Computational Study of Combustion and Emissions Behaviors in Petrol Engine Fuel by Natural Gas and Hydrogen

Authors

Ahmed A. Elshenawy, Mechanical Engineering Dept., Faculty of Engineering, Misr University for Science and Technology, Egypt
Said Abdel Razek, Mechanical Engineering Dept., Faculty of Engineering, Misr University for Science and Technology, Egypt
Mohamed S. Gad, Mechanical Engineering Dept., Faculty of Engineering, Fayoum University, EgyptFollow

Abstract

To assess the potential of natural gas and hydrogen mixtures as cleaner alternatives, this study presents a modeling analysis of combustion and emissions behavior in a petrol engine running on these fuels. Utilizing a two-dimensional computational fluid dynamics (CFD) code, numerical modeling was conducted to investigate the emissions and combustion characteristics of hydrogen and CNG mixtures at concentrations of 5, 10, 15, and 20%. The highest increase in cylinder temperature for HCNG20 compared to pure CNG is 3.9272% at 2500 rpm rated engine speed. The heat flux increased as the hydrogen proportion grew because both the adiabatic flame temperature and the maximum temperature of hydrogen rose. The addition of hydrogen resulted in a modest reduction in N2 output. With 20% H₂, the increased reactivity of hydrogen results in a larger concentration of OH radical and higher H₂ enrichment. The volume proportion of CH4 near the flame’s centerline fell when more hydrogen was added. Because of the rise in hydrogen and decrease in carbon content, the maximum concentration of water vapor (H2O) in the products increases as the hydrogen percentage increases. The highest decrease in CO2 emissions for 20% hydrogen was 3.12%, compared to pure CNG. As the hydrogen fraction increases, the concentrations of CO and CO2 decrease due to the reduction in carbon content and the rise in hydrogen. The density of hydrogen and CNG mixtures decreases as hydrogen is added in increments of 5, 10, 15, and 20%. NOx concentrations increased with the addition of hydrogen. The increases in NOx for CNG and HCNG20 were 12 and 43%, respectively, compared to gasoline. The CFD code’s results align with and closely match the experimental results. For HCNG 20%, the difference in CO2 between the code and the experimental results is approximately 3.7%. Because they burn cleaner and produce less pollutants than gasoline, HCNG combinations have been proposed as alternative fuels.

Recommended Citation

Elshenawy, Ahmed A.; Razek, Said Abdel; and Gad, Mohamed S. (2026) "Computational Study of Combustion and Emissions Behaviors in Petrol Engine Fuel by Natural Gas and Hydrogen," Engineering and Technology Journal: Vol. 44: Iss. 1, Article 7.