Optimizing an H2 combustion system and investigating abnormal combustions through advanced visualization techniques

The rapidly evolving mobility sector is facing the dual challenge of market expansion and the need for significant emissions reduction. Most of the transition tends to go in favor of electrification, yet it’s widely assumed that no single solution is perfect. Thus, hydrogen as an energy-vector presents a compelling alternative. H2 internal combustion engine use a well-known architecture and utilizes existing production facilities making it a viable short-term and cost-effective option. This context prompted us to investigate the hydrogen spark-ignited internal combustion engine, focusing specifically on critical combustion issues. Various studies have identified recurring challenges such as managing abnormal combustion and achieving high specific power. During our in-house developments, we also faced abnormal combustions and sought to determine the root cause of these issues. Initially, using a modular single-cylinder engine, a combustion system has been optimized regarding injection timing, NOx production, combustion efficiency and more… We notably focused on the effects of different parameters of the hydrogen injection system, such as its positioning, the jet targeting and the injection pressure. Subsequently, a specific cylinder-head has been designed with endoscopic optical access into the combustion chamber which allows to visualize the combustion / expansion stroke with a high-speed UV intensified camera. We specially stalked abnormal combustions such as pre-ignition but also used this setup to analyze different spark plug behaviors and perform combustion analysis. We tested different injection configurations and gauge their effects using both combustion analysis and in-cylinder movies. It provides very valuable data about combustion propagation, mixture preparation and cycle to cycle repeatability. Common combustion analysis gives macro data of the combustion stroke whereas the endoscopic access provides 2D fields that help to understand the real behavior of the combustion. This work finally leads to a useful interpretation of abnormal combustion occurrences and guides towards the relevant choice of injection and ignition strategies especially on critical full load points.