Combustion and Flame 210 (2019) 222–235 Contents lists available at ScienceDirect Combustion and Flame journal homepage: www.elsevier.com/locate/combustfame The autoignition of iso-dodecane in low to high temperature range: An experimental and modeling study Yebing Mao, Yuan Feng, Zhiyong Wu, Sixu Wang, Liang Yu, Mohsin Raza, Yong Qian, Xingcai Lu ∗ Key Laboratory for Power Machinery and Engineering of M. O. E., Shanghai Jiao Tong University, Shanghai 200240, PR China a r t i c l e i n f o Article history: Received 8 July 2019 Revised 4 August 2019 Accepted 23 August 2019 Keywords: Iso-dodecane 2,2,4,6,6-pentamethylheptane Kinetic modeling Ignition delay time Rapid compression machine Shock tube a b s t r a c t 2,2,4,6,6-pentamethylheptane, a highly branched alkane, is a promising component candidate of branched alkanes in the surrogates for jet fuels and a major component in alternative fuels. In spite of its great rel- evance and importance in real fuels, it has only attracted very little interest. This work provides a new set of experimental data and a newly proposed detailed kinetic mechanism for this hydrocarbon. In the experiments, the autoignition characteristics of 2,2,4,6,6-pentamethylheptane, was measured in a rapid compression machine and a shock tube spanning over the equivalence ratios of 0.5, 1 and 1.5, pres- sures of 15 and 20 bar and temperature range of 603–1376 K. The dependence of ignition delay times on pressure, mole fraction of fuel, mole fraction of oxygen and dilution ratio were systematically investi- gated. Negative temperature coefficient (NTC) behavior was observed during the autoignition event, but the NTC temperature window was found to be much lower than the counterpart normal paraffin. A de- tailed kinetic model containing 729 species and 3390 reactions was proposed to describe the combustion behavior of this compound over low-to-high temperature range. The model was validated against the present experimental data, as well as the limited datasets in literature. Good agreements were observed between the experimental data and the predictions from the proposed model. Kinetic analyses, including sensitivity analysis and reaction pathway analysis, were carried out to provide insight into the combus- tion characteristics from the kinetic perspective. Comparisons were also carried out with the datasets for other branched alkanes and normal-paraffin with same carbon numbers over the same conditions to reveal the effects of the molecular structure. © 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved. 1. Introduction Comprehensively validated kinetic models of fuels potentially promise the accurate simulation of the combustion in engines and provide insight into the effect of fuel composition on the performance of engines. Therefore, with the increasingly stringent demand for efficiency and emissions, reliable kinetic models play a growingly significant role in the design of high-efficiency and low- emission engines and the development of advanced combustion technologies. Given the complex composition of real fuels (e.g., jet fuels), mixtures of limited well-studied components, usually called surrogate fuels, are utilized to describe the combustion behavior of these fuels. Branched alkanes account for around 35–40% (wt.%) of all hydrocarbons present in conventional jet fuels [1–3] and even higher quantities in non-petroleum-derived alternative fuels [4–8], and thereby have a great influence on the reactivity of these fuels. ∗ Corresponding author. E-mail address: lyuxc@sjtu.edu.cn (X. Lu). Consequently, it is essential to include representative branched alkanes in the surrogate palette. In the previous studies, iso-octane or iso-cetane or the combi- nation of the two have been extensively used in jet fuels surrogate formulation. However, the carbon numbers of the two compounds are outside the range of 10–14 [3,9], the average carbon number of isoparaffin in jet fuels. Hence, this would restrict the emula- tion of properties that depend on the molecular size, e.g., molecu- lar weight, distillation curve and diffusion flame extinction [9,10]. This situation is true in the surrogate fuels proposed by Kim et al. [11,12]. The addition of an isoalkane with molecular weight and boiling range similar to the average of target fuel to the surrogate palette would be beneficial for the better match. Iso-dodecane (viz 2,2,4,6,6-pentamethylheptane, PMH) is a highly branched alkane of low reactivity and satisfies the need of similar molecular weight to jet fuels, and thus it would be a good alternative to iso-octane and iso-cetane. There have been some studies using PMH as a sur- rogate component [6,9,13–15]. In the study of Kim et al. [9], they found that PMH is an attractive surrogate candidate component for a kind of coal-derived jet fuel and recommended it as the next https://doi.org/10.1016/j.combustflame.2019.08.030 0010-2180/© 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.