Formation of oxygenated and hydrocarbon intermediates in premixed combustion of 2-methylfuran

Moshammer K, Lucassen A, Togbé C, Kohse-Höinghaus K, Hansen N. Formation of oxygenated and hydrocarbon intermediates in premixed combustion of 2-methylfuran. ZEITSCHRIFT FÜR PHYSIKALISCHE CHEMIE. 2015;229(4):507-528

An experimental and kinetic modeling study of n-hexane oxidation

Ignition delay times for n-hexane oxidation have been measured in a rapid compression machine (RCM) at stoichiometric conditions and at 15 bar. Due to the high reactivity of n-hexane and non-ideal experimental effects associated with measuring short ignition delay times in the RCM (i.e. under 5 ms), further experiments were performed in a high-pressure shock tube for multiple fuel mixtures at equivalence ratios of phi = 1 and = 2 over the temperature range of 627-1365 K at pressures of 15 and 32 bar. To further study the concentration of intermediate species during the oxidation process, experiments have also been carried out in a jet-stirred reactor over a wide temperature range of 530-1160 K at 10 atm pressure and at equivalence ratios of phi = 0.5, 1.0 and 2.0. Species which include reactants, intermediates and products were identified and quantified as a function of temperature. These experimental results were used to aid the development and validation of a detailed kinetic model. The low-temperature chemistry of n-hexane has been refined by adopting alternative isomerization reactions for peroxyl alkylhydroperoxide (O(2)QOOH) radicals, leading to more detailed chemistry for this type of intermediate with multiple product channels. This mechanism has adopted a series of new reaction rates and rate rules mostly from recently reported high-level calculations. Slight modifications have been made to the suggested reaction rates and rate rules within their reported uncertainty ranges to achieve better agreement with the experimental results for both ignition delay times and speciation measurements. The new model has been validated against the experimental data presented here, with an overall good agreement compared to the experimental results. The molecular structure of n-hexane is more representative of normal alkanes that may be found in transportation relevant fuels (e.g. gasoline) compared to those with shorter carbon chains which is important in developing a robust sub-mechanism of base chemistry for larger, more practical fuels. Since the modified reaction rate rules presented in this work have shown to successfully predict the oxidation kinetics of n-hexane, these rate rules could be the basis for the development of mechanisms for even larger normal alkanes that are more representative of diesel and jet fuels. As a further demonstration of the utility of the rate rules they are shown to predict well ignition delay times and species concentrations measured at low temperature for n-heptane oxidation from previous studies. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.At NUIG, the research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union\u27s Seventh Framework Programme FP7/2007-2013/under REA Grant agreement no. 607214.2017-09-1

An experimental and modeling study of n-octanol combustion

International audienc

Species measurements of the particulate matter reducing additive tri–propylene glycol monomethyl ether

Reducing particulate matter formation and emissions by using fuel additives is a topic of interest for the petrochemical and automotive engineering industries. A compound which has been shown to be effective in this regard is tri-propylene glycol monomethyl ether (TPGME). This molecule consists of three ether linkages, an alcoholic group and alkyl branching including primary, secondary and tertiary C-H bonds. Its exotic structural features make it challenging to accurately model its oxidation. It is these same structural features that make this molecule both an exciting additive and a challenging fuel for kinetic modelers to understand. To provide insight into the oxidation of this molecule, species measurements have been performed in a jet- stirred reactor. Species concentrations are measured at three equivalence ratios; 0.5, 1.0 and 2.0, at a constant TPGME concentration of 1000 ppm, a pressure of 1 atm, a constant residence time of 70 ms and over the temperature range of 530-1250 K. The species measured include global reactant and product species, molecular oxygen, carbon monoxide, carbon dioxide, water and molecular hydrogen. In addition, a number of soot precursor species are measured namely, ethylene, propene, acetylene, allene, 1-butene, propyne and butadiene. A literature model is used to predict the experiments and erroneous low-temperature reactivity is predicted by the model. The low-temperature reaction kinetics and the base-mechanism of the model is updated using recent kinetic insights. Despite the large uncertainties in the assignment of the kinetic parameters for this large molecule these erroneous predictions are removed and the model is capable of rationalizing the formation of all species measured. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.NUIG would like to thank Science Foundation Ireland (SFI) for the funding for this work via their Principal Investigator Program through project number 15/IA/3177. The research leading to these results has received funding from the European Research Council under the European Community\u27s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 291049−2G-CSafe.2020-07-2

An experimental and modelling study of n-pentane oxidation in two jet-stirred reactors: The importance of pressure-dependent kinetics and new reaction pathways

Two jet-stirred reactors (JSRs) coupled to gas chromatographic and spectroscopic techniques have been utilised to detect chemical species evolved during n -pentane oxidation at 1 and 10 atm, in the temperature range 500-1100 K, and at equivalence ratios of 0.3-2.0. To the authors\u27 knowledge, this is the first study of a fuel\u27s oxidation in two JSRs. In addition, the choice of experimental conditions results in there being the same concentration of n -pentane in all investigated mixtures; 1% at 1 atm, and 0.1% at 10 atm. This permits the additional assessment of the importance of pressure-dependent kinetics in predicting species concentration profiles. A recently published literature model Bugler et al. (2016) served as the starting point in simulating these experiments, with only minor additions and modifications necessary to achieve good overall agreement. The main adjustments were made to account for multi-oxygenated species (C 5 aldehydes, ketones, diones, etc.) detected mainly at low temperatures (The work at NUIG was supported by the Irish Research Council under Grant number EPSPG/2012/380. The collaboration between LRGP and NUIG was supported by COST Action 1404. The work at CNRS Orléans was supported by the ERC Advanced Researcher Grant no. 291049-2G-CSafe.2018-06-1

An experimental and modelling study of n-pentane oxidation in two jet-stirred reactors: The importance of pressure-dependent kinetics and new reaction pathways

International audienceTwo jet-stirred reactors (JSRs) coupled to gas chromatographic and spectroscopic techniques have been utilized to detect chemical species evolved during n-pentane oxidation at 1 and 10 atm, in the temperature range 500–1100 K, and at equivalence ratios of 0.3–2.0. To the authors' knowledge, this is the first study of a fuel's oxidation in two JSRs. In addition, the choice of experimental conditions results in there being the same concentration of n-pentane in all investigated mixtures; 1% at 1 atm, and 0.1% at 10 atm. This permits the additional assessment of the importance of pressure-dependent kinetics in predicting species concentration profiles. A recently published literature model Bugler et al. (2016) served as the starting point in simulating these experiments, with only minor additions and modifications necessary to achieve good overall agreement. The main adjustments were made to account for multi-oxygenated species (C5 aldehydes, ketones, diones, etc.) detected mainly at low temperatures (<800 K) in both JSRs. In this paper we present new experiments, the most important of which are very well predicted using the aforementioned literature model. The effect of adding chemical pathways, which have been postulated to contribute to the generation of multi-oxygenated species, has been investigated. Finally, a brief account on the importance of pressure-dependent kinetics in the modelling of these experiments is provided

Experimental and modeling study of the oxidation of n- and iso-butanal

Veloo PS, Dagaut P, Togbé C, et al. Experimental and modeling study of the oxidation of n- and iso-butanal. Combustion And Flame. 2013;160(9):1609-1626.Understanding the kinetics of large molecular weight aldehydes is essential in the context of both conventional and alternative fuels. For example, they are key intermediates formed during the low-temperature oxidation of hydrocarbons as well as during the high-temperature oxidation of oxygenated fuels such as alcohols. In this study, an experimental and kinetic modeling investigation of n-butanal (n-butyraldehyde) and iso-butanal (iso-butyraldehyde or 2-methylpropanal) oxidation kinetics was performed. Experiments were performed in a jet stirred reactor and in counterflow flames over a wide range of equivalence ratios, temperatures, and pressures. The jet stirred reactor was utilized to observe the evolution of stable intermediates and products for the oxidation of n- and iso-butanal at elevated pressures and low to intermediate temperatures. The counterflow configuration was utilized for the determination of laminar flame speeds. A detailed chemical kinetic interpretative model was developed and validated consisting of 244 species and 1198 reactions derived from a previous study of the oxidation of propanal (propionaldehyde). Extensive reaction pathway and sensitivity analysis was performed to provide detailed insight into the mechanisms governing low-, intermediate-, and high-temperature reactivity. The simulation results using the present model are in good agreement with the experimental laminar flame speeds and well within a factor of two of the speciation data obtained in the jet stirred reactor. (c) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved

Flame structure and kinetic studies of carbon dioxide-diluted dimethyl ether flames at reduced and elevated pressures

Liu D, Santner J, Togbé C, et al. Flame structure and kinetic studies of carbon dioxide-diluted dimethyl ether flames at reduced and elevated pressures. COMBUSTION AND FLAME. 2013;160(12):2645-2668