Three-dimensional thermodynamic analysis of hydrogen-enriched methanol combustion enabled by integrated steam reforming

Due to growing concerns over carbon emissions and the need for cleaner alternative fuels, methanol has emerged as a promising candidate for internal combustion engines owing to its high hydrogen content, low carbon intensity, and ease of storage. However, methanol encounters considerable difficulties during cold start conditions, mainly attributed to its low volatility and high latent heat of vaporization. To address this challenge, this study proposes an integrated approach combining in-cylinder steam reforming and hydrogen-enriched combustion of methanol. A comprehensive equilibrium-based thermodynamic model is developed to simulate the combustion–reforming coupling process, accounting for key parameters such as pressure ratio, air fuel ratio, and ambient conditions. The results demonstrate that methanol steam reforming significantly enhances hydrogen yield, with the content of combustible gaseous components in the fuel increasing by 70 % compared to non-reformed conditions. A high pressure ratio in compression stroke is beneficial for improving internal combustion engine performance and methanol steam reforming, whereas the air fuel ratio exhibits the opposite effect on internal combustion engine performance. Following dual-objective optimization of an Otto cycle incorporating methanol steam reforming, the optimal operating conditions were determined to be a pressure ratio no lower than 17 and an air-fuel ratio of approximately 14, yielding a thermal efficiency of 34.11 % and a hydrogen conversion of 33.67 %. This study aims to establish a foundational theoretical framework to guide the future design and optimization of methanol-fueled internal combustion engines.