Combustion and Emission Characteristics of a Diesel Engine Fuelled with Biodiesel Having Varying Saturated Fatty Acid Composition

Abstract

The present work is concerned with the performance, emission, and combustion characteristics of vegetable oil esters with varying saturated and unsaturated fatty acid composition tested in a stationary direct injection compression ignition engine. Saturated fatty acids (SFAs) are long-chain carboxylic acids that usually have between 12 and 24 carbon atoms and have no double bonds. Unsaturated fatty acids resemble SFAs, except that the chain has one or more double bonds. SFAs have all the hydrogen that the carbon atom can hold and therefore have no double bond between the carbon atoms. The biodiesels were derived from Pongamia, Ricebran, Sunflower, and Palm oil, respectively. The results show that Pongamia biodiesel gives a higher brake thermal efficiency (33.36% when compared to diesel, which has 32.57%) slightly higher Oxides of Nitrogen [NO_X] and reduced carbon monoxide (CO), unburnt hydrocarbon (UHC), and smoke emissions when compared to diesel and other biodiesels. The cetane number for Pongamia oil, Ricebran oil, Sunflower oil, Palm oil, and diesel are 52, 50, 51, 56, and 48, respectively. The higher cetane number reduces ignition delay and also reduces NO_X emissions when compared to other esters that have a greater unsaturated fatty acid composition.