Effect of Cylindrical Combustion Chamber Shape on the Performance and Emission Characteristics of C.I. Engine Operated on Pongemia: Optimizing Combustion Chamber Shape for Improved Performance and Emissions

Abstract

The use of biodiesel blends in the diesel engine decreases the exhaust emissions (except NOx) but the performance of the engine is found to decrease. This is due to poor air mixing and insufficient 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 shape of the combustion chamber. The present work investigates the effect of varying the combustion chamber geometry on the performance and emission characteristics of biodiesel operated diesel engine. Engine tests have been carried out on a single cylinder –four stroke direct injection diesel engine using various blends of Pongamia oil methyl esters (POME) with standard diesel as a fuel and with two types of combustion chambers namely hemispherical combustion chamber (HCC) and a cylindrical combustion chamber (CCC). For comparison, the compression ratio of the engine is kept constant. The test results showed that brake thermal efficiency obtained for hemispherical combustion chamber is higher than that obtained using cylindrical combustion chamber. Significant improvement in reductions of Carbon Dioxide (CO2), carbon monoxide (CO) was observed for hemispherical combustion chamber as compared to the cylindrical combustion chamber. However oxides of nitrogen were slightly higher for hemispherical combustion chamber. The unburnt hydrocarbon (UBHC), oxides of nitrogen (NOx) and CO emissions are reduced in CCC shape compared to HCC shape.