US3806307A

US3806307A - Burners

Info

Publication number: US3806307A
Application number: US00267621A
Authority: US
Inventors: P Ware
Original assignee: Dunlop Ltd
Current assignee: LANEMARK Ltd 32/34 QUEEN'S RD COVENTRY CV1 3FJ
Priority date: 1971-07-03
Filing date: 1972-06-29
Publication date: 1974-04-23
Anticipated expiration: 1991-04-23
Also published as: DE2232639A1; FR2145217A5; CA955515A; NL7209310A; BE785805A; AU4411872A

Abstract

A burner element for fluid fuels provided with a plurality of tubular combustion air passages which extend through a fuel supply gallery, the fuel gallery being provided with a number of fuel outlet passages and a surface member in the form of a sheet of metal material arranged to extend ajacent one end of the combustion air passages, the surface member being provided with a plurality of tubular projections corresponding with the plurality of combustion air passages, the tubular projections being arranged to extend outwardly from the element, of which the following is a specification.

Description

United States Patent [191 Ware Apr. 23, 1974 l BURNERS l,968,395 7/1934 Henson 431 353 7, [75] Inventor: Peter G. Ware, Rugby, England 394,545 7 1905 Phlllips 431 354 s g Dunlop Limited, London, England Primary Examiner-Carroll BIDority, Jr.

[22] F June 29 7 Attorney, Agent, or Firm-Stevens, Davis, Miller &

Appl. No.: 267,621

Foreign Application Priority Data July 3, 1971 Great Britain 31272 71 r [52] us. Cl... 431/353, 431/354, 239/4255, 239/557 [51] Int. Cl. F23d 13/02 [58] Field of Search 431/353, 354; 239/4245, 239/4255, 557, 424

5 1 1 References Cited UNITED-STATES PATENTS 1,703,684 2 1929 Morley...... 239/4245 621,248 3/1899 Heller 1. 239/424 7 6,494 8/1904 Crone 239/424 Mosher [5 7] ABSTRACT A burner element for fluid fuels provided with a plurality of tubular combustion air passages which extend through a fuel supply gallery, the fuel gallery being provided with a number of fuel outlet passages and a surface member in the form of a sheet of metal material arranged to extend ajacentone end of the combustion air passages, the surface member being provided with a plurality of tubular projections corresponding with the plurality of combustion air passages, the tubular projections being arranged to extend outwardly from the element, of which the following is a specification.

7 Claims, 5 Drawing Figures l PMEMTEBAPR 23 m4 SHEET 3 OF 3 i-EQSOBLBOT hot.

BURNERS through a fuel supply gallery so that the emission of fuel into the combustion zone of the burner element can be arranged to entrain combustion air.

In one such burner element construction of this kind I the fuel supply gallery is formed between two sheet or strip members arranged in a superimposed spaced relationship. The combustion air passages are defined by forming corresponding pairs of apertures in the two sheet or strip members and forming the material surrounding at least one of the apertures of each pair into a tubular projection which is arranged to extend into interfitting relationship with either the other aperture of thepair or a tubular projection extending from the material surrounding the other aperture of the pair. Fuel outlet passages are provided in the fuel supply gallery to enable fuel to flow from the gallery into the air flow through the combustion air passages. Burner elements of this kind are described in British Pat. No. 1,325,443 and U. S. Pat. No. 3,648,665.

In the operation of burner elements of the kind described in the preceding paragraph it may be necessary to limit the heat output rate of the element to prevent lift off of the flames. The phenomenon of ?lift off occurs when the velocity of the gas issuing from the element exceeds the flame velocity of the gas, the base of the flames then rising from the surface of the element so that theflame becomes unstable and subsequently extinguishes itself. a

Alternatively it may be necessary to limit the heat output rate of the burner element in order to prevent the material of the element from becoming excessively Whether it is the phenomenon of lift off" or excessive heating of the element which limits the heat output I rate of. the burner element will depend on the type of fuel being used and on the constructional details of the element. I

One object of the present invention. isto provide an improved burner element for use with liquid or gaseous fuel.

According to one aspect of the present invention a burner element for fluid fuels comprises a fuel supply gallery provided with a plurality of tubular combustion air passages extending therethrough, the fuel supply gallery being provided with a number of fuel outlet passages and a surface member in the form of a sheet of metal material arranged to extend adjacent one end of :the combustion air passages, the surface member being provided with a plurality of tubular projections corresponding with the plurality of combustion air passages, the tubular projections being arranged to extend outwardly from the element. I a

The surface member may be arranged adjacent the lower or inlet ends of the combustion air passages so as to reduce the temperature of the element .by improving the rate of heat transfer between the element and the combustion air flowing into thecombustion air passages. Alternatively the surface member may be arranged adjacent the upper or outlet ends of the combustion air passages so as to improve the flame stability of the element, and raise the heat output rate at which the burner element can operate without the occurrance of lift off. If desired a surface member may be provided adjacent both'ends of the combustion air passages in orderto' derive the benefits associated with both these arrangements.

According to another aspect of the present invention a burner element for fluid fuels comprises an upper and a lower sheet member arranged in spaced superimposed relationship and sealed around their edges to form a fuel supply gallerytherebetween, the members being provided with a plurality of apertures arranged in pairs, each pair comprisingone aperture in each member and the apertures of each pair being superimposed, at least one member being of sheet metal material and the sheet metal surrounding one aperture of each pair extending as a tubular projection into association with the material surrounding the other aperture of the pair thus defining a plurality of combustion air passages extending through the gallery, the areas of at least one member around the said apertures being arranged to permit fuel to pass from the fuel supply gallery, a surface member of sheet metal. material being arranged adjacent one sheet member, the surface memberbeing provided with a plurality of tubular projections corresponding with the combustion air passages and arranged to extend outwardly from the element.

Four embodiments of the invention will now be described by way of example with reference to FIGS. 1. to 4 of the accompanying drawings in which: I

FIGS. 1 and 2 show cross-sectional views through burner elements in accordance with the present invention;

FIG. 3 is a plan view of a circular rosette-shaped burner element in accordance with the present inventron, I

FIG. 4 is a cross-sectional view on the line X-X of FIG. 3, j I

FIG. 5 is a view similar to FIG. 4 ofa modification of the rosette shaped burner element. I

In a first embodiment of the invention, shown in FIG. 1, a burner element comprises anupper sheet metal member 1 and a lower sheet metal member 2 which are arranged in spaced superimposed relationship and sealed together around their edges so as to, form a fuel supply gallery 3 therebetween. A surface. member 4 is Each combustion air passage isformed by forming a plurality of pairs of apertures in the sheet members,

one aperture of each pair being formedin each sheet member, and then forming the material which surrounds the apertures in the lower sheet member into tubular projections 8 which extend from the lower member towards the upper sheet member and into in terfltting association with correspondingtubular projections 9 which are of slightly larger diameter, and

which extend towards the lower sheet member from the material which surrounds the apertures in the upper.

sheet member. a

Axially extending grooves 6 are broached or otherwise formed on the radially inner surface of each tubuf lar projection 9 of the upper sheet member so that when the projections on the upper and lower sheet are brought into interfitting relationship the grooves form small fuel outlet passages in combination with the projections extending from the lower sheet member. Thus each combustion air passage is provided with a number of fuel outlet passages spaced around its periphery through which fuel can flow from the gallery into the air flow through the combustion air passages during operation of the burner.

The surface member 4, which is substantially identical to the upper sheet member except that the tubular projections 12 are formed without grooves, is spotwelded or otherwise secured to the upper sheet member so that the tubular projections of the surface member correspond with the combustion air passages and extend outwardly from the burner element.

Suitable techniques for forming the tubular projections in the upper and lower sheet members and the surface member and for forming the grooves in the projections extending from the upper sheet member are described in the specification of our previously referred to British and US. Pats.

In operation of the burner element, gas or the vapor of liquid fuel, issues from each of the small fuel outlet passages and entrains combustion air from the associatedcombustion air passage. The fuel and air mixture burns with a diffusion flame in a combustion zone above the surface member, and the tubular projections of the surface member assist in stabilizing the diffusion flame.

The heat output rate of the kind of burner described above is determined by the level of pressure existing within thefu'el gallery. The higher the level of this internal pressure the higher the velocity of the fuel emerging from the fuel outlet passages and the higher the potential heat output rate of the burner.

As previously described, with low flame velocity gases, such as natural gas, lift off occurs when the velocity of the gas issuing from the burner element exceeds the flame velocity of the gas. By arranging the length of the projections extending from the surface member to delay combustion until the velocity of the gas emerging has fallen to a level at which it can burn without lift off a burner element in accordance with the present invention can be arranged to operate at higher levels of internal pressure than a comparable burner element not provided with a surface member.

In a second embodiment of the invention, shown in FIG. 2, a burner element comprises upper and lower sheet members 1 and 2, substantially as described above, arranged in a superimposed spaced relationship to form a fuel supply gallery 3 therebetween and a surface member 10 secured in superimposed relationship with the lower sheet member. The surface member is provided with tubular projections 11 which extend outwardly (i.e., downwardly) from the burner element. The surface member is substantially identical to the lower sheet member, the tubular projections 11 of the surface member being formed without grooves and being of substantially the same diameter as the tubular projections of the lower sheet member. A fuel inlet pipe 5 is connected to the gallery as in the preceding embodiment.

In operation of the burner element, gas or the vapor of liquid fuel, issues from each of the small fuel outlet passages 6 and entrains combustion air, in the manner described in connection with the preceding embodiment, so as to support a diffusion flame in a combustion zone above the surface member. The tubular projections of the surface member assist in conducting heat from the element to the air flowing through the combustion air passages and thereby reduce the temperature of the burner element. A further feature of the surface member is that the tubular projections induce turbulence in the flow of air through the combustion air passages, thereby improving the uniformity of mixing between the fuel and air and increasing the flame stability.

Where the burner operates on a high flame velocity gas, such as a composite gas having a hydrogen content of, for example, 30 per cent or more, the flame tends to sit on the surface of the upper sheet member adjacent the combustion zone except when operating at very high internal pressures associated with a heat output rate which is far in excess of that which would cause the element to overheat. Therefore, in general, the element attains a higher temperature than when operating on a low flame velocity gas at a given heat output rate. The provision of a surface member adjacent the lower sheet'member improves the rate at which heat is conducted away from the upper sheet member, by reducing the temperature of the lower sheet member to which heat is conducted from the upper sheet member. The surface member is cooled by air flowing into the combustion air passages, thus cooling the lower sheet member by conduction.

The arrangement described in the preceding paragraph enables the element to be operated at a higher heat output rate, without causing overheating, than if no surface member were present.

In a third embodiment of the invention, shown in FIGS. 3 and 4, a rosette-shaped burner element comprises a pair of circular sheet metal members 1 and 2 which are secured together in spaced superimposed relationship and sealed around their edges to form a fuel supply gallery 3 therebetween in the manner previously described. Combustion air passages 7 extend through the fuel supply gallery and are each provided with a plurality of axially extending fuel supply passages 6 of the kind previously described. Circular surface members 4 and 10 of sheet metal material, which correspond to the similarly numbered surface members previously described with respect to the two preceding embodiments, are secured to the upper and the lower sheet members, and a fuel inlet pipe 5 is attached to the periphery of the fuel supply gallery.

The four circular sheet metal members are each provided with one central tubular projection and six peripheral tubular projections disposed symmetrically in a circular arrangement relative to the central projection.

Each surface member is secured to a sheet member of the fuel supply gallery by spot welds or other suitable means and the projections of each surface member are of the same diameter as the projections of the adjacent sheet member.

In operation of the burner element, gas or the vapor of liquid fuel, issues from each of the small fuel outlet passages and entrains combustion air, in the manner described in connection with the first embodiment, so as to support a diffusion flame in a combustion zone above the surface member. The tubular projections of the upper surface member assist in stabilizing the diffut and the tubular projections of the lower surface member have the effects, as described in respect of the sec ond embodiment of the invention, of reducing the temperature of the burner element and of inducing turbulence in the air flow so as to improve mixing of the fuel and the air.

A rosette-type burner element of the kind described is capable of providing a high heat output rate compared with known burner elements of an equivalent surface area, and is particularly suitable for use asa modular type unit. Thus, several burner elements of .this kind may be combined readily by, for example,

connecting each to a common gas supply so as to form a composite element capable of giving a range of desired heat output rates. lf desired,]the tubular projections 9 of the upper sheet 1 in FIGS. 3 and 4 can be replaced by reticulated ,foam metal material 20 illustrated in FIG. 5. Reticuvapor of a liquid fuel.

Although in various constructions described above both the sheet members defining the fuel supply gallery are formed from sheet metal, if desired the upper sheet member can be formed wholly or in part from porous foam metal material. Similarly the grooves which form the fuel outlet passages in the constructions described .above can be replaced by an annulus of porous foam metal material surrounding the combustion air passages and through which fuel can flow from the fuel supply gallery. Examples of burner elements which utilize an upper sheet member formed from foam metal and foam metal annulii surrounding the combustion air passages are described in the specification of our previously referred to British and US. Patents.

Similarly, although in the constructions described above the tubular projections of the surface members have been described as a being of the same crosssectional shape and substantially the same size as the tubular projections of the respective adjacent sheet member, this is not essential and numerous variations in the cross-sectional shapes and relative sizes of the projections on the surface members and their respective associated sheet member can be used without departing fromthe principles of the present invention.

Having now described my invention what I claim l. A burner element for fluid fuels comprising a fuel supply gallery provided with a plurality of tubular combustion air passages extending therethrough, the fuel supply gallery being provided with a number of fuel outlet passages intermediate the ends of each combustion air passage anda surfacemember in the form of a sheet of metal material contiguous with the fuel supply gallery, thesurface member being provided with a plurality of tubular projections corresponding with the plurality of combustion air passages, each tubular projection being arrangedto extend outwardly from the burner element in alignment with one of said combustion air passages.

2. A burner element for fluid fuels comprising an upper and a lower sheet member arranged in spaced superimposed relationship and sealed around their edges to form a fuel supply gallery therebetween, the

members being provided with a plurality of apertures arranged in pairs, each pair comprising one aperture in each member and the apertures of each pair being superimposed, at least one member being of sheet metal material and including sheet metal surrounding one aperture of each pair extendingas a tubular projection into association with material surrounding the other aperture of the pair thus defining a plurality of combustion air passages extending through the gallery, the areas of at least one member around the said apertures being arranged to permit fuel to pass from the fuel supply gallery into said air passages, a surface member of sheet metal material being contiguous with the fuel supply gallery, the surface member being provided with a plurality of tubular projections each arranged to extend from one aperture of a respective pair outwardly from the elementas an extension of the combustion air passage defined by said pair.

3. A burner element according to claim 2 wherein the areas around each aperture in the upper sheet member comprise annular inserts of porous foam metal through which the fuel is permitted to pass from the fuelsupply gallery.

, 4. A burner element according to claim 2 wherein the surface member is contiguous with the upper sheet member. I

5. Aburner element according to claim 2 wherein the surface member is contiguous with the lower sheet member.

6. A burner element according to claim 2 provided I spaced, superimposed relationship and sealed around the edges to form a fuel supply gallery therebetween,

the members being provided with a plurality of apertures arranged in pairs, each pair comprising one aperture in each member and the apertures of each pair being superimposed and sheet metal surrounding each aperture extending as a tubular projection into interfitting relationship with a tubular projection surrounding the aperture paired therewith, one of each pair of interfitting projections being provided with a number of axially extending slots circumferentially spaced around said projections and co-operating with the other projection of said pair to form a number of fuel outlet passages circumferentially spaced around each combustion air passage, and a surface member of sheet metal secured in contiguous relationship to one of the gallery forming sheet metal members and having a number of apertures correspondiing to those of said galleryelement.

Claims

1. A burner element for fluid fuels comprising a fuel supply gallery provided with a plurality of tubular combustion air passages extending therethrough, the fuel supply gallery being provided with a number of fuel outlet passages intermediate the ends of each combustion air passage and a surface member in the form of a sheet of metal material contiguous with the fuel supply gallery, the surface member being provided with a plurality of tubular projections corresponding with the plurality of combustion air passages, each tubular projection being arranged to extend outwardly from the burner element in alignment with one of said combustion air passages.

2. A burner element for fluid fuels comprising an upper and a lower sheet member arranged in spaced superimposed relationship and sealed around their edges to form a fuel supply gallery therebetween, the members being provided with a plurality of apertures arranged in pairs, each pair comprising one aperture in each member and the apertures of each pair being superimposed, at least one member being of sheet metal material and including sheet metal surrounding one aperture of each pair extending as a tubular projection into association with material surrounding the other aperture of the pair thus defining a plurality of combustion air passages extending through the gallery, the areas of at least one member around the said apertures being arranged to permit fuel to pass from the fuel supply gallery into said air passages, a surface member of sheet metal material being contiguous with the fuel supply gallery, the surface member being provided with a plurality of tubular projections each arranged to extend from one aperture of a respective pair outwardly from the element as an extension of the combustion air passage defined by said pair.

3. A burner element according to claim 2 wherein the areas around each aperture in the upper sheet member comprise annular inserts of porous foam metal through which the fuel is permitted to pass from the fuel supply gallery.

4. A burner element according to claim 2 wherein the surface member is contiguous with the upper sheet member.

5. A burner element according to claim 2 wherein the surface member is contiguous with the lower sheet member.

6. A burner element according to claim 2 provided with two surface members, one surface member being contiguous with the upper sheet member and the other surface member being contiguous with the lower sheet member.

7. A burner element for fluid fuels comprising an upper and a lower sheet metal member arranged in spaced, superimposed relationship and sealed around the edges to form a fuel supPly gallery therebetween, the members being provided with a plurality of apertures arranged in pairs, each pair comprising one aperture in each member and the apertures of each pair being superimposed and sheet metal surrounding each aperture extending as a tubular projection into interfitting relationship with a tubular projection surrounding the aperture paired therewith, one of each pair of interfitting projections being provided with a number of axially extending slots circumferentially spaced around said projections and co-operating with the other projection of said pair to form a number of fuel outlet passages circumferentially spaced around each combustion air passage, and a surface member of sheet metal secured in contiguous relationship to one of the gallery-forming sheet metal members and having a number of apertures correspondiing to those of said gallery-forming member, each said aperture of the surface member being surrounded by a tubular projection aligned with a respective combustion air passage and extending from the gallery outwardly from the burner element.