Comparison of the conversion efficiency of DOC and DPOC to unregulated emissions from a DMDF engine

The experimental research on reducing unregulated emissions (included unburned methanol, formaldehyde, formic acid, 1,3-butadiene, benzene and toluene) of diesel/methanol dual fuel (DMDF) engine with different after-treatment devices was carried out on a turbocharged inter-cooling diesel engine. The DMDF engine was operated under 25%, 50%, 75% and 100% of full load at the engine speed of 1660 rpm and 2090 rpm with the same injection parameters for the different methanol substitution ratios (MSR). Unregulated emissions of DMDF engine with and without after-treatment devices single diesel oxidation catalyst (DOC) and DOC coupled with particulate oxidation catalyst (DPOC) were studied in comparison. The results show that compared with pure diesel mode, the unregulated emissions tested in this research are all increased in different degrees when the engine operates on diesel/methanol dual fuel mode, and they are all increased with increasing fumigation methanol. The conversion efficiency of DPOC for unregulated emissions tested in this research is higher than that of single DOC. Single DOC could significantly reduce the unburned methanol, 1,3-butadiene and formic acid emissions from DMDF engine, especially at medium and high load when exhaust gas temperature is relative high, but formaldehyde emissions after DOC are increased at low load. After the catalytic oxidation of DPOC, the unburned methanol, formaldehyde, formic acid, benzene and toluene emissions of diesel/methanol dual fuel mode under all load at the speed of 1660 rpm, all except low load at the speed of 2090 rpm are not much different from pure diesel mode.