Exploring gasoline oxidation chemistry in jet stirred reactors

Abstract

Recent decades have seen increasingly restrictive regulations applied to gasoline engines. Gasoline combustion chemistry must be investigated to achieve a better understanding and control of internal combustion engine efficiency and emissions. In this work, several gasoline fuels, namely the FACE (Fuel for Advanced Combustion Engines) gasolines, were selected as targets for oxidation study in jet-stirred reactors (JSR). The study is facilitated by formulating various gasoline surrogate mixtures with known hydrocarbon compositions to represent the real gasolines. Surrogates included binary mixtures of n-heptane and iso-octane, as well as more complex multicomponent mixtures. The oxidation characteristics of FACE gasolines and their surrogates were experimentally examined in JSR-1 and numerically simulated under the following conditions: pressure 1 bar, temperature 500-1050K, residence time 1.0 and 2.0 s, and two equivalence ratios (ϕ=0.5 and 1.0). In the high temperature region, all real fuels and surrogates showed similar oxidation behavior, but in the low temperature region, a fuel's octane number and composition had a significant effect on its JSR oxidation characteristics. Low octane number fuels displayed more low temperature reactivity, while fuels with similar octane number but a larger number of nalkane components were more reactive. A gasoline surrogate kinetic model was examined with FACE gasoline experiments either measured in JSR-2, or taken from previous work under the following conditions: pressure 10 bar, temperature 530-1200K, residence time 0.7s, and three equivalence ratios (ϕ=0.5, 1.0 and 2.0). Comparison between FACE gasoline experimental results with surrogate model predictions showed good agreement, demonstrating considerable potential for surrogate fuel kinetic modeling in engine simulations.

Chemical kinetic study of triptane (2,2,3-trimethylbutane) as an anti-knock additive

“…The oxidation experiment of triptane was performed at atmospheric pressure in a jet-stirred reactor (JSR) at KAUST. The experimental setup was previously validated with n-heptane oxidation and the results reached good agreement with other groups [49,50] . A 76 cm 3 spherical quartz reactor consists of four opposing nozzles (0.3 mm diameter) to attain the homogeneity of species and temperature distribution.…”

Polycyclic aromatic hydrocarbons in pyrolysis of gasoline surrogates (n-heptane/iso-octane/toluene)

“…The JSR with volume of 76 cm 3 and the sampling systems are similar to those of Dagaut et al [22]. Details of the KAUST JSR is described in [23]. The experiments were conducted at a fuel concentration of 0.25% and residence time 1s.…”

Autoignition behavior of gasoline/ethanol blends at engine-relevant conditions

“…FACE-F is selected as the base gasoline for this work. Detailed chemical and physical properties of FACE-F can be found in [15] and have been well documented in recent studies from KAUST [11,43,44]. It is a mid-octane fuel with an anti-knock index (AKI) of 91.6, which consists of relatively lower fractions of n-paraffinic and aromatics but higher fractions of naphthenes and olefins as compared to other FACE gasolines, leading to an octane sensitivity (S = RON minus MON) of 6.8.…”