Experimental study on performance and emission characteristics of non-road methanol/diesel dual-fuel engine with after-treatment system at full loads

The low-temperature combustion and homogeneous charge compression ignition achieved by the methanol/diesel dual-fuel premixed mode in an agricultural engine. This study explores the emission characteristics and post-treatment system performance in diesel only mode and dual-fuel mode. The results show that under the same operating conditions, the maximum brake specific fuel consumption (BSFC) in dual-fuel mode is 7% lower than that in diesel only mode. The hydrocarbons (HC) and carbon monoxide (CO) emissions significantly increase in dual-fuel mode, and this difference increases with the increase of engine speed. In dual-fuel mode, the emissions of nitrogen oxides (NOx) and particulate matter (PM) both decreased, with the highest reductions of 53% and 57%, respectively. The emissions of formaldehyde and methanol in dual-fuel mode will rapidly increase with the increase of engine speed. After being equipped with a post-treatment system, diesel oxidation catalyst (DOC) has a conversion efficiency of over 95% for CO and HC emissions in dual-fuel mode. At different engine speeds, catalyzed diesel particulate filter (CDPF) maintains a capture efficiency of over 98% for PM. The conversion efficiency of selective catalytic reduction (SCR) for NOx is greatly affected by engine speed. When the engine speed increases from 2000r/min to 2400r/min, the conversion efficiency decreases from 95.6% to 37.1%. SCR reduces NOx while increasing dinitrogen oxide (N₂O) emissions. This study clarifies the impact mechanism of the aftertreatment system on the emission components of dual-fuel engines at different speeds, providing key parameters for the collaborative optimization of methanol/diesel engine aftertreatment systems.