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

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 CO2 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 NOx 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 NOx emissions. In the present study, hydrogen enrichment overcome the inherent penalization of NOx–smoke tradeoff common under such EGR operation and was able to simultaneously decrease NOx emissions and smoke emissions effectively. As an indicator, 20% cooled EGR registered a decrease of 9.2% and 12.3% in NOx 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.