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Pierre-Alexandre Glaude

Publications and source records attributed to Pierre-Alexandre Glaude.

At least 19 recordsLinked to original sources
arXiv2009

A Comparative Study of the Formation of Aromatics in Rich Methane Flames Doped by Unsaturated Compounds

For a better modeling of the importance of the different channels leading to the first aromatic ring, we have compared the structures of laminar rich premixed methane flames doped with several unsaturated hydrocarbons: allene and propyne, because they are precursors of propargyl radicals which are well known as having an important role in forming benzene, 1,3-butadiene to put in evidence a possible production of benzene due to reactions of C4 compounds, and, finally, cyclopentene which is a source of cyclopentadienylmethylene radicals which in turn are expected to easily isomerizes to give benzene. These flames have been stabilized on a burner at a pressure of 6.7 kPa (50 Torr) using argon as dilutant, for equivalence ratios (?) from 1.55 to 1.79. A unique mechanism, including the formation and decomposition of benzene and toluene, has been used to model the oxidation of allene, propyne, 1,3 butadiene and cyclopentene. The main reaction pathways of aromatics formation have been derived from reaction rate and sensitivity analyses and have been compared for the three types of additives. These combined analyses and comparisons can only been performed when a unique mechanism is available for all the studied additives.

physics.chem-ph↗
arXiv2009

Theoretical Kinetic Study of the Ring Opening of Cyclic Alkanes

This work reports a theoretical study of the gas phase unimolecular decomposition of cyclobutane, cyclopentane and cyclohexane by means of quantum chemical calculations. A biradical mechanism has been envisaged for each cycloalkane, and the main routes for the decomposition of the biradicals formed have been investigated at the CBS-QB3 level of theory. Thermochemical data (?H\degree f, S\degree, C\degree p) for all the involved species have been obtained by means of isodesmic reactions. Rate constants have been derived for all elementary reactions using transition state theory at 1 atm and temperatures ranging from 600 to 2000 K. These values have been compared with the few data available in the literature and showed a rather good agreement.

physics.chem-ph↗
arXiv2009

Modeling Study of the Low-Temperature Oxidation of Large Methyl Esters

This study focuses on the automatic generation by the software EXGAS of kinetic models for the oxidation of large methyl esters using a single set of kinetic parameters. The obtained models allow to well reproduce the oxidation of n-decane / methyl palmitate mixture in a jet-stirred reactor. This paper also presents the construction and a comparison of models for methyl esters from C7 up to C17 in terms f conversion in a jet-stirred reactor and of ignition delay time in a shock tube. This comparison study showed that methyl esters larger than methyl octanoate behave similarly and have very close reactivities.

physics.chem-ph↗
arXiv2009

Theoretical Study of the Thermal Decomposition of a Jet Fuel Surrogate

In a scramjet, the fuel can be used to cool down the engine walls. The thermal decomposition of the jet fuel changes the reacting mixture before its combustion. A numerical study of the pyrolysis of norbornane, a jet fuel surrogate, has been performed. Rate constants of some sensitive reaction channels have been calculated by means of quantum chemical calculations at the CBS-QB3 level of theory. The mechanism has been validated against experimental results obtained in a jet-stirred reactor and important and/or sensitive pathways have been derived.

physics.chem-ph↗
arXiv2009

Experimental Autoignition of C4-C6 Saturated and Unsaturated Methyl and Ethyl Esters

Autoignition delay times, ?, of methyl crotonate, methyl acrylate, ethyl butanoate, ethyl crotonate, and ethyl acrylate were studied in shock tube experiments. A series of mixtures diluted with argon, of varying fuel/oxygen equivalence ratios (?=0.25, 0.4, 1.0, and 2.0), were measured behind reflected shock waves over the temperature range of 1280-1930 K, pressure range of 7-9.65 atm, during which the logarithm of ? varies linearly as a function of the inverse temperature for all equivalence ratios. The ignition delay time decreases as temperature rises. The dependence of ? on temperature, and reactant concentrations is given in an empirical correlation. The results provide a database for the validation of small saturated and unsaturated esters kinetic mechanisms at elevated temperatures and pressure combustion.

physics.chem-ph↗
arXiv2009

Detailed kinetic models for the low-temperature auto ignition of gasoline surrogates

In the context of the search for gasoline surrogates for kinetic modeling purpose, this paper describes a new model for the low-temperature auto-ignition of n-heptane/iso-octane/hexene/toluene blends for the different linear isomers of hexene. The model simulates satisfactory experimental results obtained in a rapid compression machine for temperatures ranging from 650 to 850 K in the case of binary and ternary mixtures including iso octane, 1-hexene and toluene. Predictive simulations have also been performed for the autoignition of n heptane/iso octane/hexene/toluene quaternary mixtures: the predicted reactivity is close to that of pure iso octane with a retarding effect when going from 1- to 3-alkene.

physics.chem-ph↗
arXiv2009

Theoretical kinetic study of the low temperature oxidation of ethanol

In order to improve the understanding of the low temperature combustion of ethanol, high-level ab initio calculations were performed for elementary reactions involving hydroxyethylperoxy radicals. These radicals come from the addition of hydroxethyl radicals (?CH3CHOH and ?CH2CH2OH) on oxygen molecule. Unimolecular reactions involving hydroxyethylperoxy radicals and their radical products were studied at the CBS-QB3 level of theory. The results allowed to highlight the principal ways of decomposition of these radicals. Calculations of potential energy surfaces showed that the principal channels lead to the formation of HO2 radicals which can be considered, at low temperature, as slightly reactive. However, in the case of CH3CH(OOH)O? radicals, a route of decomposition yields H atom and formic peracid, which is a branching agent that can strongly enhance the reactivity of ethanol in low temperature oxidation. In addition to these analyses, high-pressure limit rate constants were derived in the temperature range 400 to 1000 K.

physics.chem-ph↗
arXiv2009

Formation of aromatics in rich methane flames doped by unsaturated compounds

In order to better understand the importance of the different channels leading to the first aromatic ring, we have investigated, the structure of a laminar rich premixed methane flame doped with several unsaturated hydrocarbons: allene and propyne, as they are precursors of propargyl radicals, which are well known as having an important role in forming benzene, 1,3-butadiene, to put in evidence a possible production of benzene due to reactions of C4 compounds, and, finally, cyclopentene, which is a source of cyclopentadienyl methylene radicals which are supposed to easily isomerizes to give benzene. A ratio additive / CH4 of 16 % and an equivalence ratio of 1.79 have been used. These flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant. A new mechanism for the oxidation of allene, propyne, 1,3 butadiene and cyclopentene has been proposed including the formation and decomposition of benzene and toluene. The main reaction pathways of formation of aromatics have been derived from flow rate analyses and have been compared for the three types of additives.

physics.chem-ph↗
arXiv2009

A Lean Methane Prelixed Laminar Flame Doped witg Components of Diesel Fuel. Part I: n)Butylbenzene

To better understand the chemistry involved during the combustion of components of diesel fuel, the structure of a laminar lean premixed methane flame doped with n-butylbenzene has been investigated. The inlet gases contained 7.1% (molar) of methane, 36.8% of oxygen and 0.96% of n-butylbenzene corresponding to an equivalence ratio of 0.74 and a ratio C10H14 / CH4 of 13.5%. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as diluent, with a gas velocity at the burner of 49.2 cm/s at 333 K. Quantified species included the usual methane C0-C2 combustion products, but also 16 C3-C5 hydrocarbons, 7 C1-C3 oxygenated compounds, as well as 20 aromatic products, namely benzene, toluene, phenylacetylene, styrene, ethylbenzene, xylenes, allylbenzene, propylbenzene, cumene, methylstyrenes, butenylbenzenes, indene, indane, naphthalene, phenol, benzaldehyde, anisole, benzylalcohol, benzofuran, and isomers of C10H10 (1-methylindene, dihydronaphtalene, butadienylbenzene). A new mechanism for the oxidation of n-butylbenzene is proposed whose predictions are in satisfactory agreement with measured species profiles in flames and flow reactor experiments. The main reaction pathways of consumption of n butylbenzene have been derived from flow rate analyses.

physics.chem-ph↗
arXiv2009

Experimental study of the structure of a lean premixed indane/CH4/O2/Ar flame

In order to better understand the chemistry involved during the combustion of components of diesel fuel, the structure of a laminar lean premixed methane flame doped with indane has been investigated. The gases of this flame contains 7.1% (molar) of methane, 36.8% of oxygen and 0.90% of indane corresponding to an equivalence ratio of 0.74 and a ratio C9H10/CH4 of 12.75%. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 49.2 cm/s at 333 K. Quantified species included usual methane C0-C2 combustion products, but also 11 C3-C5 hydrocarbons and 3 C1-C3 oxygenated compounds, as well as 17 aromatic products, namely benzene, toluene, phenylacetylene, styrene, ethylbenzene, xylenes, trimethylbenzenes, ethyltoluenes, indene methylindane, methylindene, naphthalene, phenol, benzaldehyde, benzofuran. The temperature was measured thanks to a thermocouple in PtRh (6%)-PtRh (30%) settled inside the enclosure and ranged from 800 K close to the burner up to 2000 K in the burned gases.

physics.chem-ph↗
arXiv2009

Theoretical kinetic study of thermal unimolecular decomposition of cyclic alkyl radicals

While many studies have been reported on the reactions of aliphatic hydrocarbons, the chemistry of cyclic hydrocarbons has not been explored extensively. In the present work, a theoretical study of the gas-phase unimolecular decomposition of cyclic alkyl radicals was performed by means of quantum chemical calculations at the CBS-QB3 level of theory. Energy barrier and high-pressure limit rate constants were calculated systematically. Thermochemical data were obtained from isodesmic reactions and the contribution of hindered rotors was taken into account. Classical transition state ...

physics.chem-ph↗
arXiv2008

An experimental and kinetic modelling study of the oxidation of the four isomers of butanol

Butanol, an alcohol which can be produced from biomass sources, has received recent interest as an alternative to gasoline for use in spark ignition engines and as a possible blending compound with fossil diesel or biodiesel. Therefore, the autoignition of the four isomers of butanol (1-butanol, 2-butanol, iso-butanol, and tert-butanol) has been experimentally studied at high temperatures in a shock tube and a kinetic mechanism for description of their high-temperature oxidation has been developed. Ignition delay times for butanol/oxygen/argon mixtures have been measured behind reflected shock waves at temperatures and pressures ranging from approximately 1200 to 1800 K and 1 to 4 bar. Electronically excited OH emission and pressure measurements were used to determine ignition delay times. A detailed kinetic mechanism has been developed to describe the oxidation of the butanol isomers and validated by comparison to the shock tube measurements. Reaction flux and sensitivity analysis indicate that the consumption of 1 butanol and iso-butanol, the most reactive isomers, takes place primarily by H-atom abstraction resulting in the formation of radicals, the decomposition of which yields highly reactive branching agents, H-atoms and OH radicals. Conversely, the consumption of tert butanol and 2-butanol, the least reactive isomers, takes place primarily via dehydration, resulting in the formation of alkenes, which lead to resonance stabilized radicals with very low reactivity. To our knowledge, the ignition delay measurements and oxidation mechanism presented here for 2-butanol, iso-butanol, and tert butanol are the first of their kind..

physics.chem-ph↗
arXiv2008

Experimental and modeling study of the low-temperature oxidation of large alkanes

This paper presents an experimental and modeling study of the oxidation of large linear akanes (from C10) representative from diesel fuel from low to intermediate temperature (550-1100 K) including the negative temperature coefficient (NTC) zone. The experimental study has been performed in a jet-stirred reactor at atmospheric pressure for n-decane and a n-decane/n-hexadecane blend. Detailed kinetic mechanisms have been developed using computer-aided generation (EXGAS) with improved rules for writing reactions of primary products. These mechanisms have allowed a correct simulation of the experimental results obtained. Data from the literature for the oxidation of n-decane, in a jet-stirred reactor at 10 bar and in shock tubes, and of n-dodecane in a pressurized flow reactor have also been correctly modeled. A considerable improvement of the prediction of the formation of products is obtained compared to our previous models. Flow rates and sensitivity analyses have been performed in order to better understand the influence of reactions of primary products. A modeling comparison between linear alkanes for C8 to C16 in terms of ignition delay times and the formation of light products is also discussed.

physics.chem-ph↗
arXiv2007

Experimental and modeling study of the autoignition of cyclopentane

Ignition delay times of cyclopentene-oxygen-argon mixtures were measured behind reflected shock waves. Mixtures contained 0.5 or 1 % of hydrocarbons for equivalence ratios ranging from 0.5 to 1.5. Reflected shock waves conditions were: temperatures from 1300 to 1700 K and pressures from 7 to 9 atm. When comparing to previous results obtained under similar conditions, it can be observed that the reactivity of cyclopentene is much lower than that of cyclohexene, but very close to that of cyclopentane. A kinetic mechanism recently proposed for the combustion of cyclopentene in a flame has been used to model these results and a satisfactory agreement has been obtained. The main reaction pathways have been derived from flow rate, simulated temporal profiles of products and sensitivity analyses.

physics.chem-ph↗
arXiv2007

Rich methane laminar flames doped with light unsaturated hydrocarbons. Part III : cyclopentene

In line with the studies presented in the parts I and II of this paper, the structure of a laminar rich premixed methane flame doped with cyclopentene has been investigated. The gases of this flame contains 15.3% (molar) of methane, 26.7% of oxygen and 2.4% cyclopentene corresponding to an equivalence ratio of 1.79 and a ratio C5H8 / CH4 of 16 %. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The temperature ranged from 627 K close to the burner up to 2027 K. Quantified species included usual methane C0-C2 combustion products, but also propyne, allene, propene, propane, 1-butene, 1,3-butadiene, 1,2-butadiene, vinylacetylene, diacetylene, cyclopentadiene, 1,3-pentadiene, benzene and toluene. A new mechanism for the oxidation of cyclopentene has been proposed. The main reaction pathways of consumption of cyclopentene and of formation of benzene and toluene have been derived from flow rate analyses.

physics.chem-ph↗
arXiv2007

Rich methane laminar flames doped with light unsaturated hydrocarbons. Part II: 1,3butadiene

In line with the study presented in the part I of this paper, the structure of a laminar rich premixed methane flame doped with 1,3-butadiene has been investigated. The flame contains 20.7% (molar) of methane, 31.4% of oxygen and 3.3% of 1,3-butadiene, corresponding to an equivalence ratio of 1.8, and a ratio C4H6 / CH4 of 16 %. The flame has been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The temperature ranged from 600 K close to the burner up to 2150 K. Quantified species included usual methane C0-C2 combustion products and 1,3-butadiene, but also propyne, allene, propene, propane, 1,2-butadiene, butynes, vinylacetylene, diacetylene, 1,3-pentadiene, 2-methyl-1,3-butadiene (isoprene), 1-pentene, 3-methyl-1-butene, benzene and toluene. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C3-C4 unsaturated hydrocarbons. The main reaction pathways of consumption of 1,3-butadiene and of formation of C6 aromatic species have been derived from flow rate analyses. In this case, the C4 route to benzene formation plays an important role in comparison to the C3 pathway.

physics.chem-ph↗