A numerical study on the effect of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames

A numerical study was carried out to understand the effect of CO enrichment on flame temperature and NO formation in counterflow CH4/air diffusion flames. The results indicate that when CO is added to the fuel, both flame temperature and NO formation rate are changed due to the variations in adiabatic flame temperature, fuel Lewis number, and chemical reaction. At a low strain rate, the addition of carbon monoxide causes a monotonic decrease in flame temperature and peak NO concentration. However, NO emission index first slightly increases, and then decreases. At a moderate strain rate, the addition of CO has negligible effect on flame temperature and leads to a slight increase in both peak NO concentration and NO emission index, until the fraction of carbon monoxide reaches about 0.7. Then, with a further increase in the fraction of added carbon monoxide, all three quantities quickly decrease. At a high strain rate, the addition of carbon monoxide causes increase in flame temperature and NO formation rate, until a critical carbon monoxide fraction is reached. After the critical fraction, the further addition of carbon monoxide leads to decrease in both flame temperature and NO formation rate.

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A Numerical Study on the Effect of CO Addition on Flame Temperature and NO Formation in Counterflow CH4/Air Diffusion Flames

Volume 6: Energy Systems: Analysis, Thermodynamics and Sustainability ◽

10.1115/imece2007-41438 ◽

2007 ◽

Author(s):

Hongsheng Guo ◽

W. Stuart Neill

Keyword(s):

Carbon Monoxide ◽

Strain Rate ◽

Diffusion Flames ◽

Numerical Study ◽

Formation Rate ◽

Flame Temperature ◽

No Emission ◽

No Formation ◽

Air Diffusion ◽

Emission Index

A numerical study was carried out to understand the effect of carbon monoxide enrichment on flame temperature and NO formation in counterflow methane/air diffusion flames. Detailed chemistry and complex thermal and transport properties were employed. The results indicate that when carbon monoxide is added to the fuel, both flame temperature and NO formation rate are changed due to the variations in adiabatic flame temperature, fuel Lewis number and chemical reaction. The combination effects of three factors result in the different characteristics of flame temperature and NO formation at various strain rates, when carbon monoxide is added. At a low strain rate, the addition of carbon monoxide causes a monotonic decrease in flame temperature and peak NO concentration. However, NO emission index first slightly increases, and then decreases. When the value of strain rate is moderate, the addition of carbon monoxide has negligible effect on flame temperature and leads to a slight increase in both peak NO concentration and NO emission index, until the fraction of carbon monoxide reaches about 0.7. Then with a further increase in the fraction of added carbon monoxide, all three quantities quickly decrease. When strain rate is increased to a value close to the strain extinction limit of pure methane/air diffusion flame, the addition of carbon monoxide causes increase in flame temperature and NO formation rate, until a critical carbon monoxide fraction is reached. After the critical fraction, the further addition of carbon monoxide leads to decrease in both flame temperature and NO formation rate. The paper also analyzed the variation in the mechanism of NO formation, when carbon monoxide is added.

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Effects of strain rate and CO2 on no formation in CH4/N2/O2 counter-flow diffusion flames

Thermal Science ◽

10.2298/tsci170922062r ◽

2018 ◽

Vol 22 (Suppl. 2) ◽

pp. 769-776

Author(s):

Fei Ren ◽

Longkai Xiang ◽

Huaqiang Chu ◽

Weiwei Han

Keyword(s):

Strain Rate ◽

Diffusion Flames ◽

Numerical Study ◽

Flame Temperature ◽

Co2 Concentration ◽

No Production ◽

Counter Flow ◽

Detailed Chemistry ◽

No Formation ◽

Key Factor

The reduction of nitrogen oxides in the high temperature flame is the key factor affecting the oxygen-enriched combustion performance. A numerical study using an OPPDIF code with detailed chemistry mechanism GRI 3.0 was carried out to focus on the effect of strain rate (25-130 s?1) and CO2 addition (0-0.59) on the oxidizer side on NO emission in CH4 / N2 / O2 counter-flow diffusion flame. The mole fraction profiles of flame structures, NO, NO2 and some selected radicals (H, O, OH) and the sensitivity of the dominant reactions contributing to NO formation in the counter-flow diffusion flames of CH4\/ N2 /O2 and CH4 / N2 / O2 / CO2 were obtained. The results indicated that the flame temperature and the amount of NO were reduced while the sensitivity of reactions to the prompt NO formation was gradually increased with the increasing strain rate. Furthermore, it is shown that with the increasing CO2 concentration in oxidizer, CO2 was directly involved in the reaction of NO consumption. The flame temperature and NO production were decreased dramatically and the mechanism of NO production was transformed from the thermal to prompt route.

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Two-Dimensional Numerical Study of Temperature, Species Distributions in Coflow Laminar Diffusion Flames

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.516-517.80 ◽

2012 ◽

Vol 516-517 ◽

pp. 80-83

Author(s):

You Ning Xu ◽

Jun Rui Shi ◽

Zhi Jia Xue ◽

Shu Qun Wang ◽

Mao Zhao Xie

Keyword(s):

Gas Phase ◽

Mass Fraction ◽

Diffusion Flames ◽

Numerical Study ◽

Flame Temperature ◽

Species Distributions ◽

Phase Reaction ◽

Laminar Diffusion Flames ◽

Gas Phase Reaction ◽

Air Diffusion

Abstract. temperature and species distributions of an atmosphere coflow laminar CH4/air diffusion flame was studied by numerical simulation. We solve the steady equations for the species mass fraction, energy, momentum with detailed gas-phase reaction mechanism and complex thermal and transport properties to predict the velocity, temperature, species distributions for different dilute level. Results indicated that the predicted temperature and species are in excellent with available experiment date at different dilute level. In addition, it is indicated that adding N2in the fuel has a significant influence on the flame temperature and species distribution.

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Numerical Study of Hydrogen Addition Fuel on Soot Formation in Axisymmetric Laminar Methane/Air Diffusion Flames

E3S Web of Conferences ◽

10.1051/e3sconf/202019404054 ◽

2020 ◽

Vol 194 ◽

pp. 04054

Author(s):

Bencheng Zhu ◽

Yuhan Zhu ◽

Jiajia Wu ◽

Kun Lu ◽

Yang Wang ◽

...

Keyword(s):

Diffusion Flames ◽

Soot Formation ◽

Numerical Study ◽

Flame Temperature ◽

Surface Growth ◽

Chemical Effect ◽

Oh Radicals ◽

Phase Reaction ◽

Hydrogen Addition ◽

Air Diffusion

This article employs the CoFlame Code to investigate the effects of hydrogen addition to fuel on soot formation characteristics in laminar coflow methane/air diffusion flames at atmospheric pressure. Numerical calculations were carried out using a detailed C1-C2 gas phase reaction mechanism and a soot model consisting of two pyrene molecules colliding into a dimer as soot nucleation, hydrogen abstraction acetylene addition (HACA) and pyrene condensation as surface growth, and soot oxidation by O2, O and OH radicals. Calculations were conducted for five levels of hydrogen addition on volume basis. To quantify the chemical effect of hydrogen, additional calculations are performed for addition of inert pseudo-hydrogen (FH2). The addition of H2 or FH2 does not have a strong influence on flame temperature. The results confirm that hydrogen addition can inhibit soot formation in the methane/air diffusion flame by reducing both the nucleation and surface growth steps of soot formation process. The effect of FH2 addition on soot formation suppression is more remarkable than H2, indicating that the chemical effect of hydrogen added to methane prompts soot formation. The dilution effect of hydrogen addition on soot formation suppression is stronger than its chemical effect on soot formation enhancement the present findings are consistent with those of previous numerical studies.

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A Numerical Investigation of NOx Formation in Counterflow CH4/H2/Air Diffusion Flames

Heat Transfer, Volume 2 ◽

10.1115/imece2006-14458 ◽

2006 ◽

Cited By ~ 1

Author(s):

Hongsheng Guo ◽

Stuart W. Neill ◽

Gregory J. Smallwood

Keyword(s):

Diffusion Flames ◽

Numerical Study ◽

Flame Structure ◽

Pure Hydrogen ◽

No Emission ◽

Nox Formation ◽

No Formation ◽

Hydrogen Enrichment ◽

Air Diffusion ◽

Emission Index

A detailed numerical study was carried out for the effect of hydrogen enrichment on flame structure and NOx formation in counterflow CH4/air diffusion flames. Detailed chemistry and complex thermal and transport properties were employed. The enrichment fraction was changed from 0 (pure CH4) to 1.0 (pure H2). The result indicates that for flames with low to moderate stretch rates, with the increase of the enrichment fraction from 0 to 0.5~0.6, NO emission index keeps almost constant or only slightly increases. When the enrichment fraction is increased from 0.5~0.6 to about 0.9, NO emission index quickly increases, and finally NO formation decreases again when pure hydrogen flame condition is approached. However, for flames with higher stretch rates, with the increase of hydrogen enrichment fraction from 0 to 1.0, the formation of NO first quickly increases, then slightly decreases and finally increases again. Detailed analysis suggests that the variation of the characteristics in NO formation in stretched CH4/air diffusion flames is caused by the change of flame structure and NO formation mechanism, when the enrichment fraction and stretch rate are changed.

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Numerical study of the effects of gravity on soot formation in laminar coflow methane/air diffusion flames under different air stream velocities

Combustion Theory and Modelling ◽

10.1080/13647830903342527 ◽

2009 ◽

Vol 13 (6) ◽

pp. 993-1023 ◽

Cited By ~ 21

Author(s):

Wenjun Kong ◽

Fengshan Liu

Keyword(s):

Diffusion Flames ◽

Soot Formation ◽

Numerical Study ◽

Air Stream ◽

Air Diffusion

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A Numerical Study on the Effect of Water Addition on NO Formation in Counterflow CH4/Air Premixed Flames

ASME 2005 Internal Combustion Engine Division Fall Technical Conference (ICEF2005) ◽

10.1115/icef2005-1299 ◽

2005 ◽

Author(s):

Hongsheng Guo ◽

Stuart W. Neill ◽

Gregory J. Smallwood

Keyword(s):

Numerical Study ◽

Temperature Drop ◽

Flame Temperature ◽

Premixed Flames ◽

Chemical Effect ◽

Water Addition ◽

Detailed Chemistry ◽

Effect Of Water ◽

No Formation ◽

The Rich

The effect of water addition on NO formation in counterflow CH4/air premixed flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of water to a flame suppresses the formation of NO primarily due to the flame temperature drop. Among a lean, a stoichiometric and a rich premixed flame, the effectiveness of water addition is most significant for the stoichiometric flame and least for the rich flame, since the dominant NO formation mechanism varies. The addition of water also reduces the formation of NO in a flame because of chemical effect that increases the concentration of OH, while reduces the concentrations of O and H. Compared to the stoichiometric flame, the chemical effect is intensified in the lean and rich flames.

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