An experimental and modeling study of surrogate mixtures of n-propyl- and n-butylbenzene in n-heptane to simulate n-decylbenzene ignition

Abstract

This paper presents experimental data for the oxidation of two surrogates for the large alkylbenzene class of compounds contained in diesel fuels, namely ndecylbenzene. A 57:43 molar % mixture of n-propylbenzene:n-heptane in air (≈21% O 2 , ≈79% N 2 ) was used in addition to a 64:36 molar % mixture of nbutylbenzene:36% n-heptane in air. These mixtures were designed to contain a similar carbon/hydrogen ratio, molecular weight and aromatic/alkane ratio when compared to n-decylbenzene. Nominal equivalence ratios of 0.3, 0.5, 1.0 and 2.0 were used. Ignition times were measured at 1 atm in the shock tube and at pressures of 10, 30 and 50 atm in both the shock tube and in the rapid compression machine. The temperature range studied was from approximately 650-1700 K.The effects of reflected shock pressure and equivalence ratio on ignition delay * address: time were determined and common trends highlighted. It was noted that both mixtures showed similar reactivity throughout the temperature range studied. A reaction mechanism published previously was used to simulate this data. Overall the reaction mechanism captures the experimental data reasonably successfully with a variation of approximately a factor of 2 for mixtures at 10 atm and fuel-rich and stoichiometric conditions.

Analysis of the filtered non-premixed turbulent flame

“…We have collected together, into a single chemical kinetic reaction mechanism, models for n-alkane fuels from methane to n-octane [9,10], 2-methyl alkanes from iso-butane to 2-methyl heptane [10], other branched chain hydrocarbons including the isomers of pentane and hexane [11,12] and selected isomers of heptane [13,14], and iso-octane [15]. In addition, recent mechanisms are included for alcohol fuels methanol, ethanol, and the isomers of propanol and butanol [16,17], as well as n-pentanol [18] and iso-pentanol [19], and mechanisms for benzene and alkyl benzenes as large as n-butyl benzene [15,[20][21][22][23]. New mechanisms for a wide variety of olefin fuels from propene [24,25] to heptene [26] are also included, as well as cyclic paraffin fuels cyclopentane [27], cyclohexane [28] and methyl cyclohexane [29].…”

“…We incorporated alkyl benzene mechanisms from Darcy et al [21][22][23] and Mehl et al [15] and carried out end gas autoignition engine cycle simulations for toluene, ethyl benzene, n-propyl benzene, and n-butyl benzene. The computed results for the rates of heat release and temperature for these fuels are shown in Figs.…”

Oxidation of 2-methylfuran and 2-methylfuran/n-heptane blends: An experimental and modeling study

“…In order to accurately include the change in pressure/temperature before and after compression, the non-reactive profile is converted into a normalized effective volume profile through the isentropic relationship between pressure and density, thereby allowing the calculation of the effective volume. This method of RCM simulation has been used previously in many studies [51][52][53][54][55] to simulate the various RCM facilities.…”

Reactions of HO2 with n-propylbenzene and its phenylpropyl radicals

“…In reference to thermal decomposition and pyrolysis of nPB, Robinson and Lindstedt reported theoretically-derived rate constants for abstraction of an H atom from the propyl side chain in nPB, by H and CH 3 radicals [14]. Darcy et al [4] predicted the oxidation mechanism of nPB at low temperature to be greatly influenced by the reaction sequence: RH + HO 2 → R + H 2 O 2 , H 2 O 2 + M → 2OH + M. The authors have shown that at 1000 K, HO 2 and benzyl radicals govern the overall oxidation reactivity of nPB. This reaction sequence provides a corridor for the conversion of the relatively unreactive HO 2 radicals into the chain propagating radicals of OH [15,16].…”

“…Thus, congeners of alkyl aromatics may serve as surrogates replicating intrinsic chemical and physical properties of real fuels [1,2]. In particular, n-propylbenzene (nPB) embodies well the properties of a class of alkyl benzenes in jet and diesel fuels [3,4]. Previous studies have targeted several combustion characteristics of nPB, including ignition delay [5], laminar burning velocity [6] and sooting tendency [7].…”