Experimental Evaluation of Methane-Hydrogen Mixtures for Enabling Stable Lean Combustion in Spark-Ignition Engines for Automotive Applications

Economy decarbonization will be one of the main goals for the following years. Research efforts are being focused on reducing carbon-based emissions, by increasing the efficiency of the transport power plants while developing new fuel production methods that reduce the environmental footprint of the refinement process. Consequently, the depletion of conventional fuels derived from petroleum with high carbon content, such as gasoline and diesel, motivated the development of propulsive alternatives for the transportation sector. In this paradigm, methane (CH₄) fuel appears as a mid-term solution due to its low carbon content, if compared with traditional fuels, and the low CO₂ emissions during its production from renewable sources. However, the intrinsic properties of methane compromise the combustion process, subsequently increasing the emission of CO₂. Here, several investigations demonstrated the benefits of using hydrogen (H₂) in combination with CH₄, for increasing the engine efficiency in those situations where the combustion of pure CH₄ evinces clear stability problems. In this paper, the use of methane-hydrogen fuel mixtures is experimentally evaluated in a port fuel injection light-duty spark ignition (SI) engine. The main goal is to improve the performance of this new emerging alternative fuel by hydrogen substitution. The impact of the H₂ substitution ratio is evaluated under lean combustion conditions, where the combustion stability is extremely compromised. A comparison in performance and emission levels is done between different levels of hydrogen substitution.