Water-in-Diesel Emulsions as an Alternative Fuel for Diesel Engines. Part II: Performance of Diesel Engines Fueled with Water-in-Diesel Emulsions. A Literature Review

This paper presents the recent advances of water-in-diesel emulsion fuel studies, especially the impact of using this emulsion fuel to the performance and emissions of diesel engine. Studies revealed that the onset and the strength of micro-explosion process give strong effect with regard to the combustion efficiency inside the combustion chamber. Most of the researchers tested emulsions with water content of 5-40% in diesel fuel. Some studies concluded that 20% water in the emulsion fuel gives the optimum engine performance. Many researchers and experts agree that the reason why there is a slight drop in brake power and torque is the fact that water-in-diesel emulsion fuel has a lower heating value than a neat diesel fuel, thus less energy is released during combustion. In general, the results suggest that the water emulsification has a potential to slightly improve the brake efficiency and to significantly reduce the formation of NOx, soot, hydrocarbons and PM in the diesel engine. Some factors may affect the experimental results that need to be considered, such as the effect of volatility of the base fuel, the water content of the emulsion, emulsion stability, ambient temperature, pressure, type of surfactant and engine test conditions: engine load, speed, injection timing and compression ratio