Experimental Study on Unregulated Emissions Characteristics of Alcohol-Diesel Dual-Fuel Combustion with Diesel Oxidation Catalyst

An experimental study has been conducted to investigate the effects of alcohol properties on dual-fuel (DF) combustion and unregulated emissions such as NO2, HCHO, and CH3CHO on a multicylinder turbocharged, intercooled, common-rail diesel engine with a diesel oxidation catalyst (DOC). Three alcohol fuels, i.e., methanol, ethanol, and hydrous ethanol, were injected in the intake port and diesel was directly injected into the cylinder to realize DF combustion modes called DM, DE, and DE70, respectively. Results show that under DF modes the starting point of combustion is delayed, and the proportion and rate of premixed heat release are increased as compared with diesel only. At full load, the premixed ethanol is compression ignited before diesel ignition. The NO2, HCHO, and CH3CHO emissions from DF combustion are significantly higher than those of diesel only and emissions increase with the rise in premixed alcohol ratio. DOC can effectively purify NO2, HCHO, and CH3CHO emissions of the DF mode with the average catalytic efficiencies of greater than 98%, 92%, and 91%, respectively. Research indicates that DF combustion could not cause excessive unregulated emissions with the DOC, or even lower than the original engine.