US3796212A - High temperature infra-red generator - Google Patents

Abstract

A high temperature infra-red generator includes a housing having an emitter screen and a fuel supply. A reflector is positioned in the housing between the fuel supply and the infra-red emitter. The reflector or the interior of the housing includes a fluid coolant conduit for cooling the housing or the reflector.

Description

Unite States Patent 1 1 1111 3,796,232

Heuckroth Mar. 112, 19741 [54] HIGH-ll TEMPETURE lNFRA-RED 1,304,755 5/1919 Ellis 431/328 GENERATOR 3,434,466 3/1969 Hine,Jr. 126 92 R 2,181,138 11/1939 Landis 431/328 [75] In nt Ca Q Heuckroth, Lodl, Ohm 3,310,047 3/1967 Budden 126/92 B [73] Assignee: Van Dorn Company, Cleveland,

Ohio Primary ExaminerWilliam E. Wayner Assistant ExaminerWilliam E. Tapolcai, Jr. [22] Flled' 1973 Attorney, Agent, or FirmJames H. Tilberry [2]] Appl. No.: 325,134

[57] SACT [52] US. Cl. 126/92 B, 431/329 [51] Int. Cl. F24c 3/04 A hlgh temperaturemfra'red generator mcludes a [58] Field 61 Search 126/92 R, 92 B; 431/328, musing having an emitter screen and a fuel SuPPlY- A 431/329 reflector is positioned in the housing between the fuel supply and the infra-red emitter. The reflector or the 56] References Cited interior of the housing includes a fluid coolant conduit UNITED STATES PATENTS for cooling the housing or the reflector.

3,422,811 1/1969 Strand 126/92 R 13 Claims, 6 Drawing Figures da & 88 84 /8 60 34 /2 B L j 82 7854 1 I I 30 1.111 1 86 80 75 J; 72 32 //6 50 4d //0 /04 /oz /24 /54 [4 //4 [22 1 F I06 08 5 52 44 42 56 //a /32 22 I34 I36 I 4 I 4 PATENFE MAR E 2 i973 SHEH l U? 2 N% mm mm HIGH TEMPERATURE INFRA-RED GENERATOR BACKGROUND OF THE INVENTION This application pertains to the art of infra-red generators and more particularly to a very high temperature infra-red generator. The invention is particularly applicable to infra-red generators of the type using liquid or gaseous fuels. The invention is further particularly applicable to such infra-red generators having a plurality of fine mesh screens which serve as the'infra-red emitter. Although the invention will be particularly described with respect to an infra-red generator of this type, it will be appreciated that the invention has broader applications and maay be used in generators having other types of emitters.

In infra-red generators of the type described, combustion of the fuel takes place on the outer surface of the emitter screen. The screen is heated to incandesalso transmitted backward into the housing or plenum chamber from which fuel is supplied. If the plenum chamber becomes too hot, a dangerous flashback may occur. This has limited the temperatures at which such infra-red generators can operate. Generally, temperatures at the emitter screen cannot exceed around l,600 F. without heating the plenum chamber to a dangerously high temperature.

Reflecting the radiant energy back outwardly of the housing, or cooling the plenum chamber, enables operation of the infra-red generator at considerably higher temperatures. If sufficient energy can be reflected back outward, or if the plenum chamber can otherwise be kept sufficiently cool, it is possible. to supply an air-fuel mixture in a substantially stoichiometric ratio so that temperatures up to around 2,500 F. are possible.

Previous arrangements for cooling the plenum chamber of such generators include those described in US. Pat. Nos. l,304,755 to Ellis issued May 27, 1919, and 3,422,811 to Strand issued Jan. 21, 1969. In devices of the type described in these patents, a reflector is located rearwardly of the infra-red emitter to define a plenum chamber. A fuel supply communicates with the plenum chamber between the reflector and infra-red emitter. Rearwardly of the reflector, a coolant conduit is provided for circulation of coolant to cool the reflector and housing. In arrangements of this type, the reflector must be spaced a substantial distance rearwardly of the infra-red emitter in order to allow room for the fuel supply inlet. This reduces the efficiency of the reflector because the infra-red rays lose a considerable portion of their energy. In addition, arrangements of the type described require a fuel distributor for distributing the fuel throughout the surface of the infrared emitter so that uniform combustion will take place. With such a fuel distributor located between the reflector and infrared emitter, a large amount of infra-red energy is absorbed by the fuel distributor further decreasing the efficiency of the reflector. With the reflector spaced a substantial distance rearwardly of the infra-red emitter, the efficiency of heat transfer by convection for keeping the temperature of the rear surface of the emitter low is reduced and danger of flashback to the plenum chamber still exists.

SUMMARY OF THE INVENTION A high temperature infra-red generator of the type tremely close to the infrared emitter so that the distance traveled by reflected infra-red rays is minimized. At least the rear portion of the housing, or the rear surface of the reflector, or both, are provided with coolant conduits for circulating coolant fluid therethrough.

In the preferred arrangement, at least the rear surface of the reflector is provided with such coolant conduits so that heat from the rear surface of the infra-red emitter is absorbed at the reflector by convection. However, a substantial portion of the infra-red rays are reflected back outward by the reflector.

In an arrangement of the type described, it is possible to obtain substantially higher temperatures than heretofore possible. The infra-red generator is preferably of the premix-type wherein fuel and airare mixed to a substantially stoichiometric mixture. The temperature of the flame at the outer surface of the infra-red emitter may then be at least as high as 2,500 F.

In an infra-red generator of the type described, the reflector is dimensioned to be capable of intercepting and reflecting at least around percent of the infrared rays transmitted rearwardly from the infra-red emitter. Thus, the passageway means through the reflector forallowing the fuel to flow therepast occupies not more than about 20 percent of the area. With this arrangement, the reflector also acts as a fuel distributor for distributing combustible fuel throughout the entire surface area of the infra-red emitter for uniform combustion. The mixture of air and fuel flowing past the reflector at high velocity also aids in cooling the reflector and the housing.

It is a principal object of the present invention to provide a very high temperature infra-red generator.

It is a further object of the present invention to provide a water-cooled infra-red generator which is more efficient in operation.

It is an additional object of the present invention to provide a water-cooled infra-red generator which substantially eliminates danger of flashback into the plenum chamber.

BRIEF DESCRIPTION OF THE DRAWING The invention may take form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof.

FIG. I is a side elevational cross-sectional view of an infra-red generator having the improvements of the present invention incorporated therein;

FIG. 2 is a cross-sectional elevational view looking generally in the direction of arrows 2-2 of FIG. I;

FIG. 3 is a cross-sectional elevational view looking generally in the direction of arrows 3-3 of FIG. 1;

FIG. is a cross-sectional plan view looking generally in the direction of arrows 4-4 of FIG. 1;

FIG. 5 is a view similar to FIG. 1 showing another fuel supply and water cooling arrangement; and

FIG. 6 is a cross-sectional elevational view looking generally in the direction of arrows 6-6 of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, wherein the showings are for purposes of illustrating preferred embodiments of the invention only and not for purposes of limiting same, FIG. 1 shows an infra-red generator A constructed in accordance with the present invention.

lnfra-red generator A includes a dished housing 18 having an open front Ml, a backwall l2, opposed sidewalls 14 and 16, and opposed endwalls l8 and 20. Opposed sidewalls 14 and 16 cooperate with opposed endwalls 18 and 20 to define a continuous peripheral wall for housing B. Housing B may be formed to the shape shown and described by stamping a metal blank if so desired. The terminal ends of opposed side-walls l4 and 16, and opposed endwalls l8 and 20, are turned outwardly to provide a continuous outwardly extending peripheral flange 22 around open front 10.

ln accordance with onearrangement, a secondary metal housing member C is positioned within housing B. Secondary housing member C is shaped similarly to housing B, and is simply of a smaller size. Secondary housing C includes a backwall 26, opposed sidewalls 28 and 30, and opposite end- walls 32 and 34. The terminal ends of sidewalls 28 and 30, and opposed endwalls 32 and '34, are deformed outwardly to provide a continuousoutwardly extending flange 36.'Secondary housing C is dimensioned so that the entire exterior surface thereof is spaced inwardly from the interior surface of housing B to form a space 38 defining a fluid coolant conduit for circulation of coolant.

A reflector member 42 extends the full length of housing C between opposite endwalls 32 and 34, and has a downwardly facing reflector surface 44 which is polished or coated so as to be highly reflective of infrared rays. Although reflector 42 is shown as having a flat reflector surface 44, it will be recognized that it could also be curved upwardly or downwardly. Reflector 44 has a width which is less than the distance between opposed sidewalls 28 and 30 of secondary housing C. A channel member 48 has an inverted cross-sectional configuration which is substantially U-shaped. Channel member 48 includes depending leg portions 50 and 52 which are soldered or welded to the opposite edges of reflector member 42. Channel member 48 and reflector member 42 then cooperate to define an elongated rectangular conduit or passage 54. Opposed endwalls 32 and 34 of secondary housing member C have rect angular openings 56 and 58 therein for snuggly receiving the end portions of the conduit defined by reflector 42 and channel member 48. Solder or other sealing means is then applied around the end periphery of the conduit defined by reflector 42 and channel 48, and rectangular openings 56 and 58.

Endwalls l8 and 34 of housings B and C have aligned openings 60 and 62 therethrough. Internally threaded nuts 64 and 66 are secured to endwalls l8 and 34 adajcent openings 60 and 62. A fuel supply pipe 68 has an externally threaded bushing 70 soldered thereon. Pipe 68 is extended through nuts 64 and 66 until terminal end -72 of pipe 68 is a substantial distance within housing C. Pipe 68 is then rotated to thread bushing 70 into nut 66. Another bushing 76 is then placed over pipe 68 and threaded into nut 64. A compression washer 78 is then positioned over pipe 68. Another bushing 88 is then threaded onto bushing 76. Bushings 76 and 80 have cooperating conical surfaces for compressing washer '78 around pipe 68. Another large bushing 82 is then threaded onto bushing 80 for clamping pipe 68 to an upstanding bracket member 84. Pipe 68 is con nected with a tee D. Fuel as is supplied from pipe 86 to tee D while air is supplied by a blower through pipe 88 to tee D. Fuel and air are supplied through pipe 68 in a substantially stoichiometric ratio so that extremely high temperatures can be obtained. Premixing of the fuel and air to a substantially stoichiometric mixture is the preferred operating arrangement for obtaining substantially higher temperatures than heretofore possible with infra-red generators.

A deflector member E is positioned within housing C adjacent terminal end '72 of fuel supply pipe 68. Deflector member E includes opposite legs 92 and 94 which are welded to the interior surfaces of opposite sidewalls 28 and 30 of secondary housing C. Deflector member E is curved into a substantially V-shaped configuration to provide a leading edge 96 facing terminal end 72 of pipe 68. Deflector member E is positioned, and has such a height, that around one half of the fuel coming from pipe 68 strikes deflector E to be deflected to the left in FIG. 4. The remaining fuel flows past deflector E to the right half portion of the housing shown in FIG. 4. Deflector member E insures a uniform distribution of fuel throughout housing C.

Reflector 42 had a width such that it occupies only around 80 percent of the area defined at its position between opposite sidewalls 28 and 30 of secondary housing C. Therefore, the combustible fuel may flow down around the sides of reflector 42. It will be recognized that it is also possible to extend reflector 42 completely across sidewalls 28 and 30, and to provide a plurality of spaced-apart holes or openings through reflector 42 for passage of combustible fuel. In effect, reflector 42 has passage means for allowing passage of combustible fuel therepast. in the arrangement described, reflector 42 will be capable of intercepting around 80 percent of the infra-red rays transmitted rearwardly from the infra-red emitter.

Endwall E8 of housing B has another opening H82 therethrough below opening 60. Internally threaded nut W4 is soldered to endwall 18 adjacent opening 102. A coolant inlet pipe 106 has an externally threaded bushing T108 soldered thereto. Pipe 106 is rotated to thread bushing 108 into nut 1104. Another bushing lllil is soldered onto pipe 186 near support 84. Another bushing H2 is threaded onto bushing M0 for clamping pipe 184 to support 84. it will be recognized that the size of opening 68 is greater than opening 62 and the described bushings are correspondingly dimensioned to fit through the described openings for assembly purposes. Pipe 1186 is then connected to a pressurized source of water or other coolant. Opposite endwall 20 of housing B also has an opening 114 around which internally threaded nut U6 is provided. Exhaust coolant conduit llll8 has a threaded bushing 1120 soldered thereto and threaded into nut 1116. Another externally threaded bushing 1122 is soldered onto pipe 118 and receives a bushing 1124 for clamping exhaust coolant conduit M8 to support 130.

An infra-red emitter F is provided for front opening 16 of the housing. infra-red emitter F may take many forms. In the arrangement shown, infra-red emitter F comprises three metal screens R32, 134 and 136. A reverberator screen or secondary emitter 1 .38 is spaced outwardly from screen 136. A rectangular frame member G has substantially the same dimensions as outwardly extending flanges 22 and 36. Screens 132-138, frame member G, and flanges 22 and 36 are provided with aligned holes for receiving bolt and nut fastener assemblies H to securely clamp the parts in assembled relationship. Fuel is combusted at outer surface 140 of screen 136 to heat the described screen assembly to incandescence so that its emits infra-red radiation. Screen 138 is also heated so that it emits infra-red radiation.

In the arrangement described, infra-red emitter F also emits infra-red radiation rearwardly. Reflector 42 has a polished or coated highly reflective surface 44 for intercepting around 80 percent of the rearwardly directed radiation and reflecting such rays back outwardly. Water is continuously circulated through spaces 38and conduit 54 to cool the housing and reflector 42 so that the temperature within the housing remains very low and flashback of flame does not takeplace. The high velocity flow of gas and air from pipe 68 also aids in cooling reflector 42.

Instead of premixing fuel and air, it will be recognized that it is possible to use the features of the present invention with a venturi-type of fuel and air supply. In addition, it is also possible to cool only reflector 42 so that manufacture of the generator is highly simplified. In the arrangement of FIG. 5, a venturi tube 144 is soldered or otherwise secured around an opening 146 in endwall 18 of housing B. A fuel supply pipe 148 is clamped to support 84 by bushings 150 and 152. Outlet nozzle 156 is spaced slightly from opening 146. Supply of fuel from nozzle 156 through opening 146 aspirates air in a venturi action so that air and combustible fuel are supplied through venturi tube 144.

In the arrangement of FIG. 5, secondary housing C is also omitted. Instead, reflector 42 and channel member 48 are closed at their opposite ends except for circular holes around which bushings 160 and 162 are soldered. Suitable bushings 164 and 166 then extend through holes 102 and 114 in endwalls 13 and for threading into bushings 160 and 162. Additional bushings as at 170 and 172 connect to bushings 164 and 166, and clamp to supports 84 and 130. Water inlet and outlet conduits 180 and 182 are connected for supplying water through the coolant flow passage defined by reflector 42 and channel member 48. In this arrangement, substantially all of the readiation emitted rearwardly from infra-red emitter F is intercepted by reflector 42 and reflected back outwardly. Cooling of reflector 42 maintains the temperature within housing B very low so that flashback cannot occur and combustion is maintained outwardly of screen 136.

It will be recognized that supports 84 and 130 have inwardly turned bottom legs with a suitable hole therethrough for clamping with nut and bolt clamping assembly H.

Instead of continuous passages for circulation of water as described, it will be recognized that pipe coils or the like can be used in contact with the rear surface of the reflector or housing. In all embodiments, the reflector has its edges spaced from the sidewalls of the housing or is provided with holes to define passageway means for thoroughly distributing the fuel-air mixture over substantially the entire area of emitter F.

It has been found particularly advantageous to use steam or a liquid having a high boiling point as the fluid coolant. Such a liquid may be a water and glycerin solution. It has also been found desirable to regulate the flow of coolant so that too much heat is not removed from the housing or reflector. Removal of too much heat also reduces the temperature of the emitter screen so that it cannot reach its optimum operating temperature. Therefore, it has been found desirable to regulate the flow of coolant for maintaining reflector 48 at a temperature between 450-650 F. The flow of coolant may be regulated by positioning a thermocouple in contact with the reflector for sensing the temperature of the reflector. The thermocouple may then be used for operating a motorized valve or for regulating operation of a pump. When a liquid solution is used as the coolant, it has a boiling point substantially greater than the boiling point of water. Such a solution may have a boiling point over 400 F.

Although the invention has been shown and described with reference to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present invention includes all such equivalent alterations and modifications and is limited only by the scope of the claims. I

Having thus described my invention, I claim:

1. An infra-red generator including a dished housing having an open front, a backwall and a peripheral wall, infra-red emitter means mounted in said open front for emitting infra-red radiation, reflector means mounted in said housing intermediate said backwall and emitter means for reflecting toward said open front infra-red radiation emitter from said emitter means toward said backwall, combustible fuel supply means for supplying combustible fuel into said housing between said backwall and reflector means, passage means in said reflector means for passage of combustible fuel therepast to said emitter means, and fluid coolant conduit means contacting at least said peripheral wall for circulation 2. The device of claim ll wherein said reflector means has a rear surface facing said backwall and said fluid coolant conduit means contacts said rear surface.

3. The device of claim 2 wherein said combustible fuel supply means comprises a premix-type of fuel supplier for mixing air and fuel in a substantially stoichiometric ratio for supplying a substantially stoichiometric mixture of air and fuel into said housing between said backwall and reflector means.

4. The device of claim 3 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

5. The device of claim 1 wherein said combustibie fuel supply means comprises a premix-type of fuel supplier for mixing air and fuel in a substantially stoichiometric ratio for supplying a substantially stoichiometric mixture of air and fuel into said housing between said backwall and reflector means.

6. The device of claim 5 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

7. The device of claim 1 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

8. An infra-red generator including a dished housing having an open front, a backwall and a peripheral wall, infra-red emitter means mounted in said open front for emitting infra-red radiation, reflector means mounted in said housing intermediate said backwall and emitter means for reflecting toward said open front infra-red radiation emitted from said emitter means toward said backwall, combustible fuel supply means for supplying combustible fuel into said housing between said backwall and reflector means, passage means in said reflector means for passage of combustible fuel therepast to said emitter means, said reflector means having a rear surface facing said backwall, and fluid coolant conduit means contacting at least said rear surface of said reflector means for circulation of coolant therethrough to cool said reflector means.

9. The device of claim 8 wherein said combustible fuel supply means comprises a premix-type of fuel supplier for mixing air and fuel in a substantially stoichiometric ratio for supplying a substantially stoichiometric mixture of air and fuel into said housing between said backwall and reflector means.

10. The device of claim 8 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

11. The device of claim 8 and further including means for regulating the flow of coolant for maintaining the temperature of said reflector means in the range of 450-650 F.

12. The device of claim 11 wherein said coolant comprises steam.

13. The device of claim 11 wherein said coolant comprises a liquid having a boiling point substantially greater than water.

Claims (13)

1. An infra-red generator including a dished housing having an open front, a backwall and a peripheral wall, infra-red emitter means mounted in said open front for emitting infra-red radiation, reflector means mounted in said housing intermediate said backwall and emitter means for reflecting toward said open front infra-red radiation emitter from said emitter means toward said backwall, combustible fuel supply meaNs for supplying combustible fuel into said housing between said backwall and reflector means, passage means in said reflector means for passage of combustible fuel therepast to said emitter means, and fluid coolant conduit means contacting at least said peripheral wall for circulation of coolant there-through to cool said housing.

2. The device of claim 1 wherein said reflector means has a rear surface facing said backwall and said fluid coolant conduit means contacts said rear surface.

3. The device of claim 2 wherein said combustible fuel supply means comprises a premix-type of fuel supplier for mixing air and fuel in a substantially stoichiometric ratio for supplying a substantially stoichiometric mixture of air and fuel into said housing between said backwall and reflector means.

4. The device of claim 3 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

5. The device of claim 1 wherein said combustible fuel supply means comprises a premix-type of fuel supplier for mixing air and fuel in a substantially stoichiometric ratio for supplying a substantially stoichiometric mixture of air and fuel into said housing between said backwall and reflector means.

6. The device of claim 5 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

7. The device of claim 1 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

8. An infra-red generator including a dished housing having an open front, a backwall and a peripheral wall, infra-red emitter means mounted in said open front for emitting infra-red radiation, reflector means mounted in said housing intermediate said backwall and emitter means for reflecting toward said open front infra-red radiation emitted from said emitter means toward said backwall, combustible fuel supply means for supplying combustible fuel into said housing between said backwall and reflector means, passage means in said reflector means for passage of combustible fuel therepast to said emitter means, said reflector means having a rear surface facing said backwall, and fluid coolant conduit means contacting at least said rear surface of said reflector means for circulation of coolant therethrough to cool said reflector means.

9. The device of claim 8 wherein said combustible fuel supply means comprises a premix-type of fuel supplier for mixing air and fuel in a substantially stoichiometric ratio for supplying a substantially stoichiometric mixture of air and fuel into said housing between said backwall and reflector means.

10. The device of claim 8 wherein said emitter means is of the type comprising a plurality of stacked fine mesh metal screens.

11. The device of claim 8 and further including means for regulating the flow of coolant for maintaining the temperature of said reflector means in the range of 450*-650* F.

12. The device of claim 11 wherein said coolant comprises steam.

13. The device of claim 11 wherein said coolant comprises a liquid having a boiling point substantially greater than water.

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