Numerical Analysis of Carbon Monoxide Formation in DME Combustion

Abstract

<div class="section abstract"><div class="htmlview paragraph">Dimethyl ether (DME) is an oxygenated fuel with the molecular formula CH₃OCH₃, economically produced from various energy sources, such as natural gas, coal and biomass. It has gained prominence as a substitute for diesel fuel in Japan and in other Asian countries, from the viewpoint of both energy diversification and environmental protection. The greatest advantage of DME is that it emits practically no particulate matter when used in compression ignition (CI) engine. However, one of the drawbacks of DME CI engine is the increase carbon monoxide (CO) emission in high-load and high exhaust gas circulation (EGR) regime.</div><div class="htmlview paragraph">In this study, we have investigated the CO formation characteristics of DME CI combustion based on chemical kinetics. In order to understand the equivalence ratio (φ) - temperature (T) dependence of CO formation in DME combustion, we generated the CO φ-T map through numerical calculations with detailed chemical reaction models and compared it with that of methane combustion.</div><div class="htmlview paragraph">Our results show that DME combustion has a local CO peak at a temperature of around 1000 K, which is a distinctive feature of DME, although general CO formation properties are not unlike those of methane combustion, in which the CO emission increases with temperature and equivalence ratio. The analysis of reaction paths shows that this local CO peak is produced by active low-temperature reactions during DME oxidation process.</div></div>