Gas Burner with Secondary and Tertiary Air Supplies

Abstract

A gas burner and air supply system, including at least one elongate gas burner element connected to a fuel supply and a primary air supply. Arrays of fuel/air outlets disposed on opposing sides of the gas burner element output fuel and air for combustion and to form a cooking flame. An air plenum with a low pressure air supply is disposed above the each gas burner element and has an inverted V-shaped trough disposed immediately above the gas burner. First and second low pressure inboard air outlet arrays in the trough provide a secondary air supply to the combustion process. The plenum also includes at least one outboard array of low pressure air outlets disposed above and to an outboard side of each of gas burner to create a tertiary air supply, which creates a downward curtain of pressurized air that guides and directs heat from the flames downwardly.

Claims

1. A gas burner and air supply system, comprising: at least one elongate gas burner element configured for lateral placement across a gas broiler cooking chamber top, said gas burner in fluid communication with both a fuel supply and a primary air supply, and first and second generally linear arrays of fuel/air outlets disposed on opposing sides of said gas burner element through which combined fuel and air are output for combustion and to form a flame for cooking; and at least one air plenum in fluid communication with a low pressure air supply, said at least one air plenum having an underside with an inverted V-shaped trough disposed immediately above each gas burner in said system, and further including first and second low pressure inboard air outlet arrays, one each disposed above and along each side of said gas burner element, to provide a secondary air supply to the combustion process in addition to said primary air to enhance gas combustion and shape the flame to make it more efficient in a combustion chamber of the broiler cooking chamber, and at least one outboard array of low pressure air outlets disposed above and to an outboard side of each of said gas burners to create a tertiary air supply which in operation creates a downward curtain of pressurized air that guides and directs heat from the flames downwardly.

2. The system of claim 1, wherein said first and second low pressure inboard air outlet arrays are substantially linear.

3. The system of claim 2, wherein said first and second low pressure inboard air outlet arrays are generally parallel to one another and on opposing sides of said gas burner element.

4. The system of claim 1, wherein said gas burner element is cylindrical and has a diameter.

5. The system of claim 4, wherein said first and second low pressure inboard air outlet arrays are spaced apart a distance substantially the same as the diameter of said gas burner element.

6. The system of claim 1, wherein said at least one outboard array of low pressure air outlets is generally linear.

7. The system of claim 1, wherein said at least one outboard array of low pressure air outlets is generally parallel to each of said inboard arrays of low pressure air outlets.

8. The system of claim 1, including a unitary plenum having a plurality of inverted V-shaped troughs, one each disposed over a gas burner element.

9. The system of claim 1, including a plurality of plenums, each of said plenums having first and second outboard arrays of low pressure air outlets.

10. The system of claim 1, wherein said secondary air supply may be controlled to match the air needed to completely burn the fuel output from said gas burner element.

11. The system of claim 1, wherein said first and second low pressure inboard air outlet arrays are spaced apart from said gas burner element at a distance proportional to the diameter of said gas burner element.

12. The system of claim 11, wherein said first and second low pressure inboard air outlet arrays are spaced apart from said gas burner element at a distance proportional to the pressure under which fuel is expelled from said gas burner element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

[0013] FIG. 1A is a cross-sectional side view in elevation of a broiler showing gas burners ignited and burning fuel but with neither secondary nor tertiary air turned on;

[0014] FIG. 1B is the same view with both secondary and tertiary air turned on;

[0015] FIG. 2A is a detailed cross-sectional side view in elevation showing the flame shape as shown in FIG. 1A, i.e., when secondary and tertiary air is not turned on;

[0016] FIG. 2B is the same view showing the flame shape as shown in FIG. 1B, with secondary and tertiary air supplies turned on;

[0017] FIG. 3 is a lower perspective view showing the primary, secondary, and tertiary air outlet arrays used in the improved broiler burner of the present invention;

[0018] FIG. 4 is a lower perspective view of an alternative embodiment employing a unitary plenum (air box) and alternative air outlet configurations for the supply of secondary and tertiary air, the outlets configured to supply pressurized both to constrain and direct the burner flames and to enhance and substantially complete fuel combustion; and

[0019] FIG. 5 is a cross-sectional side view in elevation thereof, as taken along section line 5-5 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring to FIGS. 1A through 3, wherein like reference numerals refer to like components in the various views, there is shown an improved gas burner with a pressurized tertiary air heat and flame guide, a secondary air supply to enhance combustion and shape generally denominated 10 herein. These views illustrate the general structural and operative elements of an embodiment of the inventive apparatus. In its most essential aspect, the invention comprises a combination 12 that includes a gas burner 14, which in embodiments is an elongate cylindrical pipe 14, and an elongate plenum 16 disposed immediately above the gas burner through which secondary and tertiary air is supplied via air conduits 18 coupled to and in fluid communication with an air supply 20. For a conventional conveyor broiler of the kind used in commercial kitchens and restaurants, there are a plurality of burner/plenum combinations disposed laterally across the top of a cooking chamber 22 above a motorized chain conveyor 24 on which food product 26 is conveyed from a product inlet 28 to a product discharge or outlet 30.

[0021] In embodiments the spaced plenums 16 are each elongate cuboids with an inverted V-shaped heat reflector and air outlet plate 32 on the underside 34 of the plenum defining an inverted V-shaped trough 36 along which the burner pipe extends. The combined burners and plenums are laterally disposed in parallel rows above the belt conveyor.

[0022] As is well known, the cylindrical burner pipe typically includes a linear array of fuel/air outlets 40 along which the fuel/air mixture is distributed and output for combustion into an essentially type A flame F. However, and essentially, the heat reflector/air outlet plate 32 is an inverted V-shape that includes two linear arrays of air outlets straddling the upper portion of the burner through which plenum air is output into the vicinity of the burner output to produce two distinct effects.

[0023] In the first instance, first and second (i.e., a pair of) outboard linear arrays of air outlets 42a, 42b, one each disposed in an angled side of the inverted V-shaped heat reflector/air outlet plate 32, straddle the upper portion of the burner to provide a low pressure curtain of downwardly directed pressurized air that guides and directs heat from the flame downwardly toward the cooking food product 26. This air curtain and heat guide system is described in detail in U.S. Pat. No. 8,272,320 to Baker et al, which, as earlier noted, is incorporated in its entirety by reference herein.

[0024] In the next instance, first and second (i.e., also a pair of) inboard linear arrays of air outlets 44a, 44b, one each also disposed in an angled side of the inverted V-shaped heat reflector/air outlet plate 32, direct low pressure air from the plenum through the heat/reflector air outlet plate, down and into the flame, thereby providing excess air to complete combustion, increase efficiency, and further shape the flame to optimize it for use in a cuboid cooking chamber. Spacing and dimensions of the inboard linear arrays of air outlets are a function of burner size, air outlet size, air pressure, and the like, but the general purpose of the combination of outlet arrays is to enhance combustion, and to that end good results have been found having the inboard linear arrays 44a, 44b, generally straddle the burner equal distances above and on each side of the burner and at a distance apart from one another substantially the same as the burner diameter, as can be clearly seen in FIGS. 2A-2B.

[0025] In an alternative embodiment, and referring now to FIGS. 4-5, the plurality of plenums can be replaced by a unitary plenum 50 having a heat reflector/air outlet plate integral with the underside of the plenum. It includes an underside 32 configured with inverted V-shaped troughs 36 with essentially the same air hole patterns as those of the earlier described embodiment; provided, however, that this unitary embodiment may eliminate the second outboard array 42b of air holes used to provide the air curtain or guide. The need for the second outboard array may be obviated because a neighboring parallel outboard array 42a in the same plenum will suffice to provide the same complementary air curtain/guide when the burner elements and air outlet arrays are sufficiently close, the useful range of spacings being quite broad and easily identified through simple observation. In effect, this embodiment dispenses with the need to couple discrete plenums with an air supply pipe and to instead provide a single plenum to provide directed air over all or most burner elements in a cooking chamber. In all other respects, this embodiment is operationally identical to, and equally efficient as, the embodiment shown in FIGS. 1-3.

[0026] The technology of the present invention is incorporated in applicant's product models MV64 and FH94, which are dual belt, four lane gas flame conveyor broilers with automatic stack feeder for food product and the air supply system described above. Equipment testing of these models has shown exceptional and unexpected improvements in combustion efficiency, with corresponding reductions in broiler emissions and decreases in operating costs. Specifically, and as is considered more fully below, heavy-load cooking test data clearly show improved energy efficiency.

[0027] The public interest, as well as business interests in cost savings, ease of use, and pollution reduction, are benefitted by using the inventive system. Many energy utilities reward purchasers of energy efficient systems with rebates on purchase prices that match the energy savings. Equipment testing in a food service technology center was conducted on an implementation of the inventive system. In a dual belt conveyor broiler with four lanes, an automatic stack feeder, and the above-described burner configured with the gas, primary, secondary, and tertiary air supplies, data was collected to determine the energy input rate, preheat time and energy, idle energy rate, heavy-load cooking efficiency and production capacity using ASTM Standard Test Method F2239-10 (2021). In the case of the instant broiler, the savings (and the reduction in greenhouse gas emissions) is approximately 30%, and savings on commercial systems can therefore be substantial when both incentivizing rebates and the cost of energy consumption are considered. Indeed, the savings in the first year may represent a substantial portion of the entire purchase price of a system incorporating the inventive system. This is accomplished with no compromise (i.e., no increase) in cooking time.

[0028] A straightforward way to reduce the energy input in open broilers is to reduce the amount of fresh air that flows through the system, which also increases the overall heat to the unit. The liability in this approach is that it restricts a source of secondary air that needed for full and proper combustion from the burners: closing off the open front side makes the burners susceptible to incomplete combustion, and the flames become discontinuous across the burner surface. This problem is exacerbated when the broiler is under heavy cooking load because of the added effluent from the cooking food product, and this further starves the burner of oxygen.

[0029] By providing fresh air to the burners at the source of the flame, the inventive system may be closed to outside air while maintaining a stable burn, full combustion, and higher heat at comparable fuel consumption.

[0030] The above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention and provides the best mode of practicing the invention presently contemplated by the inventor. While there is provided herein a full and complete disclosure of the preferred embodiments of this invention, it is not desired to limit the invention to the exact construction, dimensional relationships, and operation shown and described. Various modifications, alternative constructions, changes and equivalents will readily occur to those skilled in the art and may be employed, as suitable, without departing from the true spirit and scope of the invention. Such changes might involve alternative materials, components, structural arrangements, sizes, shapes, forms, functions, operational features or the like.

[0031] Therefore, the above description and illustrations should not be construed as limiting the scope of the invention, which is defined by the appended claims.