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Title	Development of a Vane Swirler for Use in a Low NOx Weak Swirl Burner
Creator	Yegian, D. T.; Cheng, R. K.
Publisher	Digitized by J. Willard Marriott Library, University of Utah
Date	1996
Spatial Coverage	presented at Baltimore, Maryland
Abstract	This paper describes the continuing development of the Weak-Swirl Burner (WSB) for use in low NOx applications. Weak-swirl is a unique method for stabilizing lean-burning, premixed combustion as the flame is stabilized by flow divergence, not through recirculation as is commonly seen in nonpremixed industrial burners. Earlier versions of the WSB used a tangential airjet swirler that offers flexibility for determining the range of operation and evaluating the performance of the WSB. Though common in large applications, air swirler may not be amenable to small and medium-size appliances. To reduce manufacturing costs and burner complexity, we have developed a fixed vane swirler to replace the airjet swirler in the WSB. This paper describes the operating characteristics and key design parameters of the vane swirler. A new expression for determining swirl number intensity is developed. Testing of a laboratory water heater fitted with a WSB with the new vane-swirler shows 0 < NO < 20 ng/J, 10 < CO < 70 ppm, and thermal efficiencies ~ 78% over the lean burning range of 0.70 < $ < 0.90. The continuous firing rate is robust for a 53 mm vane-swirled WSB, with initial tests ranging from 40,000 to 400,000 Btu/hr. for 0.60 < $ < 1.0. Successful development of the new vane swirler demonstrates that the low emission WSB is adaptable to a wide variety of industrial applications.
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/s6445q32
Setname	uu_afrc
ID	12824
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6445q32

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Title	Page 10
Format	application/pdf
OCR Text	Show Table I· Screens for inner tube Screen Blockage Hole diameter Hole to hole distance, s Spacing of holes 21 7705%% 23..29 mmmm 55..11 mmmm ((ssqquuaarree)) o~ 3 65% 3.2mm 4.8 mm (square) 0 4 60% 3.2mm 4.8 mm (hexagon) ~O 0 0 To Interrogate the flow field generated by the vane sWIrler, velocIty measurements were obtained by a two component Laser Doppler anemometry (LDA) systeml . It uses a two color argon ion laser separated into four intersecting beams. Differential frequencies of 5 Mhz and 2 Mhz as generated by Bragg cells were used to remove directional ambiguity for the axial and tangential components respectively. Velocity traverses at 5 mm above the burner exit tube were used as the basis for comparing the flowfields generated by the vane-swirler and by the air-swirler. The laboratory test station used to evaluate the performance of vane-swirled WSB in conjunction with the simulated spa heater is described in detail in Ref. 2. RESULTS: Redefining the swirl number The major difference between our vane-swirler and the conventional hub swirler is that our design allows for a center core of premixture which has no tangential velocity. Without a screen to distribute the flow to the annulus, the obvious consequence of this design would be to force most of the flow through the center core due to the higher pr~ssure drop associated with the annular guide-vane section .. The use of screens with different blockages to balance the pressure across center and annular regions enables us to vary the swirl rate. Starting from Equation (1), S for the new geometry should be: which reduQes to: 6
Setname	uu_afrc
ID	12808
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6445q32/12808