Effects of methyl substitution on the auto-ignition of C16 alkanes

Lapuerta, Magı́n; Hernández, Juan José Marín; Sarathy, S. Mani

doi:10.1016/j.combustflame.2015.11.024

Cited by 36 publications

(29 citation statements)

References 40 publications

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“…Simulated hydroxyl time-history profiles during the oxidation of stoichiometric mixtures of the three surrogates (PRF 60, TPRF 60, and MCS) are presented in Fig. 7 at 20 bar and 650 K. Previous studies by Merchant et al [46] and others [41,47,48] have shown that OH radical profiles provide insights into the chemical kinetics of ignition processes. The initial growth of OH radicals is similar between all the fuels, but at ~5 ms the OH radical growth for MCS slows compared to that of PRF and TPRF.…”

Section: Low-temperatures Chemical Kinetic Analysismentioning

confidence: 96%

Autoignition of straight-run naphtha: A promising fuel for advanced compression ignition engines

Alabbad

Issayev

Badra

et al. 2018

Combustion and Flame

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CitationAlabbad M, Issayev G, Badra J, Voice AK, Giri BR, et al. (2018) Autoignition of straight-run naphtha: A promising fuel for advanced compression ignition engines. Combustion and Flame 189: 337-346. Available: http://dx. AbstractNaphtha, a low-octane distillate fuel, has been proposed as a promising low-cost fuel for advanced compression ignition engine technologies. Experimental and modelling studies have been conducted in this work to assess autoignition characteristics of naphtha for use in advanced engines. Ignition delay times of a certified straight-run naphtha fuel, supplied by Haltermann Solutions, were measured in a shock tube and a rapid comparison machine over wide ranges of experimental conditions (20 and 60 bar, 620 -1223 K,  = 0.5, 1 and 2). The Haltermann straight-run naphtha (HSRN) has research octane number (RON) of 60 and motor octane number (MON) of 58.3, with carbon range spanning C3 -C9. Reactivity of HSRN was compared, via experiments and simulations, with three suitably formulated surrogates: a two-component PRF (n-heptane/iso-octane) surrogate, a threecomponent TPRF (toluene/n-heptane/iso-octane) surrogate, and a six-component surrogate. All surrogates reasonably captured the ignition delays of HSRN at high and intermediate temperatures. However, at low temperatures (T < 750 K), the six-component surrogate performed the best in emulating the reactivity of naphtha fuel. Temperature sensitivity and rate of production analyses revealed that the presence of cyclo-alkanes in naphtha inhibits the overall fuel reactivity. Zero-dimensional engine simulations showed that PRF is a good autoignition surrogate for naphtha at high engine loads, however, the six-component surrogate is needed to match the combustion phasing of naphtha at low engine loads.

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Section: Low-temperatures Chemical Kinetic Analysismentioning

confidence: 96%

Autoignition of straight-run naphtha: A promising fuel for advanced compression ignition engines

Alabbad

Issayev

Badra

et al. 2018

Combustion and Flame

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“…The surrogates for FACE F and G successfully reproduce the two-stage ignition response observed in the respective fuels, but the pressure trace comparison for FACE F shows a slight discrepancy. This is because both the FACE F and G surrogates contain slightly less paraffinic CH3 groups than the fuels, and these groups have been shown to have a greater impact on the evolution of ignition processes [49,100]. FACE I and J and their MFG surrogates do not exhibit two-stage ignition in the temperature ranges studied in the RCM.…”

Section: Iqt Ignition Delay Timesmentioning

confidence: 97%

“…CH2/CH3 ratio also governs the ignition delay of n-paraffin fuels in the boiling range of diesel fuels [48,49]. Though shown to be very constraining information, clearly the simple CH2/CH3 molecular structure metric of Won et al [47] is inadequate to differentiate the different combustion kinetic behaviors that are due to the isomeric arrangement of the fragments comprising such molecules.…”

Section: Introductionmentioning

confidence: 99%

A minimalist functional group (MFG) approach for surrogate fuel formulation

Jameel

Issayev

Touitou

et al. 2018

Combustion and Flame

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et al. (2018) A minimalist functional group (MFG) approach for surrogate fuel formulation. Combustion and Flame 192: 250-271. Available: http://dx. AbstractSurrogate fuel formulation has drawn significant interest due to its relevance towards understanding combustion properties of complex fuel mixtures. In this work, we present a novel approach for surrogate fuel formulation by matching target fuel functional groups, while minimizing the number of surrogate species. Five key functional groups; paraffinic CH3, paraffinic CH2, paraffinic CH, naphthenic CH-CH2 and aromatic C-CH groups in addition to structural information provided by the Branching Index (BI) were chosen as matching targets. Surrogates were developed for six FACE (Fuels for Advanced Combustion Engines) gasoline target fuels, namely FACE A, C, F, G, I and J. The five functional groups present in the fuels were qualitatively and quantitatively identified using high resolution 1 H Nuclear Magnetic Resonance (NMR) spectroscopy. A further constraint was imposed in limiting the number of surrogate components to a maximum of two. This simplifies the process of surrogate formulation, facilitates surrogate testing, and significantly reduces the size and time involved in developing chemical kinetic models by reducing the number of thermochemical and kinetic parameters requiring estimation.Fewer species also reduces the computational expenses involved in simulating combustion in practical devices. The proposed surrogate formulation methodology is denoted as the Minimalist Functional Group (MFG) approach. The MFG surrogates were experimentally tested against their target fuels using Ignition Delay Times (IDT) measured in an Ignition Quality Tester (IQT), as specified by the standard ASTM D6890 methodology, and in a Rapid Compression Machine [Type text] 2 (RCM). Threshold Sooting Index (TSI) and Smoke Point (SP) measurements were also performed to determine the sooting propensities of the surrogates and target fuels. The results showed that MFG surrogates were able to reproduce the aforementioned combustion properties of the target FACE gasolines across a wide range of conditions. The present MFG approach supports existing literature demonstrating that key functional groups are responsible for the occurrence of complex combustion properties. The functional group approach offers a method of understanding the combustion properties of complex mixtures in a manner which is independent, yet complementary, to detailed chemical kinetic models. The MFG approach may be readily extended to formulate surrogates for other complex fuels.

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“…It should be noted that the autoignition chemistry is evolving as the temperature evolves, and the maximum temperatures reported in Table 3 may not be the most relevant parameters to fully understand autoignition chemistry in knocking engines. 61 For our study, one temperature and pressure were chosen for each of the RON and MON conditions, which enabled a common basis for comparing the underlying chemical kinetic phenomenon driving the reactivity of different fuels.…”

Section: Methodsmentioning

confidence: 99%

Chemical Kinetic Insights into the Octane Number and Octane Sensitivity of Gasoline Surrogate Mixtures

2017

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Gasoline octane number is a significant empirical parameter for the optimization and development of internal combustion engines capable of resisting knock. Although extensive databases and blending rules to estimate the octane numbers of mixtures have been developed and the effects of molecular structure on autoignition properties are somewhat understood, a comprehensive theoretical chemistry-based foundation for blending effects of fuels on engine operations is still to be developed. In this study, we present models that correlate the research octane number (RON) and motor octane number (MON) with simulated homogeneous gas-phase ignition delay times of stoichiometric fuel/air mixtures. These correlations attempt to bridge the gap between the fundamental autoignition behavior of the fuel (e.g., its chemistry and how reactivity changes with temperature and pressure) and engine properties such as its knocking behavior in a cooperative fuels research (CFR) engine. The study encompasses a total of 79 hydrocarbon gasoline surrogate mixtures including 11 primary reference fuels (PRF), 43 toluene primary reference fuels (TPRF), and 19 multicomponent (MC) surrogate mixtures. In addition to TPRF mixture components of iso-octane/n-heptane/toluene, MC mixtures, including n-heptane, iso-octane, toluene, 1-hexene, and 1,2,4-trimethylbenzene, were blended and tested to mimic real gasoline sensitivity. ASTM testing protocols D-2699 and D-2700 were used to measure the RON and MON of the MC mixtures in a CFR engine, while the PRF and TPRF mixtures' octane ratings were obtained from the literature. The mixtures cover a RON range of 0−100, with the majority being in the 70−100 range. A parametric simulation study across a temperature range of 650−950 K and pressure range of 15−50 bar was carried out in a constant-volume homogeneous batch reactor to calculate chemical kinetic ignition delay times. Regression tools were utilized to find the conditions at which RON and MON best correlate with simulated ignition delay times. Furthermore, temperature and pressure dependences were investigated for fuels with varying octane sensitivity. This analysis led to the formulation of correlations useful to the definition of surrogates for modeling purposes and allowed one to identify conditions for a more in-depth understanding of the chemical phenomena controlling the antiknock behavior of the fuels.

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Effects of methyl substitution on the auto-ignition of C16 alkanes

Cited by 36 publications

References 40 publications

Autoignition of straight-run naphtha: A promising fuel for advanced compression ignition engines

Autoignition of straight-run naphtha: A promising fuel for advanced compression ignition engines

A minimalist functional group (MFG) approach for surrogate fuel formulation

Chemical Kinetic Insights into the Octane Number and Octane Sensitivity of Gasoline Surrogate Mixtures

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