WO2009082415A1

WO2009082415A1 - Inwardly firing burner and uses thereof

Info

Publication number: WO2009082415A1
Application number: PCT/US2008/008753
Authority: WO
Inventors: Mark A. Ferguson
Original assignee: Pvi Industries, Inc.
Priority date: 2007-12-26
Filing date: 2008-07-17
Publication date: 2009-07-02
Also published as: CA2629127C; CA2629127A1; US20090165733A1; MX2008011917A; EP2235447A1

Abstract

An inwardly firing burner design is shown which can be used in a variety of heating applications. A water heater apparatus is also shown which includes a water heating tank having generally cylindrical sidewalls with upper and lower ends, each of which is closed by a transverse wall section to define a closed tank interior. The tank also has a water inlet and a water outlet. A plurality of vertically arranged fire tubes are connected between the upper and lower transverse wall sections, each fire tube having an open interior for conducting products of combustion. A burner assembly is mounted on the tank which features the inwardly firing construction that eliminates the need for an external combustion chamber.

Description

INWARDLY FIRING BURNER AND USES THEREOF

Description

Technical Field

The present invention relates generally to a free standing burner for general burner use as well as to the design of a water heater or boiler for residential, commercial and industrial use which utilizes such an improved burner to supply heat to such devices.

Background Art

A variety of end applications exist for gas, oil and gas/oil burners in both the general consumer and commercial and industrial settings. For example, free standing burners are used in such diverse devices as ovens, grills, gas freestanding stoves, cook-tops, rotisseries and outdoor grills, to name a few. One end application or appliance which could incorporate a burner of the general type under consideration is in the area of water heaters and boilers, although the discussion which follows is not meant to be limited to one such field of use.

Water heaters and boilers (referred to collectively as water heaters in the discussion which follows) typically have a water heater tank, often of the vertical tube type which utilizes fire tubes located above a combustion chamber. A number of the typical prior art gas, oil or gas/oil fired water heaters feature a non-pressurized, external combustion chamber which was typically located on the bottom exterior of the water heater. Vertical shell or V-shell heat exchangers of the above type are well known in the industry. Thus, for many years, typical water heater construction has provided for the flow of hot gas through a series of tubes mounted in vertical fashion between top and bottom transverse wall sections or support plates within the water heater tank. The products of combustion from the combustion chamber pass vertically upward through the open interiors of the vertical tubes and out a flue outlet. Water was circulated into and out of a chamber in the prior art devices located between the transverse wall sections. The water contacted and circulated about the exterior of the vertical tubes to effect heat transfer to heat the water.

Another type of water heater or boiler arrangement is shown in U.S. Pat. Nos.4,465,024; 4,545,329 and 4,938,204, all assigned to the assignee of the present invention. These designs all feature one or more submergible, pressurized combustion chambers so that all combustion takes place in the water heater tank interior in a chamber surrounded by water. An externally mounted, forced draft burner unit was mounted on the exterior of the closed tank at a tank opening so that the burner nozzle extended in the direction of the combustion chamber for heating the combustion chamber.

Despite the above noted improvements in water heater and boiler design, a need has continued to exist for an improved burner design for supplying a mixture of combustible gases to the combustion chamber of such devices.

For example, improved burner designs are needed which provide efficient mixing of the entering burner air and gas streams. In the usual case, a low pressure natural gas stream is being introduced into a forced draft air supply fed by a power blower at a higher pressure. One function of the typical burner design is to introduce the flow of relatively lower pressure natural gas into the relatively higher pressure forced air stream, the gas mixture being passed through some sort of restriction or orifice. Also, water heaters and boilers form nitrogen oxides during combustion. Nitrogen oxide emissions are air pollutants. Various state and federal agencies regulate the amount of nitrogen oxides, or NO_x, in vented gases. Tightening state and federal regulations for emissions requirements warrant the effort to find new ways to remove or prevent the formation of nitrogen oxides in combustion processes to avoid further harmful effects on the environment.

In addition to the problem of NO_x emissions, there have been other problems with the above water heater designs, particularly the non-pressurized, external combustion chamber designs. While such designs have been used for many years, the nozzles of the burners tend to be destroyed relatively quickly because of the high temperatures which are encountered within the refractory lined combustion chambers. Even where the nozzle is mounted relatively flush with the combustion chamber wall, the mounting plate tends to be consumed by the intense heat over time. A need exists, therefore, for an improved burner design for a water heater, particularly of the non-pressurized, external combustion chamber design, which, instead of utilizing a traditional combustion chamber, utilizes more of an "inwardly firing" burner design.

A need exists for such a burner design which basically contains the majority of the flame within the burner itself, thereby eliminating the need for refractory, the burner also providing a flame which is relatively small within the length of the burner.

A need also exists for an improved vertical tube water heater design having vertical tube components and an improved burner which increase the overall efficiency of the apparatus in heating water. A need exists for such an apparatus which is simple in design and relatively easy to manufacture.

A need also exists for an improved inwardly firing burner of the above type which burner would be adapted for general burner use and not be specifically intended for a particular water heater or boiler design.

Disclosure of Invention

In one aspect, the present invention concerns an inwardly firing burner design for general burner use on gas burner applications where benefit is obtained from firing directly into a heat exchanger without the need for a separate combustion chamber, where combustion is largely completed within the burner or where low NOx operation is desired. In one of its simplest forms, the burner has an outer body assembly, the outer body having a transverse wall opening therein for communication with a blower, the outer body having an interior and one or more_.end openings.

An inner chamber assembly is mounted within the interior of the burner outer body, the inner chamber having largely opposing sidewalls. The inner chamber assembly forms a peripheral seal with respect to the openings of the outer body, thereby forming an open internal region which constitutes a combustion region for the burner and one or more end openings for exhausting the products of combustion. - A -

The burner also includes an intermediate chamber assembly having sidewalls which allow the assembly to be positioned about the inner chamber and within the interior of the outer body. The walls of the intermediate chamber assembly also have one or more openings which are located between the sealed region formed between the outer body and the inner chamber, whereby a distributed flow path is created for gases passing from the blower, between the interior of the outer body and the sidewalls of the inner chamber.

An igniter element is operatively associated with the outer body for igniting air and fuel supplied to the interior of the inner chamber to thereby produce products of combustion for heating. Preferably, the igniter element is at least one electrode mounted on the outer body assembly.

In one preferred form of the burner of the invention, the sidewalls of the inner chamber, which is mounted within the interior of the burner outer body, are formed of a heat resistant material. Another distinguishing characteristic of the present burner design is the fact that the sidewalls of the inner chamber, which is mounted within the interior of the burner outer body, are in the majority facing inward, as will be explained more fully in the detailed description which follows.

The improved burner of the invention mixes air and gas in the presence of a flame to create products of combustion, and wherein the inwardly firing design of the burner contains a majority of the flame within the burner itself, thereby eliminating the need for a separate refractory lined combustion chamber. The inwardly firing burner allows combustion to be established and largely completed within an envelope defined by the outer body of the burner itself, thereby resulting in a self-chambered burner design.

In one specific end application, the burner of the present invention meets the previously described needs by providing a burner design for a water heater in which combustion is established and completed within the envelope of the burner itself. As a result, the traditional combustion chamber, described in the above background discussion, which is needed to complete combustion prior to the heat exchange tubes is eliminated. The concept might also be expressed as providing a combustion chamber-less burner or a self-chambered burner. In the improved water heater assembly of the invention, a water heating tank is provided having generally cylindrical sidewalls with opposing closed ends which define a closed tank interior. A plurality of fire tubes are located within the closed tank interior, each fire tube having an open interior for conducting products of combustion. A blower/burner assembly is mounted at a selected one of the opposing tank ends for igniting a gas, oil, or gas/oil fuel mixture and producing products of combustion which travel within the open interiors of the fire tubes for heating water which surrounds the fire tubes within the tank interior. A flue collector chamber is located on a selected end of the tank for collecting and exhausting the products of combustion from the fire tubes.

The burner which is used with the water heater tank is a specially designed burner which features the previously described inwardly firing design which eliminates the need for an external combustion chamber mounted on the exterior of the water heater tank, as in the prior art designs. The inwardly firing design of the burner contains a majority of the flame within the burner itself, thereby eliminating the need for refractory materials and a separate refractory lined combustion chamber. The inwardly firing burner, when incorporated into an improved water heater or boiler design, allows combustion to be established and completed within an envelope defined by the outer body of the burner itself, thereby resulting in a combustion chamber-less or self-chambered burner design.

In one particularly preferred form , the burner of the burner/blower assembly of the invention has a cylindrical outer body, the outer body having a transverse wall opening therein for communication with the blower, the outer body having an interior and first and second oppositely arranged, end openings, the first end of the burner being mounted on the water heater tank in communication with the interior of the fire tubes.

An inner cylindrical chamber is mounted within the interior of the burner outer body, the inner cylindrical chamber forming a peripheral sealed end region at the first end opening of the outer body. The inner cylindrical chamber has sidewalls which form an open internal region which constitutes a combustion region for the burner and an end opening for exhausting the products of combustion to the fire tubes of the associated water heating tank. The preferred burner assembly of the invention further comprises an ignition cap assembly. The ignition cap assembly includes a cylindrical body portion having cylindrical sidewalls. The sidewalls have a selected external diameter which allows the cylindrical body portion to be received about the inner cylindrical chamber and within the interior of the cylindrical outer body. The sidewalls of the cap assembly also have a predetermined depth which is less than a corresponding depth of the cylindrical sidewalls of the outer body, thereby creating a gap with respect to the sealed peripheral region formed at the first end opening of the burner. The cap assembly also has a lid portion which seats upon and seals with the second end opening of the cylindrical outer body, whereby a serpentine flow path is created for gases passing from the blower, between the interior of the outer body and the cylindrical body portion of the cap assembly and between the sidewalls of the cap assembly and the sidewalls of the inner cylindrical chamber.

An igniter element, operatively associated with the cap assembly, is provided for igniting air and fuel supplied to the interior of the inner cylindrical chamber to thereby produce products of combustion for heating water contained within the associated water heater tank. Preferably, the igniter element comprises a pair of electrodes mounted on the lid region of the cap assembly. The lid portion of the cap assembly can conveniently comprise a planar member which is of a greater relative outer diameter than that of the outer body, whereby the lid portion forms an outwardly extending flange region which seats upon and seals with the second end opening of the cylindrical outer body.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. Brief Description of Drawings

Figure 1 is a simplified, side view of a vertical tube water heater having the improved burner of the invention mounted thereon.

Figure 2 is an isolated, side view of the blower/burner assembly of Figure 1 , portions of the burner sidewalls having been broken away for ease of illustration.

Figure 3 is a close-up view of the burner of Figure 2, showing the flow of gases through the burner in greater detail.

Figure 4 is an exploded perspective view of the burner of the invention.

Figure 5 is a view of a prior art water heater having an externally mounted burner on the combustion chamber located on the bottom of the tube assembly.

Figure 6 is a view of another prior art water heater design, again featuring an externally mounted burner, where the combustion chamber is located on the top of the tube assembly, rather than on the bottom.

Best Mode for Carrying Out the Invention

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processes and manufacturing techniques are omitted so as to not unnecessarily obscure the key features of the invention. The examples used herein are intended merely to facilitate an understanding of ways in which the invention herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the claimed invention.

As explained in the background discussion of the invention, the improved burner assembly of the invention can conceivably be incorporated into a large variety of end applications for gas burners in both the general consumer and commercial and industrial settings. When offered as a free standing burner, the improved device of the invention could be used, for example, in such diverse applications as cooking ovens, grills, gas freestanding stoves, cook-tops, rotisseries and outdoor grills, to name a few. In addition to these more general consumer oriented applications, one end application or appliance which could advantageously incorporate a burner of the general type under consideration is in the area of water heaters and boilers. The discussion which follows largely uses the example of a commercial water heater to illustrate the principles of the invention. However, as will be appreciated by those skilled in the relevant arts, it will be understood that the burner of the invention could also conceivably be used in a variety of other end applications such as the other applications noted above, and other similar applications, and the discussion which follows is not meant to be limited to one such field of use.

In order to illustrate the advantages potentially offered by the improved burner design of the invention when incorporated into a conventional water heater or boiler, reference will now be had to Figures 5 and 6 of the drawings which illustrate typical prior art water heater designs. Figure 5 shows a prior art water heater assembly, which in this case is a vertical tube water heater apparatus, designated generally as 11. The water heater apparatus 11 includes a water heating tank 13 having generally cylindrical sidewalls with upper and lower transverse wall sections or support plates 15, 17. A combustion chamber or fire box 19 is located on the bottom of the apparatus and includes a power blower/burner 21 for creating products of combustion within the fire box 19. The blower/burner 21 could be, for example, a gas fired, "FIREPOWER" forced draft burner commercially available from PVI Industries, Inc., of Fort Worth, Tex. A plurality of vertically arranged fire tubes 23 are located within a closed tank interior 25. Each fire tube 23 has an open interior for conducting products of combustion from the fire box 19 upwardly toward a flue collector (not shown) for exhausting the products of combustion from the device. Water is circulated within the tank interior 25 between a water inlet and a water outlet (not shown). The water contacts the exterior surfaces of the fire tubes 23 to effect heat transfer.

While the prior art device in Figure 5 had the external combustion chamber located on the exterior of the water tank and on the bottom of the tank, there may also be situations in which the external combustion chamber is mounted on the top of the vertical tube assembly, rather than on the bottom of the apparatus, as shown in Figure 6. In this way, the products of combustion can be passed downwardly through the vertical tubes in countercurrent fashion to the water being heated.

Thus, Figure 6 is a side, partial sectional view of a prior art water heater having a top mounted combustion chamber, designated generally as 27. The water heater apparatus 27 again includes a water heating tank 29 having generally cylindrical sidewalls with upper and lower ends 31 , 33. Each of the initially open upper and lower ends 31 , 33 is closed by an upper and lower transverse wall section 35, 37, respectively, to define a closed interior 39 for the tank. The upper and lower transverse wall sections 35, 37 are parallel in the embodiment of the invention of Figure 2. The tank 29 also has a water inlet (shown in dotted lines as 41 in Figure 2) which admits water to the lower region of the tank interior and a water outlet 43 which allows water to flow out of the tank interior from the upper region thereof. A plurality of vertically arranged fire tubes 45 are located within the tank closed interior 39. Each fire tube has an open interior and an upper end 47 and a lower end 49. There may be, for example, thirty-six such fire tubes within the closed tank interior arranged in concentric circles. The upper and lower tube ends 47, 49 are supported by means of the upper and lower transverse wall sections 35, 37, the tubes being welded within appropriate openings provided in the transverse wall sections. A combustion chamber (53 in Figure 6) is mounted on the upper end 31 of the water heating tank 29 for providing products of combustion to the open interiors of the fire tubes 45. The combustion chamber 53 includes insulation 55 which can be, for example, of a suitable refractory material. A blower/burner 57 is mounted on a sidewall of the combustion chamber 53 and communicates with the chamber interior 59 for supplying products of combustion thereto. The tank 29 is also insulated by a suitable insulating material 61 and includes a flue collector chamber 63 which is located at the bottom end 33 of the water heating tank for collecting and exhausting the products of combustion from the vertically arranged fire tubes 45. A condensate drain 64 can be used to remove any collected condensate from the flue collector chamber 63. A draft inducing means, such as induction blower 65, driven by blower motor 67, pulls the products of combustion from the chamber interior 59 through the open interior of the vertical fire tubes 45 and through the flue collector chamber 63 for exhaustion from the apparatus. The exhausted flue gases may be passed to the atmosphere or may be conveyed through an exhaust pipe to another location.

An improved water heater assembly utilizing the novel inwardly firing burner of the invention will now be described with reference primarily to Figures 1-4. The overall water heater tank assembly will bear many similarities to the previously described prior art tanks. Turning first to Figure 1 , there is shown a water heater assembly 71 with a tank arrangement which generally corresponds to the tank arrangement described in Figures 5 and 6 of the drawings. A water heating tank 73 has generally cylindrical sidewalls with upper and lower ends 75, 77, respectively. Each of the tank ends 75, 77 is closed by means of a transverse wall section 79, 81 to define a closed tank interior 83.

A plurality of fire tubes, such as tubes 85, 87, are, in this case, vertically arranged to connect between the upper and lower transverse wall section 79, 81. Each fire tube, e.g., fire tube 87, has an open interior 89 for conducting products of combustion. While the invention is illustrated with respect to a vertical tube water heater, it will be appreciated from the discussion which follows that other orientations, such as a horizontal tank configuration, would work as well. A blower and burner assembly, designated generally as 91 , is mounted on a selected one of the upper and lower ends 75, 77, respectively, of the water heating tank for providing products of combustion to the open interiors of the fire tubes.

A flue collector chamber 93 is typically located on the respective end of the tank opposite the burner assembly 91 for collecting and exhausting the products of combustion from the vertically arranged fire tubes 85, 87. In other embodiments, the flue collector could be on the same end of the tank as the burner assembly.

Figures 2-4 illustrate the improved burner assembly of the invention in greater detail. As will be appreciated in the discussion which follows, the burner assembly is an inwardly firing burner which illuminates the need for a separate, external combustion chamber (such as the combustion chamber 53 in Figure 6) mounted on the exterior or the water heater tank. The blower/burner assembly 91 , shown in Figure 2, ignites an air-fuel mixture in the presence of a spark or flame to create products of combustion. As will be apparent from the description which follows, benefit is obtained from the firing directly into a heat exchanger without the need for a separate combustion chamber, where combustion is largely completed within the burner, or where low NO_x operation is desired.

As best seen in Figures 2 and 4, the illustrated burner 95 has a cylindrical outer body 97 formed of a suitable metal. The outer body has a transverse wall opening 99 for communication with a conventional power blower 101. As can be seen in Figure 3, the outer body 97 has an interior 103 and one or more, in this case, first and second oppositely arranged, end openings 105, 107. The first end 105 of the burner 95 is mounted on the water heater tank in communication with the interior of the fire tubes, as shown in Figure 1. While the illustrated burner is shown as having a cylindrical outer body, it will be appreciated that the outer body could assume a variety of shapes, depending upon the end application. For example, the outer body could be rectangular, conical, hemispherical, etc. and still serve the necessary air/fuel capturing function.

As can also been seen with respect to Figures 3 and 4, an inner cylindrical chamber 109 is mounted within the interior 103 of the burner outer body 97. The inner cylindrical chamber 109 has cylindrical sidewalls 111 which form an open internal region 113 (see Figure 4) which constitutes a combustion region for the burner. The inner cylindrical chamber 109 also has an end opening 115 (Figure 3) for exhausting the products of combustion to the fire tubes of the associated water heating tank. The inner cylindrical chamber 109 is preferably formed of a heat resistant material. It will also be evident that, depending upon the end application, it may be possible to maintain the same burner performance and basic benefits of the inwardly firing burner even when the inner combustion region or chamber has a shape other than cylindrical. The same performance concept would apply as long as the chamber sidewalls were "mostly opposing"; that is, the combustion chamber sidewalls could be fully opposing and be cubical or multifaceted or "mostly opposing" as with a conical, pyramidal, hemispherical, etc. shape.

Again with reference to Figures 3 and 4, the illustrated water heater assembly further includes an ignition cap assembly. In the embodiment of the invention illustrated, the cap assembly comprises a cylindrical body portion 117 formed of a suitable metal and having cylindrical sidewalls (119 in Figure 4). The sidewalls 119 are of a selected external diameter which allows the cylindrical body portion 117 to be received about the inner cylindrical chamber 109 and within the interior 103 of the cylindrical outer body 97.

The sidewalls 119 of the cap assembly also have a predetermined depth, illustrated as "d" in Figure 4. The depth "d" is less than a corresponding depth of the cylindrical sidewalls of the outer body 97, thereby creating a gap ("g" in Figure 3) with respect to the sealed peripheral region formed at the first end opening 105 of the burner. The "sealed peripheral region" is indicated generally at 121 in Figure 3 and is formed between a flange region on the inner cylindrical chamber 109 and a mating flange region formed on the cylindrical outer body 97.

As shown in Figures 3 and 4, the cap assembly also has a lid portion 123 which seats upon and seals with the second end opening 107 all the cylindrical outer body. The gap ("g" in Figure 3) together with the concentric spacing of the ignition cap assembly and the inner cylindrical chamber sidewalls, forms a serpentine flow path through the burner. The flow path which is created allows gas to pass from the blower/burner, between the interior 103 of the outer body and the cylindrical body portion 119 of the cap assembly, and between the sidewalls of the cap assembly and the sidewalls 11 of the inner cylindrical chamber as the gas passes through the burner interior. The "serpentine" flow path for the hot gases is illustrated by the arrows in Figure 3.

It will be appreciated from the foregoing discussion that the sidewalls 119 of the cap assembly are a type of "baffle" which creates an intermediate chamber having sidewalls which allow the assembly to be positioned about the inner chamber and within the interior of the outer body. The walls of the intermediate chamber then have one or more openings (such as the openings 122, 124 in Figure 3) between the sealed region formed between the outer body and the inner chamber, whereby a distributed flow path is created for gases passing from the blower, between the interior of the outer body and the sidewalls of the inner chamber. It will be appreciated with reference to Figures 3 and 4 that, while the "baffle" of the illustrated burner creates a "serpentine" flow path, its primary function is to provide the appropriate distribution of the air/fuel mixture across the inward firing surfaces of the burner. This same function could conceivably be achieved by other means, such as by using one or more layers of perforated material, or a series of disrupting baffles to distribute the air/fuel mixture. Also, as the shape of the inner combustion chamber changes, a differently configured intermediate chamber may be required.

An igniter element 125 is operatively associated with the outer body and cap assembly for igniting air and fuel supply to the interior of the inner cylindrical chamber 109 to thereby produce products of combustion for heating water contained within the associated water heater tank. Preferably, the igniter element 125 comprises a pair of electrodes 127 mounted on the lid region or portion of the cap assembly. Most conveniently, the lid portion 123 of the cap assembly is a planar member which is of greater relative outer diameter than that of the outer body 97, whereby the lid portion forms an outwardly extending flange region (129 in Figure 3) which seats upon and seals with the second end opening 107 of the cylindrical outer body 97. The electrodes, shown in Figure 3, will typically be connected to conventional circuitry for producing a timed spark on the interior surface of the cap assembly for igniting the fuel and air mixture to produce products of combustion. The electrodes themselves and the accompanying electrical circuitry used to provide a timed spark are conventional in the industry and will be familiar to those skilled in the art. While the invention is described in terms of a flame being lit by a spark igniter, other types of hot surface or other igniter systems could be utilized.

As shown in Figure 2, the lid portion 123 of the cap assembly is, in this case, lined with a refractory material 126. While the inwardly firing design of the present burner contains a significant portion of the flame within the burner itself, the portion of the flame within the burner varies by end application and the available back pressure. While the illustrated burner includes the refractory material 126, other variations of the design may eliminate the need for a refractory, such as in the case of a conical inner combustion chamber, for example.

While the igniter element is shown as being installed within the lid portion of the cap assembly, it could also enter from the outer body to the inner combustion chamber at almost any location within or adjacent that chamber. Thus, the igniter element could enter through the side of the burner and the sidewall of the inner combustion chamber, if that arrangement provided a more convenient design. If the illustrated, cylindrical burner was altered to have two heat outlets or openings instead of one, as described above, the ignition source might be located outside one of these openings. While such a design might not be practical where the burner outlet is placed against the sidewall of an appliance heat exchanger, it might well be desirable in a two heat outlet design. Also, if a differently shaped combustion chamber is utilized, the end cap may be eliminated.

In operation, the blower/burner assembly 91 (Figure 1 ) provides a fuel/air mixture within the interior of the inner cylindrical chamber 109. A timed spark is provided by the electrodes 127 to produce combustion of fossil fuel, such as a natural gas, within the interior of the inner chamber 109. The air/fuel mixture path is from the blower nozzle (131 in Figure 3) through the transverse wall opening 99 and about the serpentine flow path illustrated by the arrows in Figure 3 to the interior of the inner cylindrical chamber 109. There, a timed spark is provided to the burner by means of the electrodes 127 to produce combustion of fossil fuel, such as a natural gas, within the combustion region. The products of combustion pass downwardly through the vertical tubes 85, 87 (Figure 1 ) to the flue collector 93, where they are exhausted from the apparatus. As described with respect to the prior art burner in Figure 6, cold water enters the inlet 41 and is gradually warmed by heat transfer within the fire tubes and may be stored within the tank or may flow out of the water outlet 43, as demand requires.

An invention has been provided with several advantages. The burner of the invention has an inwardly firing design which eliminates the need for an external combustion chamber mounted on the exterior of the water heater tank. The inwardly firing design of the burner contains a majority of the flame within the burner itself, thereby eliminating the need for refractory materials and a separate refractory lined combustion chamber. The inwardly firing nature of the burner allows combustion to be established and completed within an envelope defined by the outer body of the burner itself, thereby resulting in a self-chambered design. The self-chambered burner of the invention overcomes problems associated with the prior art designs in which the nozzles of the prior art burners tended to be destroyed relatively quickly because of the high temperatures which they encountered within the refractory lined combustion chambers. The new burner design is relatively simple and economical to manufacture and can readily be adapted to a number of existing water tank installations. The burner design is simple in nature, as compared to the relative complexity and cost of presently available burners and stack devices that produce equivalent NO_x levels.

While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.

Claims

1. An inwardly firing burner for use on gas burner applications where benefit is obtained from firing directly into a heat exchanger without the need for a separate combustion chamber, where combustion is largely completed within the burner or where low NOx operation is desired, the burner comprising:

a outer body assembly, the outer body having a transverse wall opening therein for communication with a blower, the outer body having an interior and one or more_end openings;

an inner chamber assembly mounted within the interior of the burner outer body, the inner chamber having largely opposing sidewalls and forming a peripheral seal to the openings of the outer body to form an open internal region which constitutes a combustion region for the burner and one or more end openings for exhausting the products of combustion;

an intermediate chamber assembly having sidewalls which allow the assembly to be positioned about the inner chamber and within the interior of the outer body, the walls of the intermediate chamber assembly also having a one or more predetermined openings between the sealed region formed between the outer body and the inner chamber, whereby a distributed flow path is created for gases passing from the blower, between the interior of the outer body and the sidewalls of the inner chamber;

an igniter element operatively associated with the outer body for igniting air and fuel supplied to the interior of the inner chamber to thereby produce products of combustion for heating.

2. The burner of Claim 1 , wherein the igniter element is at least one electrode mounted on the outer body assembly.

3. The burner of Claim 1 , wherein the sidewalls of the inner chamber, which is mounted within the interior of the burner outer body, are formed of a heat resistant material.

4. The burner of Claim 1 , wherein the sidewalls of the inner chamber, which is mounted within the interior of the burner outer body, are in the majority facing inward.

5. The burner of Claim 1 , wherein the burner mixes air and gas in the presence of a flame to create products of combustion, and wherein the inwardly firing design of the burner contains a majority of the flame within the burner itself, thereby eliminating the need for a separate refractory lined combustion chamber.

6. The burner of Claim 1 , wherein the inwardly firing burner allows combustion to be established and largely completed within an envelope defined by the outer body of the burner itself, thereby resulting in a self-chambered burner design.

7. An inwardly firing burner for use on a water heater of the type having a water heating tank having generally cylindrical sidewalls which define an interior, the tank also having upper and lower ends, a water inlet and a water outlet, and a series of fire tubes located within the tank interior, the fire tubes having open interiors which are adapted to receive products of combustion created by the burner, the burner comprising:

a cylindrical outer body, the outer body having a transverse wall opening therein for communication with a blower, the outer body having an interior and first and second oppositely arranged, end openings;

an inner cylindrical chamber mounted within the interior of the burner outer body, the inner cylindrical chamber forming a peripheral sealed end region at the first end opening of the outer body, the inner cylindrical chamber having sidewalls which form an open internal region which constitutes a combustion region for the burner and an end opening for exhausting the products of combustion to the fire tubes of an associated water heating tank;

an ignition cap assembly, the cap assembly comprising a cylindrical body portion having cylindrical sidewalls, the sidewalls being of a selected external diameter which allows the cylindrical body portion to be received about the inner cylindrical chamber and within the interior of the cylindrical outer body, the sidewalls of the cap assembly also having a predetermined depth which is less than a corresponding depth of the cylindrical sidewalls of the outer body, thereby creating a gap with respect to the sealed peripheral region formed at the first end opening of the burner, the cap assembly also having a lid portion which seats upon and seals with the second end opening of the cylindrical outer body, whereby a serpentine flow path is created for gases passing from the blower, between the interior of the outer body and the cylindrical body portion of the cap assembly and between the sidewalls of the cap assembly and the sidewalls of the inner cylindrical chamber; and

an igniter element operatively associated with the cap assembly for igniting air and fuel supplied to the interior of the inner cylindrical chamber to thereby produce products of combustion for heating water contained within an associated water heater tank.

8. The burner of Claim 7, wherein the igniter element is at least one electrode mounted on the lid region of the cap assembly.

9. The burner of Claim 7, wherein the sidewalls of the inner cylindrical chamber which is mounted within the interior of the burner outer body are formed of a heat resistant material.

10. The burner of Claim 7, wherein the lid portion of the cap assembly is a planar member which is of a greater relative outer diameter than that of the outer body, whereby the lid portion forms an outwardly extending flange region which seats upon and seals with the second end opening of the cylindrical outer body.

11. A water heater assembly, comprising:

a water heating tank having generally cylindrical sidewalls with upper and lower ends, each of which is closed by a transverse wall section to define a closed tank interior;

a plurality of vertically arranged fire tubes connected between the upper and lower transverse wall sections, each fire tube having an open interior for conducting products of combustion; a blower and burner assembly which is mounted ata selected one of the upper and lower ends of the water heating tank for providing products of combustion to the open interiors of the fire tubes;

a flue collector chamber located on the respective end of the tank opposite the burner assembly for collecting and exhausting the products of combustion from the vertically arranged fire tubes; and

wherein the burner is an inwardly firing burner which eliminates the need for an external combustion chamber mounted on the exterior of the water heater tank.

12. The water heater assembly of Claim 11 , wherein the burner mixes air and gas in the presence of a flame to create products of combustion, and wherein the inwardly firing design of the burner contains a majority of the flame within the burner itself, thereby eliminating the need for refractory materials and a separate refractory lined combustion chamber.

13. The water heater assembly of Claim 11 , wherein the inwardly firing burner allows combustion to be established and completed within an envelope defined by the outer body of the burner itself, thereby resulting in a self-chambered burner design.

14. The water heater assembly of Claim 11 , wherein the burner of the blower and burner assembly has a cylindrical outer body, the outer body having a transverse wall opening therein for communication with the blower, the outer body having an interior and first and second oppositely arranged, end openings, the first end of the burner being mounted on the water heater tank in communication with the interior of the fire tubes.

15. The water heater assembly of Claim 14, wherein an inner cylindrical chamber is mounted within the interior of the burner outer body, the inner cylindrical chamber forming a peripheral sealed end region at the first end opening of the outer body, the inner cylindrical chamber having sidewalls which form an open internal region which constitutes a combustion region for the burner and an end opening for exhausting the products of combustion to the fire tubes of an associated water heating tank.

16. The water heater assembly of Claim 15, further comprising an ignition cap assembly, the cap assembly comprising a cylindrical body portion having cylindrical sidewalls, the sidewalls being of a selected external diameter which allows the cylindrical body portion to be received about the inner cylindrical chamber and within the interior of the cylindrical outer body, the sidewalls of the cap assembly also having a predetermined depth which is less than a corresponding depth of the cylindrical sidewalls of the outer body, thereby creating a gap with respect to the sealed peripheral region formed at the first end opening of the burner, the cap assembly also having a lid portion which seats upon and seals with the second end opening of the cylindrical outer body, whereby a serpentine flow path is created for gases passing from the blower, between the interior of the outer body and the cylindrical body portion of the cap assembly and between the sidewalls of the cap assembly and the sidewalls of the inner cylindrical chamber; and

17. The water heater assembly of Claim 16, wherein the igniter element is at least one electrode mounted on the lid region of the cap assembly.

18. The water heater assembly of Claim 17, wherein the sidewalls of the inner cylindrical chamber which is mounted within the interior of the burner outer body are formed of a heat resistant material.

19. The water heater assembly of Claim 18, wherein the lid portion of the cap assembly is a planar member which is of a greater relative outer diameter than that of the outer body, whereby the lid portion forms an outwardly extending flange region which seats upon and seals with the second end opening of the cylindrical outer body.