Pyrolysis Characteristic Analysis of Particulate Matter from Diesel Engine Run on Diesel/Polyoxymethylene Dimethyl Ethers Blends Based on Nanostructure and Thermogravimetry

This paper focuses on the nanostructural and pyrolysis characteristics of particulate matter (PM) emitted from a diesel engine fueled by three diesel/polyoxymethylene dimethyl ethers (PODEn) blends. PM was collected using a metal filter from the exhaust manifold. The collected PM samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). SEM and TEM analysis showed that PM generated by the 20%-PODEn blend was looser and had a smaller average diameter than that emitted when a lower proportion of PODEn was used. Additionally, fringe length was reduced, and separation distance and tortuosity were increased, when the 20%-PODEn blend was used instead of the other blends. These changes improved the oxidation reactivity of the PM. TGA demonstrated that the PM pyrolysis process was divided into low temperature (characterized by moisture and volatile components) and high temperature (the combustion of solid carbon) stages. When the blending ratio was increased, the moisture and volatile components of the PM showed no obvious change, but the ignition temperature and activation energy were reduced. Additionally, the pyrolysis performance was enhanced; the maximum weight loss rate was higher; the combustion and burnout characteristic indices were higher; and the combustion efficiency of the PM was improved. These results show that the use of diesel blended with oxygenated fuel (PODEn) affects the nanostructure and pyrolysis of PM, and this PM is easier to oxidize and advantageous for diesel particulate filter regeneration.