BURNER WITH INTEGRAL MIXER

Abstract

A burner for an appliance having a blower includes a tube extending from an inlet end to an outlet end with radially extending openings along its length. A cap closes the outlet end in a fluid-tight manner. A mixing system downstream from the blower extends into the inlet end for delivering a pre-mixed mixture of air and fuel to the interior of the tube for ignition by an igniter.

Description

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 63/384,781, filed Nov. 23, 2022, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a fuel burner and, in particular, relates to a burner for a heating appliance in which the mixing system is downstream of the blower.

BACKGROUND

Typically, pre-mixed burners use a negative regulation gas valve attached to an inlet of a blower supplying the air for the pre-mixed mixture. In operation, the gas is pulled into the blower wheel, where it is mixed with incoming air and delivered to the burner. In such configurations, it is desirable to seal the blower housing—including the motor shaft penetration — in order to help prevent gas leakage. The connection of the blower to the burner should also be sealed.

SUMMARY

In one example, a burner for an appliance having a blower includes a tube extending from an inlet end to an outlet end with radially extending openings along its length. A cap closes the outlet end in a fluid-tight manner. A mixing system downstream from the blower extends into the inlet end for delivering a pre-mixed mixture of air and fuel to the interior of the tube for ignition by an igniter.

In another example, a burner for an appliance having a blower includes an inner tube extending along a centerline from a first end to a second end and defining a central passage. Openings extend radially through the inner tube to the central passage. An outer tube extends along a centerline from a first end to a second end and defines a central passage for receiving the inner tube. Openings extend radially through the outer tube to the central passage thereof. An end cap closes the second ends in a fluid-tight manner. A mixing system extends into the first end of the inner tube and includes a venturi having a central passage in fluid communication with the central passage of the tube. A gas supply tube has a first end for receiving fuel and a second end extending into the venturi. A fuel nozzle extends into the second end of the gas supply tube and includes radially extending openings for delivering the fuel to the central passage of the venturi. Air from the blower is received in a radial space between the venturi and the fuel nozzle such that the air is mixed with the fuel flowing through the radial openings in the fuel nozzle and delivered as a mixture of air and fuel to the central passage of the inner tube.

Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prior art burner with a negative regulator valve and blower.

FIG. 2 is a schematic illustration of a burner in use with a blower and fuel source in accordance with an aspect of the present invention

FIG. 3 is a section view of the burner of FIG. 2 taken along line 3-3.

DETAILED DESCRIPTION

The invention relates to a fuel burner and, in particular, relates to a burner for a heating appliance in which the mixing system is downstream of the blower. The appliance can be, for example, a furnace, water heater, heat exchanger, etc. FIG. 1 illustrates an existing arrangement having a burner 200 fluidly connected to an inducer blower 202 and a negative regulator valve 204. The negative regulator valve 204 is positioned upstream of the blower 202. The blower 202 is positioned upstream of the burner 200 and connected thereto through a sealed discharge outlet 208. In operation, the blower 202 is actuated to draw in air A, which creates a negative pressure at the blower, causing the negative regulator valve 204 to open and allow gas G to be drawn into the blower. The air A and gas G is then mixed within the blower 202 and delivered by a sealed discharge outlet 208 to the burner 200 to be ignited.

FIG. 2 illustrates an example combustor or burner 10 in accordance with an aspect of the invention. The burner 10 is positioned downstream of a blower 12 and fuel source 14. The blower 12 is configured to supply air A to the burner 10. The fuel source 14 is configured to supply fuel F, e.g., gas, to the burner 10. Consequently, the inlet of the burner 10 is fluidly connected to both the blower 12 and the fuel source 14. A mixing system 16 is provided at the inlet of the burner 10 for mixing the air A and fuel G from the respective blower 12 and fuel source 14 and delivering a pre-mixed mixture M of the air and gas to the burner to be ignited by an igniter 18 to produce flames F.

Referring to FIG. 3, the burner 10 includes an inner tube 20 extending along a centerline 22 from a first or inlet end 24 to a second or outlet end 26. The cross-section of the inner tube 20 can be round, circular, or the like. The inner tube 20 includes an inner surface 30 defining a central passage 32 and an outer surface 34 generally concentric with the inner surface The inner tube 20 can be made from a durable material, such as metal. In one instance, the inner tube 20 can be constructed as a flame arrester or include a flame-arresting inner liner therein (indicated in phantom at 40) covering the entire or substantially the entire inner surface

Openings 38 extend radially through the inner tube 20 from the outer surface 34 to the inner surface 30. The openings 38 can be ports, slots, louvers, etc. formed in/through the inner tube 20. The openings 38 can be arranged in a predefined pattern around the inner tube 20. To this end, the openings 38 can be arranged in rows along the length of the inner tube 20, with each row collectively encircling the centerline 22. The openings 38 in each row can be symmetrically (as shown) or asymmetrically (not shown) circumferentially arranged about the centerline 22.

The burner 10 further includes an outer tube 50 extending along a centerline 52 from a first or inlet end 54 to a second or outlet end 56. The cross-section of the outer tube 50 can be round, circular, or the like. The outer tube 50 includes an inner surface 58 defining a central passage 60 and an outer surface 62 generally concentric with the inner surface 58. The outer tube 50 can be made from a durable material, such as metal.

Openings 63 extend radially through the outer tube 50 from the outer surface 62 to the inner surface 58. The openings 63 can be ports, slots, louvers, etc. formed in/through the outer tube 50. The openings 63 can be arranged in a predefined pattern around the outer tube 50. To this end, the openings 63 can be arranged in rows along the length of the outer tube 50, with each row collectively encircling the centerline 52. The openings 63 in each row can be symmetrically (as shown) or asymmetrically (not shown) circumferentially arranged about the centerline 52. The openings 63 in the outer tube 50 can be aligned with or offset from the openings 38 in the inner tube 20. A fiber mesh 68 can optionally be provided over the exterior of the outer tube 50.

The outer tube 50 extends over the inner tube 20 with the centerlines 22, 52 aligned. The tubes 20, 50 are sized such that a radial gap or space 64 exists between the outer surface 34 of the inner tube 20 and inner surface 58 of the outer tube 50. An end cap 70 extends into and is secured to the second ends 26, 56 of the tubes 20, 50 to fix the ends relative to one another and prevent fluid from passing out of the burner 10 through the second ends of the tubes. In other words, the end cap 70 has a fluid-tight interface with the second ends 26, 56 of the tubes 20, 50. It will be appreciated that the inner tube 20 can be omitted (not shown), in which case the end cap 70 is secured to the end 56 of the tube 50 in a fluid-tight manner.

The mixing system 16 extends into the first ends 24, 54 of the tubes 20, 50 and includes a mounting flange 80 secured to the first ends of the tubes to fix the ends relative to one another. The mounting flange 80 includes an annular base 82 that abuts the axial extents of the first ends 24, 54. A wall 84 extends from the base 82 and into the central passages 32, 60 of the tubes 20, 50. The wall 84 includes a stepped portion 90 and a curved, e.g., converging, portion 92. In one example, the curved portion 92 is concave or frustoconical. The stepped portion 90 extends from the base 82. The curved portion 92 extends from the stepped portion 90. The portions 90, 92 collectively define a passage 94 through the mounting flange 80.

A venturi 100 is positioned within the passage 94 and can include a downstream, diverging portion 102 and an upstream, converging portion 104 (as viewed in a direction extending towards the second ends 26, 56). Alternatively, the diverging portion 102 can be straight (not shown). The converging portion 104 extends along and mirrors the contour of the curved portion 92 of the mounting flange 80. The diverging portion 102 extends out of the passage 94 and upstream into the central passage 32 of the inner tube 20 towards the second end 26 thereof. The venturi 100 defines a longitudinally extending passage 106 extending the entire length thereof and in fluid communication with both the central passage 32 of the inner tube 20 and the passage 94 of the mounting flange 80.

A gas supply tube 112 and fuel nozzle 120 extend through the first ends 24, 54 of the tubes 20, 50 and into the passage 106 of the venturi 100. As shown, the gas supply tube 112 has an end that is upstream of the tubes 20, 50 while the fuel nozzle 120 is positioned entirely within the tubes. The gas supply tube 112 defines a passage 114. The tube 112 can have a downstream end 116 that is flared (as shown) or straight (not shown).

The fuel nozzle 120 is positioned within the flared end 116. The fuel nozzle 120 includes a wall 122 defining a longitudinal passage 124 terminating at a closed end 126. One or more openings 128 extend radially from the passage 124 through the wall 122. In one example, multiple openings 128 are symmetrically arranged about the circumference of the fuel nozzle 120. In any case, the openings 128 are longitudinally positioned within the curved portions 92, 104 upstream of the diverging portion 102 of the venturi 100. In other words, the openings 128 are neither upstream nor downstream of the diverging portion 102. Other longitudinal positions are contemplated.

In operation, fuel, e.g., gas, G from the fuel source 14 is directed into the passage 114 of the gas supply tube 112. The fuel G flows through the passage 114, into the fuel nozzle 120, and exits the fuel nozzle through the radial openings 128 and into the interior of the venturi 100. At the same time air A from the blower 12 is injected into the first ends 24, 54 of the tubes 20, 50 between the gas supply tube 112/fuel nozzle 120 and the wall 84 of the mounting flange 80.

Due to the contour of the curved portions 92, 104, the openings 128 are positioned in the lowest pressure zone of the venturi 100. In particular, since the curved portion 94 tapers inwards in a direction heading downstream, i.e., toward the end cap 70, the curved portion 94 acts as a venturi to reduce the fluid pressure therein. With this in mind, flaring the end 116 of the tube 112 can help further constrict fluid flow between the curved portion 94 and the end 116 and thereby reduce fluid pressure. In any case, the venturi 100 is configured to create fluid pressure that is sufficient to operate a negative regulation gas valve or a conventional positive pressure valve. With this in mind, the openings 128 are sized, shaped, and arranged to provide the desired mixing and distribution characteristics between the fuel G and air A.

That said, the incoming air A mixes with the fuel G exiting the openings 128 and is delivered as a pre-mixed mixture M out of the diverging portion 102 and into the central passage 32 of the inner tube 20. The pre-mixed mixture M can then pass radially through the openings 28, 63 to the exterior of the burner 10 where the igniter 18 ignites the pre-mixed mixture to produce flames F (see also FIG. 2). The burner 10 can include flame proving means, such as a sensor (not shown), to monitor operation of the burner. A controller 150 can be connected to the blower 12, fuel source 14, igniter 18, and flame proving sensor for monitoring and control thereof.

When the inner tube 20 is configured as a flame arrestor, it can help prevent/mitigate flashback if the flame F travels radially inwards through the outer tube 50. Furthermore, the liner 40 may impede radially inward movement of the flame F sufficient to allow the controller 150 to shut the system down in response to a flame no longer being sensed at the flame sensor.

The present invention is advantageous in that it alleviates the need to seal multiple sections/components of the blower because the blower no longer mixes the air and fuel. Furthermore, the mixing is done at/within the inlet of the burner—as opposed to within the blower—and, thus, large quantities of the combustible fuel/air mixture are not kept at any time in the blower and/or outlet from the blower to the burner. This is especially advantageous when highly volatile gases, such as hydrogen, are used in the burner.

What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.

Claims

1. A burner for an appliance having a blower, comprising:

a tube extending from an inlet end to an outlet end and having radially extending openings along its length;

a cap closing the outlet end in a fluid-tight manner; and

a mixing system downstream from the blower and extending into the inlet end for delivering a pre-mixed mixture of air and fuel to the interior of the tube for ignition by an igniter.

2. The burner of claim 1, wherein the mixing system comprises:

a tubular venturi having an upstream end and a downstream end;

a gas supply tube extending into the upstream end and receiving fuel; and

a fuel nozzle including radially extending openings and positioned in the gas tube so as to be longitudinally aligned with the upstream end of the venturi, wherein air from the blower is received in a radial space between the venturi and the fuel nozzle such that the air is mixed with the fuel flowing through the radial openings in the fuel nozzle and delivered as a mixture of air and fuel to the central passage of the tube.

3. The burner of claim 2, wherein an end of the gas supply tube receiving the fuel nozzle is flared.

4. The burner of claim 2, wherein the upstream end of the venturi is converging and the downstream end of the venturi is diverging.

5. The burner of claim 2, wherein the upstream end of the venturi is converging and the downstream end of the venturi is straight.

6. The burner of claim 2, further comprising a mounting flange for connecting the inlet end of the tube to the venturi.

7. The burner of claim 6, wherein the mounting flange includes:

a planar base;

a stepped portion extending from the base into the inlet end of the tube; and

a curved portion extending over the upstream end of the venturi.

8. The burner of claim 1, further comprising a flame arrester liner defining a central passage of the tube.

9. The burner of claim 1, further comprising a fiber mesh provided over the tube.

10. A burner for an appliance having a blower, comprising:

an inner tube extending along a centerline from a first end to a second end and defining a central passage, wherein openings extend radially through the inner tube to the central passage;

an outer tube extending along a centerline from a first end to a second end and defining a central passage for receiving the inner tube, wherein openings extend radially through the outer tube to the central passage thereof;

an end cap closing the second ends in a fluid-tight manner;

a mixing system extending into the first end of the inner tube, comprising: a venturi having a central passage in fluid communication with the central passage of the tube; a gas supply tube having a first end for receiving fuel and a second end extending into the venturi; and a fuel nozzle extending into the second end of the gas supply tube and including radially extending openings for delivering the fuel to the central passage of the venturi, wherein air from the blower is received in a radial space between the venturi and the fuel nozzle such that the air is mixed with the fuel flowing through the radial openings in the fuel nozzle and delivered as a mixture of air and fuel to the central passage of the inner tube.

11. The burner of claim 10, wherein the second end of the gas supply tube is flared.

12. The burner of claim 10, further comprising a flame arrestor liner defining the central passage of the inner tube.

13. The burner of claim 10, wherein the radial openings in the fuel nozzle are longitudinally aligned with a curved portion of the venturi.

14. The burner of claim 10, wherein the venturi extends from a converging end longitudinally aligned with the radially extending openings to a diverging end for delivering the mixture of air and fuel to the central passage.

15. The burner of claim 14, wherein the converging portion is upstream of the diverging portion.

16. The burner of claim 10, wherein the venturi extends from a converging end longitudinally aligned with the radially extending openings to a straight end for delivering the mixture of air and fuel to the central passage.

17. The burner of claim 10, further comprising a mounting flange for connecting the first ends of the inner and outer tubes to the venturi.

18. The burner of claim 17, wherein the mounting flange includes:

a planar base;

a stepped portion extending from the base into the first ends of the inner and outer tubes; and

a curved portion extending over and along a curved portion of the venturi.

19. The burner of claim 10, further comprising a fiber mesh provided over the outer tube.