Reduction of NOx Formation by Water Sprays in Strained Two-Stage Flames

1997 ◽  
Vol 119 (4) ◽  
pp. 836-843 ◽  
Author(s):  
S. C. Li ◽  
N. Ilincic ◽  
F. A. Williams
Keyword(s):  
Diffusion Flames ◽  
Laser Sheet ◽  
Flame Structure ◽  
Flame Temperature ◽  
Temperature Fields ◽  
Two Stage ◽  
Two Phase ◽  
Nox Formation ◽  
Numerical Predictions ◽  
Water Sprays

Staged combustion can be employed to reduce the formation of CO and NOx, stabilize the flame, decrease the flame temperature, and create better working conditions in gas turbine combustors. To help understand influences of partial premixing and addition of water on NOx formation, we study two-stage flames in a counterflow spray burner. This paper reports experimental and theoretical results concerning two-stage combustion in which one feed stream is composed of a fuel-rich mixture of methane and air and the other is air. Water sprays are added to the air stream. This two-phase laminar counterflow configuration exhibits a green premixed flame, a blue diffusion flame, and a vaporization plane. All three are flat and parallel. The separation distances between them decrease with increasing equivalence ratio and strain rate. Flow visualization is provided through illumination by an argon ion laser sheet, velocity fields and spray structure are measured by a phase-doppler particle analyzer, concentration fields of major stable species are measured by gas chromatography of samples withdrawn from the flame, and temperature fields are measured by a thermocouple. Numerical integrations that employ a recent chemical-kinetic data base are performed to model the flame structure and NOx formation. Comparisons of experimental results with numerical predictions are made to test agreement. This work provides information on hydrocarbon combustion in both premixed flames and diffusion flames, indicates how NOx is formed in fuel-rich flames, and suggests how the pollutants can be reduced.

scholarly journals Reduction of NOx Formation by Water Sprays in Strained Two-Stage Flames

1996 ◽  
Author(s):  
S. C. Li ◽  
N. Ilincic ◽  
F. A. Williams
Keyword(s):  
Diffusion Flames ◽  
Laser Sheet ◽  
Flame Structure ◽  
Flame Temperature ◽  
Temperature Fields ◽  
Two Stage ◽  
Two Phase ◽  
Nox Formation ◽  
Numerical Predictions ◽  
Water Sprays

Staged combustion can be employed to reduce the formation of CO and NOx, stabilize the flame, decrease the flame temperature and create better working conditions in gas turbine combustors. To help understand influences of partial premixing and addition of water on NOx formation, we study two-stage flames in a counterflow spray burner. This paper reports experimental and theoretical results concerning two-stage combustion in which one feed stream is composed of a fuel-rich mixture of methane and air and the other is air. Water sprays are added to the air stream. This two-phase laminar counterflow configuration exhibits a green premixed flame, a blue diffusion flame and a vaporization plane. All three are flat and parallel. The separation distances between them decrease with increasing equivalence ratio and strain rate. Flow visualization is provided through illumination by an argon ion laser sheet, velocity fields and spray structure are measured by a phase-doppler particle analyzer, concentration fields of major stable species are measured by gas chromatography of samples withdrawn from the flame, and temperature fields are measured by a thermocouple. Numerical integrations which employ a recent chemical-kinetic data base are performed to model the flame structure and NOx formation. Comparisons of experimental results with numerical predictions are made to test agreement. This work provides information on hydrocarbon combustion in both premixed flames and diffusion flames, indicates how NOx is formed in fuel-rich flames and suggests how the pollutants can be reduced.

scholarly journals Experimental and Numerical Studies of Two-Stage Ethane-Air Flames

1999 ◽  
Author(s):  
M. M. Y. Waly ◽  
S. C. Li ◽  
F. A. Williams
Keyword(s):  
Chemical Kinetic ◽  
Two Stage ◽  
Nox Formation ◽  
Pollutant Formation ◽  
Numerical Studies ◽  
Numerical Predictions ◽  
Air Stream ◽  
Stage Combustion ◽  
Reduce Emissions ◽  
Flame Chemistry

This paper reports results of experimental and numerical investigations on ethane-air two-stage combustion in a counterflow burner where the fuel stream, which is partially premixed with air for equivalence ratios from 1.6 to 3.0, flows against a pure air stream. Similar to methane, the two-stage ethane combustion exhibits a green fuel-rich premixed flame and a blue diffusion flame. Flame structures, including concentration profiles of stable intermediate species such as C2H4, C2H2 and CH4, are measured by a gas chromatography and are calculated by numerical integrations of the conservation equations employing an updated elementary chemical-kinetic data base. The implications of the results from these experimental measurements and numerical predictions are summarized, the flame chemistry of ethane two-stage combustion at different degrees of premixing (or equivalence ratio) is discussed, and the relationship between NOx formation and the degree of premixing is established. The present work helps to increase understanding of flame chemistry of hydrocarbon fuels, identify important reactions for pollutant formation and suggest means to reduce emissions.

scholarly journals Fuel Molecular Structure and Flame Temperature Effects on Soot Formation in Gas Turbine Combustors

1990 ◽  
Vol 112 (1) ◽  
pp. 52-59 ◽  
Author(s):  
O¨. L. Gu¨lder ◽  
B. Glavincˇevski ◽  
M. F. Baksh
Keyword(s):  
Molecular Structure ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Empirical Relationship ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Smoke Point ◽  
Temperature Fields ◽  
Diesel Fuels

A systematic study of soot formation along the centerlines of axisymmetric laminar diffusion flames of a large number of liquid hydrocarbons, hydrocarbon blends, and aviation turbine and diesel fuels was made. Measurements of the attenuation of a laser beam across the flame diameter were used to obtain the soot volume fraction, assuming Rayleigh extinction. Two sets of hydrocarbon blends were designed such that the molecular fuel composition varied considerably but the temperature fields in the flames were kept practically constant. Thus it was possible to separate the effects of molecular structure and the flame temperature on soot formation. It was quantitatively shown that the smoke point height is a lumped measure of fuel molecular constitution. The developed empirical relationship between soot volume fractions and fuel smoke point and hydrogen-to-carbon ratio was applied to five different combustor radiation data, and good agreement was obtained.

Experimental and Numerical Analysis of Carbon Black Formation in Hydrocarbon/Air Diffusion Flames

2010 ◽  
Author(s):  
D. F. Heravi ◽  
H. M. Heravi ◽  
K. Bashirnezhad ◽  
Hassan Sanaei ◽  
Amirhomayun Samiee
Keyword(s):  
Carbon Black ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Mass Fraction ◽  
Diffusion Flames ◽  
Flame Temperature ◽  
Gravimetric Method ◽  
Numerical Predictions ◽  
Air Diffusion

Carbon black has been widely used in industry, especially in rubber and plastic production. The present study is concerned with measuring and simulating the carbon black formation process in Propane-air and Acetylene-Air diffusion flames. The carbon black concentrations in the furnace have been measured by means of a soot pump and gravimetric method. The flue gas analysis is also done by means of Testo XL-350 Gas Analyzer. The numerical predictions are carried out with the CFD code, Fluent. The chemical reaction formulation relates the production of the carbon black to the incomplete combustion and pyrolysis of propane and Acetylene as both the main gas and the feedstock. The effects of feedstock mass flow rate, the position of feedstock injection, the feedstock material and the shape of the furnace on carbon black are studied. The results show the effect of temperature on soot and carbon black formation in which as the temperature increases the soot and carbon black mass fraction is also increased. The results also show that as the feedstock mass flow rate increases the formation of the carbon black is increased up to point where the mass flow rate of feed stock is three times greater than the mass flow rate of the main gas and after that the carbon black production rate starts decreasing because of the decreasing of temperature due to cold fuel injection to the furnace. The position of feedstock injection affects the mixing process of air and fuel, and complete mixing causes the temperature to be increased. The injection of feedstock in the pre-combustion zone influences the maximum of the flame temperature. As the hydrocarbon initially pyrolyzes to acetylene and afterwards acetylene breaks into soot and carbon black in the present study acetylene is used as feedstock, the results show huge increasing of soot and carbon black mass fraction in the products. The results also show that predictions and the experimental measurements are in good agreement.

Effects of Fuel-Side N2, CO2, H2O Dilution on Combustion Characteristics and NOx Formation of Syngas Turbulent Nonpremixed Jet Flames

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Liying Zhuo ◽  
Yong Jiang ◽  
Rong Qiu ◽  
Jiangtao An ◽  
Wu Xu
Keyword(s):  
International Workshop ◽  
Flame Structure ◽  
Flame Temperature ◽  
Nonpremixed Flames ◽  
Nox Formation ◽  
Extinction Process ◽  
Turbulent Nonpremixed ◽  
Fuel Mixtures ◽  
The One ◽  
Good Agreement

The effects of the three fuel-side diluents N2, CO2, and H2O on the accurate flame structure and NOx formation characteristics of the turbulent syngas nonpremixed flames are investigated using the one-dimensional-turbulence (ODT) model. For nonpremixed flames, the fuel mixtures consist of H2, CO and three diluents: N2, H2O, and CO2. The proportion of diluents is varied from 10% to 30% while the H2/CO ratio is kept as a constant at 0.75 all the time. Mass fraction of main species and temperature of 30% N2 basic dilution case predicted by the ODT model are compared with the tests measuring results obtained by International Workshop on Measurements and Computation of Turbulent Nonpremixed Flames, and it is found that the results are in good agreement. Numerical results indicate that the CO2 diluted flames have the largest reduction on flame temperature as well as the NOx emission, while H2O is more effective than N2. For CO2 and H2O dilution flames, flame structure becomes unstable with an obvious lift phenomenon. Since ODT captures the flame extinction process, flames added with CO2 and H2O not only have a lower extinction temperature but also the reignition process is slower.

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

2006 ◽  
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.

scholarly journals Fuel Molecular Structure and Flame Temperature Effects on Soot Formation in Gas Turbine Combustors

1989 ◽  
Author(s):  
Ö. L. Gülder ◽  
B. Glavinčevski ◽  
M. F. Baksh
Keyword(s):  
Molecular Structure ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Empirical Relationship ◽  
Flame Temperature ◽  
Soot Volume Fraction ◽  
Smoke Point ◽  
Temperature Fields ◽  
Diesel Fuels

A systematic study of soot formation along the centerlines of axisymmetric laminar diffusion flames of a large number of liquid hydrocarbons, hydrocarbon blends, and aviation turbine and diesel fuels were made. Measurements of the attenuation of a laser beam across the flame diameter were used to obtain the soot volume fraction, assuming Rayleigh extinction. Two sets of hydrocarbon blends were designed such that the molecular fuel composition varied considerably but the temperature fields in the flames were kept practically constant. Thus it was possible to separate the effects of molecular structure and the flame temperature on soot formation. It was quantitatively shown that the smoke point height is a lumped measure of fuel molecular constitution. The developed empirical relationship between soot volume fractions and fuel smoke point and hydrogen to carbon ratio was applied to five different combustor radiation data, and good agreement was obtained.

Experimental and Numerical Studies of Two-Stage Ethane-Air Flames

2000 ◽  
Vol 122 (4) ◽  
pp. 651-658 ◽  
Author(s):  
M. M. Y. Waly ◽  
S. C. Li ◽  
F. A. Williams
Keyword(s):  
Chemical Kinetic ◽  
Two Stage ◽  
Nox Formation ◽  
Pollutant Formation ◽  
Numerical Studies ◽  
Numerical Predictions ◽  
Air Stream ◽  
Stage Combustion ◽  
Reduce Emissions ◽  
Flame Chemistry

This paper reports results of experimental and numerical investigations on ethane-air two-stage combustion in a counterflow burner where the fuel stream, which is partially premixed with air for equivalence ratios from 1.6 to 3.0, flows against a pure air stream. Similar to methane, the two-stage ethane combustion exhibits a green fuel-rich premixed flame and a blue diffusion flame. Flame structures, including concentration profiles of stable intermediate species such as C2H4,C2H2 and CH4, are measured by a gas chromatography and are calculated by numerical integrations of the conservation equations employing an updated elementary chemical-kinetic data base. The implications of the results from these experimental measurements and numerical predictions are summarized, the flame chemistry of ethane two-stage combustion at different degrees of premixing (or equivalence ratio) is discussed, and the relationship between NOx formation and the degree of premixing is established. The present work helps to increase understanding of flame chemistry of hydrocarbon fuels, identify important reactions for pollutant formation and suggest means to reduce emissions. [S0742-4795(00)01303-X]

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