The present invention relates generally to gas burners and, in particular, to a cost effective premix type gas burner.
Premix-type burners are used in boilers and other heating applications where combustion air is fed, under pressure, to a plenum chamber. The combustion air enters one or more burners which have inlets that communicate with the plenum chamber and is mixed with fuel, such as natural gas. The mixture is then burned within a combustion chamber forming part of the appliance. The efficiency of this type of appliance is in part determined by the primary air/fuel mixing capability of the burner.
It is desirable to provide a cost effective burner for this type of application which also provides effective primary air/fuel mixing capability.
In one embodiment, the invention provides a new and improved gas fireplace burner intended for use with non-combustible log members which produces a yellow flame and no sooting or substantially reduced sooting. In another embodiment, the invention provides a new and improved premix-type burner which provides efficient mixing of primary air and fuel and is also cost effective.
According to one preferred embodiment, the gas fireplace burner, which is intended to burn gaseous fuels, such as natural gas, butane, propane, etc. includes an elongate, generally tubular body having an inlet end and a closed distal end. A tubular segment extends between the ends. In one preferred and illustrated embodiment, the burner body is made from sheet metal, preferably tubular sheet metal, which can be readily formed and shaped. The inlet end of the body is formed to define a gas orifice holder which mounts a gas orifice element. The inlet end is further formed to define at least one combustion air opening which operates to admit combustion air into an interior region of the body.
A bluff body is located downstream from the gas orifice element and is positioned such that gas emitted by the orifice impinges on the bluff body. The bluff body forces the gas to move to either side of the body and, in so doing, is encouraged to mix with the incoming combustion air.
A series of flame ports are defined by the tubular segment in order to create a desired, predetermined flame pattern. The flame pattern may be dictated in part by the arrangement of the non-combustible log members.
According to a more preferred embodiment, the inlet end of the burner body is formed with a second combustion air opening. The first and second openings are preferably arranged such that the orifice holder is located intermediate the openings.
According to a feature of the invention, the cross-section of the combustion air openings are sized during the forming operation to accommodate the type of gas to be used and/or the gas flow rate sustainable by the gas orifice.
With the disclosed invention, a relatively inexpensive burner for use in artificial fireplaces is provided. The burner can accommodate a wide variety of orifice sizes and gas types. The inlet end, as indicated above, defines the combustion air openings, the size of which are determined during the forming operation. As a consequence, a single burner design can be used with a wide variety of gases and orifice sizes merely by changing the cross-section of the formed inlet end.
The flame ports are formed in the tubular segment of the burner body and, in the preferred embodiment, are arranged in a linear pattern. Although the flame ports may be simple punched holes of various sizes, in the preferred embodiment, at least some of the flame ports are slot-like in configuration and have an effective size that is determined by the orientation of a bent tab element that partially defines each of the ports. These ports are preferably formed by a “lancing” operation which utilizes a punch element that pierces the surface of the tubular segment to form the tab that bends downwardly into the burner plenum. The tab is bent downwardly to define an opening in the burner body through which the gas/air mixture is emitted. In the preferred method, the extent to which the punch is driven into the burner body determines the extent to which the port tabs are bent and, hence, the effective size of the port opening. According to the invention, certain areas of the burner may be formed with smaller sized ports in order to produce a smaller flame at that location. For example, flame ports that are located below a “crossing log”, i.e., a log that is positioned across and supported atop front and rear non-combustible logs forming part of the fireplace assembly, may be of smaller size.
In the illustrated embodiment, the flame ports are arranged in two or more spaced apart rows of adjacent slot-like openings. In the exemplary embodiment, one row of flame ports extends along a substantial length of the tubular segment. Two other row segments of flame ports are preferably arranged in a parallel relationship with the first row of ports, but are longitudinally spaced with respect to each other. In the preferred embodiment, the first row of ports is segmented and includes a central portion that is formed with smaller flame ports. This disclosed arrangement which includes a first row with a central portion having reduced flame port size coupled with two additional, spaced apart row segments of ports leaves a central region of the burner where the flame is smaller or less intense. This reduced flame in the central region allows a transverse log member to be placed across the front and rear log members used in the fireplace assembly. By providing a lower flame height below the transverse log member, sooting is eliminated, or at the very least, substantially reduced. It should be noted here that the present invention contemplates the provision of reduced size ports at other positions in the tubular body to accommodate the positioning of transverse log members. For example, if two transverse log members are used, rows of ports could be provided with reduced port sizes at opposite ends and/or the elimination of flame ports at end segments of flame port rows. In short, the present invention contemplates using either reduced flame port sizes and/or the elimination of flame ports in certain regions of the burner to provide lower flame height below log members.
The burner is especially adapted to be used in an artificial fireplace which utilizes front and rear spaced apart non-combustible log members supported on a log support, such as a grate. The lower flame present in the central portion of the burner allows a transverse log member to be placed across the front and rear log members. By providing a reduced or smaller flame in the central region of the burner body, sooting on the transverse log member is eliminated or substantially reduced.
According to an alternate embodiment of the invention, the bluff body is formed by a pair of confronting depressions formed near the inlet end of the burner body. The confronting dimples or depressions form a pair of venturi channels that communicate with the combustion air openings and control or effect air entrainment. The dimple defines structure that is in a confronting relationship with the orifice element, so that gas emitted by the element must move to either side of the dimple and through the venturi channels. In so doing, the fuel gas is mixed with the incoming combustion air in proper proportion.
It has been found that the disclosed burner provides a very effective yellow flame producing burner that is especially adapted to be used in artificial fireplaces. Unlike prior art burners of this type, relatively large combustion air openings are provided so that clogging of the air inlet by lint, etc. is inhibited. It has been found that with the disclosed construction, the port nearest the orifice can be at a distance that is less than 2½ times the diameter of the tube, which results in a short mixing chamber, i.e., a relatively short segment of the burner body devoted to receiving and mixing the combustion air with the gas.
An embodiment is also disclosed where the invention is used to provide a premix-type burner for a boiler or other appliance in which the primary air is fed under pressure to a burner. In the illustrated embodiment, the burner comprises an elongate tube having an orifice holder defined at one end for holding an orifice. In addition, a bluff structure is formed immediately downstream of the orifice holder and, in the illustrated embodiment, is defined by a pair of dimples which form mixing passages through which combustion or primary air and fuel emitted by the orifice travel and are mixed prior to being discharged through a plurality of ports defined by the tube. The primary air/fuel mixture emitted by the ports is burned in a combustion chamber.
The products of combustion are conveyed or travel through a heat exchanger structure where the heat of combustion is transferred to a heating medium which may be water or other fluid for a boiler application or air in a forced air heating application. In the construction of the disclosed premix-type burner, primary air openings are also defined downstream of the orifice holder and provide the means by which primary air, under pressure, is conveyed into the end of the burner and mixed with incoming fuel.
Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description made in connection with the accompanying drawings.
Referring also to
According to the invention, an inlet end 30 of the tube 10a defines a mounting for a gas orifice 32, as well as primary air openings 34 (shown in
In the preferred and illustrated embodiment, a circular, gas orifice support 40 is integrally formed in the inlet end 30 of the tube 10a (shown best in FIGS. 4-6). The sizing of the circular portion 40 is adjusted to provide a significant gripping force on the orifice 32 when the orifice element 32 is inserted into the orifice support portion 40. In the preferred embodiment, the combustion air openings 34 extend laterally from either side of the support portion 40. The size of the openings 34 is adjusted during the crimping operation, since combustion air requirements vary depending on the type of gas to be used and the gas input rating. Preferably, the air openings are of a generally rectangular or ovular shape and have an aspect ratio (length/width) greater than 1.5 and a minimum dimension of 0.125″.
In accordance with a feature of the invention, a bluff body 50 is located immediately downstream from the orifice 32. Referring to
As seen best in
The size of the port openings can vary and are determined during the manufacturing operation. The height of the flames emitted by each individual port is determined, at least in part, by the effective port opening.
Referring in particular to
Referring to
In the illustrated embodiment, the combination of the smaller ports 80′ and the portless region 78 result in a smaller overall flame segment below the log 20 and, hence, the potential for sooting is eliminated or substantially reduced. In short, the central portion of the burner has a smaller overall flame height or flame of less intensity as compared to the outer ends of the burner tube.
According to the preferred embodiment, the angle of the tabs in a given row of ports may vary. Referring in particular to
As seen in
It has been found that the disclosed construction provides a very efficient and cost effective burner that is especially adapted to be used in artificial fireplaces. It has been found that the disclosed inlet arrangement allows a shorter distance between the first port and the gas inlet. Generally, in the past it was desirable to have the distance from the orifice to the first port to be at least 6 times the diameter of the burner body. With the disclosed configuration, it has been found that the first port may be at a distance 2½ times the diameter or less as measured from the gas discharge point on the gas orifice 32. This relatively short mixing chamber decreases the overall size of the burner while still providing sufficient mixing of the gas with the primary air, so that flame stability is maintained.
With the disclosed invention it has been found that the distance between the bluff body and the first flame port (the flame port closest to the gas orifice) may be 2 times the burner body diameter or less. The distance between the bluff body and the gas orifice may also be 2 times the tube diameter or less.
The combination of the tube or pin and dimples provides the advantage of a shortened mixing chamber as well as substantially eliminating light back.
In the disclosed boiler application, as will be explained, the burner produces a conventional “blue” flame, rather than the “yellow” flame described in connection with the embodiments disclosed in
Referring first to
In the schematic shown in
Referring also to
A forced air blower 230 is mounted to the combustion air inlet plenum 210 and provides a source of primary air, under pressure, for the burner 220. As described in connection with the embodiments shown in
According to this embodiment, the invention is used with a pressurized or forced air combustion system where the pressurized combustion air compensates for the restriction posed by the bluff structure. The blower 230 forces a stoichiometric amount of primary air into the burner 220 which results in an efficient, blue flame. The invention, however, still effects efficient mixing of the primary air and fuel.
In the preferred construction of this embodiment, an inlet end 220a of the burner 220 is positioned within the combustion air inlet plenum 210. The remainder of the burner which include burner ports 221 (see
The combustion air inlet plenum 210 is separated from the combustion chamber 212 by an internal plenum wall 232. The burner 220 extends through the wall 232 and is preferably mounted and sealed to the plenum wall via a flange 232a (shown in
As seen best in
In the preferred and illustrated construction of this embodiment, the two confronting depressions contact each other at a region indicated by the reference character 260 (FIG. 19). As is the case with the embodiments shown in
In the embodiment shown in
In the preferred construction of this embodiment, an additional pair of confronting dimples 280a, 280b are formed downstream of the bluff structure and are preferably rotated 90° with respect to the dimples 250a, 250b forming the bluff structure 250. The additional dimple structure which defines a pair of channels the same or similar to the channels or passages 108 described above provides additional mixing of the gas and air.
The application of the invention disclosed in
Although the invention has been described with a certain degree of particularity, it should be understood that those skilled in the art can make various changes to it without departing from the spirit or scope of the invention as hereinafter claimed.
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Number | Date | Country | |
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20020132198 A1 | Sep 2002 | US |