Experimental investigation of in-cylinder soot distribution and exhaust particle oxidation characteristics of a diesel engine with nano-CeO2 catalytic fuel

According to the dispersion principle of solid particles in the liquid and polar phase solubility principle, nano-CeO2 catalytic fuels were prepared with 50 and 100 mg/L mass fractions of CeO2. The in-cylinder soot distribution was investigated on a common-rail engine using the visualization technology. The combustion characteristics and smoke emissions were also analyzed. The effects of heating rates and nano-CeO2 concentration on particle oxidation characteristics were studied using thermogravimetric analysis method. The results show that the combustion starting point of the engine with catalytic diesel advances, while the peak values of in-cylinder pressure and heat release rate increase. The location of soot flame occurrence advances, and its vanishing moment comes earlier with the addition of nano-CeO2. Compared with diesel fuel, soot concentration, soot area occupation ratio and smoke emissions are smaller with catalytic diesel. As the heating rate increases, the oxidation process of particles moves to high temperature region, however, its peak weight loss rate decreases. At a certain heating rate, the particle activation energy and initial temperature decrease with the increment of nano-CeO2 concentration. It is found that the catalytic diesel could decrease particle sizes, promote the oxidation of particles, and reduce the ignition combustion temperature of particles.