Development and experimental evaluation of common rail direct injection methanol (MD97) fuelled compression ignition engine

Methanol has emerged as a promising alternative to fossil fuels for powering internal combustion (IC) engines due to its higher fuel-to-oxygen ratio and lower tendency to form soot. Given the widespread use of compression-ignition (CI) engines in heavy-duty applications, there has been significant interest in adapting methanol for their operation. However, methanol’s inferior autoignition characteristics and longer ignition delay (ID) compared to diesel make its direct use in CI engines challenging. To overcome these limitations, engine modifications are essential to optimise the engine performance and ensure stable combustion. In this experimental study, a single-cylinder, four-stroke CI engine was modified by increasing its compression ratio (CR) and by incorporating an intake air preheating system to improve methanol ignition. The engine’s mechanical fuel injection system was replaced with a custom-built common-rail direct-injection (CRDI) system, and an in-house developed controller was utilised to inject methanol supplemented with an ignition improver (MD97: 97 % w/w methanol and 3 % w/w catalyst). The performance, combustion, and emission characteristics of MD97 were analysed and compared with baseline diesel (FIP 600 bar, SoI 14° bTDC). MD97 achieved stable ignition with a minimum ID of 7° CA, compared to the baseline diesel’s 7.5° CA. Injection timing was further optimised to achieve a balanced trade-off between the engine performance, combustion, and emission characteristics. Under optimised conditions (FIP 500 bar, SoI 13° bTDC), MD97 exhibited ∼40 % higher brake thermal efficiency (BTE), ∼88 % reduction in nitrogen oxides (NOx) emissions, and almost negligible exhaust smoke; however, hydrocarbons (HC) and carbon monoxide (CO) emissions increased by ∼23 % and ∼52 %, respectively, compared to baseline diesel.