Combustion and Flame, Vol.214, 277-286, 2020
Influence of ozone addition on the low-temperature oxidation of dimethyl ether in a jet-stirred reactor
The influence of ozone addition on the low-temperature oxidation of dimethyl ether (DME) was investigated experimentally in an atmospheric-pressure jet-stirred reactor, over the temperature range of 400-800 K. Detailed speciation information was obtained by employing synchrotron vacuum ultraviolet photoionization mass spectrometry. Experimental results revealed that the ozone addition had a positive influence on the production of the highly reactive intermediates. Moreover, the low-temperature reactivity of DME was significantly enhanced, which resulted in the broadening of the temperature window of fuel consumption and intermediates formation at lower temperatures. Therefore, novel experimental data of the low temperature regime (400-500 K) could be obtained. The data set of this special temperature regime yielded insights into the DME low-temperature kinetics, which were further supported with modeling analysis based on two existing DME models (Metcalfe et al., 2013; Wang et al., 2015) combined with an ozone sub-mechanism (Zhao et al., 2016). The analysis showed that temperature-sensitive reactions such as the second oxygen channel could be nearly "frozen" at this low temperature (T < 440 K). Furthermore, the production of some intermediates was found to be strongly governed by reaction pairs, such as CH3OCH2 + O-2 = CH3OCH2O2 and CH3OCH2 + O-2 = 2CH(2)O + OH for the CH2O formation. This finding could be useful for examining branching ratios in both models, and the analysis suggested the further modification of the branching ratios for the oxygen addition to CH3OCH2O2 pathways and the CH3OCH2O2 self-reactions were required. Finally, the influences of the O-3 addition in the sensitive reactions of the fuel initial low-temperature oxidation were investigated in this work. It was interesting to note that O-3 addition could change the dominating reactions in the initial low-temperature oxidation, by the addition of some O-3-related pathways with relatively high sensitivity. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.