Comprehensive review on technical developments of methanol-fuel-based spark ignition engines to improve the performance, combustion, and emissions

Methanol (CH3OH) is emerging as a viable alternative to fossil-based fuels, addressing the increasing global energy demand while promoting sustainability. The spark ignition (SI) engines are widely used to run the automobile sector. Methanol as a widely available and cheap source of energy can be strongly replaced with expensive and limited fossil-based fuels to power the SI engines. The prime objective of this study is to evaluate the advancements made in improving the fuel blends, performance, combustion, and emission characteristics of methanol-fueled SI engines. The investigation commences by examining the various technical improvements implemented in methanol-fueled SI engines to optimize their overall performance. These developments include advancements in fuel blends, engine design, combustion strategies, fuel injection systems, ignition systems, engine load, etc. The impacts of these developments on the performance parameters including brake thermal efficiency (BTE), power output, torque, fuel efficiency, thermal efficiency, etc., combustion parameters including ignition delay (ID), combustion duration (CD), heat release rate (HRR), in-cylinder pressure and temperature, etc., emission parameters including hydrocarbons (HC), carbon monoxides (CO), nitrogen oxides (NOx), formaldehyde (FA), unburned methanol (UBM), etc., is reviewed comprehensively. The effectiveness of emission control techniques and the potential for meeting stringent environmental regulations are explored. The review paper then considers the wider implications of methanol-fueled SI engines by examining their technical, environmental, economic, and renewable applications. The technical aspects cover the compatibility of methanol-fueled SI engines with existing infrastructure and the associated challenges and opportunities. The environmental considerations delve into the potential reduction of greenhouse gas emissions and the overall sustainability of methanol as a renewable fuel. Finally, the research direction of methanol SI engines is discussed, highlighting the emerging trends and prospects in this field. The review paper concludes with recommendations for further research and development, addressing the key areas that require attention to unlock the full potential of methanol as an efficient and sustainable fuel for spark ignition (SI) engines.