Shock Tube and Kinetic Study on the Effects of CO<sub>2</sub> on Dimethyl Ether Autoignition at High Pressures

Published on 2019-09-11T18:35:23Z (GMT) by
First-stage and overall ignition delay times of dimethyl ether (DME) were measured in a high-pressure shock tube for various mixtures containing high amounts of CO<sub>2</sub>. The data are available for DME/air mixtures diluted with 40% CO<sub>2</sub> as well as for the mixture of DME and oxidizer containing 20.5% O<sub>2</sub> and 79.5% CO<sub>2</sub>. As a reference, data were also collected for mixtures containing the corresponding amounts of N<sub>2</sub>. Measurements were conducted for pressures of 15, 35, and 50 bar and a range of temperatures (744–1316 K). For the DME/air mixture diluted with CO<sub>2</sub>, the equivalence ratio was varied in the range of 0.5–2.0. The results demonstrate that CO<sub>2</sub> dilution has a strong effect on ignition delay times in the NTC (negative temperature coefficient) region. The kinetic study that was conducted showed that this phenomenon can be attributed to a thermal effect resulting from the high heat capacity of CO<sub>2</sub>. In low and high temperature ranges, the effect of CO<sub>2</sub> is less pronounced. Additionally, a chemical effect was identified. At high temperatures this effect can be attributed mostly to the influence of CO<sub>2</sub> on third-body reactions and leads to slight acceleration of ignition. Various chemical-kinetic models available were evaluated with respect to their accuracy in prediction of ignition delay times for mixtures containing DME and large amounts of CO<sub>2</sub>.

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Djordjevic, Neda; Rekus, Mike; Vinkeloe, Johann; Zander, Lisa (2019): Shock Tube and Kinetic Study on the Effects of CO2 on Dimethyl Ether Autoignition at High Pressures. ACS Publications. Collection.