US3173470A

US3173470A - Gas-fueled radiant heater

Info

Publication number: US3173470A
Application number: US153110A
Authority: US
Inventors: John S Wright
Original assignee: General Precision Inc
Current assignee: General Precision Inc
Priority date: 1961-11-17
Filing date: 1961-11-17
Publication date: 1965-03-16
Anticipated expiration: 1982-03-16

Description

March 16, 1965 J. 5. WRIGHT 3,173,470

GAS-FUELED RADIANT HEATER Filed Nov. 17, 1961' 2 Sheets-Sheet 1 33 s2 42 4/ 43a .55 n 34 c m- 62 v 3:9

TIE-=5:

INVEN TOR.

.roH/v a. WRIGHT March 16, 1965 .1. s. WRIGHT GAS-FUELED RADIANT HEATER 2 Sheets-Sheet 2 JNVEN TOR.

J'o/wv 6. WRIGHT Y B Y M KM,

United States Patent 3,173,473 GAS-FUELED RADHANT HEATER John S. Wright, Carleton, Mich assignor, by mesne assignments, to General Precision line, Tarrytown, N.Y., a corporation of Delaware Filed Nov. 17, 1961, er.No. 153,110 Claims. (831. 1158-99) This application is a continuation-in-part of my application Serial Number 72,435, titled Infrared Gas Heating, filed November 29, 1960.

This invention relates to gas burner apparatus and particularly to gas burner apparatus of the type which is utilized to produce highly intense flames including infrared rays.

It has been known in the art that when a mixture of combustible gases and air is caused to flow through a perforated ceramic plate and is ignited on the outer surface of the plate, the burning gases, in addition to producing heat by combustion, also produce heat in the form of infrared rays. As indicated in said copending application, one of the major problems in such a combustion is the tendency for the ceramic plate and the associated casing to heat up raising the temperature of the interior of the casing and causing the burner to backfire and burn within the interior of the casing on the opposite side of the ceramic plate. This, in turn, causes a rapid deterioration of the plate. Another major problem is that the combustion gases tend to collect in the area of the ceramic plate and thereby adversely affect combustion. A further problem is that the proximity of the article being heated affects the temperature of the ceramic plate so that a combustion arrangement which is satisfactory for one type of heating is unsatisfactory for another type of heating.

According to the aforementioned patent application Serial No. 72,435, a more efficient burning of combustible gases is obtained by providing a housing around the burner casing in such a manner that a natural draft is caused by the flow of gases of combustion from the area of the surface of the burner or ceramic plate, drawing cool air across the outer surface of the casing of the burner and into the inlet of the casing for combustion.

Although the above described arrangement which is disclosed and claimed in the aforementioned application Serial No. 72,435 produces a more eflicient burning than has heretofore been obtained, the degree of temperature obtained is limited by the nature of the burner element such as the ceramic plate. Another difficulty with ceramic plates is that they are fragile and easily broken.

It is an object of this invention to provide an improved r gas burner apparatus wherein higher temperatures are achieved than have been heretofore possible.

It is a further object of the invention to provide a novel burner element for use in prior art gas burner apparatus.

It is a further object of the invention to provide gas burner apparatus having a much more effective and longer life than burner elements which have heretofore been used.

Basically, the invention comprises utilizing a novel burner element in the apparatus shown in the aforementioned application Serial No. 72,435. The burner element comprises a mat of sintered metal fibers, the mat having substantially uniform thickness throughout and preferably having fibers of particular size and shape distributed in such a fashion that a predetermined porosity is obtained. The novel burner element is also useful in apparatus of prior art design as fully described below.

In the drawings:

FIG. 1 is a part sectional elevation of an apparatus embodying the invention.

FIG. 2 is a sectional view of the radiant gas burner.

3,173,470 Patented Mar. 16, 1965 FIG. 3 is a further sectional view of the radiant gas burner.

FIG. 4 is a fragmentary partly diagrammatic view on an enlarged scale of the burner element embodying the invention.

FIG. 5 is a fragmentary partly diagrammatic view on an enlarged scale of a modified form of burner element.

Referring to FIG. 1, the apparatus 10 comprises a housing 11 that can be made of sheet metal and includes a top wall 12, side walls 13, a bottom Wall 14 and an end wall 15. Housing 11 also includes a rectangular inlet 16 that has a width substantially equal to the distance between the side walls 13. Bottom wall 14 is provided with an opening 17 in which a rectangular support 18 is provided for a burner or rayhead 19. As shown, the rayhead 19 is positioned within the housing 11 in spaced relation to the top and bottom walls 12, 14.

The upper wall 12 is inclined upwardly away from the inlet 16 and the end wall is curved upwardly and outwardly to form an outlet 20. A curved conduit 21 extends from the outlet to provide a vertical stack. Support 18 includes spaced

vertical walls

22, 23 adjacent and spaced from end wall 15.

Walls

22, 23 have vertically staggered openings 24, 25 therein through which the gases of combustion from adjacent the rayhead 19 pass and are directed upwardly toward the stack 21. Housing 12 includes a curved deflector 26 which is generally parallel to the end wall 15 and extends between the side walls 13 to guide the gases of combustion upwardly toward the stack 21. The movement of the gases toward the outlet 20 and stack 21 causes relatively cool air to be drawn through inlet 16 and across the exterior surface of the rayhead 19 to cool the casing, as presently described. At the same time, the cool air passes to the interior of the rayhead 19 where it is mixed with combustible gases and caused to burn on the surface of the rayhead as presently described.

Referring to FIGS. 2 and 3, the rayhead 19 comprises a generally rectangular dish-shaped casing 30, preferably a casting of light-weight heat dissipating material such as gray iron. Casing 30 includes a substantially flat bottom wall 31 and inclined side walls 32 and

end walls

33, 34. The housing 30 also includes an integral passage 35 that is formed in part by the bottom wall 31. Passage 35 communicates with an extension 36 exteriorly of the casing 30 which forms an inlet that is flared and diverges outwardly. The passage 35 terminates within the chamber 37 of the casing 3t) nearer the end wall 33 than the end wall 34. The inner edges of the side walls 32 and

end walls

33, 34 are formed with projections 38 for supporting a burner element 39 which is in the form of a flat uniformly thick porous mat of sintered fibers, as presently described. Bosses 55 extending from the wall which forms passage 35 support plates 39 intermediate their edges. Passages 55a in bosses 55 vent passage 35 and tend to prevent vapor lock in the passage 35.

The casing 30 also includes a secondary shoulder 40 on side wall 32 and

end walls

33, 34, intermediate the bottom wall and the burner elements 39 and in parallel spaced relation thereto, which supports a foraminous element 41 such as a screen. In addition, a flange or frame member 42 rests on the screen and surrounds the interior of the chamber 37.

A nozzle 43 is supported within the inlet 36 by a suitable plate 44 having openings therein through which air can pass to the interior area 37 of the casing 30. Damper members 45 having openings therein are mounted adjacent the member 44 and is adapted to be moved relative thereto to restrict or enlarge the openings 46 and thereby control, in part, the air passing to the interior of the casing 30.

Top wall 31 of casing 30 is formed with integral longi- 3 tudinally extending fins 56 which increase the surface area thereof and facilitate the cooling of the casing 39. I

The pressure of combustible gases through the nozzle 43 aspirates air from the exterior through inlet 16 of housing 11 and into the converging inlet 36 of the cas ing 30. The mixture of air and gases passes there-after through passage 35 to the area 37 of the casing 30. The screen 41 serves to distribute the gases throughout the chamber 37 and cause them to flow toward the burner element 39 and threafter pass through the burner element 39 to the exterior thereof where they are burned. The flange member 42 serves to prevent the concentration of the gas and air mixture adjacent the periphery of the casing 36 and thereby further facilitates the even combustion of the gases on the surface of the burner elements 39. I

The aforementioned apparatus, except for the particular burner element 39, is identical to that disclosed and claimed in the aforementioned application Serial No. 72,435.

Burner element 39 comprises a porous mat of generally uniform thickness and consisting of sintcred metal fibers.

The [mat is formed integrally with a frame 6% that has a J cross section (FIG. 3) and is held in position on the lowerend of the casing by screws 61. A gasket 52 of insulating material is provided between the flange 60 and the casing to provide an air-tight seal and prevent gases from escaping thereby insuring that the gases will pass through the mat 39.

The fiber mat is made from metal fibers which have a high temperature resistance, high coetiicient of heat transfer, and a length, size and distribution such that the mat has aporosity permitting the proper how of mixture of air and gases -therethrough and combustion thereof on the surface of the mat.

Metal fibers of stainless steel produce satisfactory re sults. Other metal fibers which can be used are tungsten, titanium diboride, platinum, and rhodium-platinum. Higher temperature resistance is obtained by making the layer adjacent the combustion area of a fiber having a higher temperature resistance than the fibers of the remainder of the mat. Thus, tungsten fibers can be used adjacent the combustion area while stainless steel fibers comprise the remainder of the mat. Alternatively, the fibers can be plated adjacent the combustion surface with a material that is more resistant to high temperatures such as nickel, platinum or tungsten. In addition, the fibers adjacent the combustion surface can be oxidized to obtain a greater resistance to oxidation.

It is also desirable to provide a reflective surface that minimizes the heat flowto the mat. Such a surface may be obtained by coating the fibers with the nickel and platinum.

The thickness of the mat can vary but preferably ranges from to A of an inch depending on the temperature required. If the temperature is higher, a thicker mat is required whereas if the opera-ting temperature is lower, a thinner mat can be used.

The size of the fibers both in cross section and length are very important in determining the density and porosity of the mat. It is preferred that the fibers be of substantially uniform cross section and length such as may be obtained by cutting up extruded wire, drawing wire or turning wire from metal stock. The length of the fibers is preferably to of an inch.

In the form of mat shown in FIG. 4, the porosity of the mat is substantially uniform throughout. In order 'to achieve this, the mat is made with substantially uniform thickness throughout and contains fibers of substantially uniform dimensions. A porosity of 20 to 36 percent is preferred.

I have found that if the porosity of the mat is such that upon aspirating gas and air, a pressure differential Li. of 0.1 inch of water exists between one side and the other of the mat excellent results are achieved.

Although the manner of forming the sintercd fiber mat does not form any part of this invention, one method that can be used is to distribute the previously sized fibers in a uniform layer onto a pallet on which frame 60 is supported and then move the pallet into a furnace which is at a temperature just below the melting temperature of the metal fiber and has an atmosphere of an inert gas such as hydrogen. The pallet is maintained at that temperature and in that atmosphere for a time sufficient to produce the sintered mat. For example, it has been found that a mat inch thick can be produced from T430 stainless steel wherein the fibers have a diameter of 0002-0003 inch if a layer of fibers is sintered for 26 minutes at 2300 degrees Fa renheit in an electric furnace wherein hydrogen is moved at the rate of 1100 cubic feet per hour. The finished mat is relatively rigid and bonded to the frame 60.

I have found that an apparatus such as shown in the drawings and embodying a metal fiber mat in accordance with the invention produces a flame of high temperature not heretofore obtainable by the use of the commercially available ceramic plates. The following examples are typical of the results that have been achieved from fiber mats made from T430 stainless steel having a diameter of 0.0020.003 inch, the length of the fibers being /8 of an inch and using natural gas:

Prcs- Orifice Vcnturi Dcn- Thicksure, Diam- Dlam- Temper- Example sity, ness, Inches ctcr, eter. aturc,

percent inches of inches inches F.

Water The porosity of the fiber mat should be such that a balance is created between incoming air and gas and the open area of the mat to insure total combustion. Inasmuch as the apparatus operates upon the aspirating principle, the porosity should not be such as to restrict the flow so that insufficient air will be aspirated to create total combustion. The porosity should not be too great so that the mixture of gas and air will escape too readily and result in combustion at an area spaced from the outer face of the mat. The porosity should thus be associated with the gas pressure and air pressure.

The thickness of the mat should not be so small that insufficient cooling will result. The thickness must be such that the heat is dissipated before passing entirely through the mat resulting in possible combustion within the casing rather than on the outer surface of the mat.

In the modified form of mat shown in FIG. 5, the mat 39a comprises a substantially uniform overall thickness comprising a relatively thick layer 65 of one porosity and a thin layer 66 of material having a greater porosity. The layer 65 comprises fibers of substantially uniform dimensions that are shorter and have a lesser cross section than the fibers in the layer 66. The thickness of the layer 66 is a fraction of the layer 65. For example, if the overall thickness is /8 of an inch, the layer 66 has a thickness of of an inch.

In use, the mat 39a is positioned such that the layer 66 is adjacent and forms the flame-producing surface.

The mat 39a is made by applying the layers of fibers and then sintering simultaneously the overall mat so that the layers are simultaneously sintered.

Mat 39a can be made of two types of fibers with the fibers constituting the layer 66 being made of a material that is less susceptible to oxidation and is more highly reflective than the fibers constituting the layer 65.

It can thus be seen that I have provided a combustion apparatus which results in higher temperatures, longer life and a novel burner element which can be operated at higher temperatures and is not fragile or easily broken.

I claim:

1. In a high temperature burner apparatus, the combination comprising a casing defining an enclosed chamber, said casing having an opening in a wall thereof, a burner element closing said wall, said element being of substantially uniform thickness and comprising a gaspermeable block of randomly-oriented sintered machined metal fibers, said casing having an inlet through which a mixture of air and combustible gasses may pass to said chamber and through said burner element for combustion on the exterior surface of said burner element, a nozzle at the inlet of said casing through which gas is introduced to said inlet and caused to aspirate air from the vicinity of said nozzle into said inlet, a housing surrounding said casing and having an opening in a wall thereof into which said casing is positioned and extends, the exterior surface of said burner element being exposed to the exterior of said housing, said housing having an inlet through which air may be supplied to the casing and to the interior of the housing, said housing having an outlet, and means within said housing for directing gases from adjacent the burner element to said outlet to draw air from the exterior of said housing into said casing and across the exterior surface of said casing to cool said casing and to said outlet of said housing and to cause a portion of said air to mix with the combustion gases and pass to the interior of said casing.

2. In a high temperature burner apparatus, the combination comprising a casing defining an enclosed chamber, said casing having an opening in a wall thereof, a burner element closing said wall, said element being of substantially uniform thickness and comprising a gas-permeable block of randomly-oriented sintered machined metal fibers, said casing having an inlet through which a mixture of air and combustible gases may pass to said chamber and through said burner element for combustion on the exterior surface of said burner element, a nozzle at the inlet of said casing through which gas is introduced to said inlet and caused to aspirate air from the vicinity of said nozzle into said inlet, the porosity of said burner element being such that the difference in pressure between one side of the burner element and the other is less than 0.1 of an inch of water under operating conditions and rates of flow of said air-gas mixture, a housing surrounding said casing and having an opening in a wall thereof into which said casing is positioned and extends, the exterior surface of said burner element being exposed to the exterior of said housing, said housing having an inlet through which air may be supplied to the casing and to the interior of the housing, said housing having an outlet, and means within said housing for directing gases from adjacent the burner element to said outlet to draw air from the exterior of said housing into said casing and across the exterior surface of said casing to thereby cool said casing and pass to the outlet of said housing and to cause a portion of said air to mix with the combustion gases and pass to the interior of said casing.

3. In a high temperature burner apparatus, the combination comprising a casing defining an enclosed chamber, said casing having an opening in a wall thereof, a burner element closing said wall, said element being of substantially uniform thickness and comprising a gaspermeable block of randomly-oriented sintered machined metal fibers, said block having a porosity of 20 to 36 per cent, said casing having an inlet through which a mixture of air and combustible gases may pass to said chamber and through said burner element for combustion on the exterior surface of said burner element, a nozzle at the inlet of said casing through which gas is introduced to said inlet and caused to aspirate air from the vicinity of said nozzle into said inlet, a housing surrounding said casing and having an opening in a wall thereof into which said casing is positioned and extends, the external surface of said burner element being exposed to the exterior of said housing, said housing having an inlet through which air may be supplied to the casing and to the interior of the housing, said housing having an outlet, and means within said housing for directing gases from adjacent the burner element to said outlet to draw air from the exterior of said housing into said casing and across the exterior surface of said casing to thereby cool said casing and pass to the outlet of said housing and to cause a portion of said air to mix with the combustion gases and pass to the interior of said casing.

4. In a high temperature burner apparatus, the combination comprising a casing defining an enclosed chamber, said casing having an opening in a wall thereof, a burner element closing said wall, said element being a gas permeable, rigid block of substantially uniform thickness formed of randomly-oriented sintered machined metal fibers, said block including a layer adjacent the ex ternal surface thereof of a material having a greater thermal resistance than the remainder of the mat, said casing having an inlet through which a mixture'of air and combustible gases may pass to said chamber and through said burner element for combustion on the exterior surface of said burner element, a nozzle at the inlet of said casing through which gas is introduced to said inlet and caused to aspirate air from the vicinity of said nozzle into said inlet, a housing surrounding said casing and having an opening in a wall thereof into which said casing is positioned and extends, the external surface of said burner element being exposed to the exterior of said housing, said housing having an inlet through which air may be supplied to the casing and to the interior of the housing, said housing having an outlet, and means within said housing for directing gases from adjacent the burner element to said outlet to draw air from the exterior of said housing into said casing and across the exterior surface of said casing to thereby cool said casing and pass to the outlet of said housing and to cause a portion of said air to mix with the combustion gases and pass to the interior of said casing.

5. In combination with an air inspirating type gas burner having a wall with an outlet opening therein, a burner element mounted on said burner over the opening in the wall thereof comprising a rigid gas permeable mat of sintered machined metal fibers randomly oriented and of a size, length and distribution to provide a predetermined pressure differential between one side of the mat and the other under operation conditions and rates of flow when a mixture of air and gas introduced into the gas burner is inspirated through the mat, a metal rim positioned about the periphery of said sintered metal fiber burner mat, said fibers being sintered to said metal rim, and means for removably mounting said metal rim on said gas burner for retaining the burner mat in position thereon.

References Cited by the Examiner UNITED STATES PATENTS 1,113,174 10/14 Lucke et al. 158-99 1,256,301 2/18 Ellis 158--99 1,308,364 7/19 Lucke 158-99 1,567,691 12/25 Wiederhold.

2,518,997 8/50 Powers 49-77.5 X 2,742,437 4/56 Houdry.

2,978,323 4/61 Schmeckenb'echer 75-211 3,027,935 4/62 Sobole 158--99 3,029,802 4/62 Webster 15896 X 3,119,439 1/64 Weiss 158--99 FOREIGN PATENTS 1,128,667 8/56 France. 1,228,433 3/ 60 France.

815,100 6/59 Great Britain.

JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, JR., MEYER PERLIN,

Examiners.

Claims

1. IN A HIGH TEMPERATURE BURNER APPARATUS, THE COMBINATION COMPRISING A CASING DEFINING AN ENCLOSED CHAMBER, SAID CASING HAVING AN OPENING IN A WALL THEREOF, A BURNER ELEMENT CLOSING SAID WALL, SAID ELEMENT BEING OF SUBSTANTIALLY UNIFORM THICKNESS AND COMPRISING A GASPERMEABLE BLOCK OF RAMDOMLY-ORIENTED SINTERED MACHINED METAL FIBERS, SAID CASING HAVING AN INLET THROUGH WHICH A MIXTURE OF AIR AND COMBUSTIBLE GASSES MAY PASS TO SAID CHAMBER AND THROUGH SAID BURNER ELEMENT FOR COMBUSTION ON THE EXTERIOR SURFACE OF SAID BURNER ELEMENT, A NOZZLE AT THE INLET AND CAUSED THROUGH WHICH GAS IS INTRODUCED TO SAID INLET AND CAUSED TO ASPIRATE AIR FROM THE VICINITY OF SAID NOZZLE INTO SAID INLET, A HOUSING SURROUNDING SAID CASING AND HAVING AN OPENING IN A WALL THEREOF INTO WHICH SAID CASING IS POSITIONED AND EXTENDS, THE EXTERIOR SURFACE OF SAID BURNER ELEMENT BEING EXPOSED TO THE EXTERIOR OF SAID HOUSING, SAID HOUSING HAVING AN INLET THROUGH WHICH AIR MAY BE SUPPLIED TO THE CASING AND TO THE INTERIOR OF THE HOUSING, SAID HOUSING HAVING AN OUTLET, AND MEANS WITHIN SAID HOUSING FOR DIRECTING GASES FROM ADJACENT THE BURNER ELEMENT TO SAID OUTLET TO DRAW AIR FROM THE EXTERIOR OF SAID HOUSING INTO SAID CASING AND ACROSS THE EXTERIOR SURFACE OF SAID CASING TO COOL SAID CASING AND TO SAID OUTLET OF SAID HOUSING AND TO CAUSE A PORTION OF SAID AIR TO MIX WITH THE COMBUSTION GASES AND PASS TO THE INTERIOR OF SAID CASING.