Performance and emission characteristics of diesel and vegetable oil blends in a direct-injection VCR engine

The speedy diminution of conventional fuel and vacillation of diesel price in the global market demand an urgent need for widespread research, so that some viable alternative is obtained and sustainable energy demand with less ecological impact is met. In the present exploration, Jatropha curcas oil is used as substitute fuel to examine the emission and combustion characteristics for optimizing the compression ratio of a direct-injection, single-cylinder, four-stroke VCR diesel engine running with mineral diesel and vegetable oil blends at different compression ratios of 16, 17 and 18 and varying the load from idle to a rated load of 3.5 kW. The impact of compression ratio on fuel consumption, combustion pressures and exhaust gas emissions has been investigated and presented. The optimum compression ratio which gives best performance was identified. The result shows that the thermal efficiency, exhaust gas temperature and emission parameters such as NOX, HC and CO at optimum compression ratio 18 with blends containing up to 30 % (by volume) jatropha oil is satisfactory to run an unmodified diesel engine.