US 3809525 A
The invention relates to a flat-flame burner in which the special geometrical configuration of the burner components for introducing the fuel and the combustion air ensure proper mixing thereof and the required geometrical shape of the flames over a wide range of operating conditions.
Description (OCR text may contain errors)
United States Patent 1191 Wang et a]. May 7, 1974 1 FLAT-FLAME BURNER UTILIZING HEAVY  Field of Search 431/ 182-184, LIQUID FUELS I 431/187, 353; 239/402-406  Inventors: Robert Wang,
Saint-Germain-en-Laye, both of;  References Cted Jean-Marie Pariel, UNITED STATES PATENTS Saim-Gflmain-En-Laye, h of 3,748,087 7 1973 Shular 431/182 France  Assignee: Societe Anonyme Heurtey and Elf Union, Paris, France  Filed: Feb. 20, 1973  App]. No.: 333,796
 Foreign Application Priority Data Feb. 23, 1972 France 72.06075  US. Cl ..'431/353, 431/182, 239/403  Int. Cl. F23d 15/02 Primary Examiner-Carroll B. Dority, Jr. Attorney, Agent, or Firm-Murray Schaffer  I ABSTRACT The invention relates to a flat-flame burner in which the special geometrical configuration of the burner I components for introducing the fuel and the combustion air ensure proper mixing thereof and the required geometrical shape of the flames over a wide range of operating conditions.
4 Claims, 2 Drawing Figures 1 FLAT-FLAME BURNER UTILIZING HEAVY LIQUID FUELS The present invention relates to a flat-flame burner utilizing liquid fuels and has more particularly for its flame to the furnace wall by convection is restored by this wall by radiation and is transmitted to the items to be annealed in the furnace.
Prior art wall flame" burners can operate only on gas or domestic fuel, and it would obviously be most useful for users to have burners capable likewise of operating on fuel-oil and especially heavy fuel-oil.
it is an object of the present invention to provide a structure for a liquid fuel burner of the abovementioned kind capable of utilizing heavy liquid fuels.
Generally speaking, operation of the aforementioned kind of burner with a flat-flame requires a special geometrical configuration of the fuel and combustion-airadmitting components. Such configuration must ensure not only proper mixing of the fuel and the oxidant but also the required geometrical shape of the flame over a wide range of operating conditions.
in the paticular case of liquid fuel burners, the above requirements are particularly stringent since the geometry of fuel injection into the divergent burner tunnel must be continuously ensured. Hence protracted fouling (due to coking for instance) of the burner tip must be avoided at all costs since this could modify the angle of fuel injection into the tunnel and thereby cause a change in the geometrical shape of the flame.
Further, the position of the injector must be so chosen as to ensure absolute cleanness of the burner tunnel in operation.
A flat-flame burner according to this invention for heavy liquid fuels, comprising a cylindrical body coaxially surrounding a fuel and primary air feeding stick terminating in an injector, a divergent tunnel downstream of the injector, said body being further provided with a secondary air inlet opening in the annular cornpartment bounded by said bodyand said stick, and further means being provided for rotating said secondary air before releasing it through an annular slit surrounding the burner tip, is characterized in that said injector includes a needle-valve along which the liquid fuel flows and at the end of which it turns into droplets, said needle-valve being surrounded by a diffuser having helicoid primary air inlet passages for atomizing said droplets, the air/fuel suspension being thereafter directed towards an orifice which is formed in a disc and which is shaped as a convergent nozzle terminating in a rounded edge which joins the convergent portion of the nozzle to that face which lies in a plane perpendicular to the burner axis or very slightly inclined relative to said plane.
The description which follows with reference to the accompanying non-limitative exemplary drawingwill give a clear understanding of how the invention can be carried into practice.
' In the drawing:
FIG. 1 is a longitudinal sectional view of a flat-flame burner; and
FIG. 2 is a longitudinal sectional view of the injector built into the burner of FIG. 1.
Referring first to FIG. 1, there is shown thereon a flat-flame burner which includes a burner body 1. Inside this body, coaxially therewith, is a fuel input stick 2 which is formed with primary air channelling means (not shown in FIG. 1). Stick 2 terminates in an injector 3 which will be described in greater detail hereinafter. The body 1 is formed with a secondary air opening 4 provided with a diaphragm 5 for swirling the secondary air. This secondary air is discharged through an annular slit 6 surrounding the burner tip. The compound consisting of the burner body, the fuel stick, the injector and the secondary air distributor is fixed to a gun 7 which extends said compound and is itself fixed to-the burner unit 8 which is formed with a divergent tunnel 9 therein.
The injector will now be described in detail with ref erence to FlG. 2. Screwed into the end of fuel stick 2 is a burner tip 10 onto which is screwed .a tip nut 11. into the front face of nut 11 is set a disc 12 made of a material having refractory properties (e.g. steel or ceramics) and having moderate heat conducting properties whereby to obtain a high temperature on the flame side. The fuel stick includes a central fuel-feed duct 13 which is surrounded by a primary air-feed duct 14. Secured by ribs 15 at the end of duct 13, positioned coaxially with the latter, is a needle-valve 16. The walls of duct 13 surrounding said needle-valve form a diffuser having helicoid passages 17 formed therethrough. The disc 12 has a central hole therein to form a convergent 18 terminating in a flared portion which blends the convergent portion with the front face of the disc. This face is shown as being flat and perpendicular to the burner axis in FIG. 2 but could alternatively by formed by a concave or convex cone having a very large apex angle. Alternatively again, the hole 18 could be made very short and consist merely of a profiled hole with flared upstream and downstream portions.
The theory of operation of a burner as hereinbefore described is as follows: a
The liquid fuel flowing along needle-valve 16 forms droplets at the end thereof and these droplets are atomized by the jet of primary air swirling about the needlevalve and delivered through helicoid passages 17. The air/fuel suspension formed thus is thereafter directed towards convergent l8, and upon issuing therefrom is mixed with the eddying secondary air escaping through slit 6. The position of the injector in the burner tunnel is so chosen that the external envelope of the jet of atomized liquid fuel lies close to the tangent to the divergent and flared portion 9 of the tunnel, the jet forming an aperture angle of close upon 40.
What we claim is:
1. A flat-flame burner for heavy liquid fuels, comprising a cylindrical body coaxially surrounding a primary air and fuel feeding stick terminating in an injector, a divergent tunnel downstream of the injector, said body being furthermore provided with a secondary air feeding opening in the annular compartment bounded by said body and said stick, and means being further provided for rotating said secondary air before it is re-' tion which blends the convergent nozzle portion with the disc face, which face lies ina plane perpendicular to the burner axis or very slightly inclined thereto.
2. A burner according to claim 1, characterized in that said orifice in said disc forming the burner tip is a very short profiled hole which is flared at either end.
3. A burner according to either preceding claim, characterized in that said disc is made of a refractory material which is a poor heat conductor.
4. A burner according to claim 1, characterized in that said injector is disposed in the burner tunnel so that the external envelope of the jet of atomized liquid fuel lies close to the tangent to the divergent and flared portion of the tunnel, the jet forming an aperture angle of close on 40.