Weakly Bound Free Radicals in Combustion: “Prompt” Dissociation of Formyl Radicals and Its Effect on Laminar Flame Speeds

Labbe, Nicole J.; Sivaramakrishnan, R.; Goldsmith, C. Franklin; Georgievskii, Yuri; Miller, James A.; Klippenstein, Stephen J.

doi:10.1021/acs.jpclett.5b02418

Cited by 79 publications

(66 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Notably, the competition between CH 2 O+H=H+CO+H 2 and CH 2 O+H=HCO+H 2 influences the flame speed calculation considerably. Inclusion of prompt dissociation of HCO in the mechanism serves to increase the predicted flame speeds by several cm/s, enhancing the agreement with experiment.…”

Section: Resultsmentioning

confidence: 77%

“…A special feature of the mechanism is that it takes into account the prompt dissociation of the weakly bound radical HCO, based on the recent work of Labbe et al . Weakly bound free radicals have low dissociation thresholds, facilitating dissociation during the vibrational‐rotational relaxation process at high temperatures where the timescales for dissociation and collisional relaxation become comparable.…”

Section: Detailed Kinetic Modelmentioning

confidence: 99%

“…The prompt dissociation of HCO yields atomic hydrogen, promoting the radical pool. We adopt the results of the dynamics calculations of Labbe et al for OH + CH 2 O and H + CH 2 O, while for other HCO‐forming reactions, an approximate method was used to derive prompt dissociation fractions . This modification of the mechanism is not important for the high pressure, intermediate temperature conditions of the present experimental work, but has an impact on flame speed calculations.…”

Section: Detailed Kinetic Modelmentioning

confidence: 99%

See 2 more Smart Citations

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Giménez-López

Rasmussen

Hashemi

et al. 2016

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

A detailed chemical kinetic model for oxidation of C 2 H 4 in the intermediate temperature range and high pressure has been developed and validated experimentally. New ab initio calculations and RRKM analysis of the important C 2 H 3 + O 2 reaction was was used to obtain rate coefficients over a wide range of conditions (0.003-100 bar, 200-3000 K). The results indicate that at 60 bar vinyl peroxide, rather than CH 2 O and HCO, is the dominant product.The experiments, involving C 2 H 4 /O 2 mixtures diluted in N 2 , were carried out in a high pressure flow reactor at 600-900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel-rich conditions. Model predictions are generally satisfactory. The governing reaction mechanisms are outlined based on calculations with the kinetic model. Under the investigated conditions the oxidation pathways for C 2 H 4 are more complex than those prevailing at higher temperatures and lower pressures. The major differences are the importance of the hydroxyethyl (CH 2 CH 2 OH) and 2-hydroperoxyethyl 1 (CH 2 CH 2 OOH) radicals, formed from addition of OH and HO 2 to C 2 H 4 , and vinyl peroxide, formed from C 2 H 3 + O 2 . Hydroxyethyl is oxidized through the peroxide HOCH 2 CH 2 OO (lean conditions) or through ethenol (low O 2 concentration), while 2-hydroperoxyethyl is converted through oxirane. [2][3][4][5][6][7], shock tubes [8][9][10][11][12] and premixed laminar flames [13][14][15][16][17], covering a wide range of stoichiometries and temperatures. Most of the reported work, however, have been carried out at near atmospheric pressure. A few results are available from flow reactor studies at 5-10 bar [6], but despite their relevance for the chemistry in engines, gas turbines, and gas-to-liquid processes, data at high pressures are limited.The objective of the present study is to obtain experimental results for the oxidation of C 2 H 4 at high pressure (60 bar) as functions of temperature (600-900 K) and stoichiometry (lean to fuel-rich) and analyze them in terms of a detailed chemical kinetic model. The oxidation pathways for C 2 H 4 under these conditions are different from those prevailing at higher temperatures and lower pressures and the results of the current work help to extend the validation range for chemical kinetic modeling of C 2 H 4 oxidation. This paper is part of a series investigating the high-pressure, medium temperature oxidation of simple fuels: previously work has been reported for CO/H 2 , CH 4 , and CH 4 /C 2 H 6 mixtures [18,19]. The present kinetic model draws on this work, as well as recent results in tropospheric chemistry. Furthermore, the important reaction of C 2 H 3 with O 2 was characterized from ab initio calculations over a wide range of pressure and temperature. 3 ExperimentalThe experimental setup is a laboratory-scale high pressure laminar flow reactor designed to approximate plug-flow. The setup is described in detail elsewhere [18] and only a brief description is provided here. The system enables well-defined investigations of...

show abstract

Section: Resultsmentioning

confidence: 77%

Section: Detailed Kinetic Modelmentioning

confidence: 99%

Section: Detailed Kinetic Modelmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Giménez-López

Rasmussen

Hashemi

et al. 2016

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

show abstract

“…The mechanism takes into account the prompt dissociation of the weakly bound radical HCO, based on the recent work of Labbe et al [66]. Weakly bound free radicals have low dissociation thresholds, facilitating dissociation during the vibrational-rotational relaxation process at high temperatures where the timescales for dissociation and collisional relaxation become comparable.…”

Section: Reaction Mechanismmentioning

confidence: 99%

High-pressure oxidation of ethane

Hashemi

Jacobsen

Rasmussen

et al. 2017

Combustion and Flame

Self Cite

View full text Add to dashboard Cite

Ethane oxidation at intermediate temperatures and high pressures has been investigated in both a laminar flow reactor and a rapid compression machine (RCM). The flow-reactor measurements at 600-900 K and 20-100 bar showed an onset temperature for oxidation of ethane between 700 K and 825 K, depending on pressure, stoichiometry, and residence time. Measured ignition delay times in the RCM at pressures of 10-80 bar and temperatures of 900-1025 K decreased with increasing pressure and/or temperature. A detailed chemical kinetic model was developed with particular attention to the peroxide chemistry. Rate constants for reactions on the C 2 H 5 O 2 potential energy surface were adopted from the recent theoretical work of Klippenstein. In the present work, the internal H-abstraction in CH 3 CH 2 OO to form CH 2 CH 2 OOH was treated in detail. Modeling predictions were in good agreement with data from the present work as well as results at elevated pressure from literature. The experimental results and the modeling predictions do not support occurrence of NTC behavior in ethane oxidation. Even at the high-pressure conditions of the present work where the C 2 H 5 + O 2 reaction yields ethylperoxyl rather than C 2 H 4 + HO 2 , the chain branching sequence CH 3 CH 2 OO −→ CH 2 CH 2 OOH +O 2 −→ OOCH 2 CH 2 OOH → branching is not competitive, because the internal H-atom transfer in CH 3 CH 2 OO to CH 2 CH 2 OOH is too slow compared to thermal dissociation to C 2 H 4 and HO 2 .

show abstract

“…[23][24][25][26][27][28] The formation and consumption of non-thermal intermediates appears to be of high importance under high-temperature and low-pressure conditions. These effects, however, are mostly neglected presently and are hard to implement in state-of-the-art numerical simulation schemes.…”

Section: K(e)mentioning

confidence: 99%

Analytic energy-level densities of separable harmonic oscillators including approximate hindered rotor corrections

Döntgen

2016

AIP Advances

View full text Add to dashboard Cite

ARTICLES YOU MAY BE INTERESTED INEnergy-level densities are key for obtaining various chemical properties. In chemical kinetics, energy-level densities are used to predict thermochemistry and microscopic reaction rates. Here, an analytic energy-level density formulation is derived using inverse Laplace transformation of harmonic oscillator partition functions. Anharmonic contributions to the energy-level density are considered approximately using a literature model for the transition from harmonic to free motions. The present analytic energy-level density formulation for rigid rotor-harmonic oscillator systems is validated against the well-studied CO +ȮH system. The approximate hindered rotor energy-level density corrections are validated against the well-studied H 2 O 2 system. The presented analytic energy-level density formulation gives a basis for developing novel numerical simulation schemes for chemical processes. © 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

show abstract

Weakly Bound Free Radicals in Combustion: “Prompt” Dissociation of Formyl Radicals and Its Effect on Laminar Flame Speeds

Cited by 79 publications

References 28 publications

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

High-pressure oxidation of ethane

Analytic energy-level densities of separable harmonic oscillators including approximate hindered rotor corrections

Contact Info

Product

Resources

About

Weakly Bound Free Radicals in Combustion: “Prompt” Dissociation of Formyl Radicals and Its Effect on Laminar Flame Speeds

Cited by 79 publications

References 28 publications

Experimental and Kinetic Modeling Study of C2H2 Oxidation at High Pressure

Experimental and Kinetic Modeling Study of C2H2 Oxidation at High Pressure

High-pressure oxidation of ethane

Analytic energy-level densities of separable harmonic oscillators including approximate hindered rotor corrections

Contact Info

Product

Resources

About

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure

Experimental and Kinetic Modeling Study of C₂H₂ Oxidation at High Pressure