A computational methodology for formulating gasoline surrogate fuels with accurate physical and chemical kinetic properties

Ahmed, Ahfaz; Goteng, Gokop; Shankar, Vijai Shankar Bhavani; Al-Qurashi, Khalid; Roberts, William L.; Sarathy, S. Mani

doi:10.1016/j.fuel.2014.11.022

Cited by 137 publications

(180 citation statements)

References 35 publications

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“…However, 4-component surrogates involving TRF/1-pentene and TRF/2-pentene have also been formulated and investigated by e.g. [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 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%

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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“…Details about FACE gasolines can be obtained from the Coordinating Research Council [36]. Fundamental ignition and heat release characteristics of FACE gasolines have also been published [37], [38], [39], [40], [41]. The effects of ethanol addition to the base fuels listed in Table 3 were investigated with the addition of ethanol addition at 0 %, 2%, 5%, 10%, and 15% by volume [42].…”

Section: Fuels and Gem Blendsmentioning

confidence: 99%

Auto-Ignition of Iso-Stoichiometric Blends of Gasoline-Ethanol-Methanol (GEM) in SI, HCCI and CI Combustion Modes

Waqas¹,

Naser²,

Sarathy³

et al. 2017

SAE Technical Paper Series

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Gasoline-ethanol-methanol (GEM) blends, with constant stoichiometric air-to-fuel ratio (iso-stoichiometric blending rule) and equivalent to binary gasoline-ethanol blends (E2, E5, E10 and E15 in % vol.), were defined to investigate the effect of methanol and combined mixtures of ethanol and methanol when blended with three FACE (Fuels for Advanced Combustion Engines) Gasolines, I, J and A corresponding to RON 70.2, 73.8 and 83.9, respectively, and their corresponding Primary Reference Fuels (PRFs). A Cooperative Fuel Research (CFR) engine was used under Spark Ignition and Homogeneous Charge Compression Ignited modes. An ignition quality tester was utilized in the Compression Ignition mode. One of the promising properties of GEM blends, which are derived using the iso-stoichiometric blending rule, is that they maintain a constant octane number, which has led to the introduction of methanol as a drop-in fuel to supplement bio-derived ethanol. A constant RON/ HCCI fuel number/derived Research octane number property was observed in all three combustion modes for high RON fuels, but for low RON fuels, the iso-stoichiometric blending rule for constant octane number did not appear to be valid. The chemical composition and octane number of the base fuel also influenced the behavior of the GEM blends under different conditions.

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“…Sarathy et al 37 used six-component surrogates to match the ignition characteristics of alkane-rich FACE (Fuels for Advanced Combustion Engines) gasolines, adding iso-pentane, 2-methylhexane, and n-butane to conventional TPRF mixtures. Recently, Ahmed et al 38 proposed an algorithm to match both ignition delay and fuel physical properties, which becomes increasingly important in modern direct injected engines. Sarathy et al 39 also utilized surrogates with up to nine components to study the effects of chemical composition on the ignition and octane sensitivity of FACE gasolines.…”

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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A computational methodology for formulating gasoline surrogate fuels with accurate physical and chemical kinetic properties

Cited by 137 publications

References 35 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

Auto-Ignition of Iso-Stoichiometric Blends of Gasoline-Ethanol-Methanol (GEM) in SI, HCCI and CI Combustion Modes

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

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