Controlled secondary air supply range burner

Abstract

A powered secondary air supply ranger burner and method thereof provide an efficient burner with improved heat transfer. An atmospheric range burner controls a burner flame by insulating the burner and supplying a secondary air to the burner. The secondary air concentrates a heating zone to a center of a cooking vessel to be heated by the burner flame. The secondary air also controls a size and a shape of the burner flame.

Claims

1. A range top burner unit to provide heat to a cooking surface, the range top burner unit comprising: a burner configured to provide an open flame for cooking, wherein the open flame provides a heating zone for the cooking surface; a gas line configured to provide fuel to the burner for combustion; a powered secondary air supply (PSAS) configured to target heat transfer from the heating zone to a center of the cooking surface, wherein the PSAS is configured to lower NOx emissions from the burner unit to preferably 35-85 ppm; and an insulation component integrated under the burner.

2. The burner unit of claim 1 wherein the heating zone comprises a plurality of open flames and wherein each flame of the open flames protrudes in a vertical direction from the burner.

3. The burner unit of claim 1 wherein the PSAS comprises a spreader element adapted to provide a flow of air to at least one flame of the plurality of open flames of the burner.

4. The burner unit of claim 3 wherein the spreader element is comprised of brass.

5. The burner unit of claim 1 wherein the PSAS is configured to provide air to a plurality of burner ports on an inner burner ring.

6. The burner unit of claim 1 wherein the burner comprises an outer burner ring, wherein the insulation component surrounds the outer burner ring.

7. The burner unit of claim 6 wherein the insulation component comprises a plurality of openings around the outer burner ring.

8. The burner unit of claim 7 wherein the plurality of openings are configured to allow air to reach a plurality of air ports on a side of the outer burner ring, wherein the air is configured to maintain a vertical shape of the open flames of the burner.

9. A burner unit for a range top, the burner unit comprising: an air supply for a burner, wherein the burner and the air supply provide at least one open flame for cooking; an insulation component integrated with a ring of the burner, the insulation component comprising a plurality of openings; and a powered secondary air supply (PSAS) for the burner, wherein the PSAS provides additional air to the burner through the plurality of openings of the insulation component, and further wherein the PSAS is configured to lower NOx emissions from the burner unit to preferably 35-85 ppm.

10. The burner unit of claim 9 wherein the insulation component comprises two openings.

11. The burner unit of claim 9 wherein the insulation component comprises three openings.

12. The burner unit of claim 11 wherein the three openings are spaced equidistance from one another around the ring of the burner.

13. The burner unit of claim 9 wherein the at least one open flame is vertical.

14. A method of operating a range burner unit to control a burner flame comprising: controlling a firing rate of a burner with knobs on the burner unit; controlling primary burner aeration with a shutter on an inlet of the burner; supplying a secondary air to at least one burner flame; concentrating a heating zone to a center of a cooking vessel to be heated by the at least one burner flame; controlling byproduct emissions from the burner unit, wherein the byproduct emissions comprise NOx and CO; and controlling a size and a shape of the at least one burner flame with the secondary air.

15. The method of operating a range burner according to claim 14, further comprising adding insulation to a ring of the burner for controlling the secondary air supply to the burner.

16. The method of operating a range burner according to claim 15 wherein the insulation is configured to prevent excessive air flow to the burner from underneath the burner unit.

17. The method of operating a range burner according to claim 14 further comprising a needle valve adapted to control an air flow rate of the secondary air supply.

18. The method of operating a range burner according to claim 17 wherein the air flow rate of the secondary air supply results in a vertical shape of the burner flame.

19. A method of operating a range burner unit to control a burner flame comprising: controlling a firing rate of a burner with knobs on the burner unit; controlling primary burner aeration with a shutter on an inlet of the burner; supplying a secondary air to at least one burner flame using a needle valve adapted to control an air flow rate of the secondary air supply; concentrating a heating zone to a center of a cooking vessel to be heated by the at least one burner flame; and controlling a size and a shape of the at least one burner flame with the secondary air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cross-sectional view of a burner according to the prior art;

(2) FIG. 2 shows a cross-sectional view of a burner according to one embodiment of the invention;

(3) FIG. 3 shows a burner unit apparatus with a cooking surface according to one embodiment of the invention;

(4) FIG. 4 shows a knob on a burner unit apparatus according to the embodiment shown in FIG. 3;

(5) FIG. 5 shows a burner according to one embodiment of the invention;

(6) FIG. 6 shows a valve assembly of a burner according to one embodiment of the invention;

(7) FIG. 7 shows a burner according to one embodiment of the invention;

(8) FIG. 8 shows a top view of a burner according to one embodiment of the invention;

(9) FIG. 9 shows a graph of NOx emissions according to one embodiment of the invention;

(10) FIG. 10 shows a graph of CO emissions according to one embodiment of the invention; and

(11) FIG. 11 shows side views of a series of burners with a cooking surface with increasing flow from a powered secondary air supply according to one embodiment of the invention.

DETAILED DESCRIPTION

(12) The present invention provides a method of supplying secondary air for atmospheric burners. An atmospheric range top burner where an open flame is located below a cooking vessel is improved to combat the shortcomings of other range top burners. While this invention applies to atmospheric burners, the invention may also apply to a variety of other heating applications with a similar heat transfer process.

(13) FIG. 1 shows a cross-section of a range top burner according to the prior art. A burner 108 includes a plurality of flames 114 for cooking. As shown, the flames 114 protrude from the burner 108 at an angle. As with most range top burners of the prior art, the flames protrude outward from the center of the burner, therefore running up the sides of a cooking vessel when the vessel is atop the burner. A range top burner according to the present invention provides an apparatus and method which causes flames on a burner to protrude vertically from the burner surface, thereby provided greater efficiency and accuracy in heating contents of a cooking vessel.

(14) FIG. 2 shows a cross-sectional view of a range top burner 108 according to one embodiment of the invention. The burner includes a plurality of open flames 114 when the burner 108 is in use. A powered secondary air supply (PSAS) 122 is included protruding from a center of the burner 108. The PSAS 122 provides a controlled and targeted air supply which in turn controls the size and shape of the open flames 114. As shown, the addition of the PSAS 122 in the claimed invention, results in flames 114 that protrude in a vertical direction from a surface of the burner 108, as opposed to the flames of the prior art shown in FIG. 1. The PSAS 122 controls flame shape to improve heat transfer from the burner 108 to a cooking vessel. The PSAS can be supplied to at least one atmospheric burner by any reasonable means within the art, such as by a manifold or an individual blower. The manifold or blower can be added to an appliance or tapped off of another existing blower. The supply of secondary air to the at least one atmospheric burner concentrates a heating zone 116 to a center of a surface to be heated. The vertical flames 114 transfer heat to a bottom of a cooking vessel as opposed to the flames creeping up the sides of the vessel. It is to be understood that the surface to be heated or cooking vessel may be any number of surfaces whereby heating the surface is desired, such as a cooking vessel (frying pan, saucepan, pot), kettle, grill, or any other suitable surface. This is contrary to current burners where the heating zone 116 distributes heat along the sides of the surface, allowing heat to be lost. The PSAS can also help control certain emissions, for example, NOx. While air is naturally supplied to burners, in part, for maintaining burner flames, the PSAS of the claimed invention is controlled so that flames can in turn be controlled to a higher degree for improved burner operation.

(15) FIG. 3 shows a range top burner unit 100 where the burner 108 is heating a cooking surface 104, particularly a center 106 of the cooking surface 104. The operation of the burner unit 100 is controlled by a knob 102 (also shown in FIG. 4), as is common for most range top burner units. The knob 102 varies the firing rate of the burner. As shown, the cooking surface 104 of FIG. 3 includes a capture hood 105. The capture hood 105 is placed on top of the cooking surface 104 to test and capture certain emissions once the cooking surface 104 is heated by the burner unit 100.

(16) In an example of the invention, the capture hood 105 was included to reduce or eliminate the dilution of flue gases coming off the burner unit, without interfering with normal operations of the burner. Flue gas samples were taken and water temperatures were monitored. The results are shown from various examples, discussed further below.

(17) FIG. 5 shows a close-up view of the burner 108. The burner 108 includes a spreader element 124. The spreader element 124 provides a flow of the PSAS to the flames from the center of the burner 108. The spreader element is preferably brass, although other suitable materials may be used as well. The spreader element 124 acts as a source to supply air near the burner 108. The overall design of the spreader element 124 can vary, particularly in reference to individual burner design, or the design of the overall appliance being used.

(18) The spreader element 124 is located in the center of the burner 108, preferably the center of the inner burner ring, so that the spreader element 124 is in the center of the flames when the burner 108 is in use. The PSAS is released from the spreader element 124 at various quantities and speeds to accurately maintain an improved flame shape. The PSAS is provided to the spreader element 124 from a pathway. FIG. 6 shows a partial view of the pathway for the PSAS to reach the burner from a gas line 118 (not shown). The pathway includes an inlet 110 to the burner. The inlet 110 is attached to a shutter 112 on one end. The inlet 110 is attached to a needle valve 126 on another end. The needle valve 126 controls the PSAS coming out of the spreader element. The shutter 112 on the inlet 110 of the burner can vary primary burner aeration. The needle valve 126 can control an air flow rate from the PSAS. The controlled air flow rate of the PSAS is therefore controlled coming out of the spreader element.

(19) FIG. 7 shows the burner 108 ignited with open flames 114. The burner 108 includes an inner burner ring 134 and an outer burner ring 136. Flames 114 protrude from burner ports 132 on the inner burner ring 134, and from air ports 138 on the outer burner ring 136. The burner 108 also includes an insulation component 128. The insulation component 128 surrounds the spreader element 124 insider a circumference of the inner burner ring 134. The insulation component 128 also surrounds the outer burner ring 136. The insulation component 128 is added under the burner 108 to prevent excess air flow to the burner from underneath the unit 100. As natural air may flow to the burner, in addition to the PSAS, this insulation component 128 allows for an additional level of control of the natural air. The PSAS can then optimally control the flame shape without the interference from natural air. The insulation component 128 can be added using any standard insulation compatible with ranges such as fiberglass insulation, Alkaline Earth Silicate (AES) fiber insulation, and ceramic fiber insulation, among others.

(20) In one embodiment of the present invention, no additional space is needed around the burner to accommodate for natural secondary air. This allows the burner to be less “open” with more insulation from the insulation component to aid in concentrating the heat on the intended cooking surface. Rather than having excess heat lost into the environment, the heat is applied more centrally and directly to the cooking surface. The addition of the controlled PSAS results in less heat loss to the environment since the heat is able to be more concentrated on the cooking surface.

(21) FIG. 8 shows an embodiment of the present invention where the insulation component 128 of the burner 108 includes a plurality of openings 130. An air supply 120 is directed to the burner 108, as with most top range burners. The openings 130 in the insulation component 128 are spaced equidistant around the outer burner ring 136, from the air supply 120. As shown, the insulation component 128 has three openings 130. In one embodiment of the invention, the insulation component may have two openings. In one embodiment of the invention, the insulation component may have more than three openings. In one embodiment of the invention the spacing of the insulation component openings may vary. The addition of openings 130 in the insulation component 128, specifically on the outer ring 136, can provide an additional pathway for the PSAS to reach the outer ring of the burner. As the spreader element 124 is inside the inner burner ring 134, PSAS is more easily supplied to the burner ports 132 of the inner burner ring 134, in comparison to the burner ports 138 of the outer burner ring 136. The openings 130 can allow some PSAS to reach the burner at the outer ring.

EXAMPLES

(22) As a goal of the claimed invention is to improve certain emissions associated with range burners, in addition to controlling the size and shape of burner flames, various examples were conducted in modifying the PSAS supply and the insulation of the burner. These examples illustrate or simulate various aspects involved in the practice of the invention. It is to be understood that all changes that come within the spirit of the invention are desired to be protected and thus the invention is not to be construed as limited by these examples. These examples specifically addressed NOx and CO emissions that were monitored and calculated (using a capture hood 105 such as shown in FIG. 3) by modifying characteristics of the insulation component and the PSAS.

(23) FIG. 9 shows NOx emissions calculated with a burner according to the present invention. Emissions were calculated with several data sets including instances where secondary air was fully blocked from the burner, and where openings (such as those shown in FIG. 8) were added to the insulation—both two openings, and three openings. The obtained data, used to create FIGS. 9 and 10, is shown further in Table 1, below.

(24) TABLE-US-00001 TABLE 1 Range Burner Data Nox Nox Cor CO CO Cor CO2 O2 Firing Secondary Test Case (ppm) (ppm) (ppm) (ppm) (%) (%) Rate Air Baseline 62.73 89.40 295.07 421.38 8.57 6.25 29482 60 Baseline 62.73 89.40 295.07 421.38 8.57 6.25 29481.77 50 Baseline 62.73 89.40 295.07 421.38 8.57 6.25 29481 77 40 Baseline 62.73 89.40 295.07 421.38 8.57 6.25 29481.77 30 Baseline 62.73 89.40 295.07 421.38 8.57 6.25 29481.77 20 SO; K3; 60SCFH 21.43 57.52 179.71 480.05 4.35 13.17 25400.90 60 SO; K3; 50SCFH 28.50452 68.78354 75.25619 183.68065 4.856844 12.30535 24920.998 50 SO; K3; 40SCFH 35.04185 72.49626 177.3606 365.62996 5.685057 10.84272 24968 40 SO; K3; 30SCFH 31.75521 62.92595 533.3701 992.44608 5.910665 10.42735 24680.292 30 SO; K3; 20SCFH S4; K3; 60SCFH 13.25479 39.41558 190.4536 560.66411 3.991675 13.87194 26689.005 60 S4; K3; 50SCFH 16.17624 42.122 181.0676 466.68767 4.519693 12.92057 25768.146 50 S4; K3; 40SCFH 16.4165 39.52922 577.2428 1057.1838 5.01844 11.9802 25456.334 40 S4; K3; 30SCFH S4; K3; 20SCFH SC; K3; 60SCPH 17.87775 53.4422 198.1668 592.37303 4.006713 13.99019 24561.627 60 SC; K3; 50SCFH 25.24161 63.02021 222.8336 556.16761 4.773908 12.5883 24486.326 50 SC: K3; 40SCFH 29.48165 72.42424 144.6033 353.71786 4.857965 12.44477 24106.218 40 SC; K3; 30SCFH SC; K3; 20SCFH S4; K3; IoX2; 60scfh 18.56 51.28 433.65 1116.30 4.32 13.39 27476.22 60 S4; K3; IoX2; 50scfh 18.90 46.79 818.08 1125.00 4.74 12.49 26726.39 40 S4; K3; IoX2; 30scfh 32.69 60.21 1125.00 1125.00 6.18 9.59 19147.43 30 S4; K3; IoX2; 10scfh 30.31 40.31 1125.00 1125.00 8.49 5.17 27184.90 20 S4; K3; IoX3; 60scfh 22.20 74.85 115.53 388.05 3.62 14.77 23975.92 60 S4; K3; IoX3; 40scfh 30.74 76.77 40.91 101.38 4.80 12.60 24715.69 40

(25) In Table 1, K3 represents the firing rate setting of the burner tested. SX represents the settings of the shutter on the inlet of the burner. The shutter settings included 0, 1, 2, 3, 4 and C (closed). The PSAS, or secondary air, was given to the burner in units of SCFH (standard cubic feet per hour). IoXx represents the number of openings that were placed in the insulation component. These examples were tested with secondary air being completely blocked off by insulation (the baseline), with two openings in the insulation component (IoX2), and with three openings in the insulation component (IoX3). The examples were used when heating a gallon of water with the burner from 0° to 190° F.

(26) The baseline values from Table 1 are shown in FIG. 9. Even at the baseline, the present invention showed improved NOx emissions, reducing NOx emissions from 120 ppm as with prior systems, to 90 ppm for the present invention. Additional reduction in NOx emissions was observed by changing the flowrate for the PSAS and primary sir shutter for the burner. The data from Table 1, and shown in FIG. 9, also shows that NOx emissions were reduced even further when two openings were added to the insulation (see S4; K3; IoX2 values), and when three openings were added (see S4; K3; IoX3 values). With two openings in the insulation, NOx emissions were reduced to approximately 30-70 ppm, preferably 40-60 ppm. With three openings in the insulation, NOx emissions were reduced to approximately 60-90 ppm, preferably 70-80 ppm.

(27) Data from the examples was also used to improve CO emissions within the acceptable range of ANSI range burner requirements, which requires CO emissions of less than 800 ppm, corrected to 0% O.sub.2. In particular, improvement was observed at data point SO K3 50 SCFH for the air shutter in the 0 position and a PSAS flow rate of 50 SCFH. This results in NOx emission of 69 ppm, and CO emissions at 180 ppm (both corrected to 0% O.sub.2).

(28) FIG. 10 shows CO emissions calculated with a burner according to the present invention, also using the data from Table 1. CO emissions improved where the insulation component included three openings (see S4; K3; IoX3 values). With three openings in the insulation, CO emissions were reduced to approximately under 500 ppm, preferably 100-400 ppm. The best results were obtained for IoX3 at a shutter of S4 and PSAS flow rate of 40 SCFH for a NOx emission of 77 ppm and a CO emission of 101 ppm, both corrected to 0% O.sub.2.

(29) FIG. 11 shows additional examples of the present invention for changing the flame shape of the burner with the PSAS. A series of fired burners 108 included cooking surfaces 104. The PSAS was delivered to the center 106 of the cooking surfaces 104 at varying quantities based on standard cubic feet per hour (SCFH). The flame shape changed as PSAS was provided to the burner. At 0 PSAS in SCFH, the flame shape included long blue fingers extended to the sides of the cooking surface throughout the heating zone 116. As the PSAS increased, up to preferably 50 SCFH, the flames were contained under the pot in the heating zone 116. The results shown in FIG. 11, combined with those shown in FIGS. 9-10, concluded that the present invention could control flame shape of a burner while also improving NOx and CO emissions.

(30) In terms of cooking efficiency, range burners are generally less than about 40% efficient. Atmospheric range burners rely heavily on secondary air to complete combustion. When a pot or pan, or any other cooking vessel, is over a burner on conventional range burners, secondary air is limited and therefore a flame from the burner begins to seek additional air elsewhere. This may cause the flame to lengthen up sides of the cooking vessel which results is less efficient heat transfer from the burner to the cooking vessel. With the present invention, the flame of the burner shortens, allowing the flame and heat concentration to remain closer to a center of the surface to be heated. This therefore may improve efficiency and cooking performance of the subject burner by forming a more uniform heat transfer from the burner to the surface to be heated.

(31) In addition to the above, the present invention may also be less costly than conventional burners. The PSAS range burner may be less expensive than pre-mix powered burners. In one embodiment, the PSAS range burner may be retrofitted onto an existing range. In another embodiment, the PSAS range burner may be part of an entirely new range system.

(32) While in the foregoing detailed description the subject development has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the subject development is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.