Flame structure and a compact reaction mechanism for combustion of dimethyl ether at atmospheric pressure

Abstract

To extend the available experimental database on DME flame speciation, this paper reports new measurement data on the chemical structure of premixed stoichiometric and fuel-rich (ϕ = 2.2) DME/O2/Ar flames stabilized on a Botha-Spalding burner at atmospheric pressure. Flame sampling molecular beam mass spectrometry with soft electron ionization was used to detect many DME combustion intermediates, including labile species such as H, CH3, and HO2. The new experimental data were used to develop and validate a compact mechanism of DME combustion which is able to reproduce not only laminar burning velocity and ignition delay times, but also peak mole fractions of important species in DME combustion at a minimum number of species and reactions included. The compact chemical kinetic mechanism consisting of 41 species and 110 elementary reactions is proposed based on the literature kinetic mechanism of DME combustion. Comparison of predictions made using the compact mechanism and detailed literature models with three sets of measurement data (chemical speciation profiles reported in this paper, laminar burning velocity and ignition delay time data obtained by other authors) shows that they are in satisfactory agreement, which generally proves the good predictive capability of the mechanism. Further investigations, however, are needed to better understand the kinetics of H2O2 and C2H2 included in the mechanism, because under fuel-rich conditions, the compact mechanism as well as other detailed models do not adequately predict the peak mole fractions of these important intermediates.