In this study, a co-flow methane/air diffusion flame at Reynolds number of 6000 was numerically simulated. The co-flow air and fuel streams were diluted with Nitrogen in the range of 0% to 20%. The thermal and composition fields in the far-burner reaction zone (close to the exhaust) were computed, and the effects of diluent’s addition to the air stream (simulating FGR) and to the fuel stream (simulating FIR) were investigated. The results show that air-side dilution is very effective up to 5% diluent’s addition. For which, 95% and 65% drops in NO and CO emissions, respectively, along with a 16% increase in temperature, are predicted compared to the baseline case (0% dilution). However, beyond 5% dilution, no effect (reaction) has been predicted. On the other hand, the fuel-side dilution has shown an effect for all simulated diluent’s addition (i.e. 0%–20%). However, that effect is not systematic neither on temperature, CO or NO concentrations. For a similar 5% dilution to the fuel-side, a 14% increase in NO and a 97% decrease in CO are predicted, along with a 5.6% increase in temperature. The simulated results revealed that air-side dilution (simulating FGR) has a dramatic greater effectiveness in NO reduction, whereas, fuel-side dilution (simulating FIR) has a greater effectiveness in CO reduction. Besides, the results suggest an important role for Prompt-NO Fenimore mechanism.

1.
Hopkins, K. C., Czerniak, D. O., Youssef, C., Radak, L., and Nylander, J., 1991, ASME paper 91-JPGC-EC-3, International Power Generation Conference, San Diego, CA, October 6–10.
2.
Reese, J. L., Reddy, V., Lange, H. B., Chang, C., Radak, L. J., and Youssef, C. F., 1994, American And Japanese Flame Research Council, Pacific Rim International Conference on Environmental Control of Combustion Processes, Maui, HI, October 16–20.
3.
Feese
J.
, and
Turns
S.
,
1998
, “
Nitric Oxide Emissions from Laminar diffusion Flames
,”
Combustion and Flame
,
113
,
66
78
.
4.
Turns, S. R., 2000, An Introduction to Combustion: Concepts and Applications. McGraw-Hill Inc., NY.
5.
Fenimore, C. P., 1970, “Formation of Nitrie Oxide in Premixed Hydrocarbon Flames,” Thirteenth Symposium (International) on Combustion, Combustion Institute, Pittsburgh, PA. pp. 373–380.
6.
Miller
J. A.
, and
Bowman
C. T.
,
1989
, “
Mechanisms and Modeling of Nitrogen Chemistry in Combustion
,”
Progress in Energy and Combustion
,
15
, p.
287
287
.
7.
Bowman, Craig. T., 1992, “Control of Combustion-Generated Nitrogen Oxide Emissions: Technology Driven By Regulations,” Twenty-Fourth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, p. 859–878.
8.
Van doormaal
J. P.
, and
Dryer
F. L.
,
1984
, “
Enhancements of the SIMPLE Methods for Predicting Incompressible Fluid Flows
,”
Numerical Heat Transfer
,
7
, pp.
147
163
.
9.
Qubbaj, A. R., 1998, “An Experimental and Numerical Study of Gas Jet Diffusion Flames Enveloped by a Cascade of Venturis,” Ph.D. Dissertation, School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK.
10.
Warnatz, J., 1984, “Rate Coefficients in the C/H/O System,” Combustion Chemistry, W. C. Gardiner, Jr., Editor, Springer-Verlag, New York, pp. 197–360.
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