US3237679A

US3237679A - Radiant burner with vented burner surface

Info

Publication number: US3237679A
Application number: US165598A
Authority: US
Inventors: Willie H Best
Original assignee: Thermal Engr Corp
Current assignee: Thermal Engr Corp
Priority date: 1962-01-11
Filing date: 1962-01-11
Publication date: 1966-03-01
Anticipated expiration: 1983-03-01

Description

March 1, 1966 w. H. BEST 3,237,679

RADIANT BURNER WITH VENTED BURNER SURFACE Filed Jan. 11, 1962 2. SheetsSheet 1 H 48 H ,20 F/g./ I li Jinnnuunnunupnj i 3 4 2 3 30 Fig.2 30

Willie H. Besf IN VENTOR.

BY W

March 1, 1966 w. H. BEST 3,237,679

RADIANT BURNER WITH VENTED BURNER SURFACE Filed Jan. 11, 1962 2 Sheets-Sheet 2 20 Fig. 3

Will/e h. Best IN VENTOR.

' slot.

United States Patent 3,237,679 RADIANT BURNER WITH VENTED BURNER SURFACE Willie H. Best, Thermal Engr. Corp., R0. Box 868, Columbia, S.C. Filed Jan. 11, 1962, Ser. No. 165,598 8 Claims. (Cl. 158-99) The present invention generally relates to a novel and improved radiant burner construction and more particularly to a radiant burner having a flue stack or vent communicated with the central portion of the burner surface for enabling more etficient combustion of the combustible mixture thus reducing the formation of carbon monoxide in the combustion products and also enabling more eflicient operation of the radiant burner surface.

The radiant burner of the present invention is constructed generally in the same shape and configuration as that disclosed in my copending application Serial No. 55,077, filed Sept. 9, 1960, for Radiant Burner Utilizing Flame Quenching Phenomena. In such a burner, it is desirable to have 100% primary air injection but this is substantially impossible under most operating conditions. Thus, it becomes necessary to provide secondary air to the surface of the burner for proper combustion of the combustible mixture. When the burner is of relatively small size or has at least one dimension which is relatively small, no particular problem exists since the secondary air may proceed from the adjacent edge of the burner to the central portion thereof with no particular problem. However, when the burner surface area is increased and there is considerable distance between the center of the combustion surface and any edge of the burner, an adequate supply of secondary air is diflicult to obtain since the products of combustion including carbon dioxide and water vapor is not displaced rapidly enough from the burner surface. When this condition is encountered, carbon monoxide is produced in undesirable quant-ities due to the inadequate supply of oxygen being present. Also, the failure of the combustion products to be exhausted properly leaves a layer of carbon dioxide and water vapor overlying a portion of the face of the burner. These products of combustion including carbon dioxide and water vapor absorb certain wave lengths of infra red energy thereby decreasing the efiiciency of the burner surface. Thus, it is desirable to remove the combustion products as rapidly as possible from the burner surface to eliminate absorption of the energy by the layer of carbon dioxide and water vapor. Of course, high velocity air circulation over the burner surface is undesirable since it would destroy the desirable characteristics of flame impingement upon the inclined surfaces of the divergent end portions of the burner Thus, a fan or similar device for forcing air over the burner surface would be undesirable from this standpoint.

Accordingly, in order to overcome the above mentioned problems encountered when supplying secondary air to a relatively large radiant burner, the present invention has for its primary object the provision of a flue stack or vent communicating with the burner surface at the center thereof and extending upwardly through the ceramic burner plate or plaquette, through the combustion mixture plenum and thus to the atmosphere.

A further object of the present invention is to provide air inlet at the edges of the burner surface to enable inlet of secondary air so that it may flow over the burner surface toward the center to replace the exhausted combustion products which, of course, proceed through the flue stack which forms a chimney and which has a chimney elfect for exhausting the combustion products.

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Still another object of the present invention is to provide a novel method of displacing the excess carbon dioxide and other products of combustion on the surface of the burner thus allowing the secondary air for combustion to move adjacent and in close proximity to the surface of the burner in order that complete combustion can be accomplished thus resulting in very low carbon monoxide concentration in the products of combustion.

Yet another important feature of the present invention is the use of the flue passage or stack to preheat the fuel or air mixture within the confines of the plenum thus returning some of the energy normally lost in the heated exhaust products to the incoming fuel and air mixture thus increasing the efliciency of the burner.

A still further important feature of the present invention is to provide a radiant burner having a flue passage or passages disposed therein together with bafile plates disposed below the inlet end of the passages thus assuring that the secondary :air will be drawn into the burner surface from the edges thereof thus assuring that the combustion products will be moved from substantially the entire surface area of the burner.

Another arrangement which is important to the present invention is the provision of the ceramic burner plates in an inclined manner with the flue passage being disposed at the apex thereof thereby using a natural air flow or draft to remove the combustion products from the surface of the burner.

When accomplishing all of the above objects, the present invention still is quite simple in construction, easy to install, eflicient in its operation and adds very little to the over-all cost of a radiant burner unit.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a side elevational view of a radiant burner of the present invention incorporating the vent or flue passage therein;

FIGURE 2 is a bottom plan view of the radiant burner unit illustrating the orientation of the flue passage and bafile plate;

FIGURE 3 is a transverse, sectional view taken substantially upon a plane passing along section line 33 of FIGURE 1 illustrating the orientation of the flue passage in relation to the burner and also illustrating the air inlet openings peripherally of the burner plate;

FIGURE 4 is a transverse, sectional view taken substantially upon a plane passing along section line 4-4 of FIGURE 3 illustrating further structural details of the flue passage; and

FIGURE 5 is a detailed sectional view similar to FIG- URE 4 but illustrating a modified form of the invention in which the ceramic burner plates are disposed in inclined relation and the flue passage disposed at the apex thereof.

Referring now specifically to the drawings, the numeral 10 generally designates the radiant burner of the present invention which includes a ceramic burner plate or plaquette 12, the details of which are set forth in the aforementioned application and which briefly include a plurality of parallel slots 14 having divergent surfaces 16 on the burning surface thereof. The width of the slots 14 is such that anyflame endeavoring to pass through the slots 14 from the burner surface to the plenum surface will be extinguished or quenched, thus eliminating the necessity for the velocity of the combustible mixture to exceed the rate of flame propagation. The divergent surfaces 16 provide troughs for better flame impingement and more effective emission of infra red radiant energy. The burner plate 12 is mounted in the open end of a plenum chamber 18 secured to an overhead support by any suitable bracket members 20 or the like. For supplying a combustible mixture into the plenum chamber 18, there is provided a pair of venturi 22 each associated with a fuel or gas inlet line 24 and the atmosphere in such a manner that the primary combustion supporting air and gas will be discharged by the venturi 22 into the interior of the plenum 18 and thus through the slots 14 to the burner surface of the ceramic plate 12 in substantially the same mannner as that disclosed in the aforementioned copending application.

The lower end of the plenum 18 is connected with the ceramic plate 12 in any suitable manner such as by a bonding material 26 or the like and also a depending peripheral wall 28 is provided together with a shroud or reflector 30 of any suitable configuration. The reflector 30 generally diverges outwardly and is attached to the wall 28 by any suitable means such as by

flanges

32 and 34 on the wall 28 and reflector 30 respectively secured together in any suitable manner and sandwiching therebetween a grid 36 of Nichrome wire.

Extending through the ceramic burner plate 12 and through the plenum 18 is a flue passage 38 defined by a tubular fiue member 40 which is in the form of a chimney and uses a natural convection draft for discharge of combustion products from the burner surface. The tubular member 40 isv either integral with or attached to the upper Wall of the plenum 18 and also has a peripheral flange 42 on the lower end thereof attached to the ceramic burner plate 12 by any suitable bonding which also is disposed between the exterior surface of the tubular member 38 and the central aperture formed in the ceramic plate 12. The tubular member 40 is constructed preferably of metallic material such as sheet metal or the like and is in good heat exchange relation to the primary air and fuel mixture which has been introduced into the plenum 18 by the aspirating-venturi 22.

Thus, the combustion products lying along the surface of the radiant burner plate 12 will be discharged upwardly through the tubular member 40. The tubular member v40 may be of any suitable shape or configuration and may be concentric with the center of the burner plate or there may be a plurality of flue passages orientated at equally spaced distances along the center line of an elongated burner plate. Preferably, the flue passages should be orientated so that the same surface area thereof is vented by each flue passage when a multiple of flue passages is employed.

The depending peripheral wall 28 is provided with a plurality of apertures 44 which form inlet means for secondary air so that the secondary air will flow inwardly over the. surface of the ceramic burner plate 12 thus enabling complete combustion of the combustible. mixture and eliminating excessive formation of carbon monoxide. Also, secondary air will be drawn upwardly through the grid wire 36 and in order to prevent air from being drawn directly into the flue passage 38 through the center of the grid wire 36, a deflector plate 46 is mounted on the grid wire 36 in any suitable manner and in alignment with the flue passage 38. As illustrated in FIGURE 3 and also in FIGURE 4, the baflie plate 48 is slightly larger in area than the flue passage 38 and is also spaced therefrom since it is secured to the grid wire 36thus assuring that air coming in through the grid wire 36 will pass peripherally over the baflie plate 46 to assure that it will serve to support combustion secondarily over the burner surface of the ceramic plate 12 outwardly of the flue passage 38.

FIGURE illustrates a form of the invention in which .the plenum 50 has a pair of ceramic plates 52 mounted therein in inclined relation to each other with a. flue passage 54 defined by a tubular member 56 communieating with the space between the upper spaced ends of the ceramic burner plates 52. In this form of this invention, inclined grid wires 58 are provided and a baffle 60 extends between the upper ends of the grid wire 58 and is supported from the tubular member 56 by suitable lugs 62. This enables secondary combustion supporting air to move along the inclined surface of the burner plates 52 and either enter through the grid wires 58 or enter at the bottom edge thereof which is spaced from the burner plates 52. With this assembly, the natural draft formed by the chimney or flue passage 54 serves to remove the combustion products from two burner plates thus enabling more effective removal of the combustion products and also enabling the burner plate to be formed in a manner having a greater burner surface for a given area of burner unit.

Thus, with the previously described method of displacing the excess carbon dioxide and other products of combustion on the surface of the burner and allowing the secondary air for combustion to move adjacent and in close proximity to the surface of the burner in order that complete combustion can be accomplished and will be result in very little carbon monoxide concentration in the products of combustion. This is accomplished basically by providing the flue passage leading from the burner and passing through the plenum and exiting out of the rear of the plenum. This has been illustrated when the burner plate is in horizontal position or the burner plates are arranged in inclined position so that the flue passage is vertical. However, the flue passage may just as well be disposed horizontally and work just as effectively as long as the flue passage has a component that would provide a natural chimney draft effect, such as an upwardly extending portion on the exit end thereof.

The slots in the ceramic plate form the only opening for the gas and air mixture which of course are so narrow to prevent backflash therethrough. Secondary air for combustion is pulled in through the openings 44 across the surface of the ceramic burner plate thus allowing proper combustion of the combustible mixture. The peripheral wall 28 or frame may extend around the periphery of the burner plate on all sides or on all sides except the injector side with the wall on the injector side being either apertured or solid due to its proximity to the aspirating venturies. As the products of combustion are expelled through the flue passage, secondary air will also enter directly through the Nichrome wire grid. In order that the secondary air entering through the Nichrome wire grid does not immediately pass through the flue passage, the metallic baflie plate 46 is attached thereto thus causing a deflection of the secondary air across the ceramic plate burner surface.

FIGURE 5 illustrates a configuration that will allow the secondary air for combustion to be used when the ceramics are mounted on a slight angle and the ceramic surfaces themselves act as a guide for the products of combustion to enter the flue passage. The usual closedtype plenum is incorporated and conventional venturies attached to these plenums allows for proper aspiration of the primary air. The sealed air mixture then proceeds through the thin apertures incorporated in the ceramic plates and combustion occurs on the surface. The secondary air is allowed to enter to the surface of the ceramic plates as shown by the arrows and the products of combustion are expelled through the flue passage as also shown by the arrows.

The present invention becomes quite important when large combustion areas are incorporated since the use of the flue passage will eliminate the problem of incomplete combustion which will occur at the central portion of a large radiant burner. By utilizing the flue passage 38 and the tubular member of metallic material forming such passage, the performance of the burner is further rendered more eflicient by returning some of the energy in the exhaust products to the fuel air mixture within the confines of the plenum. The hot products of combustion causes heat transfer to occur through the tubular member 40 'thus raising the temperature of the fuel air mixture and thus preheating this mixture before passing through the apertures of the ceramic plate for combustion thereof. Thus, the transpiration heating of the fuel air mixture contained within the plenum in order to raise the flame temperature of the burner resulting in higher surface temperatures is obtained and of significance.

A greater amount of heat transfer area can be realized by increasing the number of flue passages over the surface of the burner. An increase in the number of the flue passages also aids in removing the products of combustion for allowing the proper amount of secondary air to enter and accomplish complete combustion. Also, the flue passage or passages eliminate the layer of carbon dioxide and water vapor which form part of the combustion products thus eliminating the absorption of the infra red radiant energy by these combustion products which will absorb a relatively high percentage of infra red radiant energy of a particular wave length.

It is pointed out that the flue passages may be used alone, with or without the baflle plate and with or without the peripheral wall and either on a flat burner plate or on an arrangement of inclined burner plates such as shown in FIGURE 5. Primarily, the products of combustion are drawn from the surface of the ceramic allowing the secondary air to enter thereby preventing accumulation of the products of combustion over the surface of the burner which normally prevents the proper amount of secondary air to come into contact with the burner surface. The flue passage arrangement not only enables proper supply of secondary air but also preheats the combustible gas and air mixture for enabling a higher surface temperature because higher flame temperature could be accomplished when using preheated gas and air and, of course, the surface temperature of the ceramic plate is dependent upon the flame temperature and with a higher surface temperature, a greater quantity of infra red radiant energy is provided by the ceramic plate.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and de scribed, and accordingly all suitable modifications and equivalents may resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. In combination with a radiant burner having a ceramic burner plate with passageways therethrough and including a burning surface and a plenum chamber communicated with the opposite surface of the ceramic plate for supplying a combustible mixture thereto, a fine passage forming member extending through the central area of the ceramic plate and through the plenum chamber, said member being of substantially constant cross-sectional area for venting the burning surface of the ceramic plate for discharge of combustion products therefrom thereby enabling secondary air to pass inwardly along the burning surface of the ceramic plate thereby supporting complete combustion of the combustible mixture, said flue passage forming member terminating at the burning surface, and a deflector plate supported in spaced alignment with the flue passage forming member and in spaced relation to the burning surface thereby assuring that secondary combustion supporting air will pass over the burning surface rather than directly into the flue pas.- sage forming member.

2. The structure as defined in claim 1 wherein said deflector plate is of larger area than the cross sectional area of the flue passage forming member.

3. In combination with a radiant burner having a ceramic burner plate with passageways therethrough and including a burning surface and a plenum chamber communicated with the opposite surface of the ceramic plate for supplying a combustible mixture thereto, a flue passage forming member extending through the central area of the ceramic plate and through the plenum chamber, said member being of substantially constant cross-sectional area for venting the burning surface of the ceramic plate for discharge of combustion products therefrom thereby enabling secondary air to pass inwardly along the burning surface of the ceramic plate thereby supporting complete combustion of the combustible mixture, said plenum chamber including an extension disposed peripherally of and outwardly of the burning surface of the ceramic plate thereby forming a peripheral wall therefor, said peripheral wall having a plurality of openings therein for admitting secondary combustion supporting air.

4. The combination as defined in claim 3 wherein said peripheral wall has a Nichrome grid wire mounted on the lower edge thereof, and a depending reflector shroud engaging the lower surface of the wire grid, a deflector plate mounted on the grid wire in alignment with the flue passage forming member, said deflector plate being of larger area than the cross sectional area of the flue passage forming member for assuring that secondary combustion supporting air will pass peripherally of the deflector plate for passage along the burning surface of the ceramic plate.

5. In combination with a pair of ceramic burner plates arranged in inclined relation to each other and including a plenum chamber for supplying a combustible mixture to the inner surface of the ceramic burner plates, the outer surface of the ceramic burner plates forming a radiant burner surface, a flue passage extending upwardly from the spaced upper ends of the inclined burner plates and extending upwardly through the plenum chamber for providing a passage for combustion products as they flow upwardly along the burner surfaces, thereby enabling secondary combustion supporting air to pass over the burner surface of the ceramic plates, and a deflector plate mounted outwardly of the inlet end of the flue passage thereby deflecting secondary combustion supporting air toward the burner surface of the ceramic plates.

6. In combination with a radiant burner having a plenum chamber and a ceramic plate having one surface communicated with the plenum chamber and the other surface forming a burner surface, a flue passage defining member communicated with the burner surface of the ceramic plate, said member being of substantially constant cross-sectional area and extending through the plenum chamber for discharge exteriorly thereof thereby enabling combustion products to be discharged from the burner surface and enabling secondary combustion supporting air to have access to the burner surface thereby enabling complete combustion of the combustible mixture for reducing the carbon monoxide content of the combustion products, and a baflie plate disposed in spaced relation to the inlet end of the flue passage defining member for assuring passage of secondary air over the burner surface thus eliminating a layer of infra red radiant energy absorbing combustion products.

7. A radiant burner assembly comprising a hood including a plenum chamber, a ceramic plate having a plurality of apertures therethrough forming a closure for one side of the plenum chamber whereby combustible mixture may pass from the plenum chamber through the ceramic plate for combustion on the surface of the ceramic plate, said plate having an enlarged centrally disposed aperture therein, a vent tube extending through the enlarged aperture in the ceramic plate and disposed through the plenum chamber for forming a vent for combustion gases disposed along the burning surface of the ceramic plate thereby exhausting such gases for enabling secondary combustion supporting air to pass along the burning surface of the ceramic plate, said vent tube defining a flow passage for combustion gases which laterally confines such gases but permits unrestricted axial flow thereof, and a depending flange on said hood peripherally of the ceramic plate, said flange including a plurality of circumferentially spaced apertures providing air inlets for secondary combustion supporting air.

8. The structure as defined in claim 7 together with a reflecting shield attached to said flange, and a meshed wire member connected to said flange in spaced relation to the ceramic plate, and a deflector plate disposed in alignment with the vent tube and orientated against the Wire mesh for deflecting air therearound, said deflector 15 plate having a cross-sectional area greater than the crosssectional area of the vent tube for assuring that the secondary combustion supporting air Will pass over the ceramic plate.

8 UNITED STATES PATENTS References Cited by theExaminer 2,042,690 6/ 1936 Weber 15 8--96 2,051,213 8/1936 Hamilton 12692 FOREIGN PATENTS 1,228,433 3/1960 France. 1,242,087 8/ 1962 France.

251,567 10/1912 Germany. 842,596 7/1960 Great Britain.

OTHER REFERENCES German printed application No. 1,092,623, printed November 10, 1060.

FREDERICK L. MATTESON, JR., Primary Examiner.

PERCY L. PATRICK, JAMES W. WESTHAVER,

Examiners.

Claims

1. IN COMBINATION WITH A RADIANT BURNER HAVING A CERAMIC BURNER PLATE WITH PASSAGEWAYS THERETHROUGH AND INCLUDING A BURNING SURFACE AND A PLENUM CHAMBER COMMUNICATED WITH THE OPPOSITE SURFACE OF THE CERAMIC PLATE FOR SUPPLYING A COMBUSTIBLE MIXTURE THERETO, A FINE PASSAGE FORMING MEMBER EXTENDING THROUGH THE CENTRAL AREA OF THE CERAMIC PLATE AND THROUGH THE PLENUM CHAMBER, SAID MEMBER BEING OF SUBSTANTIALLY CONSTANT CROSS-SECTIONAL AREA FOR VENTING THE BURNING SURFACE OF THE CERAMIC PLATE FOR DISCHARGE OF COMBUSTION PRODUCTS THEREFROM THEREBY ENABLING SECONDARY AIR TO PASS INWARDLY ALONG THE BURNING SURFACE OF THE CERAMIC PLATE THEREBY SUPPORTING COMPLETE COMBUSTION OF THE COMBUSTIBLE MIXTURE, SAID FLUE PASSAGE FORMING MEMBER TERMINATING AT THE BURNING SURFACE, AND A DEFLECTOR PLATE SUPPORTED IN SPACED ALIGNMENT WITH THE FLUE PASSAGE FORMING MEMBER AND IN SPACED RELATION TO THE BURNING SURFACE THEREBY ASSURING THAT SECONDARY COMBUSTION SUPPORTING AIR WILL PASS OVER THE BURNING SURFACE RATHER THAN DIRECTLY INTO THE FLUE PASSAGE FORMING MEMBER.