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According to thermodynamic analysis of ideal engine cycles, Otto cycle thermal efficiency exceeds that of the Diesel and Sabathe (or Dual) cycles. However, zero-dimensional calculations indicated that the brake thermal efficiency (BTE) of an actual Otto or Diesel engine could be higher with a Sabathe (or Seilliger) type cycle, within a limited peak firing pressure (PFP). To confirm these results with an actual engine, a three-injector combustion system (center and two sides) was utilized to allow more flexibility in the heat release rate (HRR) profile than the conventional single injector system in the previous study. The experimental result was qualitatively consistent with the calculated results even though its HRR had less peak and longer duration than ideal. In this study, a new thermodynamic cycle with higher HRR in the expansion stroke than the ideal Sabathe cycle, was thus developed. The proposed (higher) HRR was achieved by overlapped fuel injection with the three injectors.

Hydrogen may be used to feed a fuel cell or directly an internal combustion engine as an alternative to current fossil fuels. The latter option offers the advantages of already existing hydrocarbon fuel engines - autonomy, pre-existing and proven technology, lifetime, controlled cost, existing industrial tools and short time to market - with a very low carbon footprint and high tolerance to low purity hydrogen. Hydrogen is expected to be relevant for light and heavy duty applications as well as for off road applications, but currently most of research focus on small engine and especially spark ignition engine which is easily adaptable. This guided us to select modern high-efficient gasoline-based engines to start the investigation of hydrogen internal combustion engine development. This study aims to access the properties and limitations of hydrogen combustion on a high-efficiency spark ignited single cylinder engine with the support of the 3D-CFD computation.