Effect of oxygen enrichment on CI engine behavior fueled with vegetable oil: an experimental study

The present study investigated the effect of oxygen enrichment in a CI engine on performance, emission and combustion characteristics with mahua oil (MO) as base fuel. Poor physical properties of MO, namely high viscosity and density, cause atomization problems leading to higher smoke, HC and CO emissions. The purpose of this paper is to curb smoke emissions from MO operation and to examine the possibility of direct use of straight vegetable oil in CI engine, which can mitigate CO(2)emission and be cost effective. The difficulty in the mixture formation with usage of straight vegetable oil in CI engine is addressed by increasing the oxygen concentration; a separate oxygen cylinder is used to induct oxygen. The engine used for this experimentation is a twin-cylinder tractor engine that operates at a constant speed of 1500 rpm. Performance, emission and combustion parameters were determined at different loading conditions (25, 50, 75 and 100% of rated power) with varying intake-oxygen concentration from 21% (by volume) (no enrichment) to 24% (by volume) with MO and compared with diesel. Oxygen enrichment of 24% reduced smoke, HC and CO emissions by 36, 34 and 50%, respectively, at maximum load condition. The study revealed that oxygen enrichment improved the direct combustion of MO with reduced smoke, HC and CO emissions. BTE was reduced by about 5% with MO in comparison with diesel at maximum load condition. BTE was improved by 10% with 24% (by volume) with MO at maximum load in comparison with neat MO.