scholarly journals Effect of Burner Wall Material on Microjet Hydrogen Diffusion Flames near Extinction: A Numerical Study

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8266
Author(s):  
Aravind Muraleedharan ◽  
Jithin Edacheri Veetil ◽  
Akram Mohammad ◽  
Sudarshan Kumar ◽  
Ratna Kishore Velamati
Keyword(s):  
Thermal Radiation ◽  
Wall Thickness ◽  
Hydrogen Diffusion ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Flame Temperature ◽  
Flame Height ◽  
Wall Material ◽  
Minor Effect ◽  
Near Extinction

Characteristics of microjet hydrogen diffusion flames stabilized near extinction are investigated numerically. Two-dimensional simulations are carried out using a detailed reaction mechanism. The effect of burner wall material, thickness, and thermal radiation on flame characteristics such as flame height and maximum flame temperature are studied. Results show that the flame stabilizes at lower fuel jet velocities for quartz burner than steel or aluminum. Higher flame temperatures are observed for low conductive burners, whereas the flame length increases with an increase in thermal conductivity of the burner. Even though thermal radiation has a minor effect on flame characteristics like flame temperature and flame height, it significantly influences the flame structure for low conductive burner materials. The burner tip and its vicinity are substantially heated for low conductive burners. The effect of burner wall thickness on flame height is significant, whereas it has a more negligible effect on maximum flame temperature. Variation in wall thickness also affects the distribution of H and HO2 radicals in the flame region. Although the variation in wall thickness has the least effect on the overall flame shape and temperature distribution, the structure near the burner port differs.

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

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.

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.

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.

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.

Experimental and numerical study of OH* chemiluminescence in hydrogen diffusion flames

2018 ◽  
Vol 197 ◽  
pp. 369-377 ◽  
Author(s):  
Mengmeng Zhao ◽  
David Buttsworth ◽  
Rishabh Choudhury
Keyword(s):  
Hydrogen Diffusion ◽  
Diffusion Flames ◽  
Numerical Study

scholarly journals An Experimental and Numerical Study on Supported Ultra-Lean Methane Combustion

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2168 ◽  
Author(s):  
Ho-Chuan Lin ◽  
Guan-Bang Chen ◽  
Fang-Hsien Wu ◽  
Hong-Yeng Li ◽  
Yei-Chin Chao
Keyword(s):  
Low Temperature ◽  
Numerical Study ◽  
Flame Temperature ◽  
Methane Combustion ◽  
External Support ◽  
Flame Height ◽  
Temperature Oxidation ◽  
Sandwich Type ◽  
Major Chemical ◽  
Wall Proximity

With a much larger global warming potential (GWP) and much shorter lifespan, the reduction of methane emissions offers an additional opportunity and a relatively quick way of mitigating climate change in the near future. However, the emissions from coal mining in the form of ventilation air methane (VAM), usually in ultra-lean concentration, pose the most significant technical challenge to the mitigation of methane emission. Therefore, a better understanding of ultra-lean methane combustion is essential. With three 5 mm × 50 mm rectangle cross-section slot jets, a novel sandwich-type triple-jet burner is proposed to provide stable combustion of an ultra-lean methane–air mixture with equivalence ratios from 0.3 to 0.88, and 0.22 in extreme conditions. The ultra-lean methane flame in the center of the triple-jet burner is supported by the two lean outer flames at an equivalence ratio φ = 0.88. The flow field and combustion chemical reactions are predicted by detailed numerical simulation with GRI-Mech 3.0 reaction mechanisms. Two-dimensional numerical results are validated with those obtained by experimental particle image velocimetry (PIV), as well as visual flame height and temperature measurements. An ultra-lean methane–air mixture has to burn with external support. In addition, the ultra-lean flame is non-propagating with a relatively low temperature. The ultra-lean center flame is seen to start from the outer flame and incline perfectly to the post-flame temperature and OH concentration profiles of the outer lean flame. The adjacent stronger flame provides heat and active radicals, such as OH and HO2, from the post-flame region and in the wall proximity of the gap between the adjacent flame and the central ultra-lean jet to initiate and maintain the combustion of the central ultra-lean flame. The outstanding wall-proximity radical of HO2 is found to be the main contributor to the initiation and stabilization of the central ultra-lean flame by providing a low-temperature oxidation of fuel through the following reaction: HO2 + CH3 ⇔ OH + CH3O. The major chemical reaction paths contributing to fuel decomposition and oxidation of the supported ultra-lean center flame are also identified and delineated.

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