A Numerical Study on the Effects of CO2/N2/Ar Addition to Air on Liftoff of a Laminar CH4/Air Diffusion Flame

Guo, Hongsheng; Min, Jiesheng; Galizzi, Cédric; Escudié, Dany; Baillot, Françoise

doi:10.1080/00102202.2010.497074

Cited by 35 publications

(16 citation statements)

References 20 publications

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“…It is known that increasing the CO 2 concentration in the combustible mixture reduces the concentration of CH in the flames [59] . The production of OH * is then penalized because this excited radical is mainly produced through the formation reaction: CH + O 2 ⇋ OH* + CO [16,23] .…”

Section: Effects Of Co 2 and N 2 Dilution On Oh * And Ch *mentioning

confidence: 99%

Flame chemiluminescence from CO2- and N2-diluted laminar CH4/air premixed flames

Guiberti

Durox

Schuller

2017

Combustion and Flame

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a b s t r a c tAn experimental and numerical investigation of the chemiluminescence signals from OH * , CH * , and CO 2 * is conducted for laminar premixed conical CH 4 /air flames diluted with CO 2 or N 2 . Experiments are conducted either at fixed equivalence ratio or fixed adiabatic flame temperature. An ICCD camera, equipped with different narrow bandpass filters, is used to record flame images at 307 nm (OH * ), 430 nm (CH * ), and 455 nm (CO 2 * ). A spectrometer is also used to correct the OH * and CH * emissions from the CO 2 * broadband background emission. Measured chemiluminescence intensities are then compared to one dimensional freely-propagating-flame direct simulations accounting for the chemistry of the excited radicals. Simulations predict accurately the OH * chemiluminescence intensity, independently of the diluent nature and concentration. Correction for the CO 2 * background has a weak influence on the recorded OH * signal. Predictions of CH * emissions are also in good agreement with experimental data if the CO 2 * background intensity is subtracted from intensity measurements. Measured and calculated CO 2 * emissions lead to acceptable results using a simplified chemistry mechanism for CO 2 * and an heuristic model for its emission intensity. Finally, it is shown that CO 2 dilution modifies chemiluminescence intensity couples and particularly the OH * /CO 2 * intensity ratio. These ratios regularly decrease with CO 2 dilution, a feature which is reproduced by the simulations. It is then shown that the ratio OH * /CO 2 * is well suited to infer the CO 2 diluent concentration in diluted CH 4 /air flames, a method which appears not feasible for sensing N 2 in N 2 -diluted CH 4 /air flames.

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Section: Effects Of Co 2 and N 2 Dilution On Oh * And Ch *mentioning

confidence: 99%

Flame chemiluminescence from CO2- and N2-diluted laminar CH4/air premixed flames

Guiberti

Durox

Schuller

2017

Combustion and Flame

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“…It has already been reported that air-side dilution in a coflow jet flame was much more effective than fuel-side dilution in altering flame stability. The relative influence of the three effects occurring with CO 2 -dilution has been determined by Guo et al [22]: pure dilution (68%) appears as having the most important impact on flame stabilization, followed by thermal (22.5%) and chemical (9.5%) effects. Radiation and transport effects were found to be negligible in this flame configuration.…”

Section: Introductionmentioning

confidence: 98%

“…Even though diluted combustion systems have interested many researchers, the way the dilution effects interact with a higher initial temperature has not been thoroughly investigated, and motivates the present study. In our previous work [22,24,25], the influence of air-side dilution on flame stabilization mechanisms and on transitions leading to flame lift-off and extinction was carefully studied at room temperature. Pursuing this initial decoupled approach, results are presented here considering at first only preheating effects for five initial temperatures in addition to experiments at room temperature.…”

Section: Introductionmentioning

confidence: 99%

On preheating and dilution effects in non-premixed jet flame stabilization

Lamige

Min

Galizzi

et al. 2013

Combustion and Flame

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The impact of preheating and dilution on methane/air non-premixed flame stability are studied experimentally. Six preheating levels are considered for initial reactant temperature between 295 K and 850 K in a round jet configuration. Four diluent gases are added on the air-side, either CO 2 , N 2 , Ar or a (CO 2 + Ar) mixture having the same molar heat capacity as N 2. For undiluted flames, jet transition velocities between attached and lifted states are investigated depending on initial reactant temperature. The hysteresis zone defined by these stability limits is shifted towards higher jet velocities with preheating. Whereas jet and coflow temperatures were identical in similar previous experiments, the present work allows examination of the thermal effects from either fuel or oxidizer streams. Flame stability is described based on the propagative aspects of the flame leading-edge, by analogy with the temperature dependency of the laminar burning velocity of a stoichiometric mixture. Results show that the jet temperature has a major influence on the lifting of an attached flame, whereas the coflow temperature remains important for the reattachment of a lifted flame. In addition, flame stability experiments have been performed at high levels of both preheating and dilution. Stability maps of critical dilution ratios at lifting have been obtained with preheating. It appears that the ability of a diluent to break flame stability keeps the same relative order as at ambient temperature. It is even enhanced with preheating because higher temperature widens the gap between diluent molar heat capacities Cp. The Cp approach is however not sufficient to interpret the temperature dependency of the relative influence of the different dilution effects. Furthermore, the role played by the jet flow regime on attached flame stability in dilution-induced lifting experiments is highlighted when dilution is coupled with preheating.

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“…Guo et al [24] investigated experimentally the effects of different additives to air on the lift-off of a laminar CH 4 /air diffusion flame. Results show that the addition of CO 2 causes flame lift-off due to the dilution, thermal and chemical effects, with the dilution effect being the most significant one, followed by the thermal effect.…”

Section: Introductionmentioning

confidence: 99%

Combustion of hythane diluted with CO2

et al. 2015

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With increasing concern about energy shortage and environmental protection, improving engine fuel economy and reducing exhaust emissions have become major research topics in combustion and engine development. Hythane (a blend of hydrogen H 2 and natural gas NG) has generated a significant interest as an alternative fuel for the future. This paper describes an experimental study of the effects of CO 2 addition on the stability of a turbulent jet diffusion NG-H 2 flame. The mole fraction of hydrogen (% H 2 ) in NG-H 2 mixture was varied from 0% to 50%. The equivalence ratio of the hythane/CO 2 /air mixture was kept at stoichiometry. The results show that the lift-off height increases with the addition of CO 2 at various % H 2 content in hythane. However, we observe that with 20% H 2 , we can obtain a stable flame diluted with 40% CO 2 , while for 0% H 2 , the flame is blown out above 20% CO 2 . This means that the limits of flame blowing out are pushed with the additions of H 2 . Moreover, the results show that for %H 2 content in NG-H 2 fuel up to 10%, the addition of CO 2 could produce lifted flame if the % CO 2 is low. At higher % CO 2 dilution, flame would remain attached until blow-out. This is mainly due to the fact that the dilution leads to ejection velocities very high but reactivity of the mixture does not change so the flame tends to stretch.

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A Numerical Study on the Effects of CO₂/N₂/Ar Addition to Air on Liftoff of a Laminar CH₄/Air Diffusion Flame

Cited by 35 publications

References 20 publications

Flame chemiluminescence from CO2- and N2-diluted laminar CH4/air premixed flames

Flame chemiluminescence from CO2- and N2-diluted laminar CH4/air premixed flames

On preheating and dilution effects in non-premixed jet flame stabilization

Combustion of hythane diluted with CO2

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