P. Dagaut

Detailed Kinetic Reaction Mechanism for Cyclohexane Oxidation at Pressure up to ten Atmospheres

A detailed reaction mechanism for cyclohexane oxidation has been evaluated by comparison of computed and experimental species mole fraction profiles measured in a jet-stirred reactor at 0.5≤≤1.5 and 1, 2, and 10 atm. Major and minor species mole fractions were obtained by gas chromatography: O2, CO, CO2, H2, CH2O, CH3HCO, acrolein, CH4, C2H6, C2H4, C3H6, C2H2, allene, 1-C4H8, 2-C4H8 (trans and cis), 1.3-C4H6, cyclopentene, cyclohexadiene, 1-hexene, cyclohexene, and C6H6. The main objective of this work was to extend the validity of a previously proposed mechanism for cyclohexane oxidation at 10 atm to lower pressure and to refine it by taking into account some new species analyzed in this work: 1-C4H8, 2-C4H8 (trans and cis), and aC6H12. Good agreement was obtained for most molecular species, especially intermediate olefins, dienes, and oxygenated species (CH2O, acrolein). Computed benzene, cyclopentene, and cyclohexene concentrations are also in reasonable agreement with experimental data. The mechanism also was validated at higher temperature by modeling the laminar flame speeds of cyclohexane/air flames measured by Davis and Law in a wide range of equivalence ratios. The model correctly reproduces experimental values. Reaction path analyses were used to interpret the results.

SHORT COMMUNICATION High Pressure Oxidation of Liquid Fuels from Low to High Temperature. 3.n-Decane

Abstract The oxidation of n-decane in a high-pressure jet-stirred reactor (JSR) has been investigated experimentally in a wide range of conditions covering the low and high temperature oxidation regimes (550-1150K, lOatm, O = 0.1 to 1.5), Reactants, intermediates and final products have been measured providing a detailed picture of n-decane oxidation. Cyclic ethers resulting from the so-called Iwo-temperature oxidation chemistry of n-decane were identified. The results are interpreted in terms of reaction mechanism. A detailed chemical kinetic modeling of the high-temperature oxidation of n-decane is used to assess the influence of low temperature chemistry in the intermediate temperature range.

Benzene Oxidation: Experimental Results in a JDR and Comprehensive Kinetic Modeling in JSR, Shock-Tube and Flame

New experimental results have been obtained for the oxidation of benzene in a jet-stirred reactor at high temperature (950–1350 K) at atmospheric pressure and variable equivalence ratio (0·3≤ 0 ≤1·5). Molecular species concentration profiles of reactants, stable intermediates and final products were obtained by probe sampling followed by on-line and off-line GC analyses. The oxidation of benzene in these conditions was modeled using a detailed kinetic reaction mechanism (120 species and 921 reactions, most of them reversible). The proposed mechanism was also used to simulate the oxidation of benzene at low pressure (0·46 atm) and high pressure in stirred reactor conditions. The burning velocities of benzene-air mixtures were well-predicted by the proposed kinetic scheme that was also used to simulate the MBMS results of Bittner and Howard obtained for a fuel-rich benzene-oxygen-argon premixed flame. The ignition delays of benzene-oxygen-argon mixtures measured by Burcat over the range of equivalence ratios 0·25–2 were modeled. Sensitivity analyses and reaction path analyses, based on species rates of reaction, were used to interpret the results. The routes involved in benzene oxidation have been delineated and are presented in the paper.

Acetaldehyde Oxidation in a JSR and Ignition in Shock Waves: Experimental and Comprehensive Kinetic Modeling

ABSTRACT Acetaldehyde oxidation in a jet-stirred reactor has been investigated at high temperature (∼900-1300 K) in the pressure range l-10atm. Molecular species concentration profiles of O0, H2, CO, CO2, CH2O, CH4, C2H2, C2H4, C2H6, C3H6, and CH3HCO were obtained by probe sampling and GC analysis. Acetaldehyde ignition in shock waves has been investigated in a wide range of conditions (0.5 ≤ φ ≤,2, 1230-2530 K., 2-5 aim), and ignition delay times have been measured. Acetaldehyde oxidation in these conditions was modeled using a comprehensive kinetic reaction mechanism. The proposed mechanism is able to reproduce experimental data obtained in our high-pressure jet stirred reactor and ignition delays measured in shock tube. The same mechanism has also been validated for the oxidation of CH4,C2H2, C2H4, C2H6, C3H6, C3H8, 1-butene, n-butane, mixtures of CH4 with C2H6 and/or C3H8 in the same conditions.

The Oxidation of N-Propylcyclohexane: Experimental Results and Kinetic Modeling

Abstract The oxidation of n-propylcyclohexane has been studied in a jet-stirred reactor at atmospheric pressure. New experimental results have been obtained over the high temperature range 950-1250 K, and variable equivalence ratio (0.5< φ<1.5). Concentration profiles of reactants, stable intermediates and final products were obtained by probe sampling followed by on-line and off-line GC analyses. The oxidation of n-propylcyclohexane in these conditions was modeled using a detailed kinetic reaction mechanism (176 species and 1369 reactions, most of them reversible). Sensitivity analyses and reaction path analyses, based on species rates of reaction, were used to interpret the results. The routes involved in n-propylcyclohexane have been delineated: n-propylcyclohexane oxidation proceeds via H-atom abstraction forming seven distinct propyl-cyclohexyl radicals that react by p-scission yielding ethylene, propene, methylene-cyclohexane, cyclohexene, and 1-pentene. Further reactions of these intermediates yields the other products measured in this study.

Experimental Study of the Oxidation of N-Tetradecane in a Jet-Stirred Reactor (JSR) and Detailed Chemical Kinetic Modeling

The kinetics of oxidation of n-tetradecane was studied experimentally in a jet-stirred reactor (JSR) at high pressure (10 atm), at temperatures ranging from 560 to 1030 K, at a constant residence time (τ) of 1 s, and for three equivalence ratios (φ = 0.5, 1.0, and 2.0). Chemical analyses by Fourier transform infrared spectrometry and gas chromatography yielded mole fractions of reactants, stable intermediates, and final products as a function of temperature. A kinetic reaction mechanism based on previous studies from this laboratory was developed and validated by comparison with the present experimental results. The proposed reaction mechanism consisted of 7,885 reversible reactions involving 1,813 species. Experimental data and simulation results obtained in the current work were found in good agreement. Ignition delays of n-tetradecane/air mixtures were also simulated.

Synthetic Jet Fuel Combustion: Experimental and Kinetic Modeling Study

Fischer-Tropsch liquid fuels synthesized from syngas, also called synthetic paraffinic jet fuel (SPK), can be used to replace conventional petroleum-derived fuels in jet engines. Whereas currently syngas is mostly produced from coal of natural gas, its production from biomass has been reported. These synthetic liquid fuels contain a very high fraction of iso-alkanes, while conventional jet fuels contain large fractions of n-alkanes, cycloalkanes (naphtenes), and aromatics. In that contest, a jet-stirred reactor (JSR) was used to study the kinetics of oxidation of a 100% SPK and a 50/50 SPK/Jet A-1mixture over a broad range of experimental conditions (10 atm, 560 to 1030K, equivalence ratios of 0.5 to 2, 1000 ppm of fuel). The temperature was varied step-wise, keeping the mean residence time in the JSR constant and equal to 1s. Three combustion regimes were observed over this temperature range: the cool-flame oxidation regime (560–740K), the negative temperature coefficient (NTC) regime (660–740K), and the high-temperature oxidation regime (>740K). More than 15 species were identified and measured by Fourier transform infrared spectrometry (FTIR), gas chromatography/mass spectrometry (CG/MS), flame ionization detection (FID), and thermal conductivity detection (TCD). The results consisting of concentration profiles of reactants, stable intermediates and products as a function of temperature showed similar kinetics of oxidation for the fuels considered, although the 100% SPK was more reactive. A surrogate detailed chemical kinetic reaction mechanism was used to model these experiments and ignition experiments taken from the literature. The kinetic modeling showed reasonable agreement between the data and the computations whereas model improvements could be achieved using more appropriate surrogate model fuels. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results.Copyright