WO2024025752A2

WO2024025752A2 - Systems and methods for gas combustion

Info

Publication number: WO2024025752A2
Application number: PCT/US2023/027868
Authority: WO
Inventors: Shubham Srivastava; Valeriy Smirnov
Original assignee: Rheem Manufacturing Company
Priority date: 2022-07-26
Filing date: 2023-07-17
Publication date: 2024-02-01
Also published as: WO2024025752A3

Abstract

Devices and methods for mixing fuel and air are presented. A device may include an air pipe extending within a firing tube configured to receive a flow of air; and a plurality of fuel pipes extending within the firing tube in parallel with one another and with the air pipe and configured to receive a flow of fuel; wherein the air pipe includes first apertures configured to release the air from inside the air pipe radially outward from the air pipe, the first apertures arranged around a circumference of the air pipe, and wherein a first fuel pipe of the plurality of fuel pipes includes second apertures configured to release the fuel from inside the first fuel pipe radially outward from the first fuel pipe, the second apertures arranged around a circumference of the first fuel pipe.

Description

SYSTEMS AND METHODS FOR GAS COMBUSTION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present disclosure claims priority to and the benefit of US provisional patent application No. 63/392,221, filed July 26, 2022, which is hereby incorporated by reference herein in its entirety.

FIELD

[0002] The present disclosure is generally in the field of nozzle mix burners. In particular, the present disclosure is related to draft burners for gas combustion.

BACKGROUND

[0003] Many applications use combustion systems that employ burners. Full mixing (e.g., premixing) of fuel gas and combustion air before a burner entry may result in a flame flashback to the burner internals that may be detrimental to upstream system components due to a sudden rise in temperature and pressure. Controlling the mixing of gas and air is important for combustion systems with burners.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The detailed description is set forth with reference to the accompanying drawings. In some instances, the use of the same reference numerals may indicate similar or identical items. Various embodiments may utilize elements and/or components other than those illustrated in the drawings, and some elements and/or components may not be present in various embodiments. Throughout this disclosure, depending on the context, singular and plural terminology may be used interchangeably.

[0005] FIG. 1 A is a perspective view of a nozzle mix burner of one embodiment of the present disclosure.

[0006] FIG. IB is a perspective view of the nozzle mix burner of FIG. 1A.

[0007] FIG. 1C is a top cross-section view of the nozzle mix burner of FIG. 1A.

[0008] FIG. 2A is a side view of a nozzle mix burner of one embodiment of the present disclosure.

[0009] FIG. 2B is a perspective view of the nozzle mix burner of FIG. 2A.

[0010] FIG. 2C is a perspective view of a portion of the nozzle mix burner of FIG. 2A. [0011] FIG. 2D is an illustrative schematic view of the firing tube portion of the nozzle mix burner of FIG. 2A.

[0012] FIG. 3A is a side view of a nozzle mix burner of one embodiment of the present disclosure.

[0013] FIG. 3B is a side view of the nozzle mix burner of FIG. 3A.

[0014] FIG. 3C is a top cross-section view of the nozzle mix burner of FIG. 3 A.

[0015] FIG. 4 is a schematic diagram illustrating components of a water heater of one embodiment of the present disclosure.

DETAILED DESCRIPTION

[0016] In gas burners, fuel and oxidant are mixed with one another and ignited inside a chamber or firing tube of the burner. The resulting hot combustion gases then flow at high velocity through an outlet and into a furnace chamber for direct heating, or into a radiant tube for indirect heating, for example. The combustion of the fuel gas with an oxidant within the burner firing tube, for example, results in a significant increase in temperature and pressure (temperature expansion) inside the firing tube.

[0017] Hydrogen is a promising fuel for a sustainable future as its use can reduce carbon emissions. At the same time, careful designing of the burner is needed because hydrogen is a fuel with high burning velocities that can cause flashback thus damaging the equipment. Flashback may occur within flammability limits of particular fuel when mixed with air as an oxidant, for example, and when flame propagation speed is exceeding the physical velocity of the fuel/air mixture coming out the burner combustor, for example. That will allow the flame front to travel upstream of the flame jet flow, forming a flashback effect.

[0018] Flashback arrestors and other tools may prevent flashback, but not by allowing the mixing of fuel and air while preventing mixing upstream of the burner. For example, flashback arrestors may stop or reverse the flow of fuel. Flame arrestor screens may permit a flow of fuel, and may prohibit a flame from propagating upstream once ignited. However, flashback arrestors may wear down and require replacement over time, and may not facilitate optimal mixing of air and fuel.

[0019] An enhanced design of burner and method of operation is needed to ensure the safe combustion without a chance of flashback (e g., upstream flame travel) [0020] Tn one or more embodiments, an enhanced burner (e.g., a device or system for mixing fuel and air) may use gas such as hydrogen as fuel while providing safety to an upstream burner assembly. Hydrogen may be used as an alternative to natural gas, but natural gas and other fuel may be employ ed by the enhanced burners herein, including the nozzle mix burner and other enhanced burners described herein. Any suitable fuel may be used herein. The enhanced burners described herein may bum hydrogen efficiently in a water heater, for example, and may not allow the flame to travel back to the burner internals and further back to a combustion air blower or mixing station fuel pipe. Whereas draft burners may refer to burners in which combustion air may be drafted through the burner internals by the negative pressure created by a suction fan, the enhanced burners herein may be referred to as nozzle mix burners, referring to burners having a nozzle to control the flow of air and fuel. The use of nozzles in nozzle mix burners may control the location where air and fuel may mix, allowing ignition and combustion to occur near the nozzle, preventing flashback. The nozzle may include an air distribution plate (e.g., air flow plate) and a fuel gas plate. The nozzle may be positioned within a firing tube, which may be cylindrical, for example, and may end with a conically shaped outlet. The flame diameter may form in the outlet, but the flame may be stabilized inside of the firing tube near the nozzle. The nozzle may be manufactured from a material such as stainless steel, and may constitute a single piece of material forming the air distribution plate and the fuel head as shown in FIGs. 1A-3C.

[0021] In one or more embodiments, the enhanced burners described herein may include a cylindrical radiative mesh head. Inside the head, a fuel and air mixing assembly may be arranged. The assembly may include a central pipe for combustion air delivery, and may be surrounded by group of smaller pipes for fuel gas delivery to be mixed with the combustion air. The tubes may include plurality of holes (e.g., apertures, ports) for air and fuel supply to a mixing chamber upstream of the mesh element entry. Hydrogen may be sent through the fuel pipe while the combustion air is sent separately through the air pipe (e.g., to control where the mixing of the gas and air occurs). The fuel and air may mix in a crossflow stream after exiting the holes in the pipes. Due to the crossflow, intense mixing may occur, and the combustible mixture is formed, which then passes through the burner mesh where it is ignited, and the flame may be stabilized inside the porous structure of the mesh. Because there is no mixing of fuel and air upstream of the burner, the enhanced design avoids the problem of flashback to the burner housing and achieves a stable uniform flame stabilized in the mesh structure of the burner head.

[0022] In one or more embodiments, the enhanced burners described herein may include a housing with an air inlet, mounting flange with a fuel pipe inlet, a firing tube attached to the housing outlet flange, a mixing nozzle, which may include an air distribution disk and a fuel gas distribution head. Both the disk and the head may be connected with air and fuel supply lines, respectively. Hydrogen may be sent through the fuel pipe, while the combustion air may be sent separately through the air pipe. There may be mixing between the fuel and air when the fuel exits the fuel nozzle. The mixture then travels downstream where the flame may be established inside the firing tube. Because there is no mixing of fuel and air upstream of the burner nozzle, the enhancement avoids the problem of flashback and achieves proper combustion.

[0023] In one or more embodiments, the enhanced burners described herein may include a housing with an air inlet and a fuel gas inlet. The housing may be connected with an air pipe having multiple holes (e.g., apertures) arranged in rows. The fuel gas pipe may be arranged inside the air pipe along the axis of the burner. The fuel pipe may be equipped with multiple holes, and those holes may be concentric with holes in the air pipe. The outlet of each fuel pipe hole may be equipped with a nipple to form a jet of hydrogen fuel directed to the air hole of the air pipe. The assembly creates multiple venturi elements for perfect mixing of fuel and oxidant. Each air pipe hole in outlet may be equipped with a stabilizer cone attached to the air pipe and placed at a distance from outer surface of the air pipe. Hydrogen may be sent through the fuel pipe, while the combustion air may be sent separately through the air pipe. The fuel and air exit and flow around the stabilizer cones, thus forming a recirculating zone (e.g., vortex) inside the cone where the flame is anchored and permanently re-ignited by that vortex (e.g., stabilized on the cone). The combustion zone may be divided into multiple flamelets on the stabilizer cones, providing even heating and combustion stability. Because there is no mixing of fuel and air upstream of the venturi zones of the burner, the enhancement avoids the problem of flashback to the burner housing and further on and achieves stable combustion.

[0024] Modifications and variations of the methods and devices described herein will be obvious to those skilled in the art from the foregoing detailed description. Such modifications and variations are intended to come within the scope of the appended claims. [0025] Turning now to the drawings, FIG. 1 A is a perspective view of a nozzle mix burner 100 of one embodiment of the present disclosure.

[0026] Referring to FIG. 1A, the nozzle mix burner 100 may intake fuel 102 (e.g., hydrogen or any other gas) and combustion air (oxidant) 104. The nozzle mix burner 100 may include a gas inlet 106 through which the fuel 102 may enter the nozzle mix burner 100, and an air pipe 108 through which the air 104 may enter the nozzle mix burner 100. The fuel 102 may flow from the gas inlet 106 to an upper portion 110 that opens into gas pipes 112. The upper portion 110 may form a cylindrical ring, which may surround the air pipe 108. As shown, the gas pipes 112 may extend within the nozzle mix burner 100 along the Y-axis from the upper portion 110, parallel to the air pipe 108. The gas pipes 112 may pass through a cap 114 and extend about the air pipe 108, encircling the air pipe 108. The air pipe 108 may also pass through the cap 114. In this manner, the fuel 102 and the air 104 may not mix until they are within a firing tube portion 113 of the nozzle mix burner 100 below the cap 114.

[0027] Still referring to FIG. 1 A, the gas pipes 112 may include apertures 116 through which the fuel 102 may flow (e.g., radially outward) from (e.g., exit) the perimeter of the gas pipes 112 within the firing tube portion 113. Any of the gas pipes 112 may include apertures 116 along any portion of the gas pipes 112. In some instances, the apertures 116 may be disposed in rows on diametrically opposite sides of each gas pipe 112 and configured to direct the flow of gas tangentially into the firing tube portion 113. The air pipe 108 may include apertures 118 within the firing tube portion 113. The apertures 118 may be arranged such that the air 104 may flow outward (e.g., radially outward) from the perimeter of the air pipe 108 (e g., along the Z-axis) in between the respective gas pipes 112, allowing for the fuel 102 and the air 104 to mix as they exit their respective pipes in the firing tube portion 113. In this manner, the apertures 116 and the apertures 118 may be arranged substantially perpendicular to one another so as to direct flows of gas and air perpendicular to one another.

[0028] The nozzle mix burner 100 may include a burner mesh 120 (e.g., a wire mesh material) that may extend from the cap 114 to a bottom portion 122, resulting in the firing tube portion 113 being contained within the nozzle mix burner 100. The mixing of the fuel 102 and the air 104 may result in combustion. Because the flow and location of the mixing occur in a controlled manner due to the arrangement of the gas pipes 112 and the air pipe 108 within the firing tube portion 113, flashback to the burner housing and further on may be prevented. The mixing of the fuel 102 and the air 104 may be accomplished within the volume of the firing tube portion 113, and then pass through the mesh 120, where the mixture may be ignited, allowing the flame to be stabilized inside the burner mesh 120 (e.g., a porous structure).

[0029] In one or more embodiments, the length and diameter of the air pipe 108 and the gas pipes 112 may vary, as may the number and diameter of the apertures 116 and the apertures 118. The distance of the apertures 116 and the apertures 118 from the cap 114 also may vary, with some non-zero distance allowing for the controlled mixing intensity that may reduce possibility of the flashback. Each of the gas pipes 112 may have multiple rows of the apertures 116, with each respective row of the apertures 116 being oriented toward a different respective gas pipe 112. The apertures 118 may be oriented such that the air 104 exits from the apertures 118 in between respective gas pipes 112 (e.g., and the respective apertures 116 of the gas pipes 112).

[0030] In one or more embodiments, the mesh 120 may form a side wall portion with which to hold the flame caused by the mixing of the air 104 and the gas 102. Alternatively, in place of the mesh 120, the nozzle mix burner 100 may use another material having fuel/air discharge openings therein such as, for example, a ported wall structure, a porous ceramic wall construction, etc., and is not limited to the representatively illustrated mesh 120. The resulting fuel/air mixture may impinge on an interior side surface of the mesh 120, providing a flame stabilizing structure, and may flow through the mesh 120.

[0031] FIG. IB is a perspective view of the nozzle mix burner 100 of FIG. 1A. Referring to FIG. IB, the gas pipes 112 and the air pipe 108 are shown extending along the Y-axis. The gas pipes 112 and the air pipe 108 are shown as cylindrical, with the apertures 116 and the apertures 118 arranged radially (e.g., around the perimeter) about the circumference (e.g., in respective rows each parallel to a circumferential plane) of the gas pipes 112 and the air pipe 108, respectively. As shown, the gas pipes 112 may have multiple sets of the apertures 116 along the Y-axis such that the fuel 102 may exit radially outward (e.g., from the respective pipe perimeters) at different locations respective to the X-axis. In this manner, the air 104 exiting radially outward from the air pipe 108 may mix with the fuel 102 between respective gas pipes 112.

[0032] FIG. 1C is a top cross-section view of the nozzle mix burner 100 of FIG. 1 A. Referring to FIG. 1C, the radially outward flow of the fuel 102 from the gas pipes 112 and of the air 104 from the air pipe 108 are shown. For example, two respective gas pipes 112 may be arranged so that the fuel 102 exiting from one gas pipe flows toward another of the gas pipes 112. The flow of the air 104 from the air pipe 108 may be radially outward from the air pipe 108 and toward the gas pipes 112 (e.g., toward the mesh 120 of FIG. 1A), allowing the air 104 and the fuel 102 to mix outside of the air pipe 108 and the gas pipes 112, but within the enclosure of the firing tube portion 113. In this manner, the flow of fuel 102 may be substantially perpendicular to the flow of air 104 to promote good mixing upstream of the mesh 120 within the enclosure of the firing tube portion 113.

[0033] Referring to FIGs. 1A-1C, the dimensions of the nozzle mix burner 100 may be based on the burner’s application and maximum fire capacities. In one or more embodiments, a length Al (FIG. 1A) of the nozzle mix burner 100 may be between 2-80 inches, possibly within a range of 4-30 inches. A diameter B2 (FIG. 1C) of the mesh 120 may be 1-20, possibly within a range of 2-10. A ratio of length of the pipes A2 (FIG. IB), including the air pipe 108 and the fuel pipes 112, to the burner head diameter Bl may be 1-20, possibly within a range of 2-10. A ratio of an outer diameter B2 (FIG. 1C) of the pipes, including the air pipe 108 and the fuel pipes 112, to the burner head diameter Bl may be 0.5-0.9, possibly within a range of 0.6-0.9. Using a fire capacity of 100 KBTU/H, Al may be 7-9 inches, B2 may be 2-2.5 inches, A2/B1 may be 3.5-4.5, and B1/B2 may be 0.8-0.9.

[0034] FIG. 2A is a side view of a nozzle mix burner 200 of one embodiment of the present disclosure. Referring to FIG. 2A, the nozzle mix burner 200 may intake fuel 202 (e.g., hydrogen or any other gas) and combustion air 204. The nozzle mix burner 200 may include a gas pipe 206 through which the fuel 202 may flow, and an air pipe 208 through which the air 204 may flow. The air 204 may flow into a burner housing 209 through which the gas pipe 206 may extend (e.g., as shown in FIG. 2B). The fuel 202 and the air 204 may flow into a firing tube 210, where they may mix, as shown and explained further with respect to FIGs. 2B and 2C. The nozzle mix burner 200 may include a flame shaping location 212, which is shown as frustoconical, but may be another shape through which the flame caused by the mixture of the fuel 202 and the air 204 may flow from the firing tube 210.

[0035] FIG. 2B is a perspective view of the nozzle mix burner 200 of FIG. 2A. Referring to FIG. 2B, the gas pipe 206 extension along the Y-axis through the burner housing 209 is shown. In this manner, the fuel 202 is not exposed to the air 204 until the fuel 202 and the air 204 reach the firing tube 210. In particular, the gas pipe 206 may be operatively connected to an air flow plate 220 and a fuel nozzle 222 within the firing tube 210. The air flow plate 220 may extend along the inner circumference of the firing tube 210 so that the air 204 must flow through apertures 224 in the air flow plate 220. The fuel nozzle 222 may extend higher along the Y-axis with respect to the air flow plate 220 so that the fuel 202 exits (e.g., radially) from the gas pipe 206 via apertures 226 in the fuel nozzle 222. Because the fuel 202 may exit radially from the gas pipe 206 via the apertures 226 in the fuel nozzle 222, and because the air 204 may flow upward along the Y -axis through the apertures 224, the fuel 202 and the air 204 may mix and start combustion in the firing tube 210. Due to the nozzle mixing design employed herein, flashback into the gas pipe 206 and the burner housing 209 is prevented. The resulting flame may flow outward through the firing tube outlet (e.g., the flame shaping location 212). An example of the gas and air flow mixing patterns within the firing tube 210 is shown in more detail in FIG. 2D.

[0036] FIG. 2C is a perspective view of a portion of the nozzle mix burner 200 of FIG. 2A. Referring to FIG. 2C, a portion of the gas pipe 206 is shown attached to the fuel nozzle 222, which is composed of the air flow plate 220 with the fuel discharge head in the center (e.g., having the apertures 226). As shown, the air flow plate 220 may include multiple apertures 224 in multiple locations and having various sizes (e.g., diameters). The fuel discharge head of the fuel nozzle 222 may have the apertures 226 arranged radially to allow for an outward flow of the fuel 202 from the gas pipe 206, resulting in interaction between the fuel 202 and the air 204.

[0037] FIG. 2D is an illustrative schematic view of the firing tube portion of the nozzle mix burner 200 of FIG. 2A. Referring to FIG. 2D, fuel 202 enters the firing tube 210 from the gas pipe 206 by flowing from the fuel discharge apertures 226 of the nozzle 222, and the air 204 enters the firing tube 210 by flowing through the air flow plate 220 of the nozzle 222. FIG. 2D shows an example of the way in which the fuel 202 and the air 204 may mix and recirculate, resulting in a flame 230 that may exit via the flame shaping location 212. As shown in FIG. 2D, the air flow plate 220 may be angled with respect to the Z-axis (e.g., at an angle 9 from 0-20°). The angle 9 may cause the flow of the air 204 to be angled toward the center of the firing tube 210 to facilitate the mixing with the fuel 202 that may flow from the fuel nozzle 222 radially outward, resulting in the gas-air mixture flowing toward the firing tube outlet (e.g., the flame shaping location 212), and some of the mixture recirculating back along the center line (e.g., toward the nozzle 222) for the permanent re-igniting of the fresh mixture coming out of the nozzle 222. That back flow recirculating vortex constantly re-ignites the mixture, stabilizing the flame inside the firing tube of the burner.

[0038] In one or more embodiments, with reference to FIGs. 2A-2D, the shape and surface profile of the burner nozzle 222 may vary. For example, the nozzle 222 may be flat (e.g., an angle 6 of 0 in FIG. 2D), rounded, conical, cylindrical, elliptical, or the like, as long as it has the aperture 224 allowing the air 204 to flow from the burner housing 209 to the firing tube 210. The length and diameter of the gas pipe 206 may vary, as may the number and diameter of the apertures 224 and the apertures 226. The distance of the apertures 224 and the apertures 226 from the burner housing 209 also may vary, with some non-zero distance allowing for the controlled mixing which allows for required changing of the flame parameters. The length of the firing tube 210 may vary as well as the shape of the outlet (e.g., the flame shaping location 212). For example, while the flame shaping location 212 is shown as conical, other shapes and profiles may be implemented.

[0039] Referring to FIGs. 2A-2D, the range of possible burner dimensions based on application and burner’s maximum high fire capacities may be as follows: The total burner’s apparatus length LI (FIG. 2A) = 5-100 inches; burner’s housing diameter D2 (FIG. 2A) = 2-30 inches; the firing tube length over diameter ratio L3/D1 = 1- 20 (FIG. 2A); the nozzle inside the firing tube positioning ratio L4/L3 = 0. 1 - 0.9 (FIG. 2D). More likely dimensions may be preferably within: LI = 8 - 30 inches; burner’s housing diameter D2 = 3 -20 inches; the firing tube length over diameter ratio L3/D1 = 2- 10; the nozzle inside the firing tube positioning ratio L4/L3 = 0.3 - 0.7. The specific example of likely commercial dimensions of the burner lOOKBtu/h high fire capacity may be preferably within: LI = 9-11 inches; burner’s housing diameter D2 = 4 -5 inches; the firing tube length over diameter ratio L3/D1 = 2- 3; the nozzle inside the firing tube positioning ratio L4/L3 = 0.6 - 0.7.

[0040] In some instances, the flame shaping location 212 may be omitted. In such instances, the firing tube 210 may be formed of a metallic mesh material and the distal end of the firing tube 210 may be capped (i.e., closed off). In this manner, the flame 230 may exit the firing tube 210 radially outward through the mesh and be disposed about the outer mesh surface of the firing tube 210. [0041] FIG. 3 A is a side view of a nozzle mix burner 300 of one embodiment of the present disclosure. Referring to FIG. 3A, the nozzle mix burner 300 may intake fuel 302 (e.g., hydrogen or any other gas) and air 304. The nozzle mix burner 300 may include a gas pipe 306 through which the fuel 302 may enter the nozzle mix burner 300, and an air pipe 308 through which the air 304 may enter the nozzle mix burner 300. As shown in FIGs. 3B and 3C, the fuel 302 and the air 304 may not interact until the fuel 302 exits from the gas pipe 306 within the air pipe 308. The mixture of the fuel 302 and the air 304 within the air pipe 308 may exit the air pipe 308 and flow around stabilizers 310, a number of which may be operatively attached to the air pipe via respective arms 312 (e.g., each stabilizer 310 may have multiple arms 312 extending between and connecting to the air pipe 308 and the stabilizer 310) such that the stabilizers are separated from the air pipe 308. The nozzle mix burner 300 may include a profiled plate 314 arranged around a circumference of the air pipe 308, preventing backflow of the fuel 302 or the air 304 after the mixture of the fuel 302 and the air 304 exits the gas pipe 306.

[0042] FIG. 3B is a side view of the nozzle mix burner 300 of FIG. 3 A. Referring to FIG. 3B, the gas pipe 306 is shown as extending along the Y-axis within the air pipe 308, preventing the immediate interaction between the fuel 302 and the air 304 within the air pipe 308. Because the fuel 302 and the air 304 do not interact until the fuel 302 exits from the gas pipe near the stabilizers 310, and because the stabilizers 310 may be downstream of the gas pipe 306 and the intake of the air 304, flashback may be prevented.

[0043] FIG. 3C is a top cross-section view of the nozzle mix burner 300 of FIG. 3A. Referring to FIG. 3C, the fuel 302 may exit the gas pipe 306 radially (e.g., via apertures 316), allowing the fuel 302 to flow into the air pipe 308 outside of the gas pipe 306, where the fuel 302 may mix with the air 304. The outlet of the apertures 316 may be equipped with nipples 318 to form a jet of gas flow directed to respective apertures 320 in the air pipe 308 (e.g., venturi elements). The apertures 316 and the apertures 320 may be concentric with one another so that a mixture 322 of the fuel 302 and the air 304 may flow through the apertures 320 toward respective stabilizers 310. As shown, the mixture 322 may flow around the stabilizers 310, resulting in a vortex stabilizing effect (e.g., because the stabilizers 310 may be hollow, providing a recirculating zone within the stabilizers 310 to anchor and stabilize the resulting flame) that may facilitate an efficient mixing and stabilizing of the fuel 302 and the air 304. Because of the controlled mixture of the fuel 302 and the air 304 (e.g., upstream of a burner), flashback is avoided. [0044] Referring to FIGs. 3A-3C, the length and the diameter of the air pipe 308 and the gas pipe 306 may vary, as may the number and diameter of the apertures 316 and the apertures 320, as may the number of stabilizers 310 and their distances from the air pipe 308 (e.g., based on the lengths of the arms 312). The size and geometry of the stabilizers 310 may vary as well. For example, while the stabilizers 310 are shown as spherical they may be conical or another geometry that facilitates the vortexes for mixing and stabilizing the fuel 302 and the air 304. The number and positioning of the gas pipe 306 may vary. For example, the gas pipe 306 may be multiplied into multiple gas pipes extending along the Y-axis within the air pipe 308, as long as the apertures 316 of any respective air pipe are concentric with a respective aperture of the air pipe 308 to facilitate the flow of the fuel 302 and the air 304 from the air pipe 308 via the apertures 316.

[0045] Still referring to FIGs. 3A-3C, the range of possible burner dimensions based on application and burner’s maximum high fire capacities may be preferably within: the burner head length Ml = 2-100 inches (FIG. 3 A); the burner flame stabilization length M2 = 1-60 inches (FIG. 3A); the burner head diameter N1 = 1-20 inches (FIG. 3C); the burner head length to burner head diameter ratio Ml/Nl = 2-20; the burner stabilizer circumference diameter to burner head diameter ratio N2/N1 = 2-4 (FIG. 3C). More likely dimensions may be preferably within: the burner head length Ml = 4-60 inches; the burner flame stabilization length M2 = 2-30 inches; the burner head diameter N1 = 1-10 inches; the burner head length to burner head diameter ratio Ml/Nl = 3-15; the burner stabilizer circumference diameter to burner head diameter ratio N2/N1 = 2-3. The specific example of likely commercial dimensions of the burner lOOKBtu/h high fire capacity may be preferably within: the burner head length Ml = 7-9 inches; the burner flame stabilization length M2 = 4-5 inches; the burner head diameter N1 = 2-2.5 inches; the burner head length to burner head diameter ratio Ml/Nl = 3-3.5; the burner stabilizer circumference diameter to burner head diameter ratio N2/N1 = 1.3-1.6.

[0046] Referring to FIGs. 1A-1C and 3A-C, the nozzle mix burners shown may be radiant type burners with the outer wall portion being a flame holding wall formed from a metal mesh material (e.g., the mesh 120 of FIG. 1A). However, the present disclosure is not limited to a combustion system employing a radiant type burner, as other types of burners may be implemented based on the present disclosure, and using outer burner walls of other types, such as ceramic, porous, woven materials, and the like. [0047] Referring to FIG. 2B, in one or more embodiments, a first row of the apertures 224 (e.g., closest to the fuel nozzle 222) may have a respective aperture diameter dl of 0.055-1.0 inches, with a possible preferred range of 0.055-0.250 inches, and may include eight of the apertures 224. A second row of the apertures 224 (e.g., next closest to the fuel nozzle 222) may have a respective aperture diameter d2 of 0.075-1.5 inches, with a possible preferred range of 0.075-0.350 inches, and may include eight of the apertures 224. A third row of the apertures 224 (e.g., the furthest away from the fuel nozzle 222) may have a respective aperture diameter d3 of 0.095-1.8 inches, with a possible preferred range of 0.095-0.420 inches, and may include sixteen of the apertures 224. The apertures 226 of the fuel nozzle 222 may have a respective aperture diameter d4 of 0.040-0.65 inches, with a possible preferred range of 0.040-0.165 inches, and may include sixteen apertures. The diameters of the apertures 224 and the apertures 226 may apply to the apertures of the other figures (e.g., the apertures 116 and 118 of FIG. 1A, the apertures 316 and 320 of FIG. 3C).

[0048] FIG. 4 is a schematic diagram illustrating components of a water heater 400 of one embodiment of the present disclosure. Referring to FIG. 4, the water heater 400 may be a gas-fired water heater, or alternatively may be another type of fuel-fired heating apparatus such as, by way of non-limiting example, a boiler or a furnace. The water heater 400 may be supportable on a horizontal surface, such as a floor, and may have an insulated tank 414 that overlies a combustion chamber 416 and is adapted to hold a quantity of pressurized water 418 to be heated. A flue 420 may communicate at its lower end with the combustion chamber 416 and may extend upwardly therefrom through an interior of the tank 414. Disposed within the combustion chamber 416, generally beneath the open lower end of the flue 420, are a main burner 422 (e.g., representing the nozzle mix burner 100 of FIGs. 1A-1C, the nozzle mix burner 200 of FIGs. 2A-2D, and the nozzle mix burner 300 of FIGs. 3A-3C), and an associated pilot fuel burner 424 operative in a conventional manner to ignite the main burner 422.

[0049] During firing of the water heater 400, a flame 426 emanates from the main burner 422 (e.g., based on the combustion techniques described with respect to FIGs. 1A-3C), creating hot combustion products 428 that flow upwardly through the flue 420 and transfer combustion heat through to the stored water 418. The interior of the tank 414 is typically communicated, via a hot water supply pipe 430, with various plumbing fixtures such as sinks, tubs, showers, dishwashers and the like which, on an on- demand basis, receive pressurized hot water from the interior of the tank 414. Hot water outflow from the tank 414 is automatically replaced therein with an inflow of pressurized cold water, from a source thereof, via a cold water inlet pipe 432.

[0050] A normally closed thermostatic fuel valve 444 may be supplied at an inlet thereof with fuel (representatively a fuel gas) from a source thereof by a fuel supply line 446, and is respectively coupled at an outlet portion thereof to the main and pilot fuel burners 424, 424 by fuel supply lines (or conduits) 448, 450. Fuel supply line 448, at its discharge end, is operatively coupled to a fuel discharge orifice 452 (e.g., feeding into the gas inlet 106 of FIG. 1 A, the gas pipe 206 of FIGs. 2A, 2B, and 2D, and the gas pipe 306 of FIGs. 3A-3C). [0051] During firing of the water heater 400, fuel 454 (e g , gas) is discharged through the orifice 452. Combustion air 456 may be ducted from outside the combustion chamber 416, or may be suitably introduced into the combustion chamber 416 and permitted to flow, un-ducted, into a suitable air inlet opening. Fuel 454 and air 456 may mix in the main burner 422 (e.g., as shown and described with respect to FIGs. 1 A-3C), and then exits therefrom to form the flame 426.

[0052] Without the enhancements to the main burner 422 as provided by FIGs. 1 A-3C, a flame flashback condition may occur at the main burner 422. If this occurs, the flame 426 undesirably bums within the interior of the hollow body of the main burner 422 instead of burning externally thereto. Because of the controlled mixing of fuel and air provided by FIGs. 1 A-3C, flashback may be avoided.

[0053] During normal firing of the main burner 422, the maximum temperature of its hollow body may be on the order of about 600 degrees Fahrenheit. However, when a flame flashback condition occurs at the main burner 422, its body temperature may increase to approximately 1250 degrees Fahrenheit or above. The enhancements herein uniquely prevent flashback and the corresponding temperature increase, which may otherwise result in melting of the materials of the components of the water heater 400. [0054] The description above is not meant to be limiting.

[0055] Embodiments according to the disclosure are in particular disclosed in the attached claims directed to a method, and a device (e.g., for mixing fuel and air) wherein any feature mentioned in one claim category, e.g., method, can be claimed in another claim category, e.g., system, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However, any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims.

[0056] The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments.

[0057] Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language is not generally intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation.

[0058] Many modifications and other implementations of the disclosure set forth herein will be apparent having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0059] In this specification, terms denoting direction, such as vertical, up, down, left, nght etc. or rotation, should be taken to refer to the directions or rotations relative to the corresponding drawing rather than to absolute directions or rotations unless the context require otherwise. [0060] Wherever it is used, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of’. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear. [0061] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention.

[0062] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims

CLAIMS That which is claimed is:

1. A device for mixing fuel and air, the device comprising: an air pipe extending within a firing tube configured to receive a flow of air; and a plurality of fuel pipes extending within the firing tube in parallel with one another and with the air pipe and configured to receive a flow of fuel, wherein the air pipe comprises first apertures configured to release the air from inside the air pipe radially outward from the air pipe, the first apertures arranged around a circumference of the air pipe, and wherein a first fuel pipe of the plurality of fuel pipes comprises second apertures configured to release the fuel from inside the first fuel pipe radially outward from the first fuel pipe, the second apertures arranged around a circumference of the first fuel pipe.

2. The device of claim 1, wherein the fuel pipes are arranged encircling the air pipe.

3. The device of claim 1, further comprising a mesh material arranged encircling an exterior circumference of the firing tube.

4. The device of claim 3, wherein the device has a length of 4-30 inches, and a ratio of a diameter of the plurality of fuel pipes to a diameter of the mesh material is 0.6-0.9.

5. The device of claim 1, wherein the second apertures comprise a first aperture oriented in a first direction and a second aperture oriented in a second direction, wherein a second fuel pipe of the plurality of fuel pipes comprises a third aperture oriented in a third direction and a fourth aperture oriented in a fourth direction, and wherein the first direction, the second direction, the third direction, and the fourth direction are not oriented toward the air pipe.

6. The device of claim 5, wherein the first apertures comprise a row of apertures parallel to a circumferential plane of the air pipe, and wherein a fifth aperture of the first apertures is oriented in a fifth direction between the first fuel pipe and the second fuel pipe-

7. The device of claim 6, wherein the fifth direction is different than the first direction, the second direction, the third direction, and the fourth direction.

8. A device for mixing fuel and air, the device comprising: an air pipe extending into a chamber and configured to receive a flow of air; and a fuel pipe extending through the chamber and into a firing tube and configured to receive a flow of fuel; and a nozzle attached to the fuel pipe within the firing tube, the nozzle comprising an air distribution plate arranged within the firing tube and around an exterior circumference of the fuel pipe, wherein the air distribution plate of the nozzle comprises first apertures configured to release the air from inside the chamber into the firing tube, and wherein the nozzle comprises second apertures configured to release the fuel from inside the fuel pipe into the firing tube, the second apertures arranged around a circumference of the nozzle.

9. The device of claim 8, wherein the second apertures are configured to release the fuel into the firing tube radially outward from the nozzle.

10. The device of claim 8, wherein the first apertures are oriented toward a firing tube outlet portion attached to the firing tube, and wherein the firing tube outlet portion is configured to receive a flame from the firing tube, the air distribution plate being positioned within in the firing tube at a distance from the firing tube outlet portion.

11. The device of claim 10, wherein the firing tube outlet portion is frustoconical.

12. The device of claim 10, wherein the firing tube outlet portion is elliptical.

13. The device of claim 8, wherein the air distribution plate of the nozzle is arranged at an angle with respect to an axis extending radially outward from the fuel pipe, the angle greater than zero.

14. The device of claim 8, wherein the air distribution plate of the nozzle is arranged in parallel with respect to an axis extending radially outward from the fuel pipe.

15. The device of claim 8, wherein the device has a length of 8-30 inches, the chamber has a diameter of 3-20 inches, the firing tube has a length to diameter ratio of 2-10, the first apertures having a diameter between 0.055-1.0 inch, and the second apertures having a diameter of 0.040-0.65 inches.

16. A device for mixing fuel and air, the device comprising: an air pipe configured to receive a flow of air; a fuel pipe extending within the air pipe and configured to receive a flow of fuel; and stabilizer devices attached to an exterior circumference of the air pipe via arms extending between the stabilizer devices and the exterior circumference of the air pipe, and wherein the fuel pipe comprises first apertures configured to release the fuel from inside the fuel pipe into the air pipe, the first apertures arranged around a circumference of the fuel pipe, and wherein the air pipe comprises second apertures configured to release the fuel from inside the air pipe toward the stabilizer devices.

17. The device of claim 16, wherein a first aperture of the first apertures and a second aperture of the second apertures are aligned axially in a direction that is radially outward from the air pipe and the fuel pipe.

18. The device of claim 16, further comprising nipples respectively connected to the first apertures and extending radially outward from the fuel pipe.

19. The device of claim 16, wherein a first stabilizer device of the stabilizer devices, a first aperture of the first apertures, and a second aperture of the second apertures are axially aligned.

20. The device of claim 16, wherein the stabilizer devices are hollow conical devices.

21. The device of claim 16, wherein the first apertures comprise a first row of apertures and a second row of apertures, wherein the second apertures comprise a third row of apertures concentric with the first row of apertures and a fourth row of apertures concentric with the second row of apertures, wherein a first stabilizer device of the stabilizer devices is axially aligned with a first aperture of the first row of apertures and with a second aperture of the third row of apertures, and wherein a second stabilizer device of the stabilizer devices is axially aligned with a third aperture of the first row of apertures and with a fourth aperture of the third row of apertures.

22. The device of claim 16, wherein a diameter of the air pipe is 1-10 inches, and a ratio of a diameter of the device to the diameter of the air pipe is 2-3.

23. A method for mixing fuel and air, the method comprising: receiving air using an air pipe of a nozzle mix burner; receiving fuel using a fuel pipe of the nozzle mix burner; and mixing the air and the fuel in a firing tube of the nozzle mix burner based on a release of the air via first apertures of the nozzle mix burner and based on a release of the fuel via second apertures of the nozzle mix burner.