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  Inshot burner flame retainerUSPTO Application #: 20070082309Title: Inshot burner flame retainer Abstract: A flame retainer for an inshot burner has a plurality of secondary openings that take full advantage of the space available to limit their size in one dimension to prevent flashbacks but are sufficient in size to allow for the flow of sufficient primary air so as to prevent yellow tipping and soot formation. The slots are elongated in radially cross-sectional shape, and their widths are limited to a dimension of 0.13 inches. The width is also limited to dimensions equal to or greater than 0.09 inches so as to prevent the formation of soot. (end of abstract) Agent: Marjama & Bilinski LLP - Syracuse, NY, US Inventors: Ninev Karl Zia, Duane D. Garloch USPTO Applicaton #: 20070082309 - Class: 431354000 (USPTO) Related Patent Categories: Combustion, Mixer And Flame Holder The Patent Description & Claims data below is from USPTO Patent Application 20070082309. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] This invention relates generally to residential furnaces and, more particularly, to inshot burners with flame retainers. BACKGROUND OF THE INVENTION [0002] Gas fired appliances, such as residential and light commercial heating furnaces, often use a particular type of gas burner commonly referred to as an inshot burner. In this type of burner, fuel gas under pressure passes through a central port disposed at the inlet of a venturi burner nozzle. Atmospheric air is drawn into the burner nozzle and mixes with the fuel gas as it passes through the burner nozzle. In some constructions, a burner head insert, also referred to as a flame retention insert, made of compressed sintered or powdered metal is mounted in the outlet end of the tube. In operation, as gas is injected into the inlet end of the nozzle, it entrains air into the nozzle. This primary air/gas mix flows through the nozzle to the burner head insert. The primary air/gas mix passes through outlet openings defined by the insert and burns as it exits the insert forming a flame projecting downstream from the burner head insert. Secondary air flows around the outside of the venturi tube and is entrained in the burning mixture downstream of the insert in order to provide additional air to complete the combustion process. [0003] Some of the problems associated with conventional inshot burner designs are improper ignition, flame instability, noise and nitrogen oxides formation. Ignition problems can arise when the ignition location is critical. The velocity of the primary air/gas flow from the insert can be greater than the flame speed. Under this condition, the flame lifts off from the burner insert, i.e. the flame begins to burn at a location spaced from the outer face of the flame retention insert. Flame liftoff is a major cause of the noise associated with the operation of inshot burner nozzles. If the velocity of the air/gas mixture is too slow when compared to the flame speed, flashback can occur. Flashback is the burning of the gas within the burner nozzle itself. This condition can cause overheating and deterioration of the nozzle. [0004] Flame retention or burner head inserts have been designed in an attempt to achieve better flame stability and reduction of noise. U.S. Pat. No. 6,036,481 provides a burner head insert having an inner flow passage and a plurality of second flow passages with tapered splines therebetween. U.S. Pat. No. 5,186,620 provides a central passage, secondary openings of smaller diameters arranged circularly around the central insert and a plurality of peripheral openings with stepped notches. While such designs are helpful in addressing the problems discussed hereinabove, they do not adequately address the problem of flashback and the propensity for producing soot, particularly when using propane rather than natural gas as the fuel. That is, the applicants have found that flashback of flame to the outer perimeter flow passages in a burner insert can be substantially reduced or prevented if certain dimensional limitations are placed on the passages. However, when dealing with other design limitations on the overall size of the burner, simply downsizing the perimeter passages results in insufficient primary air for combustion. That is, as the size of the passages is reduced to prevent flashback, there is a tendency to cause a yellowing of the flame tip which, in turn, tends to cause the formation of soot. Further, attempting to increase the number of the passages eventually reaches the minimum limit of wall thickness (i.e. the recognized industry standard of 0.045-0.060 inches) for powdered metal parts, which is the most viable and economical method of producing flame retainers. DISCLOSURE OF THE INVENTION [0005] The applicants have found that if the perimeter flow passages are formed having at least one dimension which is approximately 0.13 inches or less, a flamelet which might otherwise propagate upstream through that channel can be quenched and halted by the proximity of the channel wall. In order to obtain the necessary flow of air through the passages to prevent sooting, while maintaining the minimum limit of wall thickness, the passages are preferably formed having a radial cross sectional shape that is elongated in form, essentially by tying multiple holes together to form slots to increase the flow area while preserving the wall thickness between passages and also maintaining a criteria of having a passage dimension (i.e. slot width) no greater than the 0.13 inches. [0006] In accordance with one embodiment of the invention, the passages are V-shaped in radial cross section. This is accomplished in one way by having a plurality of circular openings at one radius and a second plurality of openings at a greater radius, and removing the material between the outer openings and inner opening to provide a V-shape with the apex toward the center. [0007] Another embodiment of the present invention is to provide passages having radial cross sections that are elongated in shape with their elongations being disposed radially. This, again, is accomplished by having a plurality of openings formed at a smaller radius and a plurality of openings at a greater radius, and removing material therebetween to provide elongated slots that are radially disposed. [0008] According to another embodiment of the invention, the passages are formed such that in radial cross section, they are annular in form and are circumferentially equally spaced around a central opening. The restricted radial width prevents flashback, while the circumferential length is sufficient to prevent sooting. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIGS. 1A and 1B are illustrations of a flame retainer device in accordance with the prior art. [0010] FIG. 2 is a modified version of a flame retainer. [0011] FIG. 3 is a further modified flame retainer. [0012] FIG. 4A is a flame retainer in accordance with a preferred embodiment of the invention. [0013] FIG. 4B is an alternative embodiment thereof. [0014] FIG. 4C is another alternative embodiment thereof. [0015] FIG. 5 is a graphic illustration of the relationship between slot width and tendencies to form soot or allow flashback. [0016] FIG. 6 is an alternative embodiment of the invention. [0017] FIG. 7 is a further alternative embodiment thereof. DETAILED DESCRIPTION OF THE INVENTION [0018] Referring now to FIGS. 1A and 1B, there is shown a flame retainer structure in accordance with the prior art. The flamer retainer, shown generally at 11 comprises a cylinder 12 having an outer surface 13 and a central passage 14 extending therethrough. A plurality of secondary openings 16 of smaller diameter are arranged circularly around the central passage 14. [0019] While the size of the central passageway 14 is somewhat decided by other considerations, the designers have taken some liberty with the size of the secondary openings 16 to bring about desired results. Generally, the size of the secondary openings 16 has been chosen to bring about the desired performance characteristics. While the number and particular location of the secondary openings has been varied to bring about particular results, the secondary openings have generally been circular in form with their axes aligned with the axes of the central passage 14. Continue reading... Full patent description for Inshot burner flame retainer Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Inshot burner flame retainer patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Inshot burner flame retainer or other areas of interest. ### Previous Patent Application: Catalytic microcombustors for compact power or heat generation Next Patent Application: Method for controlling heating apparatus Industry Class: Combustion ### FreshPatents.com Support Thank you for viewing the Inshot burner flame retainer patent info. 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