Performance of DI Diesel Engines Fueled by Water Emulsions with Equal Proportions of Gas Oil-Rapeseed Oil blends and the Characteristics of the Combustion of Single Droplets

This investigation reports how water emulsification influences spray characteristics, combustion characteristics, and engine performance and emissions using equal proportions of rapeseed oil and gas oil as the base fuel. The experiments used two types of DI diesel engines with different combustion chambers and injection systems. The results showed that the NOx emissions and smoke densities with the emulsified fuel decreased remarkably although the spray angle decreases and atomization becomes poorer due to increasing kinematic viscosity. To discuss the influence of water addition on evaporation, ignition, and combustion characteristics, basic experiments with single droplets suspended from a quartz bar were also performed. The experiments used an electric furnace maintained at high temperatures (1133K) at atmospheric pressure. The quartz bar used has a spherical suspending part (0.6 mm diameter), and droplets were placed manually, quickly, in the chamber. The evaporation and combustion behaviors of the fuel droplets were analyzed with images taken by a high speed video camera. The results showed that the ignition lag of the water emulsions with equal proportions of rapeseed oil and gas oil is longer, but that the combustion speed is similar to that with gas oil emulsions.