Potential of H₂-Assisted Light-Off of Oxidation Catalyst in H₂-Diesel Dual-Fuel Engines

Hydrogen (H₂) appears as a fundamental alternative to conventional fuels to lead the decarbonization of the transportation sector based on internal combustion engine propulsion. Being well assumed that neat H₂ combustion demands the analysis of the exhaust aftertreatment systems (ATS) requirements and performance, this is also very relevant when considering dual-fuel strategies. This work addresses the impact of H₂ presence in the exhaust gases on the conversion efficiency of CO and THC in an oxidation catalyst operating under representative real driving conditions. A reaction mechanism is proposed to cover the main conversion paths of CO, HC, and H₂, including the formation and consumption of high-energy surface reaction intermediates. The mechanism has been implemented into a faster-than-real-time reduced-order model for multi-layer washcoat honeycomb catalytic converters and validated against experimental data. The model is applied to analyze the influence of the H₂ concentration on the CO and HC light-off time during a vehicle driving test cycle. A wide span of concentrations, ranging from expected amounts in the exhaust of a dual-fuel Diesel engine to post-injected H₂ strategies, was considered. Post-injection interest is analyzed regarding the eventual tradeoff between light-off and cumulative conversion efficiency in driving cycles and increased energy consumption. Additionally, the benefits in light-off time and increased reactivity were also assessed as a potential for catalyst downsizing at the expense of stress on the reactor in terms of bulk mass transfer limitations and pressure drop increase.