Effects of vary ing the compression ratio on the performance of a biodiesel fuelled diesel engine

Abstract

Improved thermal efficiency, reductions in fuel consumption and pollutant emissions from biodieselfuelled diesel engines are important issues in engine research. To achieve these, rapid and better air -fuel mixing is the most important requirement. The mixing quality of biodiesel with air can begenerally improved by selecting the best engine design parameters. Experiments were performed usinga single cylinder Direct Injection (DI) diesel engine at different compression ratios. The effects ofvarying the compression ratio on the combustion, performance and exhaust emissions using a blend of20% Pongamia Oil Methyl Ester (POME20) by volume in diesel were evaluated. The test resultsshowed that improvement in terms of brake thermal efficiency and specific fuel consumption forengine having higher compression ratio, particularly with compression ratio of 18.5. Substantialimprovements in reduction of emission levels were observed for higher compression ratio in terms ofcarbon monoxide, hydrocarbon and smoke. However improved air motion inside the cylinder and highpressure injection increases the oxides of nitrogen (NOx). The change of compression ratio from 17.5to 18.5 resulted in reduction in delay period and improvement in heat release rate.