A comprehensive review on technical developments of methanol-fuel-based compression ignition (CI) engines to improve the performance, combustion, and emissions

Methanol (CH 3 OH) emerges as a highly promising, economically feasible, environmentally friendly, and renewable energy source amid the rising global energy demand. As contemporary energy utilization techniques advance and the imperative to curtail dependence on depleting fossil fuels intensifies, the focus on methanol-fueled compression ignition (CI) engines, particularly in the automotive sector, becomes dominant. Over the past decade, the exceptional resistance of methanol fuel to engine knocking and its capacity to mitigate harmful emissions have gained substantial attention from researchers. While numerous review articles have been published, few have delved comprehensively into the technical advancements of methanol-fueled CI engines with an increased investigation of their environmental and renewable applications. This research review endeavors to address this gap by offering a comprehensive analysis of methanol, whether in its pure form or as a blended fuel, in technically developed CI engines. The main goal is to review enhanced engine performance, combustion efficiency, and emission characteristics. The review examines the impact of critical parameters, including the incorporation of blended fuels with controlled volume fractions (VF), engine load (EL), engine speed (ES), injection methods, compression ratio (CR), ignition timing (IT), intake fuel temperature, injection timing (I/T), combustion methods, crank angle (CA), and air-to-fuel (A/F) ratio. These parameters are assessed by performance indicators such as brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), and thermal efficiency (TE). Additionally, combustion parameters, including combustion duration (CD), ignition delay (ID), heat release rate (HRR) and injection timing, phasing, are studied, along with emissions parameters including nitrogen oxides (NOx), carbon oxides (CO), hydrocarbons (HC), unburned methanol (UBM), formaldehyde (FA), particulate matter (PM) and soot in methanol-fueled CI engines. Finally, the research summary and future direction of methanol-fueled compression ignition (CI) engines have been concluded based on the previous work.