Abstract:
An atmospheric burner assembly for a gas log fireplace comprises a mixing chamber adapted to receive gas from a gas supply and mix gas and air therein. The burner assembly also comprises a manifold adapted to receive gas from a gas supply. The burner assembly also has a burner with a first port communicating with the mixing chamber and a second port communicating with the manifold. The second port is adapted to generate a flame pattern that is embedded within the first port. When installed in the fireplace, the burner assembly combusts pure gas at the second port for rich combustion and a mixture of gas and air at the first port for lean combustion, thereby promoting stage combustion at the burner assembly and producing a yellow chemiluminescent flame.

Description:
BACKGROUND 
       [0001]    The disclosure relates generally to gas burner systems, and specifically to gas burner systems for open flame display, such as gas logs for fireplaces, and even more specifically gas burner systems for vent free or direct vent applications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a top view of an embodiment of the burner assembly comprising a top plate with six dual port burners with a portion of the top plate being partially broken away to show further detail of an interior of the burner assembly that includes a mixing chamber with ceramic pellets disposed therein that supplies a gas-air mixture to lean flame burner ports of the dual port burners of the burner assembly and a receiver comprising a manifold assembly that delivers gas to rich flame burner ports of the dual port burners of the burner assembly; 
           [0003]      FIG. 2  is a perspective view of an underside of a top plate of the burner assembly of  FIG. 1 , showing additional detail of the manifold assembly used to deliver gas to the rich flame burner ports of the dual port burners of the burner assembly; and 
           [0004]      FIG. 3  is a schematic diagram of a fireplace in which the burner assembly is installed showing additional detail of valves and orifices used in connection with the manifold and receiver to vary the flow of gas to the lean and the rich flame burner ports of the dual port burners of the burner assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0005]    Referring to the figures, a gas burner assembly is generally designated by the reference numeral  10  in  FIG. 1 , and generally comprises a box shape with top plate  12  and a base  14  spaced from the top plate to form a mixing chamber  16  therebetween. Attached to the periphery of the base  14  are front and back walls  18 , 20  that partially enclose the burner assembly leaving the left and right sides open for piping and an air intake associated with the burner assembly. It should be appreciated that the directions top, bottom, left, right, front, and back are used merely for illustrative purposes as they correspond to the general orientation shown in the drawings, and the directions top, bottom, left, right, front, and back are not intended to be limiting in any sense to a specific orientation or structure. Preferably, the top plate  12  and the base  14  are generally flat and the walls  18 , 20  are perpendicular to the top plate and the base so that the burner assembly  12  takes the shape of a rectangular solid for ease of construction. However, sloped walls, a curved base, or other convenient shapes could be used as desired to form the burner assembly  10 . Preferably, the top plate, front and back sides, and base are made of metal or other material that can endure prolonged intense heat as well as the frequent cycling between temperature extremes. Ceramic materials may also be used for forming the top plate, base, and/or front and back sides. 
         [0006]    As shown in the  FIGS. 1 and 2 , six dual port burners  30  are located in the burner assembly top plate  12 , as will be described in greater detail below. A pilot for ignition of the burner assembly may be provided, and carryover holes  34  are arranged in lines extending across the top plate in a random pattern to carry the flame after ignition across the burner assembly top plate  12  to ignite the dual port burners  30 . As best shown in  FIG. 3 , a log support, grate, or other convenient support  36  may be disposed above the top plate  12  for supporting log materials  38 , and material  40  resembling burning embers, such steel or rock wool or spun glass, is preferably piled under the grate or log support around and atop the burner top plate  12  over the carry-over holes  34 . The grate may also be formed integral with the burner assembly top plate and the logs held in place with pins extending from the top plate. 
         [0007]    A gas delivery system  50  ( FIG. 3 ) connects the burner assembly  10  to an external combustible gas source, including but not limited to natural gas and propane (“LP”). The gas delivery system  50  carries gas (or feed) from the external source through a main cut-off valve  52  to a “tee” connection  54  where a first portion of the gas is directed to a receiver  56  for eventual delivery to rich flame burner ports associated with each dual port burner  30 , and second portion of the gas is delivered to the mixing chamber  16  via a main gas manifold  58  to be mixed with air for eventual delivery to the carry over holes  34  and lean flame burner ports associated with each dual port burner  30 . In the mixing chamber  16 , the gas and air is mixed in order to produce a lean flame zone with highly efficient combustion and reduced emissions of NO x  and CO. Preferably, the air to gas ratio/mixture developed in the mixing chamber  16  to be combusted in the lean flame zone is between about five (5) percent and about thirty (30) percent more than the stoichiometric air to gas ratio mixture needed for complete combustion. The rich flame zone at the rich flow burner has an air to gas ratio/mixture that is theoretically or about zero. During the combustion process at the dual port burner  30 , the average air to gas ratio/mixture reaches a fuel rich environment creating higher theoretical flame temperature and taller flames. The higher theoretical flame temperature produces more heat. The receiver  56  preferably receives between about five (5) and about thirty (30) percent of the gas flow while the main gas manifold  58  receives between about seventy (70) and ninety-five (95) percent of the gas flow. The percentage of gas flow may be regulated by orifices  60 . Valves, orifices and/or the pipe size associated with each of the receiver (including tube branches  68  extending from the spider manifold, as will be explained below) and main gas manifold may also be used in combination to regulate and apportion flow to the main gas manifold, and the receiver and the tube branches. As shown by example in  FIGS. 1 and 2 , the receiver  56  preferably comprises a spider manifold with the tube branches  68  extending therefrom to each of the dual port burners  30 . The receiver  56  is preferably disposed under the burner top plate  12  in the mixing chamber  16 . The main gas manifold may connect to a side of the burner assembly and discharge directly into the mixing chamber  16 . Valves and controls associated with the valves may be disposed under the bottom support to protect them from the heat of the fireplace. While the gas delivery system  50  is shown in  FIG. 3  as a single pipe with the “tee” connection  54  to the receiver  56  and the main gas manifold  58 , it is understood that multiple pipes could be used to deliver the gas to the receiver or main gas manifold or mixing chamber, and that the pipe(s) could enter the burner assembly through the front and/or back sides, or even the base for connection to the receiver or main gas manifold. 
         [0008]    The burner assembly mixing chamber  16  may contain ceramic pellets  70  ( FIG. 1 ) comprising a conglomeration of particles sufficiently disparate in size and/or shape to form a loosely packed permeable barrier for the gas to flow through. The ceramic pellets  70  may completely fill the mixing chamber  16  or only a portion of it. The irregularity of the ceramic particles diffuses the gas so that the gas is mixed and dispersed in the mixing chamber prior to being directed to the carry over holes  34  and/or the lean flame burner port(s) of the dual port burners  30 , where it is ignited and combusted. The use of ceramic pellets in the mixing chamber reduces the occurrence of flash-back or flame extinction problems when the burner system is turned on or off. Because of the diffuse gas flow that reaches the burners at different rates and times, the combustion flames at the burners “dances” much like a woodburning flame. 
         [0009]    Each dual port burner  30  of the burner assembly comprises a lean flame burner port  80  and a rich flame burner port  82 . As shown by example in  FIGS. 1 and 2 , the lean flame burner port  80  comprises a plurality of slots in the top plate arranged in a pattern communicating with the mixing chamber, and the rich flame burner port  82  comprises a distal end of the tube branch  68  extending from the receiver or spider manifold  56 . The rich flame burner port  82  combusts pure gas to produce a rich flame, i.e., a yellow flame, and solid state C 2 . The lean flame burner port  80  combusts the gas/air mixture from the mixing chamber  16  and the C 2  produced by the rich flame zone thereby producing a yellow flame and providing an aesthetically pleasing simulation of wood burning in a conventional fireplace. Additionally, burning the C 2  and the soot particle, which were produced in the rich flame zone, inside the lean flame zone increases the heat output of the fireplace unit, as a higher theoretical flame temperature is achieved for the fireplace unit. Further, burning the C 2  and the soot particle, which were produced in the rich flame zone, inside the lean flame zone, tends to increase flame height. Preferably, the rich flame burner port  82  produces a flame pattern that is embedded within a flame pattern produced by the lean flame burner port  80 , thus allowing the C 2  produced by the rich flame burner port to be introduced directly into the flame pattern of the lean flame burner port, thereby reducing potential emissions and excess soot deposits. As shown in  FIG. 1 , the rich flame and lean flame burner ports  82 , 80  of each dual port burner  30  are aligned such that the lean flame burner port surrounds and is co-axially aligned with the rich flame burner port. The distal end of the tube branch  68  may be positioned in the center of the slot pattern of the lean flame burner port as one method of embedding the rich flame burner port flame pattern within the lean flame burner port flame pattern. The opening forming the rich flame burner port may be dimensioned to correspond to a #55 drill size. It should be appreciated that the rich flame burner port may also be spaced from and/or arranged at an angle relative to the lean flame burner port in such a way that the flame pattern produced by the rich flame burner port impinges or is embedded within the flame pattern produced by the lean flame burner port. To increase flame height, each dual port burner may be provided with a flame venturi  84  comprising an upstanding wall enclosing the lean flame burner port. As shown in  FIG. 3 , the flame venturi extends around the periphery of the slot pattern of the lean flame burner port. Holes  86  may be provided in the upstanding wall of the flame venturi to draw additional combustion air into the lean flame burner port  80  and to accelerate the flame upward from the burner  30 . 
         [0010]    As shown in  FIG. 3 , a valve  90  may be positioned in the gas supply preferably between the “tee” connection  54  and the receiver or spider manifold  56  to control a rate of gas flow to the rich flame burner ports  82  and thus the rate of rich flame combustion. The valve  90  may throttle the flow or secure the flow, as may be desired. The valve  90  may be manually actuated or operatively connected to a control  92  that automatically sets the position of the valve for a specific operation or function. The control  92  may comprise a microprocessor unit on the fireplace that integrates and controls some or all of the functions the fireplace. The control  92  may also be operated via remote controls associated with the fireplace. For instance, to assist in the generation of a “dancing flame,” the control  92  may dynamically cycle the valve  90  to vary the flow rate of gas to the receiver or spider manifold  56 . The control&#39;s dynamic cycle may be based upon a timer, or ambient conditions in the area in which the gas-log fireplace is situated, for instance, room temperature or sound. The control  92  may also be operatively connected to or interfaced with a thermostatic control associated with the gas-log fire place for automatic or manual temperature control based upon ambient conditions. The control may also be selectively controlled by the user, as may be desired, to increase, decrease “yellow” flame height, change flame color, change temperature, or to suspend the “yellow” flame appearance by stopping rich flame combustion. The control  92 , and/or other valves (not shown) provided in addition to the orifices  60  in the any of the connections to the main gas manifold and spider manifold, may be used for fine tuning of the combustion process for a specific configuration at set-up or installation of the fire place, for instance, to fine tune operations for direct vent and vent-less configurations, high altitude installations, and/or LP and natural gas applications. 
         [0011]    Use of stage combustion increases the heat output of the fireplace for a given gas usage. For instance, by producing higher theoretical flame temperature, stage combustion generates the heat of a 38,000 BTU unit while only expending the gas of a 28,000 BTU unit, thus allowing smaller units to be used and/or conservation of gas. 
         [0012]    It should be appreciated the dual port burner may comprise an arrangement other than the plate arrangement shown in the drawings. For instance, the dual port burner may comprise coaxially aligned tubes with the lean flame port comprising an outer tube communicating with the mixing chamber and the rich flame port comprising an inner tube disposed in the outer tube communicating with the receiver. As a further example as shown in  FIGS. 1 ,  2 , and  3 , lean flame burner port may comprise an tube extension  100  projecting away from the top plate in register with a hole  102  in the top plate  12  that communicates with the mixing chamber, and the spider manifold tube branch  68  may be lengthened to extend through the top plate inside the tube extension  100  so that the distal ends of the tube extension and tube branch are elevated from the top plate thereby allowing combustion and flame generation to be elevated relative to the top plate. As shown by example in  FIG. 3 , the tube extension  100  and lengthened tube branch  68  may extend through an aperture  104  in a log of the log set  38  to simulate burning logs in positions elevated from the top plate. 
         [0013]    While specific embodiments have been described in detail in the foregoing detailed description and illustrated in the accompanying drawings, those with ordinary skill in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.