Combustion and emission characteristics of methanol/diesel dual-fuel engine
The investigation of the effects of the methanol substitution ratio and the pilot injection tim-ing on the combustion and emission characteristics of methanol/diesel dual-fuel engine at low and me-dium load conditions were conducted on a modified turbocharged four-cylinder engine.The results show that at low load,the indicated thermal efficiency of dual-fuel mode is lower than that of pure diesel mode,the incomplete combustion increases,and the emissions of total hydrocarbons(THC),carbon monoxide(CO),unburned methanol and formaldehyde increase with the increase of the metha-nol substitution ratio.Advancing the pilot injection timing can improve the indicated thermal efficien-cy of the dual-fuel mode and reduce THC,CO,unburned methanol and formaldehyde emissions,but it will sharply increase nitrogen oxides(NOx)emissions.At medium load,as the methanol substitu-tion ratio increases,the indicated thermal efficiency first increases and then decreases for too much methanol lowers the initial temperature in the cylinder,which deteriorates the combustion.With the advancement of pilot injection timing,the emissions of THC,CO,unburned methanol and formalde-hyde are reduced,but the reduction is less than that at low load.At the same time,NOxemissions in-crease sharply.
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