AN EXPERIMENTAL INVESTIGATION ON THE POTENTIAL OF HYDROGEN IN THE REDUCTION OF THE EMISSION CHARACTERISTICS OF AN EXISTING FOUR-STROKE SINGLE-CYLINDER DIESEL ENGINE OPERATING UNDER EGR

摘要

The present work attempts to explore the emission characteristics of an existing single-cylinder four-stroke compression-ignition engine operated in dual-fuel mode with hydrogen as an alternative fuel. Experimental investigation was carried out with the engine being subjected to different loads at a predefined flow rate of hydrogen induction. The emission characteristics revealed a 71% and a 40.5% reduction of CO_2 emissions at 20% and 80% load, respectively, for non-EGR (exhaust gas recirculation) hydrogen enrichment. In CO emissions, non-EGR hydrogen enrichment registered a 69.5% and a 64.3% reduction at 20% and 40% load, respectively. Smoke emissions saw a 61.5% and a 64.3% reduction during non-EGR hydrogen enrichment at 20% and 40% load, respectively. Hydrocarbon (HC) emissions were reduced by 80% and 60.9% as compared with diesel operation at 20% and 60% loads, respectively. Hydrogen enrichment operations without EGR were penalized, however, with an increase of 79.3% and 81.3% in NO_x at 40% and 60% load, respectively, as compared with diesel operation. EGR (hot and cold) technique has been implemented in the present work to reduce NO_x emissions. In the present study, hydrogen enrichment overcome the inherent penalization of NO_x-smoke tradeoff common under such EGR operation and was able to simultaneously decrease NO_x emissions and smoke emissions effectively. As an indicator, 20% cooled EGR registered a decrease of 9.2% and 12.3% in NO_x emissions at 60% and 80% load, respectively, as compared with diesel operation and simultaneously reduced smoke emissions by 10% and 8.3% as compared with diesel operation.