Hydrogen produced from regenerative sources has the potential to be a sustainable substitute for fossil fuels. A hydrogen internal combustion engine has good combustion characteristics, such as higher flame propagation velocity, shorter quenching distance, and higher thermal conductivity compared with hydrocarbon fuel. However, storing hydrogen is problematic since the energy density is low. Hydrogen can be chemically stored as a hydrocarbon fuel. In particular, an organic hydride can easily generate hydrogen through use of a catalyst. Additionally, it has an advantage in hydrogen transportation due to its liquid form at room temperature and pressure. We examined the application of an organic hydride in a spark ignition (SI) engine. We used methylcyclohexane (MCH) as an organic hydride from which hydrogen and toluene (TOL) can be reformed. First, the theoretical thermal efficiency was examined when hydrogen and TOL were supplied to an SI engine. Next, we conducted an experiment on an SI engine fueled with hydrogen and gasoline to investigate the characteristics of hydrogen mixed combustion. We then examined an SI engine with an onboard MCH reforming system.
Hydrogen and TOL were successfully produced from MCH by warming the reactor to above 300C. The thermal efficiency of the total system was improved by 30% in comparison with a conventional SI engine by use of the reformed fuel having 40% hydrogen (LHV%).