Effects of integrated aftertreatment system on regulated and unregulated emission characteristics of non-road methanol/diesel dual-fuel engine

In order to ensure that output power, fuel economy and harmful emissions of non-road diesel engines meet the limit requirements, and reduce the dependence on fossil fuels, methanol/diesel dual-fuel combustion mode was conducted on an agricultural four-cylinder common-rail engine, and the effects of DOC + DPF + SCR aftertreatment system on overall performance and emission characteristics of dual-fuel mode were systematically investigated. Results show that dual-fuel mode can reduce both nitrogen oxide (NOx) and soot emissions, but increase nitrogen dioxide (NO₂), methanol and formaldehyde (HCHO) emissions. With the increase of load, the conversion efficiency of diesel oxidation catalyst (DOC) to carbon hydrogen (HC), carbon monoxide (CO), methanol and HCHO emissions is continuously improved. DOC can increase NO2/NOx ratio for diesel mode, but reduce NO2/NOx ratio for dual-fuel mode. At full load, the average soot capture efficiency of diesel particulate filter (DPF) for dual-fuel engine is 98.84%, basically realizing zero soot emission, while the conversion efficiency of selective catalytic reduction (SCR) for NOx is 95.22%. The increase of methanol ratio can reduce NOx emissions and nitrous oxide (N₂O) generation in SCR for dual-fuel mode. Under non-road steady cycle (NRSC), the maximum brake thermal efficiency (BTE) of diesel mode and dual-fuel mode are 39.4% and 41.0%, respectively. The regulation emissions of dual-fuel engine coupling with integrated DOC + DPF + SCR aftertreatment system can meet non-road Euro-V and US-Tier 4 emission standards.