US20200173689A1

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Publication number: US20200173689A1
Application number: US16/615,553
Authority: US
Inventors: Robert Shaw
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2017-05-24
Filing date: 2018-05-23
Publication date: 2020-06-04
Also published as: WO2018217915A1

Abstract

A burner assembly (40) for providing a flame and combustion gas to a plurality of inlets includes a support member (70) having a back surface and an inner surface. An elongated opening (72) is formed in the support member. A burner (74) is connected to the support member adjacent the opening and extending upstream from the back surface. The burner is arranged in fluid communication with the plurality of inlets. An interior surface of the burner is contoured to direct flames generally inwardly.

Description

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 prior art construction is shown inFIG. 1. Aburner10 is located external to aheat exchanger12. Theburner10, often referred to as aninshot burner10, receives a flow of fuel from afuel source14. Anignition source16 combusts the flow of fuel to create acombustion flame18.

Another type of burner is a premix burner in which fuel and air are mixed in a burner inlet tube prior to injection into acombustion zone19 where theignition source16 ignites the mixture. Premix burners, compared to inshot burners, typically emit much lower levels of NO_x, the emissions of which are tightly regulated and restricted by many jurisdictions. Because of this advantage of premix burners, it may be desirable to utilize premix burners in furnaces.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a burner assembly for providing a flame and combustion gas to a plurality of inlets includes a support member having a back surface and an inner surface. An elongated opening is formed in the support member. A burner is connected to the support member adjacent the opening and extending upstream from the back surface. The burner is arranged in fluid communication with the plurality of inlets. An interior surface of the burner is contoured to direct flames generally inwardly.

In addition to one or more of the features described above, or as an alternative, in further embodiments the interior surface of the burner is concave.

In addition to one or more of the features described above, or as an alternative, in further embodiments the interior surface of the burner is contoured to direct flames from the interior surface to a focus.

In addition to one or more of the features described above, or as an alternative, in further embodiments an outlet of the burner is arranged within a plane, and the focus is arranged opposite the burner relative to the plane.

In addition to one or more of the features described above, or as an alternative, in further embodiments the interior surface of the burner is elliptical in shape.

In addition to one or more of the features described above, or as an alternative, in further embodiments the interior surface of the burner is circular in shape.

In addition to one or more of the features described above, or as an alternative, in further embodiments the burner is formed from a porous material.

In addition to one or more of the features described above, or as an alternative, in further embodiments an outlet end of the burner comprises a flange, the flange being mounted to the inner surface of the support member such that the burner extends through the opening.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising an igniter arranged adjacent a first end of the opening and a flame sensor positioned adjacent a second, opposite end of the opening.

In addition to one or more of the features described above, or as an alternative, in further embodiments the igniter is offset from the inner surface of the support member such that the igniter is positioned downstream from the burner relative to a direction of flow through the burner.

According to another embodiment, a furnace includes a heat exchanger having a plurality of coils and a burner unit. The burner unit includes a burner box defining a mixing chamber for receiving a mixture of fuel and air. A burner assembly includes a burner arranged within the mixing chamber and substantially aligned with the plurality of coils. An interior surface of the burner is contoured to direct flames generally inwardly.

In addition to one or more of the features described above, or as an alternative, in further embodiments the burner unit further comprises a support member having an opening, the burner being positioned generally adjacent the opening.

In addition to one or more of the features described above, or as an alternative, in further embodiments an outlet of the burner is arranged within a plane, the focus and the burner being disposed on opposing sides of the plane.

According to yet another embodiment, a method of operating a furnace includes providing a mixture of fuel and air to a mixing chamber, igniting the mixture of fuel and air as it flows from the mixing chamber through a burner assembly including a burner, and supplying flames and combustion from the burner to a plurality of coils of a heat exchanger.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising directing flames from an interior surface of the burner generally inwardly.

In addition to one or more of the features described above, or as an alternative, in further embodiments directing flames from an interior surface of the burner generally inwardly comprises directing the flames to a focus.

In addition to one or more of the features described above, or as an alternative, in further embodiments an outlet of the burner is arranged within a plane and the focus and the burner are disposed on opposing sides of the plane.

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 an example of a typical prior art burner arrangement;

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

FIG. 3 is a perspective view of an expanded burner unit according to an embodiment;

FIG. 4 is a perspective view of an expanded burner unit according to an embodiment; and

FIG. 5 is a cross-sectional view of a portion of the burner assembly according to an embodiment.

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

Referring now to the FIGS., an improvedfurnace20 is illustrated. Thefurnace20 may include aheat exchanger22 having a plurality of individualheat exchanger coils24. Theheat exchanger coils24, which may be metallic conduits, may be provided in a serpentine fashion to provide a large surface area in a small overall volume of space, the importance of which will be discussed in further detail below. Eachheat exchanger coil24 includes aninlet26 andoutlet28. Aburner unit30 is operatively associated with eachinlet26, and avent32 is operatively associated with eachoutlet28. Theburner unit30 introduces a flame and combustion gases (not shown) into theheat exchanger coils24, whilevent32 releases the combustion gases to atmosphere (through a flue or the like) after the heat of the flame and combustion gases is extracted by theheat exchanger22.

In order to extract the heat, ablower motor36 may be provided to create a significant air flow across theheat exchanger coils24. As the air circulates across thecoils24, it is heated and can then be directed to a space to be heated such as a home or commercial building for example, by way of appropriate ductwork as indicated by arrow37. Thefurnace20 may also include areturn38 to enable air from the space to be heated to be recirculated and/or fresh air to be introduced for flow across theheat exchanger coils24.

Turning toFIG. 3, to generate the flame and hot combustion gases, a mixture of fuel and air is formed and then provided to aburner assembly40 of theburner unit30 for ignition. The fuel may be natural gas or propane introduced to aninlet44 of amixing tube42 from afuel source46 via a fuel orifice or ajet48. Substantially all of the air necessary for combustion is introduced into theburner assembly40 via anupstream mixing chamber49. Such air may be introduced by inducing an airflow using a motorized induction fan50 (FIG. 2) downstream of a burner outlet. More specifically, amotor52 having thefan50 associated therewith may be operatively associated with theoutlets28 of the heat exchanger coils24. When energized, thefan50 may rotate and induce an air flow through the heat exchanger coils24 andburners30. Control of themotor52, may be controlled by aprocessor54 such as an integrated furnace control (IFC).

Returning toFIG. 3, in an embodiment, one ormore openings56 are formed in the sidewall of the mixingtube42 generally adjacent theinlet44. As the fuel moves through the mixingtube42 towards the mixingchamber49, air is drawn into thetube42 through theopenings56 and becomes entrained within the fuel. As a result, the fluid expelled from anoutlet58 of the mixingtube42 into the mixingchamber49 is a mixture of both fuel and air.

With specific reference now toFIGS. 3-5, theburner unit30 is illustrated in more detail. As shown, theburner unit30 includes aburner box60 having a generally hollow interior commonly referred to as the mixingchamber49. Theburner box60 generally includes atop wall62,bottom wall64,back wall66, and opposingsidewalls68 such that one side of the burner box is open. Theburner unit30 additionally includes aburner assembly40 mounted within the mixingchamber49 of theburner box60.

Theburner assembly40 generally includes asupport member70 having anopening72 formed therein. In the illustrated, non-limiting embodiment, theopening72 is generally elongated such that theopening72 is substantially aligned with theinlet26 of each of the plurality of heat exchanger coils24. However, embodiments where thesupport member70 includes a plurality ofopenings72, each of which is associated with at least one of the heat exchanger coils24, are also contemplated herein. Aburner74 configured to function as a flame retainer is connected to thesupport member70 generally adjacent theopening72. Theburner74 extends beyond aback surface76 of the support member (seeFIG. 4) into the mixingchamber49. In an embodiment, theburner74 is coupled to thesupport member70, such as via a welding operation for example. Theburner74 may include a flange78 (seeFIG. 5) configured to couple to theback surface76 of thesupport member70. Alternatively, theflange78 may be mounted in overlapping relationship with an opposite, interior surface80 such that theburner74 generally extends through theopening72.

Theburner74 is formed from a porous material, such as a wire mesh or steel wool for example, so that a fluid is able to pass from the mixingchamber49 through theburner74. As best shown in the cross-sectional view ofFIG. 5, theburner74 has a generally tubular contour. The contour of theburner74 may be selected such that at least a portion of the flames directed from aninterior surface82 of theburner74 are angled generally inwardly. In an embodiment, theburner74 has a generally curved shape that directs the plurality of flames formed about theinterior surface82 of theburner74 towards acentral focus84. For example, the interior surface of theburner74 is concave, having a generally circular or elliptical shape. In embodiments where theburner74 has a generally circular or elliptical contour, thefocus84 is located on an opposite side of plane P defined by the inner surface80 as theburner74. By selecting a contour that positions thefocus84 at a position generally aligned with or in front of the plane P, the length of the jet of flames created by theburner74 exceeds that of flames formed from conventional outward fired burners.

To light theburner74, an igniter86 (FIG. 3) is located near theburner74, generally between an outlet of theburner74 and theheat exchanger24 to ignite the fuel/air mixture. As shown, theigniter86 may be mounted to thesupport member70 at a location offset from the interior surface80 thereof such that theigniter86 is generally downstream from theburner74 relative to a direction of flow through theburner74. Theigniter86 may be aligned with a portion of theopening72 such that theigniter86 is arranged in fluid communication with the fuel/air mixture within theburner74. Similarly, aflame sensor88 may be disposed on an opposite side of thesupport member70 from theigniter86. In an embodiment, theigniter86 and theflamer sensor88 are generally aligned. Theflame sensor88 is configured to determine if the ignition has carried over across theentire opening72 by sensing the presence of a flame at an end of the opening furthest from theigniter86.

Theburner assembly40 is positioned within the mixingchamber49 of theburner box60 such that an outlet of the burner74 (generally aligned with plane P) is adjacent anopen end90 of thebox60. Connected to thesupport member70 is arefractory panel92 including at least onerefractory opening94 aligned with theinlet26 of one or more heat exchanger coils24. Therefractory panel92 is configured to protect not only the adjacent surface of thesupport member70, but also the interface between thesupport member70 and the heat exchanger coils24, from overheating. Therefractory panel92 may overlay a portion or theentire support member70. Alternatively, as shown in the illustrated, non-limiting embodiment, therefractory panel92 may be received within a cavity (seeFIG. 3) formed in thesupport member70. In such embodiments, therefractory panel92 has a size and shape generally complementary to the cavity.

In an embodiment, agasket96 having at least oneopening98 formed therein may be arranged between apressure distribution bracket100 and thecell panel101 to provide a seal there between. Each of theopenings98 formed in thegasket96 is substantially aligned with anopening94 formed in therefractory panel92 and/or aninlet26 of a correspondingheat exchanger coil24.

A burner unit having anelongated burner74 as illustrated and described herein provides a system having consistently “smooth” ignitions during both normal and abnormal conditions. By eliminating multiple premix burners, the occurrence of pressure waves which can disrupt the attachment between the flame and the burner at the time of ignition is prevented.

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

What is claimed is:

1. A burner assembly for providing a flame and combustion gas to a plurality of inlets, comprising

a support member having a back surface and an inner surface, an elongated opening being formed in the support member; and

a burner connected to the support member adjacent the opening and extending upstream from the back surface, the burner being arranged in fluid communication with the plurality of inlets, wherein an interior surface of the burner is contoured to direct flames generally inwardly.

2. The burner assembly ofclaim 1, wherein the interior surface of the burner is concave.

3. The burner assembly ofclaim 1, wherein the interior surface of the burner is contoured to direct flames from the interior surface to a focus.

4. The burner assembly ofclaim 3, wherein an outlet of the burner is arranged within a plane, and the focus is arranged opposite the burner relative to the plane.

5. The burner assembly ofclaim 4, wherein the interior surface of the burner is elliptical in shape.

6. The burner assembly ofclaim 3, wherein the interior surface of the burner is circular in shape.

7. The burner assembly ofclaim 1, wherein the burner is formed from a porous material.

8. The burner assembly ofclaim 1, wherein an outlet end of the burner comprises a flange, the flange being mounted to the inner surface of the support member such that the burner extends through the opening.

9. The burner assembly ofclaim 1, further comprising:

an igniter arranged adjacent a first end of the opening; and

a flame sensor positioned adjacent a second, opposite end of the opening.

10. The burner assembly ofclaim 9, w herein the igniter is offset from the inner surface of the support member such that the igniter is positioned downstream from the burner relative to a direction of flow through the burner.

11. A furnace comprising:

a heat exchanger including a plurality of coils; and

a burner unit including:

a burner box defining a mixing chamber for receiving a mixture of fuel and air; and

a burner assembly including a burner arranged within the mixing chamber and being substantially aligned with the plurality of coils, wherein an interior surface of the burner is contoured to direct flames generally inwardly.

12. The furnace ofclaim 11, wherein the burner unit further comprises a support member having an opening, the burner being positioned generally adjacent the opening.

13. The furnace ofclaim 11, wherein the interior surface of the burner is contoured to direct flames from the interior surface to a focus.

14. The furnace ofclaim 13, wherein an outlet of the burner is arranged within a plane, the focus and the burner being disposed on opposing sides of the plane.

15. The furnace ofclaim 14, wherein the interior surface of the burner is elliptical in shape.

16. The furnace ofclaim 13, wherein the interior surface of the burner is circular in shape.

17. A method of operating a furnace, comprising:

providing a mixture of fuel and air to a mixing chamber;

igniting the mixture of fuel and air as it flows from the mixing chamber through a burner assembly including a burner; and

supplying flames and combustion from the burner to a plurality of coils of a heat exchanger.

18. The method ofclaim 17, further comprising directing flames from an interior surface of the burner generally inwardly.

19. The method ofclaim 18, wherein directing flames from an interior surface of the burner generally inwardly comprises directing the flames to a focus.

20. The method ofclaim 19, wherein an outlet of the burner is arranged within a plane and the focus and the burner are disposed on opposing sides of the plane.