Low- and Intermediate-Temperature Oxidation of Dimethyl Ether Up to 100 Atm in a Supercritical Pressure Jet-Stirred Reactor

Understanding the low-and intermediate-temperature oxidation chemistry of oxygenated fuels like dimethyl ether (DME) at high pressure is paramount to the development of advanced engines with low carbon emissions. The supercritical pressure jet-stirred reactor (SP-JSR) recently developed at Princeton provides a new platform for conducting kinetic studies at low and intermediate temperatures at ex-tremely high pressures with a uniform temperature distribution and a short flow residence time. This paper uses the SP-JSR to investigate DME oxidation at equivalence ratios of 0.175, 1.0, and 1.72, for pres-sures of 10 and 100 atm, and temperatures ranging from 400 to 900 K. The results demonstrate weakened NTC behavior at 100 atm relative to 10 atm due to increased flux through QOOH + O 2 = O2QOOH rela-tive to QOOH = 2 CH2O + OH at 100 atm. Furthermore, the intermediate-temperature oxidation window is shifted to lower temperatures at 100 atm. The experimental data are compared with several chem-ical kinetic models from the literature. The existing models are seen to agree quite well with the ex-perimental data at 10 atm. However, the models fail to properly capture the NTC behavior at 100 atm. Reaction pathway analyses indicate that both the low-and intermediate-temperature chemistries are con-trolled by RO2 consumption pathways. The reaction rates for several of the important reactions, such as DME + OH = CH3OCH2 + H2O, H2O2 ( + M) = 2 OH ( + M), and 2 HO2 = 2 OH + O 2 are updated in this work. The updated model improves the predictability for all key species compared to the original model.(c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.