WO2019165378A1

WO2019165378A1 - Compact inward-firing premix mesh surface combustion system, and fluid heating system and packaged burner system including the same

Info

Publication number: WO2019165378A1
Application number: PCT/US2019/019441
Authority: WO
Inventors: Carl Nicholas NETT; Alireza BAHRAMI; Keith Richard WALTZ
Original assignee: Fulton Group NA Inc
Current assignee: Fulton Group NA Inc
Priority date: 2018-02-23
Filing date: 2019-02-25
Publication date: 2019-08-29
Anticipated expiration: 2020-08-23

Abstract

An inward-firing surface combustion burner includes a burner casing configured to receive a fuel-air mixture at a burner inlet and to provide hot combustion gas at a burner output, a combustion substrate disposed within the burner casing, the substrate having a shape comprising at least a semi-cone, having a substrate angle measured from a longitudinal axis, having a substrate porosity defined by a plurality of pores, and having a substrate inner surface and a substrate outer surface, a mesh disposed on the inner surface of the combustion substrate, the substrate configured to receive the fuel-air mixture at the outer surface of the substrate, the fuel-air mixture passing through the pores of the substrate and through the pores of the mesh at a mixture flow rate from the substrate outer surface toward the substrate inner surface, the burner configured such that, in operation, the fuel-air mixture ignites directly upon or largely in contact with the plurality of pores of the mesh.

Description

COMPACT INWARD-FIRING PREMIX MESH SURFACE COMBUSTION SYSTEM, AND FLUID HEATING SYSTEM AND PACKAGED BURNER

SYSTEM INCLUDING THE SAME

CROSS REFERENCE TO RELATED APPLICATIONS

[1] This application claims priority to ET.S. provisional patent application serial number 62/634,520, filed on February 23, 2018, the content of which is incorporated herein by reference in its entirety to the extent permissible under applicable law.

BACKGROUND

(1) Field

[2] This application relates to a compact premix mesh surface fuel combustion system for the purpose of heat generation, methods of using a premix mesh surface fuel combustion system, and methods of fluid heating incorporating a compact premix mesh surface fuel combustion system.

(2) Description of the Related Art

[3] Premix fuel combustion systems are used to provide a heated thermal transfer fluid for a variety of commercial, industrial, and domestic applications such as hydronic, steam, and thermal fluid boilers, for example. Because of the desire for improved energy efficiency, compactness, reliability, and cost reduction, there remains a need for improved premix fuel combustion systems, as well as improved methods of manufacture thereof.

[4] Incomplete combustion, suboptimal combustion product flow fields, and large temperature gradients can result in a decrease in overall burner system performance. This is particularly true of combustion systems incorporated into fluid heating systems for the production of hot water, steam, and thermal fluid for hot liquid or steam for ambient temperature regulation, hot water consumption, or commercial and industrial applications. Moreover, residential, commercial, industrial and government uses of combustion systems for a variety of applications benefit from improvements that decrease the size, volume and footprint of these apparatuses, particularly those that utilize premix fuel and air (oxygen) combinations. Thus there remains a need for an improved compact premix fuel combustion system having improved performance and efficiency. SUMMARY

[5] Disclosed herein is an inward-firing premix surface combustion burner system with a composite semi-cone diffuser comprising a perforated substrate and a mesh insulating layer (together, a diffuser).

[6] The above described and other features are exemplified by the following figures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[7] Referring to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike.

[8] FIG. 1 A shows an illustration of the elements used to define semi-cone geometry, in accordance with embodiments of the present disclosure.

[9] FIG. 1B shows a perspective diagram of a truncated cone in accordance with embodiments of the present disclosure.

[10] FIG. 1C shows a perspective diagram of a semi-cone in accordance with embodiments of the present disclosure.

[11] FIG. 1D shows a perspective diagram of a composite semi-cone in accordance with embodiments of the present disclosure.

[12] FIG. 1E shows a perspective diagram of a composite semi-cone without cylindrical sections in accordance with embodiments of the present disclosure.

[13] FIG. 2 shows a cutaway diagram of an embodiment of a premix combustion system with a single semi-conical combustion substrate in accordance with embodiments of the present disclosure.

[14] FIG. 3 shows cutaway diagram showing an expanded view of an embodiment of the mesh and substrate structure of the combustion diffuser in accordance with

embodiments of the present disclosure.

DETAILED DESCRIPTION

[15] In the U.S. Provisional Application No. 62/634,476, filed Feb. 23, 2018, the inventors disclosed improvements to premix burner combustion systems comprising inward firing geometries, including the use of composite semi -cone burner combustion substrates and flow guides or baffles. The inventors have further discovered that premix fuel-air burner combustion systems with composite semi-cone substrates that further comprises a metal fiber mesh layer on the inner surface of the substrate improves the performance and reliability of embodiments, particularly when operated in the“surface combustion” regime, as described herein.

[16] Disclosed is an improved inward firing premix fuel-air surface combustion burner system for applications that require heat generation which provides improved efficiency, apparatus lifecycle and performance by alleviating or eliminating these disadvantages.

[17] While not wanting to be bound by theory, the following nomenclature is useful in the detailed description that follows:

[18] Consistent with convention, a cone is a geometric surface that can be used to describe certain aspects of embodiments of the present disclosure, e.g., a combustion surface or substrate (as discussed hereinafter). FIG. 1 A illustrates key concepts. A cone 118 is a surface defined by a ray called the generator 116 emanating from a fixed point called the vertex 102 which intersects a fixed plane curve called the directrix 112. The directrix, as a geometric curve, need not be either continuous or convex but, when it is, it defines an

interior to the cone (normal vector oriented toward the volume containing the intersection with the axis) and an exterior. The axis 114 of the cone is the straight line passing between the vertex 102 and center 120 of the plane curve defined by the directrix 112. If the axis is perpendicular to the plane of the directrix, it is a right cone; otherwise, it is an oblique cone.

If the directrix is a circle, the cone is a circular cone. If the axis is perpendicular to the directrix plane for a circular cone, the cone is a right-circular cone. A semi-cone 100 is a section of a cone surface bounded between by intersecting a cone with at most two 2- dimensional surfaces. In FIG. 1A, the illustrated cone is intersected by a surface 104 proximal to the vertex 102, forming an upper or proximal semi-cone edge 106. The surface 104 need not be planar or perpendicular to the axis 114 or any generator 116, and the proximal edge 106 need not be a plane curve. The illustrated cone in FIG. 1 A is also intersected by a surface 108 distal from the vertex 102, forming a lower or distal edge 110. The surface 108 need not be planar or perpendicular to the axis 114 or any generator 116, and the distal edge 110 need not be a plane curve. The resulting semi-cone 100 is the surface of the cone 118 bounded above by the proximal edge 106 and by the distal edge 110 below. In the degenerate case, the proximal surface 104 intersects the cone 118 only at the vertex 102, wherein the semi-cone 100 is the surface of the cone 118 between the vertex 102 and the distal edge 110. FIG. 1C show a perspective diagram of a semi-cone 124 with a non-planar proximal edge 126. A semi-cone wherein the cone 118 is intersected by proximal 104 and distal planar surfaces 108 is a truncated cone. A semi-cone wherein the cone 118 is intersected by parallel proximal 104 and distal planar surfaces 108 is a frustum. A semi cone wherein the cone 118 is a right circular cone, the proximal 104 and distal surfaces 108 are planar and perpendicular to the axis 114 is a right frustum. FIG. 1B shows a perspective diagram of a right frustum 122. A composite semi-cone is a composition of one or a plurality of semi-cones and zero, one or a plurality of cylinders disposed along their edges. FIG. 1D shows a perspective diagram of a composite semi-cone 128. FIG. 1E shows a perspective diagram of a composite semi -cone 129 without a cylindrical section.

[19] For a semi-cone, the generator angle (alpha or a, as discussed further herein, e.g., regarding an angle of a combustion surface or substrate) is the angle 114 formed between a specific generator ray 116 and the axis 114 at the vertex 102. For a right circular semi-cone, right circular truncated cone or right circular frustum, all the generator angles are equal and a unique generator angle can be determined.

[20] A burner is a combustion system designed to provide thermal energy through a combustion process to apparatuses used for a variety of applications. The burner may include, depending upon the fuel, combustion geometry and target application, a burner head that supports the combustion process, one or a plurality of nozzles or orifices, air blower with damper, burner control system, shut-off devices, fuel regulator, fuel filters, fuel pressure switches, air pressure switches, flame detector, ignition devices, air damper and fuel valves and fittings. Typical burner systems range in capacity from 30kW to l,500kW

(approximately 40 HP to 2,100 HP) are can be adapted to a wide range of uses including incinerators, boilers, drying systems, industrial ovens and furnaces.

[21] A package burner is a burner combustion system designed to be incorporated as a standalone modular subsystem unit into apparatuses used for a variety of applications. The package burner may include, depending upon the fuel, combustion geometry and target application, an integrated subsystem comprising a burner head that supports the combustion process, one or a plurality of nozzles or orifices, air blower with damper, burner control system, shut-off devices, fuel regulator, fuel filters, fuel pressure switches, air pressure switches, flame detector, ignition devices, air damper and fuel valves and fittings. Typical package burner systems range in capacity from 30kW to l,500kW (approximately 40 HP to 2,100 HP) are can be adapted to a wide range of uses including incinerators, boilers, drying systems, industrial ovens & furnaces.

[22] In the discussion that follows, we distinguish three types of physical combustion mechanisms. First,“volume combustion” occurs where a fuel-air mixture is ignited in a spatial volume. A physical structure may contain the combustion process, such as in a cavity burner, but the details of the structure do not directly participate in the thermodynamic combustion process. Second, for“surface combustion” the combustion process (or a majority thereof) occurs directly upon - or very near, or largely in contact with - a burner combustion surface. In some cases, some form of physical insulating or separation layer may be needed at the burner surface to ensure the burner surface does not get too hot or to provide otherwise needed separation from the surface. The physical, geometrical and material characteristics of the surface contribute to determining the thermodynamic physics. Third, in“suspended flame combustion” (SF combustion), the combustion process (or a majority thereof) occurs near - but not directly on- the surface of a combustion substrate. which provides physical support for the generation of the flame front. In some conditions, a small portion of the flame may contact the burner surface (as described more hereinafter). In SF combustion, the flame front (or a majority thereof) is suspended near a positional equilibrium at a distance from the substrate determined partly by a balance of opposing forces due to fuel-air mass flow and flame migration toward its fuel source. If the fuel-air mass flow is reduced below a threshold, the flame front can approach the substrate and enter a regime of surface combustion. If the fuel-air mass flow is increased above a threshold, the flame front can enter a regime of volume combustion.

[23] A boiler is a fluid heating system incorporating a heat exchanger that may be used to exchange heat between any suitable fluids, e.g., a first fluid and the second fluid, wherein the first and second fluids may each independently be a gas or a liquid. In the disclosed system, the first fluid, which is directed through the heat exchanger core, is a thermal transfer fluid, and may be a combustion gas, e.g., a gas produced by fuel fired combustor, and may comprise water, carbon monoxide, nitrogen, oxygen, carbon dioxide, combustion byproducts or combination thereof. The thermal transfer fluid may be a product of combustion from a hydrocarbon fuel such as natural gas, propane, or diesel, for example.

[24] Also, the second fluid, which is directed through the pressure vessel and contacts an entire outer surface of the heat exchanger core, is a production fluid and may comprise water, steam, oil, a thermal fluid (e.g., a thermal oil), or combination thereof. The thermal fluid may comprise water, a C2 to C30 glycol such as ethylene glycol, a

unsubstituted or substituted Cl to C30 hydrocarbon such as mineral oil or a halogenated Cl to C30 hydrocarbon wherein the halogenated hydrocarbon may optionally be further substituted, a molten salt such as a molten salt comprising potassium nitrate, sodium nitrate, lithium nitrate, or a combination thereof, a silicone, or a combination thereof. Representative halogenated hydrocarbons include l,l,l,2-tetrafluoroethane, pentafluoroethane, difluoroethane, l,3,3,3-tetrafluoropropene, and 2,3,3, 3-tetrafluoropropene, e.g.,

chlorofluorocarbons (CFCs) such as a halogenated fluorocarbon (HFC), a halogenated chlorofluorocarbon (HCFC), a perfluorocarbon (PFC), or a combination thereof. The hydrocarbon may be a substituted or unsubstituted aliphatic hydrocarbon, a substituted or unsubstituted alicyclic hydrocarbon, or a combination thereof. Commercially available examples include Therminol® VP-l, (Solutia Inc.), Diphyl® DT (Bayer A. G.), Dowtherm® A (Dow Chemical) and Therm® S300 (Nippon Steel). The thermal fluid can be formulated from an alkaline organic compound, an inorganic compound, or a combination thereof. Also, the thermal fluid may be used in a diluted form, for example with a concentration ranging from 3 weight percent to 10 weight percent, wherein the concentration is determined based on a weight percent of the non-water contents of the thermal transfer fluid in a total content of the thermal transfer fluid.

[25] An embodiment in which the combustion products (equivalently, thermal transfer fluid) comprises predominately gaseous products from combustion of natural gas or propane, and further comprises liquid water, steam, or a combination thereof and the production fluid comprises liquid water, steam, a thermal fluid, or a combination thereof is specifically mentioned.

[26] The inventors have unexpectedly discovered that an inward-firing burner geometry using a composite semi-cone mesh diffuser alleviates many of the disadvantages described above, particularly when operated in the surface combustion regime. FIG. 2 shows a cutaway diagram of an embodiment of an inward-firing premix burner comprising a semi cone combustion substrate and mesh insulator, although some advantages of inward-fining premix burner embodiments discovered by the inventors are not limited to the composite semi-cone geometry. A semi-cone shaped combustion substrate 213 is disposed between the burner top head 206 and the inner surface of the furnace 230. In this embodiment, the burner combustion substrate 213 is a right circular frustum wherein the proximal edge 202 (or top edge) is a planar circle perpendicular to a longitudinal (or aial) axis 216 with proximal diameter D_p and distal edge 236 (or bottom edge) a planar circle perpendicular to the longitudinal axis 216 with diameter D_d, with height H. The burner combustion substrate angle, a, in a right frustum embodiment, is then determined to be:

a = arctan[(D_d - D_p)/H] Eq. 1

[27] Dimensions of the combustion substrate 213 and metal fiber mesh 232 depend upon the burner power, capacity, performance and size requirements of a specific application. Proximal diameters (D_p) between 1 inch and 59 inches is specifically mentioned. Distal diameters (Dd) between 2 inches and 60 inches is specifically mentioned. Substrate height (H) between 1 inch and 60 inches is specifically mentioned.

[28] The semi-cone sections of the burner combustion substrate angle may have any suitable generator angle between 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 10 degrees to 11 degrees, 12 degrees, 13 degrees, 14 degrees, 15 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, 20 degrees, 21 degrees, 22 degrees, 23 degrees, 24 degrees, 25 degrees, 26 degrees, 27 degrees, 28 degrees, 29 degrees, 30 degrees, 31 degrees, 32 degrees, 33 degrees, 34 degrees, 35 degrees, 36 degrees, 37 degrees, 38 degrees, 39 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, and 85 degrees wherein the foregoing upper and lower bounds can be independently combined. For the right circular semi-cone, right circular truncated cone, and the right circular frustum, the burner combustion substrate angles between 18 degrees and 35 degrees is specifically mentioned. For the right circular semi -cone, right circular truncated cone, and the right circular frustum, the burner combustion substrate angle of 25 degrees is also specifically mentioned.

[29] The burner combustion substrate is porous to the flow of premix fuel-air mixtures predominately in a vapor state. Substrate pores 212 are distributed over the area of the burner combustion substrate 213. The combustion process may be monitored by a sensor 204 which can detect if the flame is extinguished.

[30] In the embodiment shown, a premix(ed) fuel-air mixture 210 enters the inlet 238 of the burner and flows 222 within a burner pre-combustion cavity 217 and around and through the burner combustion substrate 213 inward toward the longitudinal axis 216. The fuel-air mixture 210 ratio is arranged so that the premix fuel is ignited 220 within the burner combustion cavity 218.

[31] In a boiler application comprising a shell and tube heat exchanger, the combustion products (e.g., hot gases, particulate byproducts) flow 220 towards the tubesheet 224 where they pass through the openings 228 of the heat exchanger tubes 226. Heat generated by the combustion process is transferred across the walls of the heat exchanger tubes 226 to production fluid occupying the space between the outer surfaces of the furnace 230 and heat exchanger tubes 226 and the inner surface of the pressure vessel 214, sealed at one end by the boiler top head 208.

[32] FIG. 3 shows a cutaway view of the diffuser 300 comprising (in its entirety) a right circular semi-cone combustion substrate 212A with circular proximal edge 202A and distal edge 236A. A pattern of pores (alternatively, perforations) 213A in the combustion substrate admit the passage of the premix fuel-air to pass 308 from an exterior of the substrate, through a metal fiber mesh 232A disposed on the substrate 212A into a interior of the diffuser 310. The mesh 232A is likewise in the shape of a semi-cone with proximal edge 306 and distal edge 304.

[33] The metal fiber mesh can be of any type or construction. Woven metal fiber (warp and weave construction), knitted, sintering techniques are all specifically mentioned, as are equivalent methods. Final mesh fabric thickness can be between 0.05” to 0.30”, with the threads forming the mesh being between 0.005 to 0.1. The threads, if used can be made from fibers which are 0.0005 to 0.005”. If sintered metal mesh is used, fibers which are 0.0005 to 0.005” can be used to create the sintered mat. Joining the mesh with itself, or affixing it to a metal substrate is typically done using electric resistance spot welding, with multiple spot welds done in series to create a continuous seam where required for strength and durability.

[34] If an insufficient amount of diffuser (layered substrate and mesh) area is dimensioned, the flame can lift off of the mesh surface and extinguish. This is one key advantage of cavity or cone burners; the high blow off threshold condition supports flame stability in both surface and SF combustion and, as a result, can potentially reduce the amount of surface area needed in comparison with other alternatives, thereby enhancing compactness of the apparatus and reduce material requirements in the manufacturing process.

[35] There are several important advantages to the arrangements in the disclosed embodiments. A first aspect is that the mesh insulation layer enables the premix fuel-air burner combustion system to be operated in the“surface combustion” regime where the mass flow rate through the diffuser is low. In the absence of a mesh insulating layer, the close proximity of the flame front to the substrate can result in excessively high temperatures of the substrate, which can lead to thermal stresses and material failure. Additionally, these high temperatures can ultimately exceed autoignition temperature for premixed fuel and air, resulting the flame igniting behind the substrate, causing combustion in the annular region between the burner casing and substrate.

[36] A second aspect is that the metal fiber mesh distributes and homogenizes the premix fuel-air flow stream emanating through the substrate pores or perforations, and contributes to a more uniform distribution of fuel on the combustion diffuser surface.

Moreover, the mesh serves to further direct the passage of the premix fuel-air flow stream so that it emerges close to orthogonal to the inner diffuser surface (also called flow

stratification), further creating a uniform fuel stream for the surface combustion process. [37] A third aspect is that the action of the metal fiber mesh to distribute and direct the premix fuel-air mixture to produce a uniform flow field for surface combustion reduces the risk of flashback. That is, it reduces the risk that the flame front locally migrates from the interior combustion surface, through the pores in the substrate, and into the annular region between the burner casing and the substrate.

[38] A fourth aspect is that fine control of the delivery of the premix fuel-air to the interior of the burner cavity, or the burner combustion cavity, by the metal fiber mesh implies that the pores or perforations in the combustion substrate can be coarser and less uniform than if the substrate pores were solely responsible for the diffusion of the fuel mixture. Thus, the incorporation of the metal fiber mesh disposed on the inner substrate surface relaxes the manufacturing requirements and tolerances for the combustion substrate, reducing cost and enabling a broader range of usable materials and fabrication methods.

[39] For example, conventional fabrication methods that stamp or punch holes in sheet metal to for the combustion substrate in a uniform pattern may produce a non-uniform radial pattern in a semi-cone element. This would be problematic if the substrate is used alone since it would result in a non-uniform radial distribution of premix fuel-air to the combustion process. (More flow where the pores are larger or denser; less flow in directions where the pores are smaller or sparser.) However, the addition of the metal fiber mesh layer serves to redistribute the flow evenly through the uniform mesh openings.

[40] A fifth aspect is that in some embodiments where the premix fuel-air mixture is generated by injecting fuel into an air stream before it reaches the burner inlet conduit 238, the mesh helps provides additional mixing through the turbulent action of the fuel stream passing through the mesh openings. Thus, the metal fiber mesh contributes to the creation of a well-mixed lean fuel-air stream before it is ignited in the surface combustion process.

[41] The various components of the premix fuel burner combustion system can each independently comprise any suitable material. Use of a metal is specifically mentioned. Representative metals include iron, aluminum, magnesium, titanium, nickel, cobalt, zinc, silver, copper, and an alloy comprising at least one of the foregoing. Representative metals include carbon steel, mild steel, cast iron, wrought iron, a stainless steel such as a 300 series stainless steel or a 400 series stainless steel, e.g., 304, 316, or 439 stainless steel, Monel, Inconel, bronze, and brass. Specifically mentioned is an embodiment in which the premix fuel burner combustion system components each comprise steel, specifically stainless steel. The premix burner combustion system may comprise a burner head, a combustion substrate, a baffle, a furnace wall that can each independently comprise any suitable material. Use of a steel, such as mild steel or stainless steel this mentioned. While not wanting to be bound by theory, it is understood that use of stainless steel in the dynamic components can help to keep the components below their respective fatigue limits, potentially eliminating fatigue failure as a failure mechanism, and promote efficient heat exchange.

[42] The disclosed system can alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The disclosed system can additionally be substantially free of any components or materials used in the prior art that are not necessary to the achievement of the function and/or objectives of the present disclosure.

[43] The terms“a” and“an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term“or” means“and/or” unless clearly indicated otherwise by context. Reference throughout the specification to“an embodiment”,“another embodiment”,“some embodiments”, and so forth, means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments. “Optional” or“optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not. The terms“first,”“second,” and the like,“primary,”

“secondary,” and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms“front”,“back”, “bottom”, and/or“top” are used herein, unless otherwise noted, merely for convenience of description, and are not limited to any one position or spatial orientation.

[44] The endpoints of all ranges directed to the same component or property are inclusive of the endpoints, are independently combinable, and include all intermediate points. For example, ranges of“up to 25 N/m, or more specifically 5 to 20 N/m” are inclusive of the endpoints and all intermediate values of the ranges of“5 to 25 N/m,” such as 10 to 23 N/m.

[45] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs.

EMBODIMENTS FURTHER DISCLOSED:

[46] Embodiment A: Further disclosed is a premix burner comprising: a burner casing with an inlet conduit for a premix fuel-air mixture to be disposed in the burner casing; a porous burner combustion substrate disposed in the burner casing; a metal fiber mesh disposed on the interior surface of the combustion substrate; wherein a premix fuel-air mixture enters the inlet conduit on an outside (exterior) of the burner combustion substrate. A premix fuel-air mixture is disposed under pressure through the burner inlet to an outside of the porous burner combustion substrate; passes through pores in the burner combustion substrate and through the pores of the metal fiber mesh to an interior of the difuser; the fuel- air mixture is ignited in the interior of the burner combustion substrate; combustion gases and products flow from the interior of the burner cavity through an outlet in the burner casing.

[47] Embodiment B: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a cylinder.

[48] Embodiment C: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a composite semi-cone.

[49] Embodiment D: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a semi-cone.

[50] Embodiment E: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a truncated cone.

[51] Embodiment F: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a circular truncated cone.

[52] Embodiment G: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a right circular truncated cone.

[53] Embodiment H: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a frustum.

[54] Embodiment I: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a circular frustum. [55] Embodiment J: Further disclosed is the premix burner of Embodiment A, wherein the porous burner combustion substrate and metal fiber mesh has the shape of a right circular frustum.

[56] Embodiment K: Further disclosed is the premix burner of any of Embodiments A to K, further comprising a plurality of burner casing inlets disposed on the burner casing.

[57] Further disclosed is a hydronic fluid heating system (equivalently, a“hydronic boiler”) comprising a premix combustion system of any of Embodiments A to K or elsewhere disclosed in this specification.

[58] Further disclosed is a steam fluid heating system (equivalently, a“steam boiler”) comprising a premix combustion system of any of Embodiments A to K or elsewhere disclosed in this specification.

[59] Further disclosed is a thermal fluid heating system (equivalently, a“thermal fluid boiler”) comprising a premix combustion system of any of Embodiments A to K or elsewhere disclosed in this specification.

[60] Further disclosed is a packaged burner comprising a premix combustion system of any of Embodiments A to K or elsewhere disclosed in this specification.

[61] As will be recognized by those of ordinary skill in the pertinent art, numerous modifications and substitutions can be made to the above-described embodiments of the present disclosure without departing from the scope of the disclosure. Accordingly, the preceding portion of this specification is to be taken in an illustrative, as opposed to a limiting, sense.

[62] Although the disclosure has been described herein using exemplary techniques, algorithms, or processes for implementing the present disclosure, it should be understood by those skilled in the art that other techniques, algorithms and processes or other combinations and sequences of the techniques, algorithms and processes described herein may be used or performed that achieve the same function(s) and result(s) described herein and which are included within the scope of the present disclosure. In addition, unless otherwise recited herein, any embodiment disclosed herein may be used with any other embodiment disclosed herein.

[63] Any process descriptions, steps, or blocks in process or logic flow diagrams provided herein indicate one potential implementation, do not imply a fixed order, and alternate implementations are included within the scope of the preferred embodiments of the systems and methods described herein in which functions or steps may be deleted or performed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art.

[64] It is noted that the Figures are to be taken as an illustrative example only, and are not to scale.

[65] All cited references are incorporated in their entirety to the extent needed to understand the present disclosure, and to the extent permitted by applicable law.

[66] It should be understood that, unless otherwise explicitly or implicitly indicated herein, any of the features, characteristics, alternatives or modifications described regarding a particular embodiment herein may also be applied, used, or incorporated with any other embodiment described herein.

[67] 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 embodiments could include, but do not require, certain features, elements, or steps. Thus, such conditional language is not generally intended to imply that features, elements, or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, or steps are included or are to be performed in any particular embodiment.

[68] Although the invention has been described and illustrated with respect to exemplary embodiments thereof, the foregoing and various other additions and omissions may be made therein and thereto without departing from the spirit and scope of the present disclosure.

Claims

WHAT IS CLAIMED IS:

1. An inward-firing surface combustion burner, comprising:

a burner casing configured to receive a fuel-air mixture at a burner inlet and to provide hot combustion gas at a burner output;

a combustion substrate disposed within the burner casing, the substrate having a shape comprising at least a semi-cone, having a substrate angle measured from a longitudinal axis, having a substrate porosity defined by a plurality of pores, and having a substrate inner surface and a substrate outer surface;

a mesh disposed on the inner surface of the combustion substrate;

the substrate configured to receive the fuel-air mixture at the outer surface of the substrate, the fuel-air mixture passing through the pores of the substrate and through the pores of the mesh at a mixture flow rate from the substrate outer surface toward the substrate inner surface;

the burner configured such that, in operation, the fuel-air mixture ignites directly upon or largely in contact with the plurality of pores of the mesh.

2. The burner of claim 1, wherein the substrate angle has a range of values from 1

degree to 89 degrees.

3. The burner of claim 1 wherein a volume of the burner casing, a proximal diameter (Dp) of the substrate, a distal diameter (Dd) of the substrate, and a semi-cone angle of the substrate, are set such that the mixture rate is substantially uniform along a length of the substrate and forms a substantially uniform flame front along the inner surface of the substrate.

4. The burner of claim 1, wherein the surface combustion process provides a

substantially uniform temperature distribution across the substrate inner surface and provides a substantially uniform flow field distribution of the hot combustion gas at the burner output.

5. The burner of claim 1, wherein the substrate comprises a plurality of porous layers to create the substrate porosity.

6. The burner of claim 1, wherein the shape of the substrate comprises at least one of: cone, semi-cone, composite semi-cone, truncated cone, frustum, right frustum, right circular truncated cone, and a right circular frustum.

7. The burner of claim 1, wherein the pores have a shape comprising at least one of: circular, rectangular, symmetrical shape, and asymmetrical shape.

8. The burner of claim 1, further comprising an ignitor disposed on an inner side of the substrate where the surface combustion occurs.

9. The burner of claim 1, wherein the combustion substrate comprises a proximal

diameter (Dp) about 1 to 59 inches, a distal diameter (Dd) between 1 and 60 inches, a substrate height (H) between 1 and 60 inches, and a substrate angle between 1 degree and 89 degrees.

10. An inward-firing surface combustion burner, comprising:

a mesh disposed on the inner surface of the combustion substrate; the substrate configured to receive the fuel-air mixture at the outer surface of the substrate, the fuel-air mixture passing through the pores of the substrate and through the pores of the mesh at a mixture flow rate from the substrate outer surface toward the substrate inner surface;

the burner configured such that, in operation, the fuel-air mixture ignites directly upon or largely in contact with the plurality of pores of the mesh, such that surface combustion occurs.