Numerical Investigation of Surface-Ignition Characteristics of Ethanol in a Ceramic-Coated CI Engine

Surface ignition in compression ignition (CI) engines has emerged as a promising combustion strategy to improve ignition reliability and efficiency when operating with low-cetane renewable fuels such as ethanol. In this study, a detailed numerical investigation is carried out to analyse ethanol surface-ignition characteristics in a ceramic-coated CI engine. A three-dimensional computational fluid dynamics (CFD) model incorporating turbulence, spray breakup, evaporation, surface heat transfer, and detailed chemical kinetics is developed. The ceramic coating applied on the piston crown and combustion chamber walls increases the surface temperature by approximately 120-160 K, which promotes ethanol ignition through surface-assisted reactions rather than conventional auto-ignition.Simulation results indicate that the ceramic-coated configuration reduces the ignition delay by nearly 18-22% compared with the uncoated engine. The peak cylinder pressure increases from 62 bar to about 70 bar, while the maximum heat release rate improves by approximately 15-18%, indicating faster and more stable combustion. In addition, the enhanced surface temperature improves fuel evaporation and mixing, resulting in a 12-15% reduction in unburned hydrocarbon (HC) emissions. The improved combustion characteristics also contribute to better thermal efficiency and smoother pressure development during the combustion process.Overall, the numerical findings demonstrate that ceramic-coated combustion chambers can effectively facilitate ethanol surface ignition, providing improved ignition control, enhanced combustion stability, and reduced emissions. These results highlight the potential of ethanol-fueled surface-ignition CI engines as a viable pathway for sustainable and low-carbon transportation systems.