Fuel Design Concept for Low Emission in Engine Systems 4th Report: Effect of Spray Characteristics of Mixed Fuel on Exhaust Concentrations in Diesel Engine

In this study, the novel fuel design concept has been proposed in order to realize the low emission and combustion control in engine systems. In this fuel design concept, the mixed fuels with a high volatility fuel (gasoline or gaseous fuel components) and a low volatility fuel (gas oil or fuel oil components) are used in order to improve the spray characteristics by flash boiling. In our previous papers on this study, the fundamental characteristics of spray and its combustion of mixed fuel were reported.

In this paper, heat release and exhaust emission (smoke, NOx and THC) characteristics of single cylinder diesel engine operated with the mixed fuels were investigated under each load. The exhaust performance of diesel engine could be improved using mixed fuel, because fuel properties and spray characteristics were controlled by changing mixing fraction of the mixed fuel. Moreover, in this exhaust gas concentration measurement, initial fuel temperature was employed for experimental parameter in order to control flash boiling process in mixed fuel spray, for flash boiling can be easily occurred by increasing initial fuel temperature. As a preliminary investigation of the flash boiling effect, the spray experiment for mixed fuel was conducted using constant volume vessel. As a result, it was confirmed that flash boiling had the potential of drastic reduction of smoke emission since flash boiling improved the atomization and vaporization of mixed fuel spray with rapid fuel-air mixing.