Numerical Analysis of Carbon Monoxide Formation in DME Combustion 2011-32-0632
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.
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.
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.
