An Experimental Investigation on the Role of Hydrogen in the Emission Reduction and Performance Trade-Off Studies in an Existing Diesel Engine Operating in Dual Fuel Mode Under Exhaust Gas Recirculation

Abstract

With emission legislations getting more stringent in order to comply with the responsibilities of environmental obligations, engine manufacturers are turning to explore new avenues to meet the paradox of curtailing particulate matter (PM) and NOx emissions on one hand and maintaining consumer expectations of reduced fuel consumption and increased thermal efficiency on the other. Studies dedicated in mitigating such paradoxical objectives have established novel emission reduction systems such as the diesel particulate filter (DPF) and selective catalytic reduction (SCR) after treatment systems but at the expense of increased complexity of deployment and cost. The present work explores the emission and performance characteristics of an existing four stroke single cylinder engine operating with a predefined flow rate of hydrogen as a dual fuel. The hydrogen was premixed with the incoming air and inducted during the duration of intake valve opening by means of an indigenously developed cam actuated electromechanical timed manifold injection technique. exhaust gas recirculation (EGR) (hot and cooled) technique has been implemented in the present work to reduce NOx emissions which were enriched with the same amount of hydrogen. Research studies carried out on the efficacy of EGR techniques have reported the inherent penalty of increasing the common diesel pollutants of smoke and particulate matter and fuel consumption at the expense of reducing NOx emissions. Trade-off studies in the present work revealed contrary results, where 20% cooled EGR under hydrogen enrichment registered a decrease of 9.2% and 12.3% in NOx emissions at 60% and 80% load as compared to diesel operation while simultaneously retaining a reduction of 4.6% and 1.9% in brake specific energy consumption (BSEC) along with 10% and 8.33% corresponding decrease in smoke emissions and a reduction of 11.30% and 12.31% in total unburnt hydrocarbon (TUHC) emissions. CO emissions were simultaneously decreased by 26.6% and 20.0% while CO2 emissions decreased by 24.5% and 29.1%, respectively, while maintaining 4.8% and 2% increase in brake thermal efficiency and a reduction of 23.3% and 18.95% in specific fuel consumption (SFC) (diesel) simultaneously at the respective loads. Similar trade-off potential, as was evident in the 10% EGR strategies, provide a strong motivation to explore the role of hydrogen as in situ dual fuel solution to counter the conflicting emission and performance requirements of contemporary diesel engines made to operate under EGR.