Assessment of the effect of dimethyl carbonate on regulated/ unregulated emissions, polycyclic aromatic hydrocarbons and soot particles

Abstract

Both coal-to-liquid (CTL) and dimethyl carbonate (DMC) are alternative fuels to diesel with high potential and can be well adapted to the operating conditions of the engine, but the mechanism of the effect of DMC/CTL on harmful emissions is not clear. In this study, the DMC/CTL simplified mechanism is established, and the effects of DMC/CTL blends on regulated emissions, unregulated emissions, polycyclic aromatic hydrocarbons (benzene: A1, naphthalene: A2, phenanthrene: A3, pyrene: A4; PAHs), soot particles and the generation mechanism are investigated by numerical simulation and experiment. The results show that the constructed DMC/CTL simplified mechanism can effectively predict the combustion and emission trends, and the error is small. With the DMC addition ratio increases, the OH content in the cylinder increases, thus the THC, CO, and soot emissions decreases, and the combustion efficiency increase about 0.05 %, but the oxygen concentration in the cylinder increases, resulting in an increase of NOx emissions. The addition of DMC resulted in the concentration of C2H2 decreases, which inhibited ring formation and the continued growth of the benzene ring, and the content of PAHs (A1/A2/A3/A4) decrease, which also affected the subsequent nucleation of the particles, the density of the particle number and the area of distribution are reduced; However, the unregulated emissions do not show the same trend as the regulated emissions, PAHs, and soot particles, and the content of Methanol (CH3OH) and formaldehyde (HCHO) increased with the DMC addition increases, which indicates that when the oxygen content of blended fuels is increased, although it can reduce most of the harmful emissions, it also brings about an increase in the emission of oxygen-containing unregulated emissions, which is worth noting in the process of fuel application and promotion.