Effect Of Dimethoxymethane-diesel Fuels On The Performance Of Ci Engines And The Physicochemical Characteristics Of Exhaust Soot

Due to the advantages of high oxygen content(42.1%),easy preparation,and good miscibility with diesel,dimethoxymethane(DMM)is suitable to be an alternative to diesel to achieve the goal of energy saving and exhaust emission reducing.Precently,the investigation about DMM-diesel blending fuels applying to CI engines mainly centres on the combustion and emissions,the influences of DMM-diesel blends on phasical and chemical properties of soot particles(such as morphology,nanostructure,the degree of graphitization,surface functional groups,and oxidation relations of soot particulates)has not been clear.In the study,the influences of DMM-diesel blends on combustion and emissions performance have been studied at different loads and different rotational speeds with three blends(D100,DMM6.4,and DMM13).Especially,the phasical and chemical properties of soot particles have been conducted intensively,based on the equipments of commercial diesel,transmission electron microscopy,Raman spectroscopy,Fourier transform spectroscopy,X-ray photoelectron spectroscopy,and thermogravimetric analyzer.The concludion can be drawn as follows:First of all,the influence of DMM-diesel blends on combustion and emission under different speeds and loads has been studied,based on the equipment of CI engines.It is found that with the increase of DMM,the in-cylinder pressure,heat release rate,brake thermal efficiency,and exhaust temperature increase,and the emission of CO,soot,and concentration of particle size decrease.Secondly,the effect of DMM-diesel blends on the morphology,nanostructure,and graphitization degree of soot particles has been conducted based on the transmission electron microscopy and Raman spectroscopy.It can be observed that the addition of DMM to diesel reduces the overlap degree of primary particles,and the fuel DMM13 has a smallest diameter of primary particles,followed by DMM6.4 and D100.The addition of DMM increases the size of fringe length.Moreover,the use of DMM reduces the size of fringe separation distance and tortuosity.In addition,DMM-diesel blends have a more stable and a high degree of graphitization of soot particles than D100.Thirdly,the impact of DMM-diesel blends on the surface functional groups of soot particles has been investigated based on the Fourier transform spectroscopy and X-ray photoelectron spectroscopy.It is found that the proportion of aliphatic C-H drops with the use of DMM.And the proportion of C=O,COO,and C-O functional group accounts for 4%-12%,1%-4%,and 3%-8% of total functional groups,respectively.In addition,the use of DMM-diesel blends reduces the oxygen to carbon molar ratio.Finally,the influence of DMM-diesel fuels on the oxidation properties of soot particles is investigated.It has been recognized that the use of DMM reduces the oxidative activity and increases the activation energy of soot particles.With the comprehensive analysis between nanostructure parameters,surface functional groups,and oxidation properties,it is noted that the higher the degree of regularization and graphitization of particles,the lower the oxidation activity and the higher the activation energy.Moreover,the oxidation properties of particles are more affected by the nanostructure parameters than by the degree of graphitization and oxidative functional groups.