Investigation of effects of intake temperature on low load limitations of methanol partially premixed combustion

Methanol has unique properties as a fuel, and partially premixed combustion has promising results with high engine efficiency and low emissions. Low load studies with methanol partially premixed combustion are scarce, and the effect of intake temperature on low load methanol partially premixed combustion still remains an intriguing question. This study aims to investigate the effect of intake temperature on low load limitations of methanol partially premixed combustion by an experimental study. The engine was operated at 800 rpm under two different loads. The low load condition was performed at 3 bar Indicated mean effective pressure (IMEP), and the idle condition was commenced at 1 bar IMEP. From the results, it was seen that the intake temperature affected engine stability, engine performance, and engine emissions. The combustion stability decreased with the decrease of intake temperature. The ignition delay became longer and the peak cylinder pressure became smaller with lower intake temperature. The combustion efficiency reduced with the decrease of intake temperature from 0.99 to 0.96 at 3 bar IMEP, whereas it decreased from 0.99 to 0.98 at 1 bar IMEP for the single injection case and the split injection case. The thermodynamic efficiency remained constant at 0.43 at 3 bar IMEP, decreased from 0.30 to 0.28 at 1 bar IMEP for the single injection case, and reduced from 0.26 to 0.24 at 1 bar IMEP for the split injection case. The gross indicated efficiency increased from 0.41 to 0.42 at 3 bar IMEP, whereas it reduced from 0.29 to 0.28 and 0.26-0.24 at 1 bar IMEP at single injection and split injection, respectively. Total hydrocarbon emission increased, NO_X emission decreased or remained constant, and CO emission remained constant with the decrease in intake temperature. Finally, the combustion phasing study was performed at 1 bar IMEP at constant intake temperature to determine the effect of the start of injection timing on the engine's performance and the emissions under the idle condition.