Abstract
<jats:p>BACKGROUND: Studying the combustion process in marine gas piston engines is an important task, as it allows determining the optimal design and operating characteristics of the engine to ensure its efficiency, which helps reduce fuel consumption, improve natural gas combustion efficiency, and lower the concentration of pollutants in exhaust gases. AIM: This study presents a numerical investigation of the combustion process of a methane-air mixture and examines the patterns of changes in the kinetics of chemical reactions and the characteristics of laminar flame in a high-speed marine engine. METHODS: A numerical study of the combustion processes of a methane-air mixture was performed using the detailed kinetic mechanism GRI-Mech 3.0 and the conservation equations for mass, energy, and state, as well as the Arrhenius equation. The fuel-air ratio in the study varied from 0.7 to 1.3; the temperature of the methane-air mixture varied from 400 to 800 K; and the pressure in the combustion chamber varied from 1 to 10 MPa. RESULTS: A methodology for numerically studying the fuel combustion process in a marine gas piston engine has been developed. Patterns of changes in chemical reaction kinetics, adiabatic flame temperature, laminar flame propagation velocity, and flame sensitivity with changes in the fuel-to-fuel ratio and thermodynamic characteristics of the engine's combustion chamber have been obtained. CONCLUSIONS: It was established that the propagation velocity and adiabatic temperature of a methane-air flame depend on the excess air ratio, pressure, and temperature in the combustion chamber and reach maximum values at the stoichiometric composition of the mixture. An integrated analysis of reaction pathways showed that the excess air ratio affects the reaction pathway rather than the chemical mechanism at the flame front. Based on the sensitivity analysis of reactions occurring at the flame front, an abbreviated kinetic mechanism for methane combustion in a piston engine was proposed.</jats:p>