BURNER FOR HEATING SYSTEM

Abstract

A burner for a furnace includes an inner wall defining a central burner chamber. The inner wall includes a plurality of inner wall openings to admit a fuel flow into the central burner chamber. The burner further includes an outer wall which, defines an annulus for the fuel flow to the plurality of inner wall openings. An igniter is located in the central chamber. A furnace includes a heat exchanger and one or more burners disposed at and aligned with one or more burner openings of the heat exchanger. The one or more burners include an inner wall defining a central burner chamber. The inner wall includes a plurality of inner wall openings to admit a fuel flow into the central burner chamber. The one or more burners further include an outer wall defining an annulus for the fuel flow to the plurality of inner wall openings.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional application Ser. No. 61/521,143, filed Aug. 8, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to heating systems. More specifically, the subject disclosure relates to burners for residential and commercial heating systems.

Heating systems, in particular furnaces include one or more burners for combusting a fuel such as natural gas. Hot flue gas from the combustion of the fuel proceeds from the burner and through a heat exchanger. The hot flue gas transfers thermal energy to the heat exchanger, from which the thermal energy is then dissipated by a flow of air driven across the heat exchanger by, for example, a blower.

A typical construction is shown in FIG. 1. A burner 100 is located external to a heat exchanger 102. The burner 100, referred to as an inshot burner 100, receives a flow of fuel from a fuel source 104. An ignition source 106 combusts the flow of fuel. Even though the inshot burner 100 is in close proximity to heat exchanger 102, surfaces of the heat exchanger 102 adjacent to the combustion flame 110 are kept relatively cool by a flow of secondary air 108 to prevent damage to the surfaces of the heat exchanger 102 via the combustion flame 110.

Another type of burner is a premix burner in which fuel and air are mixed in the burner nozzle prior to injection into a combustion zone 112 where the ignition source 106 ignites the mixture. Premix burners, compared to inshot burners, emit much lower levels of NO_x, the emissions of which are tightly regulated and restricted. Because of this advantage of premix burners, it is appealing to introduce premix burners into furnaces. A premix burner having physical and operating characteristics similar to the burner 100 would not be suitable for use with heat exchanger 102. The heat exchanger walls would necessarily be in close proximity to the burner and thus the concentration of heat produced in the immediate vicinity of the burner would result in excessively high temperatures in the wall of the heat exchanger 102. Such high temperatures would increase the surface temperatures of the surrounding heat exchanger 102 and shorten the life of the heat exchanger 102. Further, premix burners have a much quicker heat release than inshot burners and do not have the benefit of secondary airflow to protect the heat exchanger surfaces from damage. Thus, simply replacing inshot burners with premix burners in an existing furnace construction would result in excessively high temperatures at adjacent heat exchanger surfaces. Further, ignition access to a premix burner surface can be difficult and result in even more energy being dumped into the heat exchanger entry surfaces.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a burner for a furnace includes an inner wall defining a central burner chamber. The inner wall includes a plurality of inner wall openings to admit a fuel flow into the central burner chamber. The burner further includes an outer wall which, together with the inner wall, defines an annulus for the fuel flow to the plurality of inner wall openings. An igniter is located in the central chamber.

According to another aspect of the invention, a furnace includes a heat exchanger and one or more burners disposed at and aligned with one or more burner openings of the heat exchanger. The one or more burners include an inner wall defining a central burner chamber. The inner wall includes a plurality of inner wall openings to admit a fuel flow into the central burner chamber. The one or more burners further include an outer wall, together with the inner wall defining an annulus for the fuel flow to the plurality of inner wall openings. An igniter is located in the central chamber.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

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 cross-sectional view of a typical burner arrangement;

FIG. 2 is a schematic view of an embodiment of a furnace; and

FIG. 3 is a cross-sectional view of an embodiment of a burner.

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 2 is an improved furnace 10. The furnace 10 includes a heat exchanger 12 with one or more burners 14 aligned with respective burner openings 60 in heat exchanger 12 walls 16. In some embodiments, the burners 14 are located substantially within the heat exchanger 12, while in other embodiments, the burners 14 may abut the heat exchanger 12. In still other embodiments, the burners 14 offset a distance from the heat exchanger 12, but are aligned with the burner openings 60 such that, once ignited, the burners 14 radiate hot flue gas 18 into the heat exchanger 12, thermal energy from which is transferred to the heat exchanger 12 structure. The thermal energy is then dissipated from the heat exchanger 12 via a flow of air 20 driven across the heat exchanger 12 by, for example, a blower 22. The heated flow of air 20 is delivered through one or more ducts 24 to provide heating to a space 26, such as a room or a building.

Referring now to FIG. 3, the burner 14 is substantially cylindrical in shape, and includes an outer wall 28 and an inner wall 30. It is to be appreciated that while a substantially cylindrical burner 14 is shown, it is merely exemplary. The burner 14 may have another cross-sectional shape, for example, elliptical, conical, parabolic, partially circular, or the like. Both the inner wall 30 and the outer wall 28 may be substantially cylindrical and in some embodiments are coaxial about a central burner axis 32. The inner wall 30 defines a central chamber 34, and together with the outer wall 28 defines a burner annulus 36 between the inner wall 30 and the outer wall 28. An igniter 38 for the burner is located in the central chamber 34 and, in some embodiments, extends along the burner axis 32. The igniter 38 is located, for example, at a closed end 52, or upstream end, of the burner 14. Further, in some embodiments, a flame sensor 40 is located in the central chamber 34, and also may be located at the closed end 52.

The inner wall 30 includes a plurality of inner wall openings 42, and in some embodiments, may be at least partially a mesh screen. In some embodiments, the inner wall 30 is a unitary, replaceable component. Replacing the inner wall 30 at the end of its service life extends the overall useful life of the burner 14. A flow of fuel 44 and a flow of combustion air 46 are delivered to the burner annulus 36 where they are premixed. The air/fuel mixture 48 then flows through the inner wall openings 42 or screen and into the central chamber 34 where the mixture 48 is ignited. The flue gas 18 is emitted from the burner 14 at a distal end 50 of the central chamber 34 and into the heat exchanger 12 structure.

The structure disclosed herein allows for the utilization of a premix burner 14 which reduces NO_x emissions compared to inshot burners, while not subjecting the heat exchanger 12 surfaces to direct effects of the combustion to prevent thermal damage to the heat exchanger 12. The cylindrical structure of the burner 14 captures the combustion thermal energy before it is emitted from the burner 14. Further, the burner 14 is sized and configured to allow for the presence of the igniter 38 and flame sensor 40 within the burner 14 structure. This results in a space savings for the burner 14 and heat exchanger 12, thus allowing for an increased cross-sectional sized burner 14 for a given heat exchanger 12 cross-sectional size. Further, the flow through the burner annulus 36 isolates the flame from the heat exchanger 12 and aids in cooling the heat exchanger 12 surfaces near the burner 14.

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 for a furnace comprising:

an inner wall defining a central burner chamber, the inner wall including a plurality of inner wall openings to admit a fuel flow into the central burner chamber;

an outer wall, together with the inner wall defining an annulus for the fuel flow to the plurality of inner wall openings; and

an igniter disposed in the central chamber.

2. The burner of claim 1, wherein the inner wall at least partially comprises a mesh screen defining the plurality of inner wall openings.

3. The burner of claim 1, wherein one or more of the inner wall and the outer wall are substantially cylindrical.

4. The burner of claim 1, wherein the inner wall and the outer wall are substantially concentric about a burner central axis.

5. The burner of claim 1, wherein the igniter is disposed at a closed end of the burner.

6. The burner of claim 1, further comprising a flame sensor disposed in the central burner chamber.

7. The burner of claim 1, wherein the burner is alignable with a respective burner opening at a heat exchanger of a furnace.

8. The burner of claim 1, wherein the plurality of inner wall openings are configured to convey a mixture of air and fuel into the central burner chamber.

9. The burner of claim 1, wherein the inner wall is a replaceable element.

10. A furnace comprising:

a heat exchanger;

one or more burners disposed at and substantially aligned with one or more burner openings of the heat exchanger, the one or more burners including:

an inner wall defining a central burner chamber, the inner wall including a plurality of inner wall openings to admit a fuel flow into the central burner chamber;

an outer wall, together with the inner wall defining an annulus for the fuel flow to the plurality of inner wall openings; and

an igniter disposed in the central chamber.

11. The furnace of claim 10, wherein the inner wall at least partially comprises a mesh screen defining the plurality of inner wall openings.

12. The furnace of claim 10, wherein one or more of the inner wall and the outer wall are substantially cylindrical.

13. The furnace of claim 10, wherein the inner wall and the outer wall are substantially concentric about a burner central axis.

14. The furnace of claim 10, further comprising a flame sensor disposed in the central burner chamber.

15. The furnace of claim 10, wherein the igniter is disposed at a closed end of the burner.

16. The furnace of claim 10, wherein the inner wall is a replaceable element.

17. The furnace of claim 10, wherein the plurality of inner wall openings are configured to convey a mixture of air and fuel into the central burner chamber.

18. The furnace of claim 10, wherein thermal energy of a flue gas emitted by the one or more burners is transferred to the heat exchanger.