Hydrogen fumigated diesel combustion for de-carbonisation and Tier III NOx compliant marine engines

Abstract The International Maritime Organisation is targeting 40% CO 2 emissions reduction by 2030 and NOx targets of 2.16 g/kWh for 1250 rpm, all whilst prioritising approaches that improve brake thermal efficiency (BTE). This work presents three primary outputs to identify how H 2 fumigated diesel engines can meet these targets. Firstly, experimental results are presented from a 2L single cylinder engine at constant load (1250 rpm, 31 kW, 195 Nm) with fumigated H 2 (0 to 9.5%Vol), at advanced and delayed diesel injection timings (A-FiT-6 and D-FiT +4 CA⁰ ATDC). The second and third outputs use ANSYS Chemkin Pro multizone digital twin engine model. Initially to, develop the modelling approach which accounts for the variation in equivalence ratio across the real combustion chamber to accurately represent performance and emissions, and then to, extend the experimental results towards identifying the optimal combustion strategy. The experimental results indicated that over 8.5%Vol H 2 offered CO 2 reduction in excess of 40% for both A-FiT and D-FiT. Whilst H 2 heating value offered substantial gain in brake specific fuel consumption (≈45% for 0 to 9.5%Vol H 2 ), it did marginally compromise BTE, with A-FiT showing greatest sensitivity (-2% points from 0 to 9.5%Vol H 2 ). Though A-FiT NOx emissions met the Tier III requirements when coupled to selective catalytic reduction (SCR) at 90% conversion efficiency, this may exceed limits in sub-optimal SCR conditions (e.g. cold start). D-FiT also showed marginal reduction in BTE (across all %Vol H 2 ), with significant reductions in NOx emissions (-56% at maximum %Vol H 2 ). Therefore, the validated model established a revised trade-off point, with 9%Vol H 2 at FiT-4 CA⁰ ATDC achieving excess of 40% CO 2 reduction compared to diesel only. This also corresponded to over 20% drop in NOx to the most A-FiT condition with fumigated H 2 , with only negligible BTE compromise (-0.2% points). These results demonstrate a low disruption pathway to meet the maritime 2030 de-carbonisation and regulated emissions targets.