Marcelline Reuillon

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.

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.

Experimental and Kinetic Modeling Study of Cyclohexane Oxidation in a JSR at High Pressure

Cyclohexane oxidation has been studied in a jet-stirred reactor in the temperature range of 750 to 1100 K. at 10 atm. Major and minor species profiles have been obtained by probe sampling and GC analysis. A chemical kinetic reaction mechanism developed from previous studies on smaller hydrocarbons is used to reproduced the experimental data. It has been updated and validated for CI to C5 submechanisms. Good agreement is obtained between computed and measured mole fractions. The major reaction paths of cyclohexane consumption and the formation and the consumption routes of the main products have been identified for our experimental conditions.

Experimental and computational investigation of the structure of a sooting C2H2-O2-Ar flame

Mole fraction profiles have been measured by molecular beam-mass spectrometer technique in a sooting C2H2-O2-Ar flame (27.5%-27.5%-45%) stabilized under reduced pressure (2.6 kPa) on a flat flame burner. Emphasis was put on the detection and concentration measurement of the intermediate species which play a role in the formation of the first aromatic rings. In addition to the major products and the radicals usually involved in acetylene oxidation mechanisms, C2H, C2H3, C3, C4 species and benzene have been measured. The mole fraction profiles have been compared with predictions from a simulation model. Care was taken to use as much as possible a detailed mechanism known to model acetylene oxidation in a wide range of experimental conditions. The mechanism proposed by Warnatz23, for the oxidation of alkanes and recently checked by Westmoreland38 for the modelling of a rich C2H2/O2 flame was adopted as a starting point. This tested mechanism was complemented by formation and consumption reactions for C4H3, C4H4, C4H5 and benzene. The satisfactory agreement between calculated and measured profiles was turned to account to specify the main steps in the route to benzene.

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.

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.

REDUCTION OF LARGE DETAILED KINETIC MECHANISMS: APPLICATION TO KEROSENE/AIR COMBUSTION

Reduction of a large detailed mechanism for kerosene, including 225 species and 3493 irreversible reactions, was executed over a wide range of parametric conditions. Numerical simulations were tested for a perfectly stirred reactor with four pressures (0.5, 1.0, 3.0, and 10.0 bar), six equivalence ratios (0.5–2.0), and six inlet temperatures (from 300 to 1800 K). The reduction process was carried out with an improved and adapted method including three different stages. First, atomic flux analysis eliminates 91 useless species and their 1361 corresponding reactions. This skeletal mechanism is squeezed again by removing the remaining redundant reactions with the principal component analysis method. A new skeletal mechanism including 134 species and 1220 reactions is obtained. The ultimate step of the reduction process consists of decreasing computational time by using the quasi-steady-state approximation for species with a short lifetime. A convergence accelerator reduces the number of iterations necessary to solve the algebraic system. Two reduced schemes including 33 and 40 differential species were achieved: they present a good compromise between predictive qualities (from 68 to 75% of species are reproduced with an error level lower than 10%) and calculation speedup (average computational time savings of a factor of 5.3 to 4.8 are obtained between reduced and initial detailed mechanisms).

Formation of Aromatic Hydrocarbons in Decane and Kerosene Flames at Reduced Pressure

The formation of frequently discussed soot precursors has been compared in decane and kerosene flames. A specific study on the influence of equivalence ratio on the formation of some species (acetylene, benzene, vinyl benzene and phenyl acetylene) showed that in decane flames aromatic hydrocarbons are formed from acetylene whereas in kerosene flames the main source is the aromatic part of the fuel. From this result it seems to be reasonable to represent kerosene as a mixture of decane (90%) and toluene (10%) when developing a detailed kinetic mechanism to predict benzene formation in flames burning kerosene. The mechanism was checked by comparison of computed mole fraction profiles with measured profiles of a sooting kerosene-oxygen-argon flame with an equivalence ratio of 2.2 and of a decane flame with the same equivalence ratio.