title: Isomer-specific influences on the composition of reaction intermediates in dimethyl ether/propene and ethanol/propene flame.
abstract: This work provides experimental evidence on how the molecular compositions of fuel-rich low-pressure premixed flames are influenced as the oxygenates dimethyl ether (DME) or ethanol are incrementally blended into the propene fuel. Ten different flames with a carbon-to-oxygen ratio of 0.5, ranging from 100% propene (phi = 1.5) to 100% oxygenated fuel (phi = 2.0), are analyzed with flame-sampling molecular-beam mass spectrometry employing electron- or photoionization. Absolute mole fraction profiles for flame species with masses ranging from m/z = 2 (H2) to m/z = 80 (C6H8) are analyzed with particular emphasis on the formation of harmful emissions. Fuel-specific destruction pathways, likely to be initiated by hydrogen abstraction, appear to lead to benzene from propene combustion and to formaldehyde and acetaldehyde through DME and ethanol combustion, respectively. While the concentration of acetaldehyde increases 10-fold as propene is substituted by ethanol, it decreases as propene is replaced with DME. In contrast, the formaldehyde concentration rises only slightly with ethanol replacement but increases markedly with addition of DME. Allyl and propargyl radicals, the dominant precursors for benzene formation, are likely to be produced directly from propene decomposition or via allene and propyne. Benzene formation through propargyl radicals formed via unsaturated C2 intermediates in the decomposition of DME and ethanol is negligibly small. As a consequence, DME and ethanol addition lead to similar reductions of the benzene concentration.
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.forename: Ulf
authors.initials: U
authors.lastname: Struckmeier
authors.forename: Bin
authors.initials: B
authors.lastname: Yang
authors.forename: Terrill A
authors.initials: TA
authors.lastname: Cool
authors.forename: Patrick
authors.initials: P
authors.lastname: Osswald
authors.forename: Katharina
authors.initials: K
authors.lastname: Kohse-Höinghaus
authors.forename: Tina
authors.initials: T
authors.lastname: Kasper
authors.forename: Nils
authors.initials: N
authors.lastname: Hansen
authors.forename: Phillip R
authors.initials: PR
authors.lastname: Westmoreland