Decarbonisation of GDI Engines Utilising On-Board Hydrogen Production in an Improved Design Thermochemical Exhaust-Assisted Fuel Reformer

Engine intake charge enrichment with hydrogen (H₂) is one way to enhance engine thermal efficiency and decrease pollutant emissions while replacing carbon-based fuel. Waste energy from hot exhaust gas can be thermochemically recovered as hydrogen in catalytic exhaust gas fuel reforming, which can then be used in combustion. This study focuses on tailoring the design of the fuel reformer, including the catalyst chemistry and coating on ceramic and metallic structures, to benefit the whole system’s fuel economy and decrease engine out emissions. The main reformer improvements focused on exhaust flow management and interaction with the engine's after-treatment system, while the final stage focused on the reformer's internal design structure. The new design iteration enabled hydrogen production improvements between 78% and 86% in the critical exhaust gas temperature range of 410°C to 520°C with gas hourly space velocities (GHSVs) in highly demanding engine operating conditions ranging from 16,000 h^-1 to 81,000 h^-1. The integration of the new fuel reformer with a modern, turbocharged, 2.0 L Hyundai GDI engine raises the fuel efficiency through a combination of higher exhaust energy recovery, improved engine thermal efficiency, and enhanced combustion at highly dilute operation. The engine fuel economy at nine engine speed and torque operating conditions was improved from around 0.5% to 7.88%, with an average of 4.62%.