Performance and Emission Analysis of Hydrogen and Conventional Fuels in PFI SI Engines Using CONVERGE 3.0

The availability of conventional fuels, such as gasoline and methane, which are used in spark-ignition (SI) engines, is increasingly limited by the finite nature of fossil fuel reserves. The inefficiencies in combustion are associated with reduced engine effectiveness, as incomplete combustion heightens the emissions of harmful pollutants, including CO₂ and CO, while also negatively impacting fuel economy. The objective of this research is to undertake a comparative study of engine performance and emissions for a selection of conventional fuels and hydrogen, while considering varying equivalence ratios and operational speeds. To accomplish this, an extensive 3-dimensional numerical simulation was carried out using CONVERGE 3.0 simulation software to model a port-fueled SI engine, with the SI8 Engine Premix SAGE model facilitating the simulations. The performance metrics assessed in this research include cylinder pressure, specific heat ratio, heat rate, thermal efficiency, and mean temperature. The emission characteristics are analyzed in cases of NO_x, CO, CO₂, and HC emissions. The simulation results are obtained by varying the equivalence ratios of hydrogen (0.4, 0.6, and 0.9) at different engine speeds (2000, 2500, and 3000 rpm). The engine setup, mesh creation, boundary conditions, turbulence, combustion, and species transport models were meticulously outlined to ensure accurate simulation results. Hydrogen fuel, when operated at an equivalence ratio of 0.4 and an engine speed of 3000 rpm, showcases the best overall performance among all tested conditions. It achieves the highest thermal efficiency of 40.94%, optimal cylinder pressure and specific heat ratio, a favorable mean temperature, and the lowest fuel consumption. Additionally, this configuration results in zero emissions of CO and HC, along with a significant reduction in CO₂ emissions due to the absence of carbon in the fuel structure. However, due to the high combustion temperatures associated with hydrogen, NO_x emissions remained present and require further mitigation strategies.