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The oxidation of di-isopropyl-ether (DIPE) was studied in a jet-stirred reactor. Fuel-lean, stoichiometric, and fuel-rich mixtures (φ = 0.5–4) were oxidized at a constant fuel mole fraction of 1000 ppm, at temperatures ranging from 500 to 1160 K, at 10 atm, and constant residence time of 0.7 s. The chosen conditions are consistent with our previous studies on ether oxidation. Mole fraction profiles were obtained through sonic probe sampling, and analyzed by gas chromatography and Fourier transform infrared spectrometry. As opposed to our previous studies on ethers (S. Thion et al. 2017, Z. Serinyel et al. 2018 and 2020), DIPE showed no low-temperature reactivity under the same experimental conditions. Oxidation of the rich mixture showed similarities to pyrolysis producing important quantities of propene and isopropanol, while no isopropanol is observed under lean conditions. In terms of overall reactivity, DIPE showed smaller fuel conversion compared to other symmetric ethers previously studied. The present data and literature experiments were simulated with our ether oxidation mechanism showing good agreement. [ABSTRACT FROM AUTHOR]

This work focuses on the diluent influence on stable methane flames in a fused silica micro flow reactor (MFR). Experimental and numerical investigations are performed. The first part presents the method of performing experiments and extracting data from an MFR in order to increase the reliability of the experimental results necessary for subsequent numerical simulations. Those methods are applied to premixed stoichiometric methane flames diluted by nitrogen, argon, helium and xenon. Methods to point out the influence of mixture thermodynamic and transport properties influence is presented. A numerical study of the influence of diluent on stable flames is also undertaken to support the experimental observations difficult to realize in such micro-devices. [ABSTRACT FROM AUTHOR]

The modern catalytic or enzymatic advances allow the production of novel biofuel. Among them, 1,3-dioxolane can be produced from formaldehyde and ethylene glycol, both can be obtained from biomass. In this study, the oxidation of 1,3-dioxolane is studied at stoichiometric conditions. The ignition delay times of 1,3-dioxolane/O 2 /inert mixtures were measured in a shock tube and in a rapid compression machine at pressures of 20 to 40 bar and temperatures ranging from 630 to 1300 K. The pressure profiles recorded in the rapid compression machine show a first stage of ignition enlightening the influence of the low temperature chemistry of combustion. Furthermore, mole fraction profiles of the stable intermediates produced during the oxidation of 1,3-dioxolane were measured in a jet-stirred reactor at 10 bar. Following these observations, a detailed kinetic model was developed with reaction rate coefficients and thermochemical data calculated by theoretical calculations or estimated by analogies to suitable molecules. In order to get an insight into the most important reaction pathways brute force sensitivity analysis and reaction pathway analysis were performed with the proposed model and discussed. It became clear that in the fuel-in-air case for the alkylhydroperoxide of 1,3-dioxolane the ring opening beta-scission pathway is favored against the further alkane-like second addition to molecular oxygen, which leads to a limited negative temperature coefficient. [ABSTRACT FROM AUTHOR]

The oxidation of pentan-2-ol was investigated at high-pressure in a jet-stirred reactor and in a shock tube. Experiments in the JSR were carried out at 10 atm, between 500 and 1180 K, for five different equivalence ratios of φ = 0.35, 0.5, 1, 2, 4 and 1000 ppm of fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were quantified using Fourier transform infrared spectrometry (FTIR) and gas chromatography (GC). Ignition delay times were measured for pentan-2-ol/O 2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1070–1460 K and for equivalence ratios of φ = 0.5, 1 and 2. Ignition delay times of a stoichiometric mixture were also measured in air at 20 bar. Under these conditions, this alcohol exhibited no low-temperature reactivity in either experimental set-ups. Based on ab initio calculations presented in the companion paper, a detailed kinetic mechanism was developed in order to reproduce the present data and analyze the reaction pathways. [ABSTRACT FROM AUTHOR]

The oxidation of di-n-propyl-ether (DPE) was performed in a jet-stirred reactor at 1 and 10 atm, at residence times of 1 and 0.7 s, respectively, and initial fuel concentrations of 5000 and 1000 ppm at 1 and 10 atm, respectively. Atmospheric pressure experiments were used for characterization of cool flame products. The 10 atm experiment provided KHPs profile vs. temperature and mole fraction profiles of stable species which were obtained through sonic probe sampling, gas chromatography, Fourier transform infrared spectrometry analyses. High resolution mass spectrometry analyses (HRMS) with syringe direct injection or ultra-high-pressure liquid chromatography coupling was used to characterize hydroperoxides (C 3 H 8 O 2 , C 6 H 14 O 3), diols (C 6 H 14 O 3), ketohydroperoxides (C 6 H 12 O 4), carboxylic acids, and highly oxygenated molecules (C 6 H 12 O 6 , C 6 H 12 O 8) resulting from up to four O 2 additions on fuel's radicals. Heated electrospray and atmospheric pressure chemical ionizations (HESI and APCI) were used in positive and negative mode. Whereas the CH 2 groups neighboring the ether function are the most favorable sites for H-atom abstraction reactions, speciation indicated that other sites can react by metathesis forming a large pool of intermediates. Our kinetic reaction mechanism represents the experimental data for most of the stable species but need to be expended for simulating the formation of newly detected species. [ABSTRACT FROM AUTHOR]

Pyrolysis of diethyl (C 4), di-n-propyl (C 6), di-isopropyl (C 6) and di-n-butyl (C 8) ethers were studied in a jet-stirred reactor between 720 and 1140 K, at 10 atm with an initial ether mole fraction of 0.1%. Major common pyrolysis products were observed to be CO, CH 4 , H 2 , and C 2 H 4. All ethers produced the n/2 alcohol and olefin as products of molecular reaction to a small extent. Under pyrolysis conditions at 10 atm, hydrogen abstraction reactions by H atoms and CH 3 radicals were found to be important. Acetylene and benzene were formed for all ethers when T > 1000 K. A kinetic mechanism is used to represent these results. This study shows that there is need of systematic studies in determining site specific rate constants of important fuel related reactions of ethers. [ABSTRACT FROM AUTHOR]

Theoretical investigations on the kinetics of pentan-2-ol radical decomposition and isomerization reactions have been carried out in this work, together with the thermochemistry data calculations for important species involved in the reaction process. The B2PLYPD3/6-311++G(d,p) level of theory was used to optimize the geometries of all of the reactants, transition states, products and also the hindered rotor treatment for lower frequency modes. Single-point energies of all species are determined at the ROCCSD(T) level using the cc-PVQZ and cc-pVTZ which were extrapolated to the complete basis set limit (CBS). RRKM/Master Equation has been solved to calculate the pressure- and temperature-dependent rate coefficients for all channels in the pressure range of 0.01–100 atm over 300–2000 K. Pressure and temperature dependent branching fractions of key species produced from different pentan-2-ol radicals shows that 1- and 2-pentene are important bimolecular products. The kinetics and thermochemistry data for the title reactions has been used in the part II of this work for model development for pentan-2-ol oxidation. [ABSTRACT FROM AUTHOR]

Abstract High pressure oxidation of 3-pentanol is investigated in a jet-stirred reactor and in a shock tube. Experiments in the reactor were carried out at 10 atm, between 730 and 1180 K, for equivalence ratios of 0.35, 0.5, 1, 2, 4 and 1000 ppm fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were recorded using Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC). Ignition delay times were measured for 3-pentanol/O 2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1000–1470 K and for equivalence ratios of 0.5, 1 and 2. The fuel did not show any low-temperature reactivity under these conditions in neither experimental set-up and produced various aldehydes and ketones as well as the olefin 2-pentene as intermediates. A kinetic sub-mechanism is developed in order to represent the present data and analyze the reaction pathways. [ABSTRACT FROM AUTHOR]

Abstract The kinetics of propanal oxidation was studied in a jet-stirred reactor (JSR) at atmospheric pressure. The investigated temperature range is from 450 to 800 K at two different equivalence ratios (0.35 and 4.0). Thanks to the synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), critical intermediates were identified, including methylperoxy, methyl hydroperoxide, ethylperoxy, ethyl hydroperoxide, α-lactone, β-propiolactone and ketohydroperoxides. A kinetic model for propanal oxidation was also developed and validated against the present experimental results, as well as those available from the literature. Main chain-branching pathways under the investigated conditions were analyzed based on present experimental data and kinetic model. The O 2 addition reaction to the propanoyl radical and subsequent oxidation reactions play an important role in determining the oxidation rate of propanal under fuel-lean conditions, especially in the low-temperature oxidation region. Under fuel-rich conditions, the decomposition of the propanoyl radical is predominant and C 2 H 5 relevant reactions consequently determine the kinetics of oxidation of propanal. [ABSTRACT FROM AUTHOR]

Abstract A kinetic investigation was carried out in this work for an oxygenated fuel additive, 1,2-dimethoxyethane (1,2-DME) to reveal the oxidation chemistry responsible for its practical function as a cetane improver. Experiments were conducted for 1,2-DME/O 2 /N 2 mixtures with different equivalence ratios (0.5, 1.0 and 2.0) in a high-pressure (10 atm) jet-stirred reactor (JSR) facility over the temperature range of 450–1100 K. Species concentration evolutions with the temperature were monitored with on-line Fourier transform infrared (FTIR) spectrometry and off-line gas chromatography (GC). The technique of photoionization molecular-beam mass spectrometry (PI-MBMS) was combined with another JSR setup operated at near-atmospheric pressure (700 Torr), for the purpose of probing reactive intermediates from 1,2-DME oxidation. A kinetic model was constructed based on the "reaction classes" strategy, which could satisfactorily predict speciation measurements in the current work. Pronounced low-temperature reactivity of 1,2-DME was observed under all investigated conditions, and crucial intermediates like ketohydroperoxides were detected with the PI-MBMS. Some specificities of 1,2-DME oxidation were elucidated through further model interpretations. The double ether groups imbedded in the fuel molecule make hydrogen abstractions easier and meanwhile hinder the chain-terminating concerted eliminations, so the low-temperature reactivity starts at relatively low temperatures (compared to n-hexane for example). Chain-branching reaction sequences following the second O 2 additions proceed in the oxidizing mixtures, leading to the remarkable low-temperature reactivity of 1,2-DME which can be utilized as a cetane-improver. [ABSTRACT FROM AUTHOR]

Abstract In this study, the oxidation of propyl acetate (PA) was investigated experimentally in a jet-stirred reactor and theoretically by electronic structure calculations. Experiments were performed at 1 and 10 atm for three different equivalence ratios (φ = 0.5, 1, and 2) at each pressure. These experimental results show the strong influence of the molecular reaction yielding propene and acetic acid throughout the investigated temperature range (700–1250 K). In order to better understand the oxidation process of propyl acetate, a detailed kinetic mechanism consisting of 628 species involved in 3927 reversible reactions has been developed laying on previous works on esters oxidation and theoretical calculations performed in this study. These calculations compare well with the rate constant experimentally determined in our jet-stirred reactor for the molecular reaction: k = 1.292 × 10 13 exp (− 25167 T) (s − 1) (700–1010 K). [ABSTRACT FROM AUTHOR]

Abstract The first kinetic study of the oxidation of methyl levulinate is reported. Fuel-lean, stoichiometric and fuel-rich mixtures were oxidized at constant mean residence time (70 ms) and fuel concentration (1000 ppm), and variable temperature (740–1250 K) in a jet-stirred reactor at atmospheric pressure. A detailed kinetic reaction mechanism was proposed based on previous kinetic models for other oxygenated fuels and theoretical calculations. The model was tested successfully against new speciation data consisting of 16 species concentration profiles vs. temperature obtained by gas chromatography (detection by mass spectrometry, flame ionization, thermal conductivity) and Fourier transform infrared spectrometry after sonic probe sampling. Some discrepancies between modeling and experiments were observed for minor species. Reaction pathways and sensitivity analyses were used to interpret the results. This study indicates that for the fuel, under the present conditions, molecular elimination is an important reaction pathway competing with H-atom abstraction by radicals (mainly OH). [ABSTRACT FROM AUTHOR]

Understanding species evolution upon gasoline fuel oxidation can aid in mitigating harmful emissions and improving combustion efficiency. Experimentally measured speciation profiles are also important targets for surrogate fuel kinetic models. This work presents the low- and high-temperature oxidation of two alkane-rich FACE gasolines (A and C, Fuels for Advanced Combustion Engines) in a jet-stirred reactor at 10 bar and equivalence ratios from 0.5 to 2 by probe sampling combined with gas chromatography and Fourier Transformed Infrared Spectrometry analysis. Detailed speciation profiles as a function of temperature are presented and compared to understand the combustion chemistry of these two real fuels. Simulations were conducted using three surrogates (i.e., FGA2, FGC2, and FRF 84), which have similar physical and chemical properties as the two gasolines. The experimental results reveal that the reactivity and major product distributions of these two alkane-rich FACE fuels are very similar, indicating that they have similar global reactivity despite their different compositions. The simulation results using all the surrogates capture the two-stage oxidation behavior of the two FACE gasolines, but the extent of low temperature reactivity is over-predicted. The simulations were analyzed, with a focus on the n-heptane and n-butane sub-mechanisms, to help direct the future model development and surrogate fuel formulation strategies. [ABSTRACT FROM AUTHOR]

Two jet-stirred reactors (JSRs) coupled to gas chromatographic and spectroscopic techniques have been utilised to detect chemical species evolved during n -pentane oxidation at 1 and 10 atm, in the temperature range 500–1100 K, and at equivalence ratios of 0.3–2.0. To the authors’ knowledge, this is the first study of a fuel's oxidation in two JSRs. In addition, the choice of experimental conditions results in there being the same concentration of n -pentane in all investigated mixtures; 1% at 1 atm, and 0.1% at 10 atm. This permits the additional assessment of the importance of pressure-dependent kinetics in predicting species concentration profiles. A recently published literature model Bugler et al. (2016) served as the starting point in simulating these experiments, with only minor additions and modifications necessary to achieve good overall agreement. The main adjustments were made to account for multi-oxygenated species (C 5 aldehydes, ketones, diones, etc .) detected mainly at low temperatures (<800 K) in both JSRs. In this paper we present new experiments, the most important of which are very well predicted using the aforementioned literature model. The effect of adding chemical pathways, which have been postulated to contribute to the generation of multi-oxygenated species, has been investigated. Finally, a brief account on the importance of pressure-dependent kinetics in the modelling of these experiments is provided. [ABSTRACT FROM AUTHOR]

This study is concerned with the identification and quantification of species generated during the combustion of cyclopentane in a jet stirred reactor (JSR). Experiments were carried out for temperatures between 740 and 1250 K, equivalence ratios from 0.5 to 3.0, and at an operating pressure of 10 atm. The fuel concentration was kept at 0.1% and the residence time of the fuel/O 2 /N 2 mixture was maintained at 0.7 s. The reactant, product, and intermediate species concentration profiles were measured using gas chromatography and Fourier transform infrared spectroscopy. The concentration profiles of cyclopentane indicate inhibition of reactivity between 850–1000 K for φ = 2.0 and φ = 3.0. This behavior is interesting, as it has not been observed previously for other fuel molecules, cyclic or non-cyclic. A kinetic model including both low- and high-temperature reaction pathways was developed and used to simulate the JSR experiments. The pressure-dependent rate coefficients of all relevant reactions lying on the PES of cyclopentyl + O 2 , as well as the C–C and C–H scission reactions of the cyclopentyl radical were calculated at the UCCSD(T)-F12b/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory. The simulations reproduced the unique reactivity trend of cyclopentane and the measured concentration profiles of intermediate and product species. Sensitivity and reaction path analyses indicate that this reactivity trend may be attributed to differences in the reactivity of allyl radical at different conditions, and it is highly sensitive to the C–C/C–H scission branching ratio of the cyclopentyl radical decomposition. [ABSTRACT FROM AUTHOR]

There is current interest in utilizing oxygenated biofuels such as carbonates in blends with conventional oil-derived liquid fuels. Carbonates, commonly used as electrolyte solvents in Li-ion cells, could ignite after abusive operating conditions. Improving the kinetic modeling of the oxidation of these bio-derived oxygenates requires further investigation under well-controlled conditions. An experimental and detailed chemical kinetic modeling study of diethyl carbonate (DEC) oxidation and combustion was performed. Experiments were carried out in a jet stirred reactor over a wide range of equivalence ratios, temperatures, and pressure. Mole fractions of stable species were measured in the jet stirred reactor at atmospheric pressure. Burning velocities of DEC/air mixtures were determined at elevated temperature over a range of pressures and equivalence ratios. A detailed chemical kinetic modeling was performed using the present experimental results and existing literature data and model. The model represents fairly well the present data. Sensitivity and reaction paths analyses were used to rationalize the results. [ABSTRACT FROM AUTHOR]

There is increasing interest for utilizing synthetic biofuels in blends with conventional oil-derived liquid fuels. In this contest, research on the combustion of synthetic jet fuels has lately gained significance because they could help addressing sustainability and security of supply for air transportation. Improving the kinetic modeling of the oxidation of synthetic fuels requires further investigations under well-controlled conditions. The combustion of a 100% naphthenic cut fitting typical chemical composition of biomass or coal liquefaction products and a 50% vol. mixture with Gas to Liquid fuel were studied in a jet-stirred reactor (JSR) under the same conditions (550–1150 K, 10 bar, equivalence ratio of 0.5, 1, and 2, and 1000 ppm of fuel). For simulating the kinetics of oxidation of these fuels, model-fuels were designed to fit fuels chemical composition and properties. They consisted of mixtures of n-decane, 2-methylheptane, 3-methylheptane, n-propylcyclohexane, decahydronaphtalene, and tetrahydronaphtalene. The proposed detailed chemical kinetic reaction scheme was validated using the whole experimental data set acquired in the present work; for the oxidation of pure GtL, we used previous obtained data. For interpreting the results, reaction pathways and sensitivity analyses were used. [ABSTRACT FROM AUTHOR]

In this work, we studied the low-temperature oxidation of a stoichiometric 2-methylhexane/O 2 /Ar mixture in a jet-stirred reactor coupled with synchrotron vacuum ultraviolet photoionization molecular-beam mass spectrometry. The initial gas mixture was composed of 2% 2-methyhexane, 22% O 2 and 76% Ar and the pressure of the reactor was kept at 780 Torr. Low-temperature oxidation intermediates with two to five oxygen atoms were observed. The detection of C 7 H 14 O 5 and C 7 H 12 O 4 species suggests that a third O 2 addition process occurs in 2-methylhexane low-temperature oxidation. A detailed kinetic model was developed that describes the third O 2 addition and subsequent reactions leading to C 7 H 14 O 5 (keto-dihydroperoxide and dihydroperoxy cyclic ether) and C 7 H 12 O 4 (diketo-hydroperoxide and keto-hydroperoxy cyclic ether) species. The kinetics of the third O 2 addition reactions are discussed and model calculations were performed that reveal that third O 2 addition reactions promote 2-methylhexane auto-ignition at low temperatures. [ABSTRACT FROM AUTHOR]

The first speciation data regarding the oxidation of methyl ethyl ketone (MEK) are presented. Fuel-lean, stoichiometric and fuel-rich mixtures were studied at constant fuel concentration (1000 ppm) in a jet stirred reactor at atmospheric and high pressure (10 atm). A detailed kinetic mechanism is proposed based on theoretical calculations at the G3//MP2/aug-cc-pVDZ level of theory. The new rate constants differ substantially from the estimations employed in the previous MEK submechanism available in the literature, and impact MEK oxidation pathways. The model was tested successfully against these new speciation data and other available data (ignition delay times, flame speeds, pyrolysis species profile). However, some deficiencies in the model were identified concerning methyl ketene and methyl vinyl ketone. Reaction path analyses are used to interpret the results. [ABSTRACT FROM AUTHOR]

The homogeneous charge compression ignition (HCCI) engine is well known as an alternative engine which could replace conventional engines (spark ignition (SI) and combustion ignition (CI) engines) in order to meet pollutant requirements and reduce fuel consumption. However, controlling this kind of combustion remains difficult and represents a real challenge. The present investigation focussed on the use of different oxidizing chemical species (ozone, nitric oxide and nitrogen dioxide) which can modify the chemical kinetic governing HCCI combustion. Experiments were conducted on a single cylinder HCCI engine fuelled with iso-octane, for constant engine parameters and for oxidizing species concentrations varying from 0 up to 100 ppm. These experimental results are coupled with kinetic analyses in a homogeneous constant volume reactor performed with a detailed kinetic mechanism. The effects of ozone, nitric oxide and nitrogen dioxide were initially studied and compared when they separately seed the intake of the engine. Results showed that all the molecules improve HCCI iso-octane combustion. The highest effect on CA50 phasing was observed for ozone while the lowest was for nitrogen dioxide. These results were confirmed and explained by a kinetic interpretation. HCCI experiments were then carried out with ozone and nitric oxide injected together in the intake of the engine. Experimental results show a combustion enhancement when these two molecules are present but a delay in CA50 phasing was observed for low ozone concentrations and a constant nitric oxide concentration until the ozone concentration becomes higher. A kinetic interpretation, through two-step computations, showed that there is a strong oxidizing reaction between nitric oxide and ozone, yielding nitrogen dioxide. Therefore, the presence of nitrogen dioxide can explain the CA50 delay observed due to its low effect among all the oxidizing chemical species studied. [ABSTRACT FROM AUTHOR]

This study presents the first investigation on the combustion chemistry of n -octanol, a long chain alcohol. Ignition delay times were determined experimentally in a high-pressure shock tube, and stable species concentration profiles were obtained in a jet stirred reactor for a range of initial conditions. A detailed kinetic model was developed to describe the oxidation of n -octanol at both low and high temperatures, and the model shows good agreement with the present dataset. The fuel’s combustion characteristics are compared to those of n -alkanes and to short chain alcohols to illustrate the effects of the hydroxyl moiety and the carbon chain length on important combustion properties. Finally, the results are discussed in detail. [ABSTRACT FROM AUTHOR]

Butenes are intermediates ubiquitously formed by decomposition and oxidation of larger hydrocarbons (e.g. alkanes) or alcohols present in conventional or reformulated fuels. This study provides new complementary data for the oxidation of trans-2-butene. The oxidation of trans-2-butene was studied for measuring stable species concentration profiles during the oxidation of the fuel at atmospheric pressure, over a range of equivalence ratios (0.5 ⩽ φ ⩽ 2), and temperatures (900–1450 K). A combustion bomb apparatus was used to determine laminar flame velocities of trans-2-butene in air at 1 atm, 300 K, and for equivalence ratios of 0.8–1.4. The oxidation of trans-2-butene was simulated under these experimental conditions using an extended detail chemical kinetic reaction mechanism (201 species involved in 1788 reactions). This mechanism is based on a previously proposed scheme for the oxidation of hydrocarbons. Good agreement with experimental data presented in this article was obtained which significantly improves kinetic modeling ability. The structure of a trans-2-butene premixed low pressure flat flame recently published was also successfully modeled. Sensitivity and reaction pathways analyses were performed to get insights into the processes involved in the oxidation of trans-2-butene. [ABSTRACT FROM AUTHOR]

Abstract: The oxidation of n-butylbenzene was studied in a jet-stirred reactor (JSR) at 10atm in dilute conditions providing new experimental results over the low- and high-temperature range 550–1180K, and variable equivalence ratio (0.25⩽ φ ⩽1.5). They consisted of concentration profiles of the reactants, stable intermediates and final products, measured as a function of temperature, at a constant residence time of 1s, by sonic probe sampling followed by on-line GC–MS and off-line GC–TCD–FID and GC–MS analyses. The oxidation of n-butylbenzene in these conditions was modeled using a detailed chemical kinetic reaction mechanism (404 species and 2210 reactions, most of them reversible) deriving from a previous scheme proposed for the ignition, oxidation, and combustion of simple aromatics (benzene, toluene, styrene, n-propyl-benzene). Sensitivity analyses and reaction path analyses, based on rates of reaction, were used to interpret the results. The proposed kinetic scheme could also be used to represent literature data (plug-flow reactor oxidation of n-butylbenzene, ignition delays in a rapid compression machine (RCM), a low-pressure methane–oxygen–argon flame doped with n-butylbenzene), to confirm its validity. [ABSTRACT FROM AUTHOR]