利用含水乙醇乳化燃料可以大幅降低柴油机碳烟排放，但其机理有待解明。含水乙醇乳化混入的影响有：燃料微观结构与粘度等物性的变化及"微爆"现象引起的液体射流雾化机理的改变对混合气形成特性的影响；燃料自着火性、含氧量等化学组分结构的变化对滞燃期、火炎温度等燃烧特性的影响；喷雾火炎几何形态的变化对碳烟的影响。本研究利用宏观与微观高速摄影技术，对定容容器内的非蒸发与蒸发喷雾气液两相的锥角、贯穿距及粒径分布进行系统地分析并建立简化数学模型，分析喷雾内卷入当量空气量分布，阐明含水乙醇混入的物理影响。采用标准燃料为基础燃料，通过改变其自着火性的策略灵活控制滞燃期，利用两色法测量火炎温度与碳烟浓度(KL值)的分布，结合反应动力学计算，阐明燃料化学组分结构的变化对碳烟的影响。最后，进行火炎lift-off特性分析，阐明喷雾火炎几何结构特征对碳烟特性的影响。本研究结果将为燃料设计及相关燃烧系统的设计提供重要信息。

Soot emissions in diesel engines can be greatly reduced through using aqueous ethanol emulsified fuels. However, the mechanism of the soot reduction is not well understood. The possible effects of aqueous ethanol addition are: 1)changes in the fuel physical properties including kinematic viscosity, surface tension,and distillation temperature may help to improve spray atomization, accelerarate droplet evaporation, and enhance mixture formation processes; 2)extended ignition delay allows more time for fuel-air mixing; 3) increased oxygenate component in the fuel helps to reduce soot emissions; 4) lowered flame temperature affacts soot formation and oxidation. In this study,the spray angle, spray tip penetration, and droplet size distribution of the non-evaporating and evaporating spray (both liquid and vapor phases)in a high-pressure, constant-volume vessel are studied by using marco/micro high speed imaging techniques. Further,a simplified model of spray mixture development based the law of momentum conservation is established and calibrated with the experimental data. Then, with the model the quantity of entrained ambient air and the fuel concentration distribution in the mixture are analyzed,and the physical effects of the aqueous ethanol addition are clarified. To understand the chemical effects of aqueous ethanol addition, experiments with spray combustion are conducted with the standard fuel (a mixture of hexadecane and 2,2,4,4,6,8,8-heptamethylnonane) as baseline fuel and the aqueous ethanol as additives. To isolate the effects of extended ignition delay due to aqueous ethanol addition, the fuel ignitability is changed with varing the ratio of the two components in the standard fuel. Two-color method is employed to visualize the distributions of soot (KL factor) and flame temperature. Flame lift-off lengths of different fuels are characterized by imaging the OH radical distribution. Finally, combining the experimental resutls with the analysis based on reaction kinetics calcualtion for soot formation and oxidation, the effects of extended ignition delay, increased oxygenate coponents in the fuel, and the lowered flame temperature are clarified.The results of this study will provide important information for the fuel design and combustion system design when using aqueous ethanol emulsified fuels.