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Shock Tube Measurements and Modeling Study on the Ignition Delay Times of n‑Butanol/Dimethyl Ether Mixtures

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journal contribution
posted on 17.12.2015, 02:43 authored by Zhuang Geng, Lili Xu, Hua Li, Jiaxing Wang, Zhen Huang, Xingcai Lu
The ignition delay times of different n-butanol/dimethyl ether (DME) mixtures (DME mole ratios of 100%, 80%, 60%, 40%, and 0%) were studied behind reflected shock waves at equivalence ratios of 0.5, 1.0, and 1.5; pressures of 6.0, 10, and 15 bar; temperatures of 1150–1650 K. The effects of a carrier gas (nitrogen or argon) on the ignition delay times of single and blended fuels were also studied. The chemical kinetic mechanism of DME/n-butanol was established based on Zhao’s DME chemical kinetic mechanism (Int. J. Chem. Kinet. 2008, 40, 1−18) and Strathy’s n-butanol chemical kinetic mechanism (Combust. Flame 2012, 159, 2028−2055), which can accurately predict the ignition delay times of both single and blended fuels. Experimental results show that the ignition delay time of DME is longer than that of n-butanol when the temperature is high (>1150 k) and that the ignition delays of blended fuels increase with an increased blending ratio of DME. However, the relationship between ignition delay time and the blending ratio is nonlinear. The main factor affecting the blended fuel’s ignition delay is temperature, and with every 200 °C increase in temperature, the ignition delay times is reduced by an order of magnitude. Additionally, pressure has a large effect on the ignition delay times. The results of reaction path analysis of blended fuels show that with an increasing DME blending ratio, the contribution rate of OH-radicals to H-abstraction decreases during the oxidation of n-butanol, and the contribution rate of H-radicals to H-abstraction of n-butanol increases slightly. However, with an increasing DME blending ratio, the pyrolysis of DME decreases, but the contribution rate of CH3 and OH to the H-abstraction of DME increases.