Elucidating the flame chemistry of monoglyme via experimental and modeling approaches

This study is concerning the flame chemistry of monoglyme (CH3OCH2CH2OCH3), an oxygenated compound recognized as a clean diesel additive and an ignition improver. Speciation diagnosis was performed for two low-pressure premixed flames fueled by monoglyme with different equivalence ratios (ϕ = 1.0 and 1.5) using the technique of photoionization molecular-beam mass spectrometry (PI-MBMS). Dozens of flame intermediates including some reactive species were quantitatively probed from the monoglyme flames. A kinetic model was proposed for the first time for the combustion of this fuel and validated against the flame structure measurements. By combining experimental observations and modeling interpretations, it has been revealed that under flame conditions, the fuel consumption is dominated by hydrogen abstractions from the central (-CH2CH2-) moiety of monoglyme. Subsequent β-scissions of the resulting fuel radical lead to the formation of fuel-specific intermediates, methyl vinyl ether and methoxy acetaldehyde. The species pool detected in monoglyme flames differs much from that of dimethyl ether (DME, CH3OCH3) flames, though a monoglyme molecule is symmetrically composed of two DME fuel radicals. This could be attributed to the presence of the central carbon-to-carbon (CC) bond in monoglyme. Further modeling analyses suggest that the CC contents together with the stoichiometry of fuel mixtures can impact the concentrations of benzene precursors under premixed flame conditions.