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

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.

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

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.

A Numerical Study of the Influence of Hydrogen Addition on Soot Formation in a Laminar Counterflow Ethylene/Oxygen/Nitrogen Diffusion Flame

2004 ◽  
Author(s):  
Hongsheng Guo ◽  
Fengshan Liu ◽  
Gregory J. Smallwood
Keyword(s):  
Diffusion Flame ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Soot Volume Fraction ◽  
Phase Reaction ◽  
Nitrogen Diffusion ◽  
Atom Concentration ◽  
Hydrogen Addition

The influence of hydrogen addition to the fuel on soot formation in an ethylene/oxygen/nitrogen diffusion flame was numerically studied by simulation of three counterflow laminar diffusion flames at atmosphere pressure. The fuel mixtures for the three flames are pure ethylene, ethylene/hydrogen and ethylene/helium, respectively, while the oxidant is a mixture of oxygen and nitrogen. A detailed gas phase reaction mechanism including species up to benzene and complex thermal and transport properties were used. The soot inception and surface growth rates were, respectively, calculated based on benzene and HACA (H-abstraction and C2H2-addition) mechanisms. The predicted results for the three flames were compared and analyzed. It is indicated that although the addition of either hydrogen or helium to the fuel can reduce the soot volume fraction, the addition of hydrogen is more efficient. While the addition of helium reduces soot formation only through dilution, the addition of hydrogen suppresses soot formation through both dilution and chemical reaction effects. This conclusion is qualitatively consistent with available experiments. The simulations revel that the chemically inhibiting effect is caused by the decrease of hydrogen atom concentration in soot formation region, due to the displacement of the primary reaction zone, when hydrogen is added to the fuel.

The influence of nitrogen and hydrogen addition/dilution on soot formation in coflow ethylene/air diffusion flames

Fuel ◽  
2022 ◽  
Vol 309 ◽  
pp. 122244
Author(s):  
Andisheh Khanehzar ◽  
Francisco Cepeda ◽  
Seth B. Dworkin
Keyword(s):  
Diffusion Flames ◽  
Soot Formation ◽  
Hydrogen Addition ◽  
Air Diffusion

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

2008 ◽  
Vol 130 (5) ◽  
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 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.

scholarly journals A computational study of soot formation and flame structure of coflow laminar methane/air diffusion flames under microgravity and normal gravity

2021 ◽  
Author(s):  
Armin Veshkini ◽  
Seth B. Dworkin
Keyword(s):  
Normal Gravity ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Computational Study ◽  
Flame Structure ◽  
Chemical Kinetic ◽  
Surface Growth ◽  
Rate Of Increase

A numerical study is conducted of methane-air coflow diffusion flames at microgravity (μg) and normal gravity (lg), and comparisons are made with experimental data in the literature. The model employed uses a detailed gas phase chemical kinetic mechanism that includes PAH formation and growth, and is coupled to a sectional soot particle dynamics model. The model is able to accurately predict the trends observed experimentally with reduction of gravity without any tuning of the model for different flames. The microgravity sooting flames were found to have lower temperatures and higher volume fraction than their normal gravity counterparts. In the absence of gravity, the flame radii increase due to elimination of buoyance forces and reduction of flow velocity, which is consistent with experimental observations. Soot formation along the wings is seen to be surface growth dominated, while PAH condensation plays a more major role on centerline soot formation. Surface growth and PAH growth increase in microgravity primarily due to increases in the residence time inside the flame. The rate of increase of surface growth is more significant compared to PAH growth, which causes soot distribution to shift from the centerline of the flame to the wings in microgravity. Keywords: laminar diffusion flame,methane-air,microgravity, soot formation, numerical modelling

Numerical study on the influence of hydrogen addition on soot formation in a laminar ethylene–air diffusion flame

2006 ◽  
Vol 145 (1-2) ◽  
pp. 324-338 ◽  
Author(s):  
Hongsheng Guo ◽  
Fengshan Liu ◽  
Gregory J. Smallwood ◽  
Ömer L. Gülder
Keyword(s):  
Diffusion Flame ◽  
Soot Formation ◽  
Numerical Study ◽  
Hydrogen Addition ◽  
Air Diffusion

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

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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