Statistical evaluation of the effect of water percentage in water-diesel emulsion on the engine performance and exhaust emission parameters

This research presents the results of statistical significance tests for evaluating the main effect of water-diesel emulsion usage (containing 2%, 5%, 8% and 10% by vol.) and engine load on the engine performance and emission parameters. To exclude inevitable random errors of measurements, the mean values of measured data were compared using Duncan's multiple range tests (MRT). The decrease in heating value and increase in fuel density and viscosity were observed with increasing water content. Although the fuel pour point decreased with water presence, but it didn't depend to water percentage. The combustion of emulsions significantly decreased the engine power and torque at 1% probability level (P < 0.01) due to the reduction in the heating value of emulsions. The lowest brake specific fuel consumption (BSFC) was observed for E2. Generally higher brake thermal efficiency was found for emulsions due to more complete combustion. The significant decrease (P < 0.01) in combustion temperature for E5, E8 and E10, increased the engine CO and decreased its CO2. Emulsion usage decreased engine NOx through reducing combustion temperature when compared to neat diesel. As a whole, E5 with highest improvement in the engine HC, NOx and CO2 could be the best suggestion to decrease undesirable engine emission.