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

Abstract

An experimental study was carried out to investigate the effect of intake air pre-heating, exhaust gas re-circulation, and hydrogen enrichment on performance, combustion, and emission characteristics of CH4/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. The CH4/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 CH4 and hydrogen-enriched CH4 energy share, respectively. The CO and HC emissions were higher in CH4 combustion with biodiesel when compared to the conventional diesel operation at full load and a reduction in CO and HC was observed with air preheating. Lower NOx were observed with gaseous fuel combustion and it further reduced with exhaust gas re-circulation but NOx increased by preheating the intake air. Improvement in thermal efficiency with a reduction in HC and CO was observed with hydrogen-enriched CH4.