Lean and Rich Premixed Dimethoxymethane/Oxygen/Argon Flames: Experimental and Modeling

Abstract

Experimental structures of two dimethoxymethane/oxygen/argon flames at equivalence ratios of φ = 0.24 and 1.72 have been studied by mass spectrometry. The detected species throughout the flame thickness were H₂, CH₃, CH₄, H₂O, C₂H₂, CO, CH₂O, CH₃O, O₂, Ar, CO₂, C₂H₄O₂, and C₃H₈O₂. The aim of this work was to extend an original model for ethylene combustion by building a sub-mechanism taking into account the formation and the consumption of oxygenated species involved in dimethoxymethane oxidation. By using kinetic data from the literature, the authors elaborated a new mechanism containing 480 reactions involving 90 chemical species in order to simulate these dimethoxymethane flames. The mechanism provides numerical results, which are in good agreement with experimental data for all species detected in both flames. Whatever the equivalence ratio of the flame, the two main degradation pathways of dimethoxymethane are the same: CH₃OCH₂OCH₃ → CH₃OCH₂OCH₂ → CH₃OCH₂ → CH₂O and CH₃OCH₂OCH₃ → CH₃OCHOCH₃ → CH₃OCHO → CH₃OCO → CH₃O → CH₂O, with the first being the fastest.

Keywords:

• Dimethoxymethane
• Flame structure
• Kinetic model
• Methylal

ACKNOWLEDGMENTS

The authors are very grateful to the Ministère de la Région Wallonne (Belgium) for financial support (Visa numbers 06/47214 and 07/47509).

Notes

Note. Units are kcal·mol⁻¹.

Note. Rate constants in the form, AT ⁿ exp(−E _a /RT) in cm, mol, cal, and K units. The following reactions are not listed in the table: k₀ = 2.7E + 38 T^−6.30 exp(−3100/T); k_∞ = 6.30E + 13; a = 0.2105, T* = 5400, T** = 8370, T*** = 83.5; H₂/2.0/ H₂O/6.0/ CH₄/2.0/ CO/1.5/ CO₂/2.0/ C₂H₆/3.0.

^a By analogy with CH₃OCH₃ (DeMore & Bayes, 1999).

^b By analogy with CH₃OCH₂ (Herron, 1988).

^c By analogy with (C₂H₅)₂O (Herron, 1988).

^d By analogy with RO (Dagaut et al., 2001).

^e By analogy with DMM + M (R.427; Daly et al., 2001).

^f By analogy with CH₃HCO (Warnatz, 1984b).

^g By analogy with CH₃HCO (DeMore et al., 1997).