The autoignition of iso-dodecane in low to high temperature range: An experimental and modeling study

Fuel molecular structure effect on autoignition of highly branched iso-alkanes at low-to-intermediate temperatures: Iso-octane versus iso-dodecane

“…Likewise, as P (OOH) and Q OOH radicals are similar in nature, the P (OOH) radicals have been modeled to undergo reactions identical to those of Q OOH radicals and analogies are used for describing the reactions of P (OOH) radicals. Furthermore, the decomposition of KHP and HPCE is one of the important reaction classes in the low temperature chemistry, but the rate for this reaction of large KHPs and HPCEs (larger than C5) unfortunately has not been studied theoretically, and the rate constant expressions used for this reaction class in the literature show significant variations with pre-Arrhenius (A) factor varying from 5×10 15 to 3×10 16 (s -1 ), and activation energies (Ea) between 39 and 43 kcal/mole [4,8,25,[31][32][33]36,43,44,50,51]. For the current mechanism, we used A=10 16 s -1 and Ea=41.2 kcal/mole, which are close to the mean of the rate expressions used in the literature mechanisms.…”

“…By contrast, limited autoignition data for iC12 have been reported [34][35][36]. Won et al [34] measured the reflected shock ignition delay times of iC12 from stoichiometric to fuel-rich at 20 and 40 atm, and compared the iC12 data to those of iC8, iso-cetane (2,2,4,4,6,8,8-heptamethylnonane, iC16), and a 50/50 molar blend of iC8/iC16, reporting that all the ignition delay times at high-to-intermediate temperatures are similar.…”

“…Recently, Mao et al [36] studied iC12 autoignition using RCM and ST with equivalence ratios of 0.5, 1.0, and 1.5, pressures of 15 and 20 bar, and temperatures of 603-1376 K. An iC12 kinetic model was also developed in [36] to predict iC12 total ignition delay times. It is noted that no first-stage ignition delay data of iC12 was reported in [36], while iC12 is expected to exhibit two-stage ignition response at low temperatures. As the controlling reactions for the first-stage and second-stage ignition are different, it is possible that both simulated first-stage and second-stage ignition delay times are off compared to the experiments while the sum yields a well-predicted total ignition delay time.…”

“…In view of the limited autoignition datasets for iC12 at low-to-intermediate temperatures, especially the first-stage ignition delay measurements, RCM experiments over a wide range of conditions are therefore conducted herein to fill this fundamental void. These newly-acquired RCM datasets, along with those reported in [36], are of importance for model validation. Moreover, the comparison of iC8 and iC12 data obtained from the same RCM provides insights into the molecular size/structure effect on autoignition as well as the development of a comprehensive chemical kinetic model for combustion of iso-alkanes from C8 to C16 (or larger).…”

“…In this investigation, RCM experiments of iC8/air and iC12/air mixtures at varying pressures (15, 20, and 30 bar), equivalence ratios (ϕ=0.7, 1.0, 1.2, and 2.0), and temperatures (600-900 K) are conducted. For some overlapped conditions, the current RCM data are compared with the RCM data of iC8 [25] and iC12 [36] and the ST data of iC8 [14] and iC12 [34,36], in order to demonstrate the consistency of the current RCM results and the literature RCM/ST data. A detailed chemical kinetic model, including low-to-intermediate temperature chemistry for both iC8 and iC12, is also developed.…”