Studies of radiation absorption on flame speed and flammability limit of CO2 diluted methane flames at elevated pressures

Chen, Zheng; Qin, Xiao; Xu, Bo; Ju, Yiguang; Liu, Fengshan

doi:10.1016/j.proci.2006.07.202

Cited by 156 publications

(50 citation statements)

References 38 publications

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“…Radiation emission/absorption brakes this balance and is able to modify both the flammability limits and the flame propagation speeds, see e.g. [16]. This is especially important in microgravity [17].…”

Section: Radiation Preheatingmentioning

confidence: 99%

Radiation Preheating can Trigger Transition from Deflagration to Detonation

Karlin¹

2010

Flow Turbulence Combust

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In this article the possibility of radiation heat transfer to trigger transition to detonation is studied. It is assumed that the premixed deflagration front is able to emit and the unburnt mixture to absorb radiation heat effectively. Under this assumption the ability of the flame to significantly preheat the unburnt mixture and to form a promoting temperature gradient is investigated. First, we estimate the temperature rise due to the radiation preheating of the unburnt mixture, when it is traveling through deep flame wrinkles. Subsequently, we carry out numerical simulations of premixed gaseous combustion in a tube. The simulations confirm the possibility of formation of promoting temperature gradients within flame folds and initiation of the detonation waves. They demonstrate the plausibility of the proposed mechanism of the deflagration to detonation transition.

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Section: Radiation Preheatingmentioning

confidence: 99%

Radiation Preheating can Trigger Transition from Deflagration to Detonation

Karlin¹

2010

Flow Turbulence Combust

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“…Ju and co-workers showed that radiation absorption and emission are important in flames with high CO 2 dilution, since CO 2 is a strong absorber [58][59]. Chen et al [58] indicated that spectral dependent radiation absorption must be included for any quantitative predictions of flame speed with CO 2 dilution.…”

Section: Effect Of Co 2 Dilution On the Pressure And Flame Temperaturmentioning

confidence: 99%

“…Chen et al [58] indicated that spectral dependent radiation absorption must be included for any quantitative predictions of flame speed with CO 2 dilution. The effect of radiation is not considered in detail here, and we refer the reader to Refs.…”

Section: Effect Of Co 2 Dilution On the Pressure And Flame Temperaturmentioning

confidence: 99%

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Reduced and Validated Kinetic Mechanisms for Hydrogen-CO-sir Combustion in Gas Turbines

Ju¹,

Dryer²

2009

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Rigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out -including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H 2 /CO/CO 2 /O 2 /diluent mixtures, revision of the H 2 /O 2 kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations. Executive SummaryRigorous experimental, theoretical, and numerical investigation of various issues relevant to the development of reduced, validated kinetic mechanisms for synthetic gas combustion in gas turbines was carried out -including the construction of new radiation models for combusting flows, improvement of flame speed measurement techniques, measurements and chemical kinetic analysis of H 2 /CO/CO 2 /O 2 /diluent mixtures, revision of the H 2 /O 2 kinetic model to improve flame speed prediction capabilities, and development of a multi-time scale algorithm to improve computational efficiency in reacting flow simulations.An accurate spectral dependent radiation model is developed to predict flame speed and flammability of H 2 /CO/CO 2 /H 2 O/Air mixtures. The results showed that radiation reabsorption significantly extended the flammability limits. It was also demonstrated that accurate prediction of coal syngas flammability is not possible without appropriate consideration of radiation absorption by CO 2 and H 2 O.Methodologies to improve flame speed measurement were developed by experimental and theoretical investigation of the effect of non-spherical (i.e. cylindrical) bomb geometry on the evolution of outwardly propagating flames and the determination of laminar flame speeds. The cylindrical chamber boundary modifies the propagation rate through the interaction of the wall with the flow induced by thermal expansion across the flame (even with constant pressure), which leads to significant distortion of the flame surface for large flame radii. It was determined that these departures from the unconfined case, especially the resulting non-zero burned gas velocities, can lead to significant errors in flame speeds calculated using the conventional assumptions, especially for large flame sizes.The methodology to estimate the effect of nonzero burned gas velocities is applied to correct the flame speed for non-zero burned gas speeds, in order to extend the range of flame radii useful for flame speed measurements. Under the proposed scaling, the burned gas speed can be well approximated as a function of only flame radius for a given chamber geometry -i.e. the correction function need only be determined once for an apparatus and then it can be used for any mixture. Results indicate that the flow correction can be used to extract flame speeds for flame radii up to 0.5 times the wall radius wi...

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“…However, a little attempt is made on the issue of flame propagation in the tube/channel with the addition of local heating. It is reported by Ju et al [17] and Chen et al [18] that the self-absorption of radiation emitted from the flame has significant effect on burning velocity and flammability limits. Obviously, this selfabsorption of emitted radiation from the flame is mild while the absorption of an external radiation is strong in nature.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of an In-line Pre-Heating Treatment along the Axis on the Propagation of a Laminar Premixed Flame in a Channel

Hossain

Oshima

Nakamura

et al. 2009

JTST

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In this study, an in-line pre-heating effect on the propagation of a laminar premixed flame in a two-dimensional channel is investigated numerically. An in-line pre-heating thickness of 1mm is generated by imposing uniform external high-temperature along the center line in the prescribed channel. It is found that the shapes of flame and propagation speeds are strongly affected by the pre-heating effect. The distribution of velocity pointed to ahead of the propagating flame (called negative velocity hereafter) is clearly observed which is susceptible to the generation of the pair of vortex in ahead of the flame tip. The evolution of negative flow field in front of premixed flame is successfully captured first ever in a time-dependent manner. The obtained flame propagation accompanied with the aforementioned negative velocity field is not only useful to elucidate the laser induced flame instability reported recently by Tsuchimoto et al. (2007), but also to consider the pure thermal effect on flame evolution, which is hard to obtain experimentally.

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Studies of radiation absorption on flame speed and flammability limit of CO2 diluted methane flames at elevated pressures

Cited by 156 publications

References 38 publications

Radiation Preheating can Trigger Transition from Deflagration to Detonation

Radiation Preheating can Trigger Transition from Deflagration to Detonation

Reduced and Validated Kinetic Mechanisms for Hydrogen-CO-sir Combustion in Gas Turbines

Numerical Study of an In-line Pre-Heating Treatment along the Axis on the Propagation of a Laminar Premixed Flame in a Channel

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