Optimization of water-emulsified diesel preparation and comparison of mechanical homogenization and ultrasonic dispersion methods to study CI engine performances

Abstract

ABSTRACT In this study, the stability of water-emulsified diesel (WED) prepared by different methods have been analyzed. In first phase, the optimum condition of Hydrophilic-Lipophilic Balance (HLB) value of the surfactant used for the preparation of emulsified diesel with respect to its stability has been determined. Different resultant HLB values have been obtained by mixing two surfactants in different proportion. The highest emulsion stability (ES) is found for WED prepared with the surfactant mixture of HLB value 8 which is obtained by mixing 65.5% Span 80 and 34.5% Tween 80. In second phase, WEDs containing 10% water and 2% surfactant mixture with resultant HLB value 8 have been prepared using mechanical homogenization as well as ultrasonication methods. In third phase, the emulsions are prepared adding 10, 20, and 30% water and 2% surfactant mixture with resultant HLB value 8 using ultrasonication process. The emulsion mixture has been kept in a cooled water bath to minimize hot spot effect during ultrasonication process. The polydispersity index (PDI), water particle size and auto correlation factor (ACF) of all four prepared WEDs have been measured by nano particle analyzer which works on dynamic light scattering (DLS) technique. These properties of the WEDs have been analyzed to investigate their stability behavior of the emulsion. Experimental investigations have also been carried out on performance and emission characteristics of a single cylinder, four-stroke diesel engine using WED prepared by both methods containing 10% water. At full load, the brake thermal efficiency is found to be marginally higher using emulsified diesel prepared using ultrasonicator compared to base diesel. The NOx and smoke emissions have been found to be lower for both types of emulsified diesel than pure diesel. The experimental results show more favorable emulsification, performance and emission characteristics for the emulsified diesel prepared by ultrasonic machine than that prepared by mechanical homogenizer. The density, viscosity, and calorific value of the emulsions prepared by the two methods have also been measured and compared with that of neat diesel.