Methodology to define gasoline surrogates dedicated to auto-ignition in engines

Pera, Cécile; Knop, Vincent

doi:10.1016/j.fuel.2012.01.008

Cited by 110 publications

(88 citation statements)

References 32 publications

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“…[14][15][16], as well as complex multicomponent surrogates for various non-oxygenated gasolines [17,18]. The reasonable extent of agreement between TRF and gasoline, in addition to the availability of well validated chemical mechanisms of its oxidation pathways, makes it currently a more feasible surrogate for gasoline in terms of ignition delay modelling compared to more complex surrogates [19] and blending effects, and hence it is used in this work.…”

Section: Surrogate Formulationmentioning

confidence: 99%

“…The method of Pera and Knop [19,21] was employed here for formulating the TRF surrogate. Based on this method for an n-component surrogate, only n-1 properties of the target fuel can be used to constrain the surrogate model.…”

Section: Surrogate Formulationmentioning

confidence: 99%

“…The ability of the surrogate to capture the true temperature sensitivity of ignition delays for the gasoline will be studied in detail here experimentally. Hence following Pera and Knop [19,21] the TRF formulation is based on the following constraints:…”

Section: Surrogate Formulationmentioning

confidence: 99%

“…The use of a linear blending rule based on a simple average of compound values weighted by the volume fractions for determination of ON of fuel mixtures, has been shown in various studies [22][23][24][25][26] to be inadequate for formulating surrogate mixtures for gasoline. The linear-by-mole blending rule for determination of ONs of TRF mixtures was demonstrated in [19,21] to produce results that are as accurate as the complex formulations found in the literature and was therefore employed for formulating the TRF surrogate mixture in this study.…”

Section: Surrogate Formulationmentioning

confidence: 99%

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The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

Agbro

Tomlin

Lawes

et al. 2017

Fuel

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The influence of blending n-butanol at 20% by volume on the ignition delay times for a reference gasoline was studied in a rapid compression machine (RCM) for stoichiometric fuel/air mixtures at 20 bar and 678 K-858 K. Delay times for the blend lay between those of stoichiometric gasoline and stoichiometric n-butanol across the temperature range studied. At lower temperatures, delays for the blend were however, much closer to those of n-butanol than gasoline despite n-butanol being only 20% of the mixture. Under these conditions n-butanol acted as an octane enhancer over and above what might be expected from a simple linear blending law. The ability of a gasoline surrogate, based on a toluene reference fuel (TRF), to capture the main trends of the gasoline/ n-butanol blending behaviour was also tested within the RCM. The 3-component TRF based on a mixture of toluene, n-heptane and iso-octane was able to capture the trends well across the temperature range studied. Simulations of ignition delay times were also performed using a detailed blended nbutanol/TRF mechanism based on the adiabatic core assumption and volume histories from the experimental data. Overall, the model captured the main features of the blending behaviour, although at the lowest temperatures, predicted ignition delays for stoichiometric n-butanol were longer than those observed. A bruteforce local sensitivity analysis was performed to evaluate the main chemical processes driving the ignition behaviour of the TRF, n-butanol and blended fuels. The reactions of fuel + OH dominated the sensitivities at lower temperatures, with H abstraction from nn-butanol and the blend. At higher temperatures the decomposition of H 2 O 2 and reactions of HO 2 and that of formaldehyde with OH became critical, in common with the ignition behaviour of other fuels. Remaining uncertainties in the rates of these key reactions are discussed.

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Section: Surrogate Formulationmentioning

confidence: 99%

Section: Surrogate Formulationmentioning

confidence: 99%

Section: Surrogate Formulationmentioning

confidence: 99%

Section: Surrogate Formulationmentioning

confidence: 99%

See 2 more Smart Citations

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

Agbro

Tomlin

Lawes

et al. 2017

Fuel

View full text Add to dashboard Cite

show abstract

“…Moreover, it is evident that real gasoline does not have iso-octane or n-heptane as its major constituent; far from it, they are not even the dominant branched or straight paraffins. 30,31 A simple surrogate used to emulate fuels with sensitivity (S > 0) comprises toluene, nheptane, and iso-octane and is termed toluene primary reference fuels (TPRF). Adding further components to the surrogate is often useful to match the thermodynamic and kinetic properties and emission behavior of gasoline fuels.…”

Section: Introductionmentioning

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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Autoignition of light naphtha and its surrogates in a rapid compression machine

Wang

2019

Energy Science & Engineering

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Gasoline Compression Ignition (GCI) is a promising combustion mode to improve engine efficiency and reduce emissions. Naphtha has higher ignitability than gasoline and could be a better fuel for GCI. Understanding the autoignition behavior of naphtha is essential for the development of GCI engines. In this study, the ignition delay of light naphtha and its three surrogates, including PRF59 (59% iso‐octane and 41% n‐heptane in volume) and two three‐component surrogates composed of methyl‐cyclohexane, n‐heptane, and iso‐octane with blending ratios of 33.8%/43.2%/23% (MRF1) and 31.4%/33.3%/35.3% (MRF2) in volume were studied using a rapid compression machine. PRF59 was selected by matching the RON of light naphtha. MRF1 was composited by matching the RON and MON of light naphtha, while MRF2 was composed by matching RON and H/C. The experiments were conducted at equivalence ratio Φ = 0.5 and 1, P = 10, 20, and 30 bar, and temperature range of 665‐965 K. It was found that MRF2 best matched the first‐stage and total ignition delays of light naphtha, while PRF59 exhibited shorter first‐stage ignition delay. Although the ignition delay times of MRF1 and MRF2 were very close to each other, uncertainty analysis showed that matching RON and H/C ratio was a better method in determining the blending ratio. In addition, the MRF experiments were compared with predictions using the detailed mechanism. The mechanism showed good performance in reproducing the total ignition delay at high‐pressure conditions, but it underpredicted the ignition delay at low pressure. Also, the mechanism predicted less pronounced NTC behavior.

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Methodology to define gasoline surrogates dedicated to auto-ignition in engines

Cited by 110 publications

References 32 publications

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

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

Autoignition of light naphtha and its surrogates in a rapid compression machine

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