Effect of air preheating, exhaust gas re-circulation and hydrogen enrichment on biodiesel/methane dual fuel engine

An experimental study was carried out to investigate the effect of intake air preheating, exhaust gas recirculation and hydrogen enrichment on performance, combustion and emission characteristics of Methane/waste cooking oil biodiesel fuelled compression ignition engine in dual fuel mode. Methyl ester derived from waste cooking oil was used as a pilot fuel which was directly injected into the combustion chamber at the end of the compression stroke. Methane/hydrogen-enriched methane was injected as the main fuel in the intake port during the suction stroke using a low pressure electronic port fuel injector which is controlled by an electronic control unit. The experiments were conducted at a constant speed and at the maximum load. Experimental results indicated that the increase in energy share of gaseous fuel extends the ignition delay. With air preheating the thermal efficiency increased to 49% and 55% of methane and hydrogen-enriched methane energy share respectively. Carbon monoxide and hydrocarbon emissions were higher in methane combustion with biodiesel when compared to the conventional diesel operation at full load and a reduction in carbon monoxide and hydrocarbon was observed with air preheating. Lower oxides of nitrogen were observed with gaseous fuel combustion and it further reduced with exhaust gas recirculation but oxides of nitrogen increased by preheating the intake air. Improvement in thermal efficiency with a reduction in hydrocarbon and carbon monoxide was observed with hydrogen-enriched methane.