Abstract
Reaction rate coefficients for the major high-temperature methyl formate (MF, CH3OCHO) decomposition pathways, MF -> CH3OH + CO (1), MF -> CH2O + CH2O (2), and MF -> CH4 + CO2 (3), were directly measured in a shock tube using laser absorption of CO (4.6 mu m), CH2O (306 nm) and CH4 (3.4 mu m). Experimental conditions ranged from 1202 to 1607 K and 1.36 to 1.72 atm, with mixtures varying in initial fuel concentration from 0.1% to 3% MF diluted in argon. The decomposition rate coefficients were determined by monitoring the formation rate of each target species immediately behind the reflected shock waves and modeling the species time-histories with a detailed kinetic mechanism [12]. The three measured rate coefficients can be well-described using two-parameter Arrhenius expressions over the temperature range in the present study: k(1) = 1.1 x 10(13) exp(-29556/T, K) s(-1), k(2) = 2.6 x 10(12) exp(-32052/T, K) s(-1), and k(3) = 4.4 x 10(11) exp(-29 078/T, K) s(-1), all thought to be near their high-pressure limits. Uncertainties in the k(1), k(2) and k(3) measurements were estimated to be +/- 25%, +/- 35%, and +/- 40%, respectively. We believe that these are the first direct high-temperature rate measurements for MF decomposition and all are in excellent agreement with the Dooley et al. [12] mechanism. In addition, by also monitoring methanol (CH3OH) and MF concentration histories using a tunable CO2 gas laser operating at 9.67 and 9.23 mu m, respectively, all the major oxygen-carrying molecules were quantitatively detected in the reaction system. An oxygen balance analysis during MF decomposition shows that the multi-wavelength laser absorption strategy used in this study was able to track more than 97% of the initial oxygen atoms in the fuel. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.