Michel Cathonnet

A WIDE RANGE MODELING STUDY OF DIMETHYL ETHER OXIDATION

A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 1.0 and 650 :5 T :5 1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME. These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g. the primary reference fuels, n-heptane and iso- octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM.

A jet-stirred reactor for kinetic studies of homogeneous gas-phase reactions at pressures up to ten atmospheres (≈1 MPa)

An homogeneous stirred reactor designed for kinetic studies of hydrocarbon oxidation in the intermediate temperature range is described. The originality of this reactor lies in its ability to operate under pressure up to 10 atm ( approximately 1 MPa). The design of the injectors makes it possible to move a thermocouple and a sampling probe throughout a whole diameter of the reactor.

High Pressure Oxidation of Liquid Fuels From Low to High Temperature. 1. n-Heptane and iso-Octane.

Abstract Abstract–Normal heptane and iso-octane oxidations in a high-pressure jet-stirred reactor have been investigated experimentally in a wide range of conditions covering the low and high temperature oxidation regimes (550· 1150K, 10atm, 0.3 ≪Φ ≪ 1.5). Reactants, intermediates and final products have been measured providing a useful picture of n-heptane oxidation. The relatively high level of oxygenated compounds formed in the low temperature oxidation regime of n-heptane contrasts with the results obtained during iso-octane oxidation in the same conditions. The results are interpreted in terms of knocking and non-knocking tendencies related to fuel structure and low temperature oxidation mechanism.

Experimental study of the oxidation of n-heptane in a jet stirred reactor from low to high temperature and pressures up to 40 atm

Abstract Normal heptane oxidation in a high-pressure jet-stirred reactor has been investigated experimentally in a wide range of conditions covering the low- and high-temperature oxidation regimes (550–1150 K, 1–40 atm, φ = 1). Reactants, intermediates, and final products have been measured in three different oxidation regimes, namely cool flame, negative temperature coefficient, and normal combustion. Concentration profiles of the major cyclic ethers formed at low temperature have been measured. The evolution of the transition from low to high temperature oxidation regime as a function of pressure was observed showing the quasi-disappearance of the negative temperature coefficient at 40 atm. The results are interpreted in terms of reaction mechanism.

The oxidation and ignition of dimethylether from low to high temperature (500–1600 K): Experiments and kinetic modeling

The oxidation of dimethylether (DME) has been studied in a fused silica jet-stirred reactor (JSR) at 10 atm, 0.2≤φ≤1, 550–1100 K. Concentration profiles of reactants, intermediates, and products of the oxidation were measured by low-pressure sonic probe sampling and off-line gas chromatography analyses. The results obtained in the cool flame regime are the first to be reported. The ignition delays of DME/O2/Ar mixtures have been measured in a shock tube at 1200 to 1600 K, at 3.5 atm and 0.5≤φ≤2. A numerical model consisting of a detailed kinetic reaction mechanism with 331 reactions (most of them reversible) among 55 species is proposed to describe both the low and high-temperature oxidation of DME in the JSR (550–1275 K, 1–10 atm) and the ignition of DME in shock tubes from low to high temperature (650–1600 K, 3.5–40 bar). A general good agreement between the data and the model was observed. A kinetic analysis involving sensitivity and reaction path analysis is used to interpret the results.

Kerosene combustion at pressures up to 40 atm: Experimental study and detailed chemical kinetic modeling

The oxidation of TR0 kerosene (jet A1 aviation fuel) was studied in a jet-stirred reactor (JSR) at pressures extending from 10 to 40 atm, in the temperature range 750–1150 K. A large number of reaction intermediates were identified, and their concentrations were followed for reaction yields ranging from low conversion to the formation of the final products. A reference hydrocarbon, n-decane, studied under the same experimental conditions gave very similar experimental concentration profiles for the main oxidation products. Because of the strong analogy between n-decane and kerosene oxidation kinetics, a detailed chemicalkinetic reaction mechanism describing the oxidation of n-decane was built to reproduce the present experimental results. This mechanism includes 573 elementary reactions, most of them being reversible, among 90 chemical species. A reasonably good prediction of the concentrations of major species was obtained by computation, covering the whole range of temperatures, pressures, and equivalence ratios of the experiments. A kinetic analysis performed to identify the dominant reaction steps of the mechanism shows that, underthe conditions of the present study (intermediate temperature and high pressure), HO2 radicals are important chain carriers leading to the formation of the branching agent H2O2.

Chemical kinetic study of dimethylether oxidation in a jet stirred reactor from 1 to 10 ATM: Experiments and kinetic modeling

The oxidation of dimethyl ether (DME) has been studied in a jet-stirred reactor (JSR). The experiments cover a wide range of conditions: 1–10 atm, 0.2≤≤2.0, 800–1300 K. Concentration profiles of reactants, internediates, and products of the oxidation of DME were measured in a fused silica JSR by low-pressure, sonic-probe sampling and off-line gas chromatography analyses. These results represent the first detailed kinetic study of DME oxidation in a reactor. They demonstrate that the oxidation of DME does not yield higher molecular weight compounds. A numerical model consisting of a detailed kinetic-reaction mechanism with 286 reactions (most of them reversible) among 43 species describes DME oxidation in a JSR. A generally good agreement between the data and the model was observed. The kinetic modeling is used to interpret the data.

Methane Oxidation: Experimental and Kinetic Modeling Study

Abstract Methane oxidation in jet-stirred reactor has been investigated at high temperature (900–1300 K) in the pressure range 1–10 atm. Molecular species (H2, CO, C02, CH4. C2,H2, C2H4, C2,H6) concentration profiles were obtained by probe sampling and GC analysis. Methane oxidation was modeled using a detailed kinetic reaction mechanism including the most recent kinetic findings concerning the reactions involved in the oxidation of C1,-C4 hydrocarbons. The proposed mechanism is able to reproduce experimental data obtained in our high-pressure jet stirred reactor and ignition delay times measured in shock tube in the pressure range 1–13 atm, for temperatures extending from 900 to 2000 K and equivalence ratios of 0.1 to 2. It is able to correctly reproduce H and O atoms concentrations measured in shock tube at ≈ 2 atm at 1850–2500 K. The same kinetic mechanism can also be used to model the oxidation of ethylene, ethane, propyne and allene in various conditions.

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.

Kinetic Modeling of Propane Oxidation

Abstract The oxidation of propane was studied in a jet-stirred flow reactor in the temperature range 900-1200 K at pressure s extending from 1 to 10 atrn for a wide range of fuel-oxygen equivalence ratios (0.15 to 4.0), A comput er program has been developed to model the experimental data using a chemical kinetic reaction mechan ism. A direct method to determine the first orde r sensitivities of the mole fraction of each species with respect to the rate constants was used to develop the kinetic scheme. The present chemical kinetic reaction mechanism is able to reproduce our experimental results, although some discrepanci es are observed for the minor products, particularly for acetylene. The validation of the present mechanism is extended to higher temperatures, in order to describe the oxidation of propane in shock tubes. The experimental ignition delays obtained behind reflected shock waves, by various authors, are compared with the pred ictions of the model. Good agreement is found in the temperature r...