ABSTRACT
The use of biodiesel in the diesel engine decreases the exhaust emissions but the performance of the engine is found to decrease. This is due improper mixing of air and inadequate turbulence. The performance of the engine can be improved by improving the mixing quality of biodiesel spray with air which can be achieved by modifying the combustion chamber shape and nozzle geometries. The present work investigates the combined effect of cylindrical combustion chamber (CCC) shape and five-hole nozzle geometry on the performance and emission characteristics of biodiesel operated diesel engine with baseline diesel fuel. Engine tests were carried out on 346a single-cylinder four-stroke direct injection (DI) diesel engines using various blends of Pongamia oil methyl esters (POME) with standard diesel as a fuel and compared with modified combined CCC shape and five-hole nozzle geometry. For comparison, the compression ratio of the engine is kept constant. The experimental results depict that brake thermal efficiency increases up to B60 blend of POME in both baseline diesel engine and modified diesel engine geometry. A drastic reduction in unburnt hydrocarbons and oxides of nitrogen (NOx) emissions was observed with modified diesel engine geometry as compared to baseline diesel engine. The percentage of carbon monoxide (CO) emissions decreases more with increasing the percentage of POME in modified diesel engine geometry up to B40 blend, thereafter increase in carbon monoxide emissions as increases in blend in modified diesel engine geometry compared with baseline diesel engine. However, the percentage of carbon dioxide emission (CO2) is more in modified diesel engine geometry as compare with baseline diesel engine for injection pressure 205 bars. The experiment is repeated with increase in injection pressure.
