The hydrogen internal combustion engine technology, with its potential for almost full carbon emissions reduction and adaptability to a wide range of fossil fuel-based internal combustion engine (ICE) platforms, offers a promising future. However, as with any innovative technology, it also presents challenges, such as abnormal combustion phenomena. These challenges, including intake backfire, which is more common when using port fuel injection (PFI), and pre-ignition in the combustion chamber, which can be experienced with PFI or direct injection (DI), require detailed investigation to understand and optimize the engine’s performance and efficiencies.
This study comprehensively investigates the main abnormal combustion events that could happen in a spark ignition (SI) hydrogen engine. It examines both direct and port fuel injection systems and uses high-resolution in-cylinder, intake, and exhaust pressure measurements alongside a suite of fast-response gas analyzers. The study provides a direct comparison between abnormal and normal combustion events, sampled over 200 consecutive cycles, and uses ultra-fast NOx, HC, and CO2 emissions analyzers to help analyze pre-ignition combustion, backfire, and partial burn events.
Seemingly for the first time, the study has demonstrated the direct link between the in-cylinder combustion events and exhaust gas emissions from a spark ignition hydrogen engine. Pre-ignition caused by lubrication oil is realised with controlled oil injection. Such pre-ignition on the in-cylinder combustion process and its impact on the instantaneous production of HC and CO2 from lubrication oil are quantified. The advanced data acquisition (DAQ) system enabled accidental pre-ignition combustion events to be detected and captured. The backfire cycles are investigated using simultaneous recordings of instantaneous intake and in-cylinder pressures alongside the fast gas analyzers to show the risk of backfire on both the intake system and the in-cylinder combustion process. Finally, the study shows how adopting highly boosted air for ultra-lean burn combustion can lead to instability and misfire under high-load operating conditions.