US20130252185A1

US20130252185A1 - Igniter air shield

Info

Publication number: US20130252185A1
Application number: US13/847,106
Authority: US
Inventors: Robert Shaw; Merle D. Sears; James F. Bicknell
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2012-03-21
Filing date: 2013-03-19
Publication date: 2013-09-26

Abstract

A burner assembly for use adjacent an igniter element in a gas appliance includes a top plate configured to form the geometric top half of at least one burner, and a bottom plate configured to form the geometric bottom half of at least one burner. The top plate and the bottom plate are joined together to form a burner and a burner carryover. An igniter air shield extends from either the top plate or the bottom plate such that the igniter air shield diverts secondary combustion air flowing around the burner and the adjacent igniter element.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/613,735 filed Mar. 21, 2012, the contents of which are incorporated herein by reference thereto.

BACKGROUND OF THE INVENTION

The invention relates generally to furnaces having igniter elements and, more particularly, to furnaces having shields for the igniter elements.
In furnace applications, igniters commonly include an igniter element. The igniter is positioned such that the “hot spot” of the igniter element, or the portion of the igniter element that reaches the hottest temperature, is placed directly in the mixture of fuel and air to create the point of ignition. If the igniter is not at a temperature hot enough to cause the fuel and air mixture to combust, the fuel flow to the furnace will automatically shut off. A predominant cause of igniter element cooling is secondary combustion airflow. Secondary combustion airflow moves quickly past the igniter causing the igniter element to cool to a temperature below that required to ignite the surrounding fuel. Systems using less power are also susceptible to igniter element cooling because less power is used to heat the igniter. Some furnace applications require the furnace to use a lower voltage power supply, such as 98V for example, rather than the typical 110V; therefore less power is applied towards heating the igniter than in a full voltage system. If the igniter is too cool to ignite the fuel and air mixture, no heat will be produced from the furnace.

BRIEF DESCRIPTION OF THE INVENTION

According to an exemplary embodiment of the invention, a burner assembly for use in a gas appliance is provided including a top plate configured to form the geometric top half of at least one burner and a bottom plate configured to form the geometric bottom half of at least one burner. The top plate and the bottom plate are joined together to form a burner and a burner carryover. An igniter air shield extends from either the top plate or the bottom plate such that the igniter air shield diverts secondary combustion air flowing around the burner.
According to another embodiment of the invention, a burner unit is provided including a burner assembly having a plurality of axially aligned burners. The burner unit also includes a burner box for receiving the burner assembly. An igniter assembly is mounted such that the igniter element is adjacent the burner assembly. The igniter assembly includes an igniter element extending from an insulative body. An igniter air shield extends from a portion of the burner assembly such that the igniter air shield diverts secondary air flowing around the burner assembly away from the igniter element.
According to yet another embodiment of the invention, a furnace is provided including a burner assembly having a plurality of axially aligned burners. A burner box receivers the burner assembly. An igniter assembly includes an igniter element connected to an insulative body. The igniter assembly is mounted such that the igniter element is adjacent the burner assembly. An igniter air shield, extending from the burner assembly, diverts secondary air flowing around the burner assembly away from the igniter element.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective cut away illustration of a gas furnace in accordance with an embodiment of the invention;

FIG. 2 is a perspective view of a burner unit in accordance with an embodiment of the invention;

FIG. 3 is a front view of a burner unit in accordance with an embodiment of the invention; and

FIG. 4 is a cross-sectional view taken at line 4-4 of FIG. 3 in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective cutaway view of a gas-fired appliance, such as a furnace 10. The furnace 10 includes burner assembly 14, burner box 12, gas valve 18, heat exchanger assembly 20, exhaust vent pipe 28, induced draft blower 30, inducer motor 32, thermostat 34, pressure switch assembly 42, and furnace control 50. In some embodiments, the furnace 10 may additionally include a combustion air pipe 16, a condensing heat exchanger 24, and a condensate collector box 26.
Burner assembly 14 is mounted within burner box 12 and is supplied with combustion air. As will be discussed in more detail below, the burner assembly 14 includes a gas manifold 36 with a gas orifice 38 (see FIG. 2) arranged at one end. Fuel gas is supplied to burner assembly 14 through gas valve 18, which may be a solenoid-operated gas valve, and is ignited by an igniter assembly 160 (see FIG. 2). The gases produced by combustion within burner assembly 14 flow through a heat exchanger assembly 20, which includes a primary or non-condensing heat exchanger. In one embodiment, the heat exchanger assembly 20 additionally includes either a secondary or condensing heat exchanger 24, or a condensate collector box 26, or both. The gases are then vented to the atmosphere by inducer motor 32 through exhaust vent pipe 28. The flow of these gases, herein called combustion gases, is maintained by induced draft blower 30, which is driven by inducer motor 32. Inducer motor 32 is driven in response to control signals that are generated by a furnace control circuit located within furnace control 50, in response to the states of the pressure switch assembly 42, and in response to call-for-heat signals received from thermostat 34 in the space to be heated.
Air from the space to be heated is drawn into furnace 10 by blower 52, which is driven by blower motor 54 in response to control signals that are generated by furnace control 50. The discharge air from the blower 52, herein called circulating air, passes over the heat exchanger assembly 20 before being directed to the space to be heated through a duct system (not shown).
Referring now to FIGS. 2 and 3, an exploded view and a front view of a burner unit 11 are illustrated. The burner unit 11 includes a burner box 12 and a burner assembly 14 that mounts within the burner box 12. The burner box 12 includes a top wall 110, a bottom wall 112, and opposing side walls 114. Disposed horizontally along the inside surface of each of the opposing side walls 114 is an elongated opening 116 for receiving the burner assembly 14.
The burner assembly 14 includes a plurality of parallel and equidistant burners 130. In the exemplary embodiment portrayed in the FIGS., the burner assembly 14 includes four burners 130. However, the burner assembly 14 may include any number of burners 130. In an exemplary embodiment, the plurality of burners 130 is formed from two stamped flat metal plates, a top plate 120 and a bottom plate 122. The top plate 120 and the bottom plate 122 of the burner assembly 14 are stamped so that the top plate 120 contains the geometry of the upper half of each burner and the bottom plate 122 contains the geometry of the lower half of each burner. Disposed between each burner half is at least one burner carryover 147 to assist in the ignition process. The plates 120, 122 thus divide the burners 130 and burner carryovers 147 symmetrically along the central axis Z of each burner 130 so that when the plates 120, 122 are assembled in face to face contact, the overall shape of each burner 130 is produced. Top and bottom plates 120, 122 may be fastened together by any suitable means so that the opposed flat surfaces of the plates 120,122 are held in close intimate contact along the length and breadth of the plates. Joining the top plate 120 and the bottom plate 122 creates a horizontal plane extending through the entire burner assembly 14 and through the center of each of the plurality of burners 130 and burner carryovers 147.
Each burner 130 within the burner assembly 14 has a fuel port 132 at a first end of the burner 130. The fuel port 132 is a cylindrical element that aligns a burner 130 with a respective fuel supply to direct pressurized fuel into the burner 130. The fuel port 132 of each burner 130 is positioned adjacent to and in axial alignment with a tubular nozzle 138. Each nozzle 138 has a flared inlet end 134 and a cylindrical outlet end 140. A flame retainer housing 142 is integrally joined to the outlet end 140 of the tubular nozzle 138 and contains a generally cylindrical flame retainer 144. The flared inlet end 134 has a larger diameter inlet opening than the fuel inlet opening defined by the fuel port 132. An opening 146 is stamped into each of the plates 120, 122 between the fuel port 132 and the inlet 134 to the tubular nozzle 138. Each opening 146 is sufficiently large so that an unimpeded airflow will be available to support the combustion when the burner is operating at capacity. The burner carryovers 147 are sized to sufficiently carry the flame to the exit of each flame retainer 144 during the ignition process.
A support piece 150 extends perpendicularly from the top surface 110 towards the bottom surface 112 of the burner box 12. Fastened to this support piece 150 is an igniter mounting structure 152 having a hole in which an igniter assembly 160 is inserted. The support piece 150 and the igniter mounting structure 152 are positioned such that the mounted igniter assembly 160 is adjacent an outlet 140 of a burner 130 located at an end of the burner assembly 14. The igniter assembly 160 includes an insulative body 162 and an igniter element 164 extending from within the insulative body 162. The igniter element 164 is arranged to provide a hot surface to the outlet section of the burner carryover 147 at start up. The igniter element will ignite the primary air/fuel mixture moving through the burner 130 and burner carryover 147 and propagate the flame to the exit of each flame retainer 144.
As the fuel is injected through the fuel port 132, air also enters the burner 130 due to the difference of the diameter of the inlet and the diameter of the fuel port 132. The fuel and air combine at the inlet 134 of the tubular nozzle 138 to create a primary fuel/air mixture. As the primary fuel/air mixture flows through the burner 130 and the burner carryover 147, the primary fuel/air mixture contacts the hot surface igniter element 164 causing the mixture to ignite at the burner carryover 147 closest to the igniter element 164. The flame is then carried across each burner carryover 147 and the exit of each flame retainer 144. Secondary combustion air (See FIG. 4) flows around the outside of the burners 130 and burner carryovers 147 and gradually mixes into the flame extending axially downstream from the exit of the flame retainers 144. At the exit of the burner carryovers 147, ignited fuel spreads laterally to ignite the other burners 130 in the burner assembly 14. A flame sensor 168 is also mounted to the burner box 12. The flame sensor 168 determines if all of the burners 130 in the burner assembly 14 are lit. If not all of the burners 130 have ignited within a given period of time, the flow of fuel to the burners 130 is shut off.
Referring now to FIGS. 3 and 4, arrows A and B represent secondary combustion air flowing around the top and bottom of the burner assembly 14 in the direction of the igniter element 164. An igniter air shield 170 extends from the burner assembly 14 adjacent first burner 130 and igniter element 164. The igniter air shield 170 diverts the secondary combustion air away from the igniter element 164 to reduce the cooling of the igniter element 164. The igniter air shield 170 also improves the stability of the flame exiting the burner carryover 147 closest to the igniter element 164. Therefore, the igniter air shield 170 improves the robustness of the ignition process within the furnace 10.
The igniter air shield 170 may be formed integrally with the burner assembly 14. In an exemplary embodiment, if the burner assembly 14 includes a stamped metal top and bottom plate 120, 122, the igniter air shield 170 may be formed as part of either the top or bottom plate 120, 122. To form the igniter air shield 170 as part of the bottom plate 122, for example, the stamped metal will include an additional area extending beyond the edge forming the outlet 140 of each burner 130. The dimensions of the area forming the igniter air shield 170 must be sufficient to create a non-turbulent flow or stable flow adjacent the outlet of the burner carryover 147 closest to the igniter element 164, and the igniter element 164. The area forming the igniter air shield 170 is then bent so that a portion of the igniter air shield 170 will extend into secondary combustion air flow B around the bottom plate 122 to divert it away from the igniter element 164. The angle of the bend of the igniter air shield 170 may range from zero to ninety degrees from the horizontal plane of the plate. In an alternate embodiment, the igniter air shield 170 may be a separate part that is then attached to the portion of the burner assembly 14 adjacent the burner carryover 147 closest to the igniter element 164. The igniter air shield 170 may be attached by welding, fastening, or any other suitable means. Additionally, a second igniter air shield 170 may extend from the top of the burner assembly 14 adjacent the igniter element 164 to divert the secondary air flow represented by arrow A away from the igniter element 164.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. A burner assembly for use adjacent an igniter element in a gas appliance comprising:

a top plate configured to form the geometric top half of at least one burner;

a bottom plate configured to form the geometric bottom half of at least one burner, wherein the bottom plate and the top plate are joined to form a burner and a burner carryover; and

an igniter air shield extending from one of the top plate or bottom plate such that the igniter air shield diverts secondary combustion air flowing around the burner carryover and away from the adjacent igniter element.

2. The burner assembly according to claim 1, wherein the size of the igniter air shield is sufficient to create a stable flow adjacent an outlet of the burner carryover.

3. The burner assembly according to claim 1, wherein the igniter air shield forms an angle with the horizontal plane of the burner assembly such that the range of the angle is between zero and substantially ninety degrees.

4. The burner assembly according to claim 1, wherein the igniter air shield is integrally formed with the bottom plate adjacent an outlet of a burner carryover.

5. The burner assembly according to claim 1, wherein the igniter air shield is fastened to the bottom plate adjacent an outlet of a burner carryover.

6. A burner unit comprising:

a burner assembly having a plurality of axially aligned burners;

a burner box for receiving the burner assembly;

an igniter assembly including an igniter element, wherein the igniter assembly is mounted to the burner box such that the igniter element is adjacent the burner assembly; and

an igniter air shield extending from a portion of the burner assembly, such that the igniter air shield diverts secondary air flowing around the burner assembly away from the igniter element.

7. The burner unit of claim 6 wherein the burner assembly further comprises:

a top plate configured to form the geometric top half of a plurality of burners; and

a bottom plate configured to form the geometric bottom half of a plurality of burners, wherein the bottom plate and the top plate are joined to form a plurality of burners and burner carryovers.

8. The burner unit according to claim 6, wherein the size of the igniter air shield is sufficient to create a stable flow adjacent the igniter element and an outlet of a burner carryover from the burner assembly.

9. The burner unit according to claim 6, wherein the igniter air shield forms an angle with the horizontal plane of the burner assembly such that the range of the angle is between zero and substantially ninety degrees.

10. The burner unit according to claim 7, wherein the igniter air shield is integrally formed with the bottom plate adjacent an outlet of a burner carryover.

11. The burner unit according to claim 7, wherein the igniter air shield is fastened to the bottom plate adjacent an outlet of a burner carryover.

12. A furnace comprising:

a burner assembly having a plurality of axially aligned burners;

a burner box for receiving the burner assembly;

an igniter air shield, extending from the burner assembly, for diverting secondary air flowing around the burner assembly away from the igniter element.

13. The furnace of claim 12 wherein the burner assembly further comprises:

a top plate configured to form the geometric top half of a plurality of burners and a bottom plate configured to form the geometric bottom half of a plurality of burners wherein the bottom plate and the top plate are joined to form a plurality of burners and burner carryovers.

14. The furnace according to claim 12, wherein the size of the igniter air shield is sufficient to create a stable flow adjacent the igniter element and an outlet of a burner carryover from the burner assembly.

15. The furnace according to claim 12, wherein the igniter air shield forms an angle with the horizontal plane of the burner assembly, the angle being between zero and substantially ninety degrees.

16. The furnace according to claim 13, wherein the igniter air shield is integrally formed with the bottom plate adjacent an outlet of a burner carryover.

17. The furnace according to claim 13, wherein the igniter air shield is fastened to the bottom plate adjacent an outlet of a burner carryover.