US3446439A - Liquid fuel burners - Google Patents

Description

y 1969 1. B. CAMPBELL 3,446,439

- LIQUID FUEL BURNERS Filed Feb. 20. 1967 3,446,439 LIQUID FUEL BURNERS Campbell, Dumbartonshire, Scotland, assignor to Babcock 8: Wilcox, Limited, London,

Iain Brown England, a company of Great Britain Filed Feb. 20, 1967, Ser. No. 618,565 Claims priority, application Great Britain, Feb. 22, 1966, 7,705/ 66 Int. Cl. F23d 13/40, 15/00 US. Cl. 239419.3 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to liquid fuel burners and, more particularly, to a liquid fuel burner arranged to be positioned in an air register which supplies air in a flow substantially parallel to the burner axis, an impellor plate with circumferentially spaced openings is positioned adjacent the burner head to impart a degree of whirl to the combustion air being supplied to an atomized spray of liquid fuel discharged from the burner head.

British patent specification No. 579,591 describes an atomizer comprising a barrel at the end of which is provided a sprayer plate which has an imperforate central part and which is formed with passages of circular crosssection diverging from an inner space adapted to be fed with elastic fluid and directed with their longitudinal axes lying on and spaced around a frustrum of a cone and other passages also of circular cross-section respectively making junctures with the first passages at locations remote from the outlets thereof and extending from an outer space adapted to be fed with liquid fuel.

However, it has been found that, at least in instances in which air is discharged at a high velocity from the register without a pronounced degree of swirl, that upon igniting the atomized spray of liquid fuel from an adjacent burner the resultant flame tends to develop at an appreciable distance from the burner head, which can, at times, be disadvantageous.

According to the present invention there is provided an atomizer head for a liquid fuel burner including mixing chambers distributed around the central axis of the head with their longitudinal axes diverging in the general direction of discharge, each chamber being provided with an inlet duct for liquid fuel and an inlet duct for elastic atomizing fluid arranged to connect with spaces defined by co-axial tubes in a barrel portion of the liquid fuel burner, wherein the atomizer head is formed with a central passage of circular cross-section discharging elastic atomizing fluid along the central axis of the atomizer head.

The provision of a dicharge along the axis of the atomizer head central of the spray cone of atomized liquid fuel tends to assist in the establishment of a stable flame at a burner upon ignition of the spray of atomized fuel from an adjacent burner and also tends to prevent deposition of carbon on the atomizer head during operation.

3,446,439 Patented May 27, 1969 The invention will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a sectional side elevation of an oil burner together with an associated impellor and air register and which shows a portion of the wall of a furnace chamber;

FIGURE 2 is a sectional side elevation of an atomizer head and part of a barrel at the front of the oil burner; and

FIGURE 3 is a front elevation corresponding to FIG- URE 2.

Referring to FIGURE 1, there is shown an oil burner 2 disposed axially of a burner opening 4 in an associated furnace wall 6, the outer end of the opening communicating with an air register 8 provided in an air box 10 mounted on the furnace chamber wall. An impellor 12 is mounted on a distance piece tube 14 adjacent the forward end of the oil burner and is formed with circumferentially spaced openings through which a central portion of the combustion air is admitted to the spray of atomized oil upon discharge thereof from the forward end of the oil burner, the air passing through the impellor 12 being circumferentially deflected by blades of the impellor. The distance piece tube 14 is mounted on a tail piece 16 coupled by a yoke 18 to a rear portion 20 of the oil burner. The tail piece 16 is formed with inlet connections (not shown) communicating respectively with a steam passage 22 and an oil passage 24 in the rear end portion 20. A burner barrel including inner and outer co-axially disposed tubes 26, 28, with the inner tube 26 threaded into the rear end portion 20 and communicating with the steam passage 22 and the outer tube 28 movably sealed to, the rear end portion 20, for example, in a manner similar to that described in British patent specification No. 891,195, and the space intermediate the inner and outer tubes in communication with the oil supply passage 24.

Referring now to FIGURES 2 and 3, an atomizer head 30 of cylindrical form has an internally threaded, central, well portion 32 formed with an annular seat 34 at the rearward end face thereof is screwed onto the forward end of the inner tube 26 to compress a gasket 36 between the annular seat 34 and a complementary seat 38 provided on a collar 40, to form a leak-tight joint. An outer, circumferential, flange 42 on the atomizer head is formed with an annular seat 44 at the rearward face thereof and compresses a gasket 46 against a complementary seat 48 formed on the forward end face of the outer tube 28 by the action of a cap nut 50 co-acting with an external thread on the forward end of the tube 28 and bearing against a shoulder 52 on the atomizer head to form a leak-tight joint between the atomizer head and the outer tube. A frusto-conical surface 54 formed as a chamfer on the front end of the atomizer head is penetrated perpendicu larly by seven, equiangularly spaced, stepped bores 56 communicating with a conical forward end 58 of the well portion. A second frusto-conical surface 60 is provided at the rear end of the atomizer head and is penetrated perpendicularly with bores 62 connecting respective stepped bores 56, at the part of larger diameter thereof, with the space intermediate the inner and outer tubes 26, 28. The front end of the atomizer head is penetrated by a single, central bore 64, also of stepped form, communicating with the conical forward end 58 of the well portion at the apex thereof. A third surface 66 in the form of a short length of a frustrum of a cone is machined on the rear end of the atomizer head and is perpendicularly penetrated by a bore 68 connecting the central bore 64 at the part of larger diameter thereof, with the space intermediate the inner and outer tubes 26, 28. The diameter of the bore 68 is somewhat greater than the diameter of the narrow part of the central bore 64 and the diameter of the larger part of the central bore 64 is such that the cross-sectional area of the larger part of bore 64 is equal to, or slightly less than, the sum of the cross-sectional area of the bore 68 and the cross-sectional area of the narrower part of bore 64, thereby assisting the mixing of streams of oil and steam in the part of larger diameter of bore 64 and atomization of oil which is supplied through the bore 68 and which intersects the axis of the central passage 64 at an acute angle, thereby further assisting the mixing and atomization process.

In operation, steam is supplied to the interior of the inner tube 26 and oil is supplied to the space intermediate the inner and outer tubes 26, 28 and pass through the respective bores to the peripherally arranged stepped bores 56 and the central bore 64. The parts of larger diameter of the various stepped bores serve as mixing chambers in which the steam and oil are intimately mixed and from which the steam and oil mixture is discharged as a finely atomized spray, the sprays from the peripherally arranged stepped bores 56 combining to form a spray of approximately frusto-conical form and the central passage discharging a stream of atomized mixture axially of the burner barrel. The stream of mixture discharged from the central passage 64 tends to stabilize the combined flame adjacent the burner following ignition of the mixture from an adjacent burner when combustion air is discharged at relatively high velocityfrom the air register 8 with little or no swirl imparted thereto. Furthermore the stream of mixture discharged from the central passage 64 substantially reduces any tendency for carbon deposits to form on the forward end of the atomizer head during operation of the burner.

In an alternative embodiment of the invention, not shown, the bore 68 connecting the central passage 64 with the space intermediate the tubes 26, 2.8 is omitted and steam alone is supplied to the central passage which is of constant diameter throughout. Such an arrangement also substantially reduces any tendency for carbon deposits to form on the burner head during operation and also enhances stabilization of the flame after ignition from an adjacent burner.

It will be appreciated that, if desired, instead of oil other liquid fuels, such as, for example, naphtha, may be utilized and also that instead of steam, other elastic atomizing fluids, such as, for example, air may also be utilized. Furthermore the liquid fuel may be supplied to the interior of the inner tube 26 and the elastic atomizing fluids supplied to the space intermediate the inner and outer tubes 26, 28. In such an arrangement, where it was desired to supply elastic fluid alone to the central passage 64, the passage is terminated short of penetrating the atomizer head and connects solely with the space intermediate the inner and outer tubes 26, 28 through the bore 68.

What is claimed is:

1. A liquid fuel atomizing assembly comprising a tubular barrel, means defining within said barrel a pair of separate passages extending the length thereof, means for supplying liquid fuel to be atomized to one of said passages extending the length thereof, means for supplying an elastic atomizing fluid to the other of said passages, a one piece atomizer head connected to said barrel, said atomizer head including mixing chambers distributed around the central axis of the head, the longitudinal axis of said chambers diverging in the general direction of discharge, a central mixing chamber discharging along the central axis of the atomizer head, each chamber having a separate inlet duct for liquid fuel and a separate inlet duct for elastic atomizing fluid, said ducts being arranged to connect the chambers with said barrel passages, said central mixing chamber having an inlet duct for elastic atomizing fluid of greater cross-sectional area than the inlet duct for liquid fuel discharging thereto.

2. A liquid fuel atomizing assembly according to claim I 1 wherein the cross-sectional area of the central mixing chamber is equal to the sum of the cross-sectional areas of the inlet duct for liquid fuel and the inlet duct for elastic atomizing fluid discharging thereto.

3. A liquid fuel atomizing assembly according to claim 1 wherein the inlet duct for liquid fuel and the inlet duct for elastic atomizing fluid leading to the central mixing chamber are disposed at an acute angle to each other.

4. A liquid fuel atomizing assembly according to claim 1 wherein said atomizer head has a flat forward end face and includes a cylindrical body having an internally threaded, central, well portion formed with an annular seat at the rearward end face thereof for engagement with a complementary seat provided on a collar on the inner co-axial tube of the barrel, an outer, circumferential, flange formed with an annular seat at the rearward face thereof for engagement with a complementary seat formed on the forward end face of the outer co-axial tube of the barrel by the action of an associated cap nut co-acting with an external thread on the forward end of the outer co-axial tube, a first frusto-conical surface formed as a chamber on the front end of the cylindrical body penetrated perpendicularly by stepped bores communicating with a conical forward end of the well portion, a second frusto-conical surface at the rear end of the cylindrical body in register with the space intermediate the inner and outer co-axial tubes of the barrel and penetrated perpendicularly with bores respectively communicating with the stepped bores at the part of larger diameter and a central bore extending from the conical forward end of the well portion to the front face of the cylindrical body.

5. A liquid fuel atomizing assembly according to claim 4 wherein said atomizer head includes a third surface in the form of a part of a frustrum of a cone is provided at the rear end of the cylindrical body in register with the space intermediate the inner and outer co-axial tubes of the barrel and is penetrated perpendicularly by a bore communicating with the central bore in an enlarged forward end portion thereof.

6. A liquid fuel atomizing assembly according to claim 1 wherein the cross-sectional area of the central mixing chamber is slightly less than the sum of the cross-sectional areas of the inlet duct for liquid fuel and the inlet duct for elastic atomizing fluid discharging thereto.

References Cited UNITED STATES PATENTS 2,933,259 4/1960 Raskin 239-422 X 2,942,790 6/1960 Starkey et al 239424 X 3,363,840 1/1968 Hall 239424.5 X

3,072,344 1/ i963 McKenzie 239433 FOREIGN PATENTS 1,259,910 3/1961 France.

EVERETT W. 'KIRBY, Primary Examiner.

U .S. C1.IX.R.

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