Pascal DIEVART | ENSTA ParisTech (original) (raw)
Papers by Pascal DIEVART
Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
ABSTRACT The rapid growth of eco-friendly biomass derived fuels in transportation requires a fund... more ABSTRACT The rapid growth of eco-friendly biomass derived fuels in transportation requires a fundamental understanding of the uniqueness of their oxidation and combustion characteristics. This paper focuses on one specific class of biofuels, namely Fatty Acids Ethyl Esters (FAEE). A counterflow configuration was employed to measure the extinction limits of the diffusion flames of four ethyl esters (ethyl-butanoate, pentanoate, heptanoate, and nonanoate). The results were compared to that of methyl esters (Diévart et al., 2012, Proceedings of the Combustion Institute, 34). It was observed that both methyl esters and ethyl esters exhibit similar high temperature reactivity against extinction. The use of the transport-weighted enthalpy metric has revealed that all esters share similar chemical kinetics in the near extinction conditions of the present study. A previous detailed kinetic model has been extended to include the oxidation chemistry of ethyl esters, and used to interpret the experimental observations. Good agreement between the computed and experimental extinction limits was observed. The rates of consumption pathway analysis have shown that ethyl esters exclusively decomposed into ethylene and a carboxylic acid through an endothermic six-centered unimolecular decomposition reaction, while methyl esters oxidation preferentially progresses through H abstraction reactions. However, the growth of the radical pool was observed to be driven indifferently between ethyl and methyl esters, therefore resulting in similar global flame reactivity.
Proceedings of the Combustion Institute, 2015
ABSTRACT As two of the most important species that characterize hydrocarbon low temperature ignit... more ABSTRACT As two of the most important species that characterize hydrocarbon low temperature ignition, HO2 and H2O2 formation during dimethyl ether (DME) oxidation was quantified using the same experimental conditions, for the first time, in an atmospheric flow reactor at low and intermediate temperature range. Dual-Modulation Faraday Rotation Spectroscopy (DM-FRS) and Molecular Beam Mass Spectrometry (MBMS) were used to measure HO2 and H2O2 respectively. DME and other important intermediate species such as CH2O and CO are also measured by MBMS between 400 and 1150 K at different fuel concentrations. Species profiles in the reactor were calculated by using both zero- and two-dimensional computations with different detailed kinetics for cross-validation and comparison with experimental results. The models predict adequately the low and intermediate oxidation temperature windows near 600 and 1000 K, respectively. However, both models over-predicted the DME consumption as well as CO, HO2 and H2O2 formations at the low temperature oxidation window by more than a factor of four. Moreover, although the model predicted reasonably well the formation of CH2O and CO/CO2 at the intermediate temperature oxidation window, the concentration of H2O2 was also over-predicted, suggesting the large uncertainties existing in the DME low temperature chemistry and in H2O2 chemistry at intermediate temperature. Furthermore, to analyze the uncertainty of the low temperature chemistry, a branching ratio of QOOH decomposition to CH2O was derived using measured DME, CH2O and CO concentrations. The large difference between the modeled and measured branching ratios of QOOH decomposition suggests an underestimated QOOH decomposition rate to form CH2O in the current DME models.
Energy & Fuels, 2014
ABSTRACT
Proceedings of the Combustion Institute, 2015
ABSTRACT A novel method to establish self-sustaining cool diffusion flames with well-defined boun... more ABSTRACT A novel method to establish self-sustaining cool diffusion flames with well-defined boundary conditions is experimentally demonstrated by adding ozone to the oxidizer stream in counterflow configuration. It is found that the atomic oxygen produced through the decomposition of ozone dramatically shortens the induction timescale of the low temperature chemistry, extending the flammable region of cool flames. Thus, it enables the establishment of self-sustaining cool flames at the pressure and timescales at which normal cool flames may not be observable. The present method, for the first time, provides an opportunity to study cool flame dynamics, structure, and chemistry simultaneously in well-known flame geometry. Extinction limits of n-heptane/oxygen cool diffusion flames are measured and a cool diffusion flame diagram is experimentally determined. Numerical simulations reveal that the extinction limits of cool diffusion flames are strongly governed by species transport and low temperature chemistry activated by ozone decomposition. The structure of cool diffusion flame is further investigated by measuring the temperature and species distributions with a micro-probe sampling technique. The kinetic model over-predicts the rate of n-heptane oxidation, the heat release rate, and the flame temperature. Measurements of intermediate species, such as CH2O, acetaldehyde, C2H4, and CH4, suggest that the model over-predicts the QOOH thermal decomposition reactions to form olefins, resulting in substantial over-estimation of C2H4, and CH4 concentrations. The new method and data of the present study will contribute to promote understandings of cool flame chemistry.
The journal of physical chemistry. A, Jan 19, 2015
In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxyme... more In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl. CH2-O-CH2-O- (1,3-dioxetane), CH3OOH ...
Volume 3A: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration, 2014
Research activities on the combustion of synthetic jet fuels and bioderived jet fuels have increa... more Research activities on the combustion of synthetic jet fuels and bioderived jet fuels have increased notably over the last 10 yr in order to solve the challenging reduction of dependence of air transportation on petroleum. Within the European Community's Seventh Framework Programme, the combustion of a 100% GtL from Shell and a 80/20% vol. GtL/1-hexanol blend were studied in a jet-stirred reactor (JSR). This synthetic GtL fuel mainly contains n-alkanes, iso-alkanes, and cyclo-alkanes. We studied the oxidation of these alternative jet fuels under the same conditions (temperature, 550–1150 K; pressure, 10 bar; equivalence ratio, 0.5–2; initial fuel concentration, 1000 ppm). For simulating the oxidation kinetics of these fuels we used a new surrogate mixture consisting of n-dodecane, 3-methylheptane, n-propylcyclohexane, and 1-hexanol. A detailed chemical kinetic reaction mechanism was developed and validated by comparison with the experimental results obtained in a JSR. The current model was also tested for the auto-ignition of the GtL fuel under shock tubes conditions (φ = 1 and P = 20 atm) using data from the literature. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results. The general findings are that the GtL and GtL/hexanol blend have very similar reactivity to Jet A-1, which is important since GtL is a drop-in fuel that should have similar performance to the Jet A-1 baseline and 1-hexanol should not significantly affect the reactivity if it is to be used as an additive.
Combustion Science and Technology, 2014
ABSTRACT
Light, Energy and the Environment, 2014
52nd Aerospace Sciences Meeting, 2014
Energy & Fuels, 2010
ABSTRACT The oxidation of a commercial diesel fuel and a diesel surrogate fuel (70% n-decane/30% ... more ABSTRACT The oxidation of a commercial diesel fuel and a diesel surrogate fuel (70% n-decane/30% 1-methylnaphthalene in moles) was performed using a fused-silica jet-stirred reactor under the same initial experimental conditions (560−1030 K, 6 and 10 atm, equivalence ratios of 0.25−1.5, and 10 300 ppm of carbon). The results of this series of experiments consisting of concentration profiles of reactants, stable intermediates, and products as a function of the temperature were compared to each other, confirming that the 70/30% mixture n-decane/1-methylnaphthalene in moles is an excellent simple diesel fuel surrogate. A chemical kinetic model consisting of 4762 reactions involving 1124 species was proposed on the basis of previous chemical mechanisms for the oxidation of n-decane and 1-methylnaphthalene in similar conditions. The kinetic modeling showed reasonable agreement between the present data and computations over the entire range of conditions considered in this study.
The journal of physical chemistry. A, Jan 19, 2015
In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxyme... more In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl. CH2-O-CH2-O- (1,3-dioxetane), CH3OOH ...
The journal of physical chemistry. A, Jan 19, 2015
In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxyme... more In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl. CH2-O-CH2-O- (1,3-dioxetane), CH3OOH ...
Proceedings of the …, Jan 1, 2012
Combustion and Flame, Jan 1, 2012
Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
ABSTRACT The rapid growth of eco-friendly biomass derived fuels in transportation requires a fund... more ABSTRACT The rapid growth of eco-friendly biomass derived fuels in transportation requires a fundamental understanding of the uniqueness of their oxidation and combustion characteristics. This paper focuses on one specific class of biofuels, namely Fatty Acids Ethyl Esters (FAEE). A counterflow configuration was employed to measure the extinction limits of the diffusion flames of four ethyl esters (ethyl-butanoate, pentanoate, heptanoate, and nonanoate). The results were compared to that of methyl esters (Diévart et al., 2012, Proceedings of the Combustion Institute, 34). It was observed that both methyl esters and ethyl esters exhibit similar high temperature reactivity against extinction. The use of the transport-weighted enthalpy metric has revealed that all esters share similar chemical kinetics in the near extinction conditions of the present study. A previous detailed kinetic model has been extended to include the oxidation chemistry of ethyl esters, and used to interpret the experimental observations. Good agreement between the computed and experimental extinction limits was observed. The rates of consumption pathway analysis have shown that ethyl esters exclusively decomposed into ethylene and a carboxylic acid through an endothermic six-centered unimolecular decomposition reaction, while methyl esters oxidation preferentially progresses through H abstraction reactions. However, the growth of the radical pool was observed to be driven indifferently between ethyl and methyl esters, therefore resulting in similar global flame reactivity.
Proceedings of the Combustion Institute, 2015
ABSTRACT As two of the most important species that characterize hydrocarbon low temperature ignit... more ABSTRACT As two of the most important species that characterize hydrocarbon low temperature ignition, HO2 and H2O2 formation during dimethyl ether (DME) oxidation was quantified using the same experimental conditions, for the first time, in an atmospheric flow reactor at low and intermediate temperature range. Dual-Modulation Faraday Rotation Spectroscopy (DM-FRS) and Molecular Beam Mass Spectrometry (MBMS) were used to measure HO2 and H2O2 respectively. DME and other important intermediate species such as CH2O and CO are also measured by MBMS between 400 and 1150 K at different fuel concentrations. Species profiles in the reactor were calculated by using both zero- and two-dimensional computations with different detailed kinetics for cross-validation and comparison with experimental results. The models predict adequately the low and intermediate oxidation temperature windows near 600 and 1000 K, respectively. However, both models over-predicted the DME consumption as well as CO, HO2 and H2O2 formations at the low temperature oxidation window by more than a factor of four. Moreover, although the model predicted reasonably well the formation of CH2O and CO/CO2 at the intermediate temperature oxidation window, the concentration of H2O2 was also over-predicted, suggesting the large uncertainties existing in the DME low temperature chemistry and in H2O2 chemistry at intermediate temperature. Furthermore, to analyze the uncertainty of the low temperature chemistry, a branching ratio of QOOH decomposition to CH2O was derived using measured DME, CH2O and CO concentrations. The large difference between the modeled and measured branching ratios of QOOH decomposition suggests an underestimated QOOH decomposition rate to form CH2O in the current DME models.
Energy & Fuels, 2014
ABSTRACT
Proceedings of the Combustion Institute, 2015
ABSTRACT A novel method to establish self-sustaining cool diffusion flames with well-defined boun... more ABSTRACT A novel method to establish self-sustaining cool diffusion flames with well-defined boundary conditions is experimentally demonstrated by adding ozone to the oxidizer stream in counterflow configuration. It is found that the atomic oxygen produced through the decomposition of ozone dramatically shortens the induction timescale of the low temperature chemistry, extending the flammable region of cool flames. Thus, it enables the establishment of self-sustaining cool flames at the pressure and timescales at which normal cool flames may not be observable. The present method, for the first time, provides an opportunity to study cool flame dynamics, structure, and chemistry simultaneously in well-known flame geometry. Extinction limits of n-heptane/oxygen cool diffusion flames are measured and a cool diffusion flame diagram is experimentally determined. Numerical simulations reveal that the extinction limits of cool diffusion flames are strongly governed by species transport and low temperature chemistry activated by ozone decomposition. The structure of cool diffusion flame is further investigated by measuring the temperature and species distributions with a micro-probe sampling technique. The kinetic model over-predicts the rate of n-heptane oxidation, the heat release rate, and the flame temperature. Measurements of intermediate species, such as CH2O, acetaldehyde, C2H4, and CH4, suggest that the model over-predicts the QOOH thermal decomposition reactions to form olefins, resulting in substantial over-estimation of C2H4, and CH4 concentrations. The new method and data of the present study will contribute to promote understandings of cool flame chemistry.
The journal of physical chemistry. A, Jan 19, 2015
In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxyme... more In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl. CH2-O-CH2-O- (1,3-dioxetane), CH3OOH ...
Volume 3A: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration, 2014
Research activities on the combustion of synthetic jet fuels and bioderived jet fuels have increa... more Research activities on the combustion of synthetic jet fuels and bioderived jet fuels have increased notably over the last 10 yr in order to solve the challenging reduction of dependence of air transportation on petroleum. Within the European Community's Seventh Framework Programme, the combustion of a 100% GtL from Shell and a 80/20% vol. GtL/1-hexanol blend were studied in a jet-stirred reactor (JSR). This synthetic GtL fuel mainly contains n-alkanes, iso-alkanes, and cyclo-alkanes. We studied the oxidation of these alternative jet fuels under the same conditions (temperature, 550–1150 K; pressure, 10 bar; equivalence ratio, 0.5–2; initial fuel concentration, 1000 ppm). For simulating the oxidation kinetics of these fuels we used a new surrogate mixture consisting of n-dodecane, 3-methylheptane, n-propylcyclohexane, and 1-hexanol. A detailed chemical kinetic reaction mechanism was developed and validated by comparison with the experimental results obtained in a JSR. The current model was also tested for the auto-ignition of the GtL fuel under shock tubes conditions (φ = 1 and P = 20 atm) using data from the literature. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results. The general findings are that the GtL and GtL/hexanol blend have very similar reactivity to Jet A-1, which is important since GtL is a drop-in fuel that should have similar performance to the Jet A-1 baseline and 1-hexanol should not significantly affect the reactivity if it is to be used as an additive.
Combustion Science and Technology, 2014
ABSTRACT
Light, Energy and the Environment, 2014
52nd Aerospace Sciences Meeting, 2014
Energy & Fuels, 2010
ABSTRACT The oxidation of a commercial diesel fuel and a diesel surrogate fuel (70% n-decane/30% ... more ABSTRACT The oxidation of a commercial diesel fuel and a diesel surrogate fuel (70% n-decane/30% 1-methylnaphthalene in moles) was performed using a fused-silica jet-stirred reactor under the same initial experimental conditions (560−1030 K, 6 and 10 atm, equivalence ratios of 0.25−1.5, and 10 300 ppm of carbon). The results of this series of experiments consisting of concentration profiles of reactants, stable intermediates, and products as a function of the temperature were compared to each other, confirming that the 70/30% mixture n-decane/1-methylnaphthalene in moles is an excellent simple diesel fuel surrogate. A chemical kinetic model consisting of 4762 reactions involving 1124 species was proposed on the basis of previous chemical mechanisms for the oxidation of n-decane and 1-methylnaphthalene in similar conditions. The kinetic modeling showed reasonable agreement between the present data and computations over the entire range of conditions considered in this study.
The journal of physical chemistry. A, Jan 19, 2015
In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxyme... more In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl. CH2-O-CH2-O- (1,3-dioxetane), CH3OOH ...
The journal of physical chemistry. A, Jan 19, 2015
In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxyme... more In this paper we report the detection and identification of the keto-hydroperoxide (hydroperoxymethyl formate, HPMF, HOOCH2OCHO) and other partially oxidized intermediate species arising from the low-temperature (540 K) oxidation of dimethyl ether (DME). These observations were made possible by coupling a jet-stirred reactor with molecular-beam sampling capabilities, operated near atmospheric pressure, to a reflectron time-of-flight mass spectrometer that employs single-photon ionization via tunable synchrotron-generated vacuum-ultraviolet radiation. Based on experimentally observed ionization thresholds and fragmentation appearance energies, interpreted with the aid of ab initio calculations, we have identified HPMF and its conceivable decomposition products HC(O)O(O)CH (formic acid anhydride), HC(O)OOH (performic acid), and HOC(O)OH (carbonic acid). Other intermediates that were detected and identified include HC(O)OCH3 (methyl formate), cycl. CH2-O-CH2-O- (1,3-dioxetane), CH3OOH ...
Proceedings of the …, Jan 1, 2012
Combustion and Flame, Jan 1, 2012