Combustion Characterization and Heat Release Rate Modeling a Heavy-Duty Hydrogen-Diesel Dual-Fuel Engine

Introducing hydrogen (H2) as a gaseous fuel into the intake air of diesel engines provides a near-term approach to reduce tailpipe CO2 emissions from heavy-duty commercial vehicles. The premixed hydrogen results in a complex H2-Diesel dual fuel (H2DF) combustion process, where H2 participates in both the non-premixed diesel combustion and premixed H2/air combustion. These interactions influence engine combustion characteristics, including heat release rate (HRR), performance, and emissions, with the extent of the impact dependent on the amount of H2 introduced (H2 energy share ratio - HES) and engine operating conditions. To optimize the HES ratio under different conditions, it is crucial to understand how H2DF combustion differs from diesel combustion and how this limits engine operation and affects emissions. This paper reports on a comprehensive analysis of the in-cylinder pressure (ICP), HRR, and corresponding combustion performance metrics (combustion phasing, duration and stability) for an H2DF engine over a range of speeds, loads, and Hydrogen energy ratios. The impacts on performance and emissions are considered from the viewpoint of the influence of the HES on HRR. Representative steady-state speed/load/HES operating points were considered on a heavy-duty class 8 truck retrofitted with H2DF technology developed by Hydra Energy Canada. The tests were conducted on a chassis dynamometer facility, including comprehensive portable emission measurement systems, ICP measurements, and monitoring of engine control parameters. The ICP and HRR data are used to develop a semi-predictive combustion model imposing the net HRR profile using a multi-Wiebe function. The developed understanding and combustion model will provide valuable tools for future studies to further improve H2 utilization strategies tailored for the retrofit heavy-duty H2DF truck applications.