Numerical Study on Formation Mechanism and Reduction Methods of NOx in Methane/Oxygen-Enriched Air Diffusion Flame

2012 ◽  
Vol 602-604 ◽  
pp. 1317-1324
Author(s):  
Yao Xun Feng ◽  
Xiao Feng Zheng ◽  
Ming Sheng Jia
Keyword(s):  
Production Rate ◽  
Diffusion Flame ◽  
Numerical Study ◽  
Nox Reduction ◽  
Flame Structure ◽  
Inert Gases ◽  
Maximum Temperature ◽  
No Production ◽  
Detailed Chemical Kinetics ◽  
Reduction Methods

In this study, a methane/oxygen-enriched air counterflow diffusion flame was analyzed numerically using detailed chemical kinetics, on the condition that the oxygen mass fraction in the oxidizer stream varied from 21% to 99%. The obtained results show that as the oxygen concentration in air increases, the maximum temperature increases; the region of combustion reaction is gradually divided into two parts, and the total NO production rate and especially the thermal NO production rate increase greatly. With consideration of the possibility of gas recirculation to minimize NOX in the industrial combustor, the usefulness of NOX reduction in combustion was analyzed numerically when the methane stream was diluted with the inert gases N2 or CO2. The obtained results show that the flame structure and dominant mechanism of NO formation change greatly with the concentration of diluents in fuel; the emission index of NO decreases gradually when the concentration of diluent CO2 increases.

Experimental and numerical study of rich inverse diffusion flame structure

2013 ◽  
Vol 34 (1) ◽  
pp. 1045-1055 ◽  
Author(s):  
B. Stelzner ◽  
F. Hunger ◽  
S. Voss ◽  
J. Keller ◽  
C. Hasse ◽  
...  
Keyword(s):  
Diffusion Flame ◽  
Numerical Study ◽  
Flame Structure ◽  
Inverse Diffusion ◽  
Inverse Diffusion Flame

Numerical Study on NOx Reduction in Pulse Detonation Combustion by Using Steam Injection Decoupled From Detonation Development

2018 ◽  
Author(s):  
Niclas Hanraths ◽  
Fabian Tolkmitt ◽  
Phillip Berndt ◽  
Neda Djordjevic
Keyword(s):  
Initial Conditions ◽  
Numerical Study ◽  
Nox Reduction ◽  
Pollutant Emissions ◽  
Nox Emissions ◽  
Reliable Operation ◽  
Detonation Cell ◽  
Pulse Detonation ◽  
Detonation Combustion ◽  
Reduction Methods

Recently, the focus has been laid on the characteristics of pollutant emissions from pulse detonation combustion. Initial studies indicate possibly high nitrogen oxides (NOx) emissions, so the assessment of potential primary reduction methods is advisable. The present work considers the following reduction methods: lean combustion, nitrogen and steam dilution as well as flue gas recirculation. Since such changes in the combustion mixture reduce its reactivity and thus detonability, they can impair a reliable operation in technical systems. In order to explore the potential and limitations of each of these reduction methods, they are compared for mixtures featuring an identical characteristic detonation cell size at given initial conditions. Furthermore, building upon the use of steam dilution, a modified method to add steam to the combustible mixture is investigated. In order to avoid the strong reduction of mixture detonability by steam addition and ensure a robust detonation formation, steam is injected into the already developed detonation front. It was found that, for sufficiently even steam distribution, NOx reduction comparable to a premixed dilution could be achieved. This approach enables the realization of NOx reduction in pulse detonation combustion also for such conditions, for which premix dilution is not feasible. Therefore, combining the premix dilution with post-shock injection offers a promising strategy to substantially reduce NOx emissions from pulse detonation combustion, while at the same time ensuring its reliable operation.

Modeling of Emissions in a Laboratory Swirl Combustor

2015 ◽  
Author(s):  
Viswanath R. Katta ◽  
William M. Roquemore
Keyword(s):  
Chemical Kinetics ◽  
Numerical Study ◽  
Flame Structure ◽  
Detailed Chemical Kinetics ◽  
Swirl Combustor ◽  
Detailed Chemistry ◽  
Hydrocarbon Emission ◽  
Recirculation Zones ◽  
Fuel Mixtures ◽  
Detailed Chemical

A swirl-stabilized combustor utilizes recirculation zones for stabilizing the flame. The performance of such combustors could depend on the fuel used as the cracked fuel products may enter the recirculation-zones and alter their characteristics. A numerical study is conducted for understanding the effects of fuel variation on the combustion and unburned-hydrocarbon-emission characteristics of a laboratory swirl combustor. A time-dependent, detailed-chemistry CFD model UNICORN is used. Six binary fuel mixtures formulated with n-dodecane and n-heptane, m-xylene, iso-octane or hexadecane are considered. A semi-detailed chemical-kinetics model (CRECK-0810) involving 206 species and 5652 reactions for the combustion of these fuels is incorporated into UNICORN code. Calculations are performed for a fuel-lean condition, which represents cruise operation of an aircraft. Combustor flows simulated with different fuel mixtures yielded nearly the same flowfields and flame structures. Production of the intermediate cracked fuel species that are key for the final flame structure and emissions seems to be independent of the fuel used. This finding could greatly simplify the detailed chemical kinetics used for obtaining cracked products. As the cracked fuel species are completely consumed with in the flame zone, no emissions are observed at the combustor exit for the considered fuel-lean condition.

scholarly journals Numerical Study of the Structure and NO Emission Characteristics of N2- and CO2-Diluted Tubular Diffusion Flames

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1490
Author(s):  
Harshini Devathi ◽  
Carl A. Hall ◽  
Robert W. Pitz
Keyword(s):  
Diffusion Flames ◽  
Numerical Study ◽  
Reaction Pathway ◽  
Flame Structure ◽  
Reaction Rates ◽  
No Production ◽  
Emission Characteristics ◽  
No Emission ◽  
Nitrogen Radicals ◽  
Lower Temperature

The structure of methane/air tubular diffusion flames with 65 % fuel dilution by either CO2 or N2 is numerically investigated as a function of pressure. As pressure is increased, the reaction zone thickness reduces due to decrease in diffusivities with pressure. The flame with CO2-diluted fuel exhibits much lower nitrogen radicals (N, NH, HCN, NCO) and lower temperature than its N2-diluted counterpart. In addition to flame structure, NO emission characteristics are studied using analysis of reaction rates and quantitative reaction pathway diagrams (QRPDs). Four different routes, namely the thermal route, Fenimore prompt route, N2O route, and NNH route, are examined and it is observed that the Fenimore prompt route is the most dominant for both CO2- and N2-diuted cases at all values of pressure followed by NNH route, thermal route, and N2O route. This is due to low temperatures (below 1900 K) found in these highly diluted, stretched, and curved flames. Further, due to lower availability of N2 and nitrogen bearing radicals for the CO2-diluted cases, the reaction rates are orders of magnitude lower than their N2-diluted counterparts. This results in lower NO production for the CO2-diluted flame cases.

scholarly journals Numerical study of the Effect of CO2 on the NH3/CH4 Counterflow Diffusion Flame in O2/CO2/N2 Atmosphere

2021 ◽  
Vol 898 (1) ◽  
pp. 012006
Author(s):  
Conghao Li ◽  
Jingfu Wang ◽  
Ying Chen ◽  
Xiaolei Zhang
Keyword(s):  
Diffusion Flame ◽  
Numerical Study ◽  
Flame Structure ◽  
Flame Temperature ◽  
Combustion Characteristics ◽  
No Emission ◽  
N2 Atmosphere ◽  
Fraction Increase ◽  
Temperature And Pressure ◽  
Counterflow Diffusion Flame

Abstract Ammonia, as a carbon-neutral fuel, draws people attentions recently. NH3/CH4 blends is considered as a kind of fuel. A numerical simulation of the effects of CO2 dilution on the combustion characteristics and NO emission of NH3/CH4 counterflow diffusion flame was conducted in this study. Diffusion flame structure, the influence of CO2 radiation characteristics on temperature and NO emission characteristics were studies at normal temperature and pressure. The dilution and radiation of CO2 reduce the flame temperature significantly. NO concentration decreased with the CO2 mole fraction increase effectively. The study extends the basic combustion characteristics of NH3 containing fuel.

Numerical Study on NOx Reduction in Pulse Detonation Combustion by Using Steam Injection Decoupled From Detonation Development

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Niclas Hanraths ◽  
Fabian Tolkmitt ◽  
Phillip Berndt ◽  
Neda Djordjevic
Keyword(s):  
Initial Conditions ◽  
Numerical Study ◽  
Nox Reduction ◽  
Pollutant Emissions ◽  
Nox Emissions ◽  
Reliable Operation ◽  
Detonation Cell ◽  
Pulse Detonation ◽  
Detonation Combustion ◽  
Reduction Methods

Recently, the focus has been laid on the characteristics of pollutant emissions from pulse detonation combustion (PDC). Initial studies indicate possibly high nitrogen oxides (NOx) emissions, so the assessment of potential primary reduction methods is advisable. The present work considers the following reduction methods: lean combustion, nitrogen and steam dilution, as well as flue gas recirculation. Since such changes in the combustion mixture reduce its reactivity and thus detonability, they can impair a reliable operation in technical systems. In order to explore the potential and limitations of each of these reduction methods, they are compared for mixtures featuring an identical characteristic detonation cell size at given initial conditions. Furthermore, building upon the use of steam dilution, a modified method to add steam to the combustible mixture is investigated. In order to avoid the strong reduction of mixture detonability by steam addition and ensure a robust detonation formation, steam is injected into the already developed detonation front. It was found that, for sufficiently even steam distribution, NOx reduction comparable to a premixed dilution could be achieved. This approach enables the realization of NOx reduction in PDC also for such conditions, for which premix dilution is not feasible. Therefore, combining the premix dilution with postshock injection offers a promising strategy to substantially reduce NOx emissions from PDC, while at the same time ensuring its reliable operation.

Numerical study on flame structure and NO formation in CH4-O2-N2 counterflow diffusion flame diluted with H2O

2004 ◽  
Vol 28 (14) ◽  
pp. 1255-1267 ◽  
Author(s):  
Dong-Jin Hwang ◽  
Jong-Wook Choi ◽  
Jeong Park ◽  
Sang-In Keel ◽  
Chang-Bo Ch ◽  
...  
Keyword(s):  
Diffusion Flame ◽  
Numerical Study ◽  
Flame Structure ◽  
No Formation ◽  
Counterflow Diffusion Flame

PARALLEL SOLVER FOR THE SIMULATIONS OF DETONATION WAVES ON UNSTRUCTURED GRIDS

2020 ◽  
Author(s):  
A. I. Lopato ◽  
◽  
A. G. Eremenko ◽  
Keyword(s):  
Chemical Kinetics ◽  
Numerical Scheme ◽  
Unstructured Grids ◽  
Numerical Study ◽  
Numerical Approach ◽  
Detonation Waves ◽  
Detailed Chemical Kinetics ◽  
Parallel Solver ◽  
Further Development ◽  
Detailed Chemical

Recently, we developed a numerical approach for the simulation of detonation waves on fully unstructured grids and applied it to the numerical study of the mechanisms of detonation initiation in multifocusing systems. Current work is devoted to further development of our numerical approach, namely, parallelization of the numerical scheme and introduction of more comprehensive detailed chemical kinetics scheme.

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