US3029866A - Radiating burner - Google Patents

Description

April 17, 1962 G. HONGER 3,029,866

RADI'ATING BURNER Filed April 3, 1956 2 Sheets-Sheet 1 INVENTOR uido Hbn er BY ATTORNEY April 17, 1962 G. HONGER 3,029,866

RADIATINGBURNER Filed April 3, 1956 2 Sheets-Sheet 2 flMM W ATTO R N EY tent 3,929,866 Patented Apr. 17, 1962 zerland Filed Apr. 3, 1956, Ser. No. 575,873 Claims priority, application Switzerland Apr. 15, 1955 2 Claims. (Cl. 158--114) The present invention relates to a radiating or incandescent burner, preferably but not exclusively to a large area radiating burner with at least two envelopes pervious to gas, these envelopes forming the external diaphragm or delimitation of the burner. Radiating burners of that type are brought to incandescence in that a mixture of gas and air is sent through the said envelopes and burn in the direct vicinity thereof. With such radiating burners with light gas pervious envelopes such as, for instance, wire nets, a relatively very high specific burner efficiency can be obtained.

One of the most important conditions required in a useful radiation burner of this type is that the mixture of gas and air must leave the external delimitation of the burner at a regular or uniform velocity in order to guarantee a uniform heating of the gas-pervious envelopes and a suflicient safety against back-lighting. Experience has proved that these conditions can only be fulfilled with great diiliculty and by applying utmost care. It will easily be understood that these difficulties increase with increasing burner area.

Since the gas-pervious envelopes have a relatively very small resistance to flow, the difiicult condition of obtaining a uniform flow pressure on all spots immediately inside the gas-pervious envelopes must be fulfilled. However, the small resistance to flow of the gas-pervious envelopes otfers the great advantage that relatively large quantities of primary air can be sucked in, resulting in a more complete combustion in close proximity to the external delimitation of the burner and, therefore, in a higher efficiency. On the other hand, this advantage must not be lost by equalizing and/or distributing systems having high flow resistance in the mixing tube and the burner.

However, even if the above-mentioned conditions are fulfilled, undesired back-lighting of the burner can only be prevented with absolute safety if the envelopes consisting, for instance, of fine wire netting are held at a minimum distance from each other over the whole burner area. It is understood that with large area burners and fine envelopes this condition cannot be fulfilled without special precautions. n the contrary, the envelopes will touch each other on some spots distributed at random over the whole gas outlet area of the burner, while on all the remaining places the envelopes lie at a'more or less large distance from each other.

The area of the gas-pervious envelopes may be subdivided into zones by supporting the envelopes along the zone boundaries from the inside, for instance, by means of spanning supports. Considering the relatively small distance between two adjacent zone boundaries along which the envelopes are approached to or contact each other, the envelopes can be held at the most suitable distance from each other so that, under normal service conditions, back-firing of the flame cannot occur.

In order to obtain a uniform distribution of the combustible mixture over the whole burner area another object of the invention resides in giving the mixing tube a flat cross section, into which the gas can be fed at least approximately in a uniform distribution over the whole area of the mixing tube intake. The gas can preferably be supplied through a row of individual nozzles arranged side by side or, if desired, through a slot extending at least approximately over the entire length of the mixing tube inlet area. Inside the external delimitation of the radiating burner according to the invention at least one equalizing chamber may preferably be provided, this chamber being separated from the mixing tube by a perforated partition wall or walls. Experience has proven that such a partition wall is of great importance for a reliable working of the burner and that it must be built in different ways in dependence on the gas quality and the gas pressure used.

The perforated partition wall serves the further important purpose of preventing as far as possible heat radiationg from the glowing envelopes from reaching the mixing tube, and for this reason the partition wall is preferably made ofhighly reflective material such as aluminum sheet, for instance. This measure is especially important in large burners where, due to the heating of the gas-air mixture in the mixing tube and the gas extension and gas acceleration caused thereby in the mixing tube, the injector elfect at a given gas jet energy can be impaired very considerably, so that, by such a heating in the mixing tube, a flow in the direction towards the gas nozzle instead of the direction towards the burner outlet may occur under certain circumstances. By the reflecting property of the partition wall such a heating is to a large extent restricted to the equalizing chamber which may have a relatively small volume so that the abovementioned decrease of the mixing tube efiect cannot occur.

The invention also relates to an apparatus for heating, by means of a burner according to the invention, cooking utensils, baking spaces or stoves, heaters for liquids or fluids of all kinds, apparatuses for room heating, implements, tools or the. like and other objects or mediums to be heated by means of a combustible mixture such as a gas-air mixture for instance.

The accompanying drawings illustrate, by Way of examples, some embodiments of the invention.

FIG. 1 is a perspectiveview of a radiating burner according to the invention.

FIGS. 2 and 3, show a longitudinal section and a cross section respectively of the burner illustrated in FIG. 1.

FIGS. 4 and 5 are a longitudinal section and a cross section respectively of another radiating burner according to the invention.

The radiating burner shown in FIGS. 1 and 2 has a parallel piped-shaped or similarly shaped burner body 21 open at one side and provided with a flange 29. Two or more superposed gas-pervious envelopes in the shape of wire nets 31 made from highly heat-resisting material are ,held or clamped between the flange 29 and a rectangular frame 30 screwed to flange 29. The mesh aperture and the wire thickness of the wire nets or grids 31 depend on the kind of gas used and may for butane, for instance, be relativelylarge sothat setting or clamping the wire nets 31 along the flange 2s, i.e., along the border of the burner body 21 is suflicient to hold the Wire nets 31.

Butane, for instance, has a very high heating value and the speed of propagation of the combustion in a butane; air mixture is relatively small. Therefore, in a burner for use with butane or gases with similar properties care must be taken that the outlet velocity of the combustible mixture is relatively small. This is obtained by using wire nets 31 with a relatively large mesh aperture so that the combustible mixture flows relatively slowly through the large openings of the wide-meshed nets 31.

It is understood that the burner illustrated in FIGS. 1 and 2 could also be used in another service position than that shown as, for instance, with the combustible mixture fiowing towards the top, i.e., with the envelopes 31 turned upwards. The body 21 may be mounted by means of two frames 22 and 23 for instance on theceiling or lid 24 of a stove, for instance a grill stove suitable for heat treatment by means of infrared radiation. Especially, the frame 23 may consist of a heatinsulating and heat-proof material in order to reduce as much as possible any heat transmission from the burner to the ceiling 24 of the stove space. A mixing tube 25 with round cross section and with an ejector 26 made, for instance, of sheet metal enters the burner body 21. The gas is fed to the mixing tube 25 by a nozzle 27 and is mixed with the sucked-in air in the mixing tube. A perforated plate or partition wall 28 is fixed to the burner body 2t.

The presence and the structure of the partition wall 28 are of greatest importance for a reliable operation of the burner.

The partition wall 28 is preferably made of a highly reflective material, such as aluminium sheet for instance, so that the heat which is radiated backwards from the glowing diaphragms or wire envelopes 31 is reflected by the partition wall 28.

It is of importance that the discharge direction of the gas from the nozzle 27 is perpendicular or at least approximately perpendicular to the discharge direction of the gas-air mixture from the envelopes 31 and that the deflection of the gas stream is not obtained by means of guide members or other flow restricting or battling means. In this way a suitable whirling or turbulance and intimate mixture of the gas with the air sucked-in in the mixing tube chamber 25 is obtained on the one hand, and, on the other hand, the outflow velocity of the gas-air mixture through the external burner delimitation 31 cannot be influenced in places by the gas jets entering locally in the mixing tube.

In place of a perforated plate or sheet 28 another gas-pervious means such as, for instance, wire netting with a suitable mesh aperture or the like could be used as a partition wall.

A grate with perpendicular longitudinal ribs 32 and transverse ribs 33 is inserted between the wire nets 31 and the perforated plate 28. This grate may either be connected with he plate 28 for instance by means of welding or screwing, or may be held loosely between the plate 28 and the wire nets 3 As shown in FIGS. 1 to 3, the lower edges of the ribs 32 and 33 rest on the inner wire net 31 and are curved in such a way that the wire nets 31 are convexly curved or rounded outwardly and, therefore, rest under a certain pressure on the lower rib edges all over the length thereof. This offers the advantage of the wire nets or envelopes 31 being under a certain stress and, along the places of support on the ribs, contacting each other or being at least approached to each other to a minimum distance, so that also on the remaining places, i.e. over the entire burner area the wire nets are held at a small distance from each other, whereby back-lighting is practically impossible. The area of the wire nets 31 is subdivided by the ribs 32, 33 into zones along the boundaries of which the envelopes 31 are approached to each other or even in contact with each other. Consequently, the nets or envelopes 31 are in contact with each other in some places, while they are maintained at a small distance in the remaining places of the burner area.

The combustible gas-air mixture produced in the mixing tube is distributed above the perforated plate 28 in the body 21 and flows through the perforated plate 28 to the compartments between the ribs 32 and and 33 and thence through the wire nets 31. The combustible mixture normally burns immediately after the exit from the outer wire net 31 and heats the latter up to red heat. Due to the supporting and spanning of the two or more superposed wire nets 3!. by means of the ribs 32 and 33 the nets 31 are held over the burner area at such a suitable distance from each other that any back-lighting of the combustion to places lying between the nets 31 is definitely avoided. Should nevertheless back-light occur in a zone due to any operating trouble, any lateral propagation of the combustion between the nets 31 from one zone to another is prevented by the fact that, between the zones, the nets 31 are supported on the edges of the ribs 32 and 33. Any possible back-lighting of the flame to between the nets 31, which may for instance occur due to air currents locally acting onto the burner area, remains in any case restricted to one single zone, so that, on the one hand, the danger of further back-lighting to the burner space inside the nets and to the mixing tube is practically eliminated, and, on the other hand, the displacement of the combustion back to the outside of the outer wire net is favoured. The subdivision of the space above the wire nets 31 by means of the ribs 32 and 33 favours the uniform distribution of the gas flow all over the burner area and thereby furthers a uniform temperature distribution on the radiating area and the safety of the burner against back-lighting.

In FIGS. 1 to 3 the height of the longitudinal ribs 32 is smaller than the height of the transverse ribs 33 so that every four compartments lying side by side in transverse direction are in connection with one another immediately below the perforated plate 28 so that a uniform pressure distribution in these compartments is obtained. Due to this connection it is, furthermore, not absolutely necessary that the mixture quantities flowing through the perforated plate 28 into these compartments be absolutely equal.

The gate consisting of the ribs 32 and 33 may preferably be enameled or coated with any other heat-proof protecting layer in order to avoid, in particular, scaling or corrosion of the rib edges supporting the wire nets 31 and, at the same time, to keep heat transmission from the wire nets to the ribs as small as possible.

it is understood that the grate consisting of the ribs 32 and 33 may be replaced by any other supporting structure supporting the wire nets 31 along continuous lines and thereby limiting the said zones on the burner area. The shape of these zones may also be other than rectangular, such as for instance, have more than four corners, the wire nets being then supported by a honeycombed supporting structure.

The zone boundaries may also be obtained in another way such as by welding, riveting or cementing in a heat-proof manner the wire nets together along uninterrupted lines so that a supporting structure may be omitted and the wire nets may possibly lie in planes.

In the radiating burner as illustrated in FIGS. 1 to 3 the wire nets 31 may be spanned by the weight of the grate 32, 33 loosely inserted between the nets 31 and the perforated plate 28, so that they lie close to each other all over the burner area. If desired, the spanning effect may even be increased by special spanning or tightening means.

FIGS. 4 and 5 illustrate a radiating burner having such a tightening device while, for the rest; the burner is built in a similar way as the one shown in FIGS. 1 to 3. Therefore, corresponding parts in FIGS. 4 and 5 need no further description and are designated by the same reference characters as in FIGS. 1 to 3.

in order to obtain an unyieldable and reliable anchoring of the two or more wire nets 31 their marginal portions are turned around the flanges 29 of the burner body 21 to the top side of the flange. The perforated plate 28 is connected with an angle piece frame 35 going around the entire circumference of the plate 28. The ribs 32 and 33 of FIGS. 1 to 3 are replaced by longitudinal ribs each with a straight middle portion 37 and two offset end portions 33 running to the corners of a longitudinal side of the frame 35, and flat transverse ribs 39 connected with the longitudinal ribs, the longitudinal and transverse ribs supporting the wire nets 31 only by means of lugs 40 so that cooling of the wire nets in practically omitted. Recesses 41 pressed into the burner body 21 have threads in their bottom, which engage tightening screws 42 cooperating with the frame 35. By tightening these screws 42 the frame 35 together with the perforated plate 28 and the supporting ribs 37, 38, 39 can be pressed downwards onto the wire nets 31 in order to tighten or stretch the latter. As illustrated in FIGS. 4 and 5 the entire burner area is slightly curved so that the wire nets 31 under the tightening force applied to them are in contact in some places and slightly spaced from each other in the remaining places as set out above with reference to FIGS. 3 to 5 in order to safely prevent any backlighting of the combustion to behind the wire nets 31.

Instead of the means described and shown in the above examples for holding the burner envelopes at a sufliciently small distance from each other, other means could be provided for the same purpose. The wire nets or other envelopes could, for instance, be fixed or clamped fast in such a way that, on operation of the burner, they are firmly pressed or tightened together by the thermal expansion of the fixing or clamping means. On using fairly strong envelopes at least one of them could be precurved to a convex shape in such a way that it can serve as a support or carrier for at least one external envelope spanned or stretched upon it. The wire nets or other gaspervious envelopes could also be connected with each other in places by a slight resistance welding, so that spe cial tightening means for the envelopes can be omitted.

The radiating burner according to the invention may, for instance, be used as a grill burner, a heat radiator for drying furnaces or kilns and for warming heating plates of cooking stoves for instance. The radiating burner may, if desired, also be used for direct warming of heaters and cooking utensils of all kind. Thereby a substantially improved efiiciency than with usual flame-heating can be obtained in that the heat transfer does not only take place by the contact of the surface to be heated with the burned gasbut also to a large extent by heat radiation.

The invention also concerns a method for heating, by means of a burner according to the invention, cooking utensils, baking spaces or stoves, heaters for liquids or fluids of all kinds, apparatuses for room heating, gasheatcd implements, tools or the like and other objects and mediums to be heated by means of a combustible mixture such as a mixture of gas and air for instance. This method is distinguished in that a radiating burner, such as, for instance, one of the embodiments described above with reference to the drawings, is heated by means of a combustible mixture, and the cooking utensil, the heater or other object or medium to be warmed is heated by means of the heat delivered by the radiating burner, especially by radiant heat. Experience with this novel method has proved that, due to the high proportion of the thermal radiation emanated by the radiating burner compared with the well-known direct heating of cooking utensils and heaters of all kinds by the burned gases, not only a substantially quicker heating up becomes possible but also the efficiency of the plant is considerably higher than with the afore-mentioned well-known heating manner. The radiating burner can be arranged directly opposite to a wall of the cooking vessel, heater or other object to be heated. However, with cooking vessels or the like reliable operation of the radiating burner may possibly be impaired by material overflowing from the vessel. To remedy this inconvenience a plate of metal or of any other suitable heat-conducting material may be disposed between the radiating burner and the cooking vessel or the like, the plate being heated by the radiating burner and transferring the heat received in this way to the cooking vessel or other object. In order to obtain a rapid heat transfer through the plate, a relatively thin, diaphragm-like plate of chromium steel for instance may be provided and be mounted on a stretching or tightening device such as a frame for instance lying within the heating range of the radiating burner so that, on operation the stretching or tightening device is heated and thereby expanded and thereby stretches the plate so that deformation of the plate due to heat influence and to the load by the cooking vessel or the like is avoided.-

While the invention has been described and illustrated with reference to specific embodiments and performances thereof it will be understood that other embodiments and performances may be resorted to without departing from the invention.

What I claim is:

l. A radiating burner having a large area combustion Zone in which at least one of a number of flexible wire nets constituting the external diaphragm of the burner is heated to incandescence by a combustible mixture flowing through and burningin close proximity of the burner diaphragm, comprising nets made of thin flexible wire material, a burner body having a burner opening covered with the said nets which define the external diaphragm, means for clamping the periphery of the diaphragm to the burner body, a grate within the burner body consisting of ribs arranged substantially perpendicular to and contacting the said external diaphragm, the diaphragm contacting portion of said grate having a slightly convex shape, and means for displacing the grate in a direction substantially perpendicular to the plane of the burner for pressing the said grate against the said nets of the external burner diaphragm to tighten and stretch the nets so they are pressed against each other and held in contact where supported by said ribs and held at a small distance from each other between such ribs.

2. A radiating burner having a large area combustion zone, comprising at least two flexible wire mesh grids constituting the external diaphram of the burner arranged so that at least one of such grids will be heated to incandescence by a combustible mixture flowing through and burning in close proximity of said burner diaphragm, a burner body having a burner opening covered with the external diaphragm, a fiat flange portion surrounding the burner opening and arranged substantially in a common plane with the burner opening, clamping means co-acting with said flange portion in a plane coinciding with said plane of the burner opening to firmly clamp the periphery of the said grids to said flange portion so that the grids are firmly anchored against removal therefrom by pulling forces, a perforated partition disposed across a medial portion of said burner body, and grate means Within the burner body abutting against said partition and extending beyond the plane of said burner opening and engaging the diaphragm at a plurality of spaced positions, the diaphragm contacting portion of said grate being slightly convex'to set up pulling stresses in the said grids when the clamping means is tightened and the said grids thereby stretched and held in contacting relationship with each other where engaged by the grate means and at a small distance in the remaining places due to the stretching thereof and to the said clamp means fastening the grids to the flange portion.

References Cited in the file of this patent UNITED STATES PATENTS 731,384 Newbold June 16, 1903 933,554 Sanford May 30, 1911 1,237,780 Hicks Aug. 21, 1917 1,572,975 Van Meter Feb. 16, 1926 1,852,443 Anderson Apr. 5, 1932 FOREIGN PATENTS 494,087 Great Britain Oct. 17, 1938

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