X.In this study,C50,C100,Mo50 and Mo100 nano fuels were prepared by adding 50mg/L and 100mg/L carbon nanoparticles and molybdenum oxide nanoparticles into diesel respectively.Physical and chemical properties of pure diesel and nano fuel were determined,including density,viscosity,calorific value,flash point,solidification point and cold filter plugging point.The spray characteristics were tested by high speed camera system and Marvin laser particle size analyzer.Bench tests were carried out on a turbocharged inter-cooled CRDI diesel engine with EGR control system using five fuels.The results are as follows:(1)Compared with D100,the density,kinematic viscosity and calorific value of the nano-emulsified fuels all increased,and the solidification point and cold filter plugging point were similar to D100.The density and calorific value of the fuel increased with the increase of nano-additive amount,while the kinematic viscosity decreased.(2)After adding nanoparticles,the atomization quality of fuel becomes worse at normal temperature and pressure.Compared with D100,the maximum spray angle of C50 and C100decreased by 3.9%and 5.1%respectively,the spray tip penetration distance was slightly increased,and the spray area decreased by 12.5%and 15.4%respectively,the maximum spray angle of Mo50 and Mo100 decreased by 5.0%and 4.4%respectively,and the spray area decreased by 17.9%and 19.3%respectively.The cumulative volume fraction of nano-emulsified fuel was shifted to the direction of large particles,and the sauter mean diameter increased.(3)Compared with D100,the ignition delay of nano-emulsified fuels were prolonged and the combustion duration were shortened.The effect of different nano additives and amounts on the ignition delay and combustion duration was not significant.Both the cylinder pressure and heat release rate of C50 are lower than that of C100,while Mo50 and Mo100 are in between.The cylinder pressure and heat release rate of the four nano-emulsified fuels were higher than D100.The cylinder temperature of nano-emulsion fuel is lower than that of pure diesel.With the addition of nanoparticles,the combustion stability decreased and the coefficient of cyclic variation increased.(4)Compared with D100,the NOx emissions of C50 and C100 decreased by 7.32%and3.51%respectively,the NOx emissions of Mo50 and Mo100 decreased by 5.59%and 8.88%respectively,and the HC emissions of four nano emulsified fuels decreased.Compared with pure diesel fuel,the emission of large particles of nano emulsified fuel is lower,the number concentration of ultrafine particles are significantly higher,and the peak particle size is around 50 nm,The ratio of nucleation mode particle has little change with the load,which is basically maintained at about 50%,At low load,the ratio of nucleation mode particle increases with the increase of nano addition,while at medium and high load,the ratio of nucleation mode particle does not change significantly with the increase of nano addition.(5)With the increase of EGR rate,the cylinder pressure,heat release rate and cylinder temperature of the five fuels gradually decreased.After the introduction of EGR,the NOx emission of the five fuels were significantly reduced,and the emissions of large particles increased.With the increase of EGR rate,The total concentration of D100 ultrafine particles increases,the particles move closer to the aggregation state.With the increase of EGR rate,the The number of ultrafine particles with peak particle size in nano-emulsified fuel decreases,the rate of nucleation mode particle decreases and the geometric average diameter increases.Different kinds and amount of nano additives have little effect on ultrafine particles. |
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