24 research outputs found

    Étude experimentale et theorique des vitesses de flammes laminaires d'hydrocarbures

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    The laminar burning velocity is a key parameter in the combustion of hydrocarbons study. It plays an essential role in the combustion science area since it is used for the validation of numerical models, the design of burners or to predict potential flashback or blow off of the flame. The goal of the thesis was the study of laminar burning velocities of many hydrocarbons found in natural gases, gasolines or diesel fuels. This work includes an experimental part and a modeling part. The experimental part allowed the implementation of the literature database for different air/hydrocarbons mixtures. The experiments were performed with a new apparatus developed at LRGP (Laboratoire RĂ©actions et GĂ©nie des ProcĂ©dĂ©s) for the measurement of laminar burning velocities by the heat flux method thanks to a flat flame adiabatic burner. This method is based on balancing of the heat loss required for the flame stabilization by the convective heat flux from the burner surface to the flame front. The burner head is a thick perforated plate included in a plenum mixing chamber and the measurement of the radial distribution of the temperature is performed with a thermocouples series. This apparatus was first used at atmospheric pressure and several temperatures to measure laminar burning velocities of gaseous compounds (alkanes, alkenes, hydrogen-enriched or oxygen-enriched methane, natural gases, methane-ethane and methane-propane mixtures) and liquid compounds (alkanes, ethanol, commercial gasoline and model fuel with addition of ethanol or not, alkylcyclohexanes, alkylbenzĂšnes). The apparatus was then placed in a chamber in order to work under pressures theoretically up to 10 atm. Laminar burning velocities of two compounds were studied at room temperature and high pressure : a gaseous compound, methane, for pressures up to 6 atm and a liquid compound, n-pentane, for pressures up to 4 atm. A modelling study completed this work by using detailed kinetic models for the combustion of studied compounds. These models were tested by the simulation of experimental results previously obtained, in various equivalence ratio, temperature and pressure conditionsLa vitesse de flamme adiabatique est un paramĂštre clĂ© dans l'Ă©tude de la combustion d'hydrocarbures. Elle joue en effet un rĂŽle essentiel dans le domaine de la combustion, dans la mesure oĂč elle est utilisĂ©e pour valider des modĂšles numĂ©riques, pour construire des brĂ»leurs, ou encore pour prĂ©dire d'Ă©ventuels retours de flamme ou souffles de la flamme. Le but de cette thĂšse a Ă©tĂ© d'Ă©tudier les vitesses de flammes laminaires d'un grand nombre d'hydrocarbures prĂ©sents dans les gaz naturels, les essences et les gazoles. Ce travail comprend une partie expĂ©rimentale et une partie de modĂ©lisation. La partie expĂ©rimentale a permis d'enrichir les bases de donnĂ©es de la littĂ©rature pour diffĂ©rentes compositions de mĂ©langes air/hydrocarbures. Les travaux ont Ă©tĂ© effectuĂ©s sur un nouveau montage mis au point au LRGP (Laboratoire RĂ©actions et GĂ©nie des ProcĂ©dĂ©s) pour la mesure de vitesses de flammes laminaires par la mĂ©thode du flux de chaleur Ă  l'aide d'un brĂ»leur adiabatique Ă  flamme plate. Cette mĂ©thode est basĂ©e sur l'Ă©quilibre des pertes thermiques nĂ©cessaires pour stabiliser la flamme par le flux de chaleur convectif allant de la surface du brĂ»leur vers le front de flamme. Le brĂ»leur est constituĂ© d'une plaque perforĂ©e montĂ©e sur une chambre de mĂ©lange des gaz et la mesure de la distribution radiale de la tempĂ©rature est rĂ©alisĂ©e grĂące Ă  une sĂ©rie de thermocouples. Ce montage a d'abord Ă©tĂ© utilisĂ© Ă  pression atmosphĂ©rique et plusieurs tempĂ©ratures pour la mesure de vitesses de flammes de composĂ©s gazeux (alcanes, alcĂšnes, mĂ©thane enrichi en hydrogĂšne ou oxygĂšne, gaz naturels, mĂ©langes mĂ©thane-Ă©thane et mĂ©thane-propane) et de composĂ©s liquides (alcanes, Ă©thanol, essences commerciale et modĂšle additionnĂ©es ou non d'Ă©thanol, alkylcyclohexanes, alkylbenzĂšnes). Le montage a ensuite Ă©tĂ© placĂ© dans une enceinte pour pouvoir travailler avec des pressions pouvant thĂ©oriquement aller jusqu'Ă  10 atm. Les vitesses de flammes de deux composĂ©s ont Ă©tĂ© Ă©tudiĂ©es Ă  tempĂ©rature ambiante et Ă  haute pression : un composĂ© gazeux, le mĂ©thane, jusqu'Ă  une pression de 6 atm et un composĂ© liquide, le n-pentane, jusqu'Ă  une pression de 4 atm. Une Ă©tude de modĂ©lisation a complĂ©tĂ© ce travail par l'utilisation de modĂšles cinĂ©tiques dĂ©taillĂ©s pour la combustion des composĂ©s Ă©tudiĂ©s. Ces modĂšles ont Ă©tĂ© testĂ©s par la simulation des rĂ©sultats expĂ©rimentaux prĂ©cĂ©demment obtenus, dans des conditions de richesse, tempĂ©rature et pression variĂ©e

    Experimental and theoretical study of laminar burning velocities of hydrocarbons

    No full text
    La vitesse de flamme adiabatique est un paramĂštre clĂ© dans l'Ă©tude de la combustion d'hydrocarbures. Elle joue en effet un rĂŽle essentiel dans le domaine de la combustion, dans la mesure oĂč elle est utilisĂ©e pour valider des modĂšles numĂ©riques, pour construire des brĂ»leurs, ou encore pour prĂ©dire d'Ă©ventuels retours de flamme ou souffles de la flamme. Le but de cette thĂšse a Ă©tĂ© d'Ă©tudier les vitesses de flammes laminaires d'un grand nombre d'hydrocarbures prĂ©sents dans les gaz naturels, les essences et les gazoles. Ce travail comprend une partie expĂ©rimentale et une partie de modĂ©lisation. La partie expĂ©rimentale a permis d'enrichir les bases de donnĂ©es de la littĂ©rature pour diffĂ©rentes compositions de mĂ©langes air/hydrocarbures. Les travaux ont Ă©tĂ© effectuĂ©s sur un nouveau montage mis au point au LRGP (Laboratoire RĂ©actions et GĂ©nie des ProcĂ©dĂ©s) pour la mesure de vitesses de flammes laminaires par la mĂ©thode du flux de chaleur Ă  l'aide d'un brĂ»leur adiabatique Ă  flamme plate. Cette mĂ©thode est basĂ©e sur l'Ă©quilibre des pertes thermiques nĂ©cessaires pour stabiliser la flamme par le flux de chaleur convectif allant de la surface du brĂ»leur vers le front de flamme. Le brĂ»leur est constituĂ© d'une plaque perforĂ©e montĂ©e sur une chambre de mĂ©lange des gaz et la mesure de la distribution radiale de la tempĂ©rature est rĂ©alisĂ©e grĂące Ă  une sĂ©rie de thermocouples. Ce montage a d'abord Ă©tĂ© utilisĂ© Ă  pression atmosphĂ©rique et plusieurs tempĂ©ratures pour la mesure de vitesses de flammes de composĂ©s gazeux (alcanes, alcĂšnes, mĂ©thane enrichi en hydrogĂšne ou oxygĂšne, gaz naturels, mĂ©langes mĂ©thane-Ă©thane et mĂ©thane-propane) et de composĂ©s liquides (alcanes, Ă©thanol, essences commerciale et modĂšle additionnĂ©es ou non d'Ă©thanol, alkylcyclohexanes, alkylbenzĂšnes). Le montage a ensuite Ă©tĂ© placĂ© dans une enceinte pour pouvoir travailler avec des pressions pouvant thĂ©oriquement aller jusqu'Ă  10 atm. Les vitesses de flammes de deux composĂ©s ont Ă©tĂ© Ă©tudiĂ©es Ă  tempĂ©rature ambiante et Ă  haute pression : un composĂ© gazeux, le mĂ©thane, jusqu'Ă  une pression de 6 atm et un composĂ© liquide, le n-pentane, jusqu'Ă  une pression de 4 atm. Une Ă©tude de modĂ©lisation a complĂ©tĂ© ce travail par l'utilisation de modĂšles cinĂ©tiques dĂ©taillĂ©s pour la combustion des composĂ©s Ă©tudiĂ©s. Ces modĂšles ont Ă©tĂ© testĂ©s par la simulation des rĂ©sultats expĂ©rimentaux prĂ©cĂ©demment obtenus, dans des conditions de richesse, tempĂ©rature et pression variĂ©esThe laminar burning velocity is a key parameter in the combustion of hydrocarbons study. It plays an essential role in the combustion science area since it is used for the validation of numerical models, the design of burners or to predict potential flashback or blow off of the flame. The goal of the thesis was the study of laminar burning velocities of many hydrocarbons found in natural gases, gasolines or diesel fuels. This work includes an experimental part and a modeling part. The experimental part allowed the implementation of the literature database for different air/hydrocarbons mixtures. The experiments were performed with a new apparatus developed at LRGP (Laboratoire RĂ©actions et GĂ©nie des ProcĂ©dĂ©s) for the measurement of laminar burning velocities by the heat flux method thanks to a flat flame adiabatic burner. This method is based on balancing of the heat loss required for the flame stabilization by the convective heat flux from the burner surface to the flame front. The burner head is a thick perforated plate included in a plenum mixing chamber and the measurement of the radial distribution of the temperature is performed with a thermocouples series. This apparatus was first used at atmospheric pressure and several temperatures to measure laminar burning velocities of gaseous compounds (alkanes, alkenes, hydrogen-enriched or oxygen-enriched methane, natural gases, methane-ethane and methane-propane mixtures) and liquid compounds (alkanes, ethanol, commercial gasoline and model fuel with addition of ethanol or not, alkylcyclohexanes, alkylbenzĂšnes). The apparatus was then placed in a chamber in order to work under pressures theoretically up to 10 atm. Laminar burning velocities of two compounds were studied at room temperature and high pressure : a gaseous compound, methane, for pressures up to 6 atm and a liquid compound, n-pentane, for pressures up to 4 atm. A modelling study completed this work by using detailed kinetic models for the combustion of studied compounds. These models were tested by the simulation of experimental results previously obtained, in various equivalence ratio, temperature and pressure condition

    Experimental and modeling study of burning velocities for alkyl aromatic components relevant to diesel fuels

    No full text
    International audienceAromatic species represent a significant fraction (about one third by weight) of both diesel and gasoline fuels. Much of the aromatics in diesel and gasoline are alkyl-benzene species. Although toluene, the lightest of the alkyl-benzenes, has been the subject of extensive literature investigations, very little experimental data are available for heavier alkyl-benzenes (9–20 carbon atoms) relevant to diesel fuel. In this work, the burning velocity of ethyl-, n-propyl-and n-butyl-benzenes were measured in a premixed flat-flame burner using the heat flux method. The burning velocities were measured as a function of the equivalence ratio at atmospheric pressure and for two unburned gas temperatures (358 and 398 K). These new experiments are compared with burning velocities for toluene previously measured by the authors. The comparisons showed that ethyl-benzene has the highest flame speed, followed by n-propyl-and n-butyl-benzenes which have similar burning velocities. Toluene has the lowest flame speed. Excellent agreement was observed between the new measurements and simulations using a mechanism for alkyl-benzenes recently published by Lawrence Livermore National Laboratory (LLNL) and National University of Ireland. Based on the strong correlation between experiments and calculations, different aspects contributing to the burning speed of the fuels (thermal effects, kinetics, 
) were analyzed using the model. A sensitivity analysis was used to determine the reaction rate constants that are most important in determining the flame speed. Reaction path analysis and species profiles in the flame were used to identify the key reaction paths that lead to increase or decrease in the burning velocities. Contrary to what is generally observed for alkanes whose flame speed is controlled by small radical fragments, the flame speed of aromatics is influenced by fuel specific intermediates such as phenyl, benzyl, or even heavier species. The new experimental data and modeling insight generated by this work will support the development of models for heavier alkyl-aromatics of great relevance to diesel fuel

    Measurements of Laminar Flame Velocity for Components of Natural Gas

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    This paper presents new experimental measurements of the laminar flame velocity of components of natural gas, methane, ethane, propane, and n-butane as well as of binary and tertiary mixtures of these compounds proposed as surrogates for natural gas. These measurements have been performed by the heat flux method using a newly built flat flame adiabatic burner at atmospheric pressure. The composition of the investigated air/hydrocarbon mixtures covers a wide range of equivalence ratios, from 0.6 to 2.1, for which it is possible to sufficiently stabilize the flame. Other measurements involving the enrichment of methane by hydrogen (up to 68%) and the enrichment of air by oxygen (oxycombustion techniques) were also performed. Both empirical correlations and a detailed chemical mechanism have been proposed, the predictions being satisfactorily compared with the newly obtained experimental data under a wide range of conditions

    Measurements of Laminar Burning Velocities above Atmospheric Pressure Using the Heat Flux MethodApplication to the Case of <i>n-</i>Pentane

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    A new adiabatic burner allowing the measurement of burning velocities at high pressure with the heat flux method has been developed. Experimental measurements of laminar burning velocities of methane and <i>n-</i>pentane were performed for pressures up to 6 atm at 298 K and at atmospheric pressure for temperatures from 298 to 398 K. Equivalence ratios varied from 0.6 to 1.9. The results for methane flames are in good agreement with the only results of literature obtained above atmospheric pressure using the heat flux method; those for <i>n-</i>pentane are to our knowledge the first application of this method to a flame of a liquid fuel above atmospheric pressure. Based on these measurements, empirical correlations of the variation of the measured laminar flame velocities with pressure and temperature have been proposed for methane and <i>n-</i>pentane. In the case of methane, these correlations lead to a satisfactory prediction of literature measurements made using constant volume bombs
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