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Title	Low NOx Production Through Lean Premixed Combustion
Creator	Johnson, M. R.; Cheng, R. K.; Kostiuk, L. W.
Publisher	Digitized by J. Willard Marriott Library, University of Utah
Date	1994
Spatial Coverage	presented at Kingston, Canada
Abstract	An approach using fuel lean premixed combustion is being explored in an attempt to reduce NOx emissions from high temperature gas phase burners. Lean premixed flames have product gas temperatures much lower than stoichiometric, fuel rich, or diffusion flames and as a results produce less NOx. The historical difficulty in the practical use of lean premixed combustion has been the very narrow stability limits exhibited by these flames and are susceptible to blow-off. This paper is a preliminary exploration of novel and simple methods to increase the stability limits of these flames. The method employed here is ti use a ring stabilizer that can anchor flames aerodynamically over a wide range of both laminar and turbulent conditions. Results show that this method permits flames to be stabilized down to an equivalence ratio of 0.5 and at flow rates up to eight times greater than those of standard burners. The ring stabilized flames are also insensitive to turbulence in the reactant flow. These results allow the use of lean premixed flames with their low NOx emissions to be considered for commercial and industrial burners.
Type	Text
Format	application/pdf
Language	eng
Rights	This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
Conversion Specifications	Original scanned with Canon EOS-1Ds Mark II, 16.7 megapixel digital camera and saved as 400 ppi uncompressed TIFF, 16 bit depth.
Scanning Technician	Cliodhna Davis
ARK	ark:/87278/s6zk5k74
Setname	uu_afrc
ID	8896
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6zk5k74

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Title	Page 4
Format	application/pdf
OCR Text	Show Flame Stabilization As a preliminary study the work presented in this paper will only compare and contrast the stabilization (or blow-off) limits of two different burner designs. The fIrst of these is a conventional or rim stabilized flame. A single embodiment of this type of burner is shown in figure 3. The fuel enters the burner and entrains a relatively small amount of air (primary air). This fuel rich mixture leaves a burner port where it is burnt. The resulting flame has an inner premixed reaction zone and an outer diffusion flame. The secondary air for the diffusion flame comes from the surroundings. The product gases are initially at a very high temperature and this results in a relatively large amount of NO being formed. These flames are stabilized by a combination of low velocity flow near the burner walls, mixing with surrounding air, and heat loss to the burner. The details of this stabilization are described in classical text of Lewis and Von Elbe [6]. If the mixture passed through this type of conventional burner were fuel lean any mixing with the surrounding air would be a destabilizing influence. To anchor lean flames an alternate form of stabilization must be employed. The second method of stabilization described here is a ring stabilizer and is shown in fIgure 4. The principle of operation is to create a stationary recirculation zone of hot gases in the wake of the ring. These hot gases continually ignite the unburnt gases as they emerge from the burner. The notion of rods to stabilize flames by creating a recirculation zone is not new to combustion research. In the 1940 and 1950's rods were used to stabilize confIned flames as part of the development of jet combustors [7-9]. The work present in this paper is at Reynolds number more than an order of magnitude less then the jet combustor work. The stability limit in this Reynold's number regime (i.e., < 1000) is not well understood. Other purely scientific work at low Reynolds number using rod stabilized flames [10-12], has never studied the blow-off limit. For use
Setname	uu_afrc
ID	8880
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6zk5k74/8880