Low NOx gas burners with carryover ignition

Abstract

A gas burner for low NO.sub.x gas furnaces is disclosed with improved flame carryover for igniting one or more adjacent burners. The burner includes a burner tube that receives a mixture of fuel and air. The burner tube is coupled to an outlet. The outlet includes a primary outlet opening which is in communication with at least one transverse slot for communicating a flame to at least one adjacent burner. The primary outlet opening may be elliptical and the outlet further may also include a concave outer face through which the primary outlet opening extends. The at least one slot may include a pair of oppositely directed transverse slots extending outward from the primary outlet opening along a semi-minor axis of the primary outlet opening.

Claims

1. A burner assembly comprising: a first burner comprising a first burner tube that receives a mixture of fuel and air, the first burner tube coupled to a first outlet; a second burner comprising a second burner tube that receives a mixture of fuel and air, the second burner tube coupled to a second outlet; the first outlet having rectilinear front walls, a first side wall and a trough formed between the front walls by a concave outer face, the first outlet comprising a primary outlet opening formed in the concave outer face of the first outlet, the primary outlet opening defining a first transverse slot for communicating a flame to the second outlet; the second outlet having rectilinear front walls, a second side wall and a trough formed between the front walls by a concave outer face, the second outlet comprising a second primary outlet opening formed in the concave outer face of the second outlet, the second primary outlet opening defining a second transverse slot for receiving a flame from the first outlet; the first transverse slot aligned with the second transverse slot, the first side wall adjoining the second side wall, the first side wall contacting the second side wall.

2. The burner assembly of claim 1 wherein each transverse slot extends from its respective primary outlet opening and terminates short of the outlet of the adjacent burner.

3. The burner assembly of claim 1 wherein each primary outlet opening is formed in a shape of an ellipse and each transverse slot is disposed along a semi-minor axis of the ellipse.

4. The burner assembly of claim 1 wherein each primary outlet opening is formed in a shape of an ellipse and each outlet further comprises a pair of oppositely directed transverse slots extending outward from their respective primary outlet opening along a semi-minor axis of the ellipse.

5. The burner assembly of claim 1 wherein each primary outlet opening is elliptical.

6. The burner assembly of claim 1 wherein only one of the first burner and second burner is coupled to an igniter.

7. A low NO.sub.x furnace, comprising the burner assembly of claim 1.

8. The furnace of claim 7, wherein the front walls are configured to connect to an inlet of a heat exchanger section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding of the disclosed methods and apparatuses, reference should be made to the embodiments illustrated in greater detail in the accompanying drawings, wherein:

(2) FIG. 1 is a perspective view of a prior art sectional gas furnace;

(3) FIG. 2 is a partial perspective view of a prior art in-shot burner assembly equipped with a flame carryover mechanism for use in a sectional gas furnace, like the furnace illustrated in FIG. 1;

(4) FIG. 3 is side view of a prior art lean pre-mix burner and flame retention device that are coupled to a heat exchanger section;

(5) FIG. 4 is a front perspective view of an outlet for a disclosed pre-mix, low NO.sub.x burner that includes an integrated flame carryover mechanism;

(6) FIG. 5 is a rear perspective view of the burner outlet illustrated in FIG. 4;

(7) FIG. 6 is a top plan view of a piece of sheet metal cut to form the burner outlet illustrated in FIGS. 4-5;

(8) FIG. 7 is a side plan view illustrating the coupling of a disclosed burner outlet to a sectional heat exchanger; and

(9) FIG. 8 is a partial perspective view of a disclosed burner assembly illustrating the flame carryover mechanism.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(10) Referring first to FIG. 1, a sectional gas furnace 10 is shown which comprises a burner assembly 11 with a burner box 12 that is decoupled from the inlets 49 of the primary heat exchanger sections, only one of which can be seen at 13. The primary heat exchanger sections 13 are in fluid communication with corresponding condensing heat exchanger sections 14 whose discharge end is fluidly connected to a collector box 16 and an exhaust vent 17. In operation, a gas valve 18 meters the flow of gas to the burner assembly 11 where combustion air from an air inlet 19 is mixed and ignited by an igniter assembly 21. The hot gas and secondary air are passed through the inlets 49 of the primary heat exchanger sections 13. The primary heat exchanger sections 13 lead to the condensing heat exchanger sections are 14, as shown by the arrows 20.

(11) The relatively cool exhaust gases then pass through the collector box 16 and exhaust vent 17 before being vented to the atmosphere, while the condensate flows from the collector box 16 through a drain line 22 for disposal. Flow of combustion air into the air inlet through the heat exchanger sections 13, 14 and the exhaust vent 17 is controlled by an inducer fan 23. The inducer fan 23 is driven by a motor 24 in response to signals from the integrated furnace control or IFC 29. The household air is drawn into a blower 26 which is driven by a drive motor 27, in response to signals received from the IFC 29. The discharge air from the blower 26 passes over the condensing heat exchanger sections 14 and the primary heat exchanger sections 13, in a counter-flow relationship with the hot combustion gases to thereby heat the indoor air, which then flows from the discharge opening 28 in the upward direction as indicated by the arrows 15 to a duct system (not shown) within the space being heated.

(12) Turning to FIG. 2, a pair of-shot burners 31 illustrated that are fabricated from two half shells 32, 33. The flame retention devices are illustrated at 34. The half shells 32, 33 provide for a convenient passageway 35 that can be used for flame carryover between the two burners 31. Such a flame carryover construction is not suitable for low NO.sub.x, lean pre-mix burners designed to meet the more stringent NO.sub.x regulations of the future.

(13) For example, turning to FIG. 3, a lean pre-mix burner 36 is illustrated as coupled to a primary heat exchanger section 13. The burner 36 includes a burner tube 37 and a fuel nozzle 38. Air is drawn into the burner to 37 under the pull of the inducer fan 23 (FIG. 1) as indicated by the arrows 39. A flame retention device 134 is illustrated at the junction between the heat exchanger section 13 and the burner tube 37. The burner tube 37 may also include a mixer 41, which is used to decrease lean blow-off and increase the stability of the flame. The burner tube 37 includes an outlet section 42 that is coupled to the inlet 49 of the heat exchanger section 13.

(14) An improved outlet section 142 is provided as illustrated in FIGS. 4-5. Turning to FIG. 4, the outlet section 142 includes an elliptical primary outlet opening 145 that includes a pair of outwardly extending transverse slots 146 that extend along a minor access 147 of the elliptical opening 145. FIG. 6 provide a top plan view of a for fabricating the burner outlet 142 from a single piece of sheet metal. Specifically, the side panels 151 are connected to a top panel 152 which, in turn, is connected to a front panel 153 which includes the elliptical primary outlet 145 and transverse slots 146. The front panel 153 is connected to a bottom panel 154. The two front walls 155, 156 may be connected to the inlet 49 of a heat exchanger section 13 as illustrated in FIG. 7. The sidewalls 151 may be connected to a joining sidewalls of other burner outlets to form a burner assembly 160 as illustrated in FIG. 8.

(15) Because the flame retainer device 134 can provide a complex flow field that allows the flame to anchor to it, mesh burners like those shown at 36 in FIG. 3 are typically used in single burner applications and are designed in such a fashion to provide a continuous burner surface. Sectional gas furnaces use multiple heat exchangers each with an individual burner. Therefore, applying a continuous burner between multiple heat exchangers will over temp both the inlet to the heat exchangers and the area between heat exchangers of the panel that the heat exchangers are mounted to. Creating a zone of lower energy release between burners as illustrated in FIGS. 4-8 will mitigate over temping while allowing a semi-continuous combustion surface for multi-burner ignition (FIG. 8).

(16) While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.