Abstract
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.
