Nitric oxide levels of turbulent jet diffusion flames; Effects of residence time and Damkohler number

Journal Article · Wed Jan 01 04:00:00 EST 1992 · Combustion and Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(92)90005-A· OSTI ID:5697792

Driscoll, J F; Chen, R H; Yoon, Y ^[1]

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1. Dept. of Aerospace Engineering, Univ. of Michigan, Ann Arbor, MI (US)

This paper reports on the global residence time and the deviations from chemical equilibrium (i.e., the Damkohler number) that were varied for a number of jet diffusion flames. The resulting effects on the nitric oxide emission index were measured and were compared with existing analysis. The global residence time is defined as L{sub f}/U{sub F}, where L{sub f} is the flame length and U{sub F} is the fuel jet velocity. Flame length is varied by increasing the jet diameter, by adding either premixed air or inerts to the fuel jet, or by adding a coaxial air stream. In particular, a unique jet flame was studied that is composed of helium-diluted hydrogen fuel; this flame is free of the complicating effects of flame radiation, buoyancy, and prompt NO and provides a useful baseline comparison to theory. It is found that NO{sub x} levels for three types of fuels were consistently less than levels predicted by thermal theory, which suggests that one or both of the two mechanisms that suppress NO{sub x}, namely strain and radiative cooling, are important. The use of a Damkohler number was found to successfully correlate the NO{sub x} data for the hydrogen/helium-air flames that have simple chemistry. As the helium concentration is increased in order to reduce the Damkohler number, the measured NO{sub x} emission index exceeds that of the equilibrium theory by as much as a factor of 24, which is further indication that it is important to add the correct nonequilibrium oxygen atom chemistry to current models.

• OSTI ID: 5697792
• Journal Information: Combustion and Flame; (United States), Journal Name: Combustion and Flame; (United States) Journal Issue: 1 Vol. 88:1; ISSN CBFMA; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
AIR
BINARY MIXTURES
CHALCOGENIDES
CONCENTRATION RATIO
COOLING
DIFFUSION
DIMENSIONS
DISPERSIONS
ELEMENTS
EMISSION
EQUILIBRIUM
FLAMES
FLUIDS
GASES
HELIUM
HYDROGEN
JETS
LENGTH
MIXTURES
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
RADIATIVE COOLING
RARE GASES
STRAINS
TURBULENCE
VARIATIONS
VELOCITY