US3485452A

US3485452A - Mineral oil burner

Info

Publication number: US3485452A
Application number: US668892A
Authority: US
Inventors: Gino Sborlino
Original assignee: IORO AND PARISINI
Current assignee: IORO AND PARISINI
Priority date: 1966-09-24
Filing date: 1967-09-19
Publication date: 1969-12-23
Anticipated expiration: 1986-12-23
Also published as: FR1540577A; AT270036B; CH452764A; GB1132030A

Description

Dec. 23, 1969 a. SBORLINO 3,485,452

MINERAL OIL BURNER Filed Sept. 19, 1967 INVENTOR. 6W0 SBQKLINQ BY Made M 1 United States Patent MINERAL OIL BURNER Gino Sborlino, Milan, Italy, assignor to Ioro & Pansim, Milan, Italy, an Italian company Filed Sept. 19, 1967, Ser. No. 668,892 Claims priority, application Italy, Sept. 24, 1966, 22,809/ 66, Patent 781,692 Int. Cl. Bb 7/12 U.S. Cl. 239-417 1 Claim ABSTRACT OF THE DISCLOSURE A burner for liquid fuel having a central jet of auxiliary air surrounded by an atomizing air jet issuing from a gap between an outer noncylindrical stationary pipe and an inner noncylindrical tubular body, in which gap the fuel is injected, the switch of said gap being adjustable by moving the said tubular body axially.

This invention relates to a burner for liquid fuels, more particularly mineral oil, of the kind in which the atomization of oil is obtained by a jet of low pressure air.

Burners of the kind referred to above are employed, for example, for heating large rotary-drum dryers within which the inert substances intended to make up the bitumen mixes for road surfacing are dried. In these burners the air blown under a low pressure is generally divided into two concentric jets, one of which is intended to atomize the oil as sprayed by specially provided nozzles, whereas the other jet supplies the secondary air which is necessary to ensure a proper formation of the flame. Ina few burners, the atomization is brought about a central air jet surrounded by a jet of secondary air. Such an arrangement, however, has the defect that the flame shows a tendency towards expansion so as to find in the surrounding annularly shaped jet the air which is necessary for combustion, it being usually preferred, in the above recalled applications, that the flame is mainly developed lengthwise and is so maintained away from the drum walls, to prevent damages thereto. The inventive burner is of the kind in which the atomization of fuel oil takes place by virtue of a jet having an annular cross-sectional shape, Within which the central jet of secondary air is located. In such burners, the flame tends to be concentrated about said central jet without being radially scattered.

A principal object of the present invention is to provide, in a burner of the kind last referred to, a satisfactory rate of flow for the atomizing air jet with a rate of flow of fuel oil which can be varied within a reasonably wide range, all this without significantly varying the rate of flow of secondary air.

This object could be acheived by varying the pressure of the air which feeds the atomization jet.

The last mentioned solution, however, would lead to shortcomings of a twofold nature; in the first place, it would require two feed mains with air at different pressures, the constructional intricacy involved being apparent and, in the second place, a variation of the rate of flow of the atomizing air would be thus obtained concurrently with and because of a variation in the speed of the atomizing air jet, so that a satisfactory atomization could not be obtained irrespective of the rate of flow.

A particular object of the present invention is to provide a burner operable at low pressures with a central jet of secondary air surrounded by an atomizing air jet, in which the rate of flow of the atomizing jet can be varied to suit a variable rate of flow for the fuel oil, still without varying the speed of the atomizing air and without varying the rate of flow of the central jet of secondary air.

To achieve this object the inventive burner comprises a pipe whose front end is open and which is fed from the rear by a source of pressurized air and containing in its front end a tubular piece leaving a gap between itself and the tube, said tubular piece being connected to a duct fed with pressurized oil which opens into said gap through a plurality of openings, and is characterized in that the inner surface of the front end of said tube and the outer surface of said tubular piece have a variable cross-sectional area, means being further provided for varying the mutual position between the front end of said tube. and said tubular piece in an axial direction.

This feature, and other additional ones, along with the advantages afforded thereby, will be more clearly understood from the ensuing disclosure of an exemplary embodiment as illustrated in the accompanying drawing which is a diagrammatical lengthwise section thereof.

The burner shown in the drawing comprises a baseplate 1, internally hollowed out, which is extended into a tubular portion 2 containing the members for dividing and delivering the primary :air and for delivering the oil.

These members comprise a tubular piece 3 inserted into the end of the part 2, whose inner surface has a circular cross-section of variable diameter, as shown in the drawing: more detailedly, starting from the interior of the body 1, said cross-sectional area is gradually decreased, to be then increased and decreased once again, it being terminated by a short substantially cylindrical portion which is confined by a sharp outlet edge.

Within the body 1 is axially and slidably supported a tube 4 by means of the bush 5 and a few fins 6 whose projecting portions 7 slide on the inner surface of the portion 2.

One end of the tube 4 is within the tubular piece 3: on said end is mounted also a piece 8, also of tubular shape, connected to the tube 4 by spokes 9 in which thin ducts 10 are formed, which communicate with the end of the tube 4 and open out of the piece 8, where the latter has its highest diameter, in the gap 11 between the pieces 8 and 3.

The shape of the outer surface of the piece 8 is not cylindrical, but it has cross-sectional areas whose diameters vary, roughly with the same trend with which the cross-sectional area of the cavity of the piece 3 varies. As a consequence, the thickness of the gap 11 is roughly constant when the piece 8 is in the position shown in the drawing, whereas it can be throttled, to a larger or lesser extent, by axially displacing the piece 8.

The other end of the tube 4 which comes out of the body 1 through the bush 5 carries a sleeve 12 which is externally splined and which meshes with a gear 13: thus the latter, by being rotated, can cause the tube 4 to be axially shifted. To this end of the tube 4 is connected a hose 14 connected to a source of pressurized oil via a valve 15. This valve is opened more or less by any conventional control, diagrammatically shown at 16 in the drawing. This valve is controlled by a lever 17 connected through a rod 18 to a lever 19 fixed to said gear 13.

The body 1 has a lower aperture which can be totally or partially closed in an adjustable way by a conventional valve which is depicted in the drawing by two symmetrical vanes 20 pivoted at 21. This opening is fed by air at a comparatively low pressure, that is, in the order of one meter of column of water, by a blower which has been omitted from the drawing for the sake of clarity.

The burner as described above operates as follows.

Mineral oil, fed through the valve 15 via the tube 14 to the tube 4, comes out in the form of tiny jets from the ducts 10 into the gap 11. Concurrently, air blown into the body 1, guided by the fins 6, enters the piece 3 and is divided into two streams: one stream enters the piece 8 and passing through the openings or spaces between the spokes 9 comes out in the form of a central jet from the piece 3, whereas the other stream enters the gap 11 and comes out also from the piece 3 in the form of a tubular jet which wraps the central jet aforesaid. This latter portion of air fulfils the task of atomizing the mineral oil issuing from the ducts 10.

When the tube 4, and concurrently therewith the piece 8, are axially displaced, the cross-sectional area of the gap 1} is more or less throttled in the vicinity of the outlet of the ducts 10. Inasmuch as the pressure of the air which is fed to the gap 11, assuming that the valve 20 is at stand-still, is always virtually constant and equals the pressure fed into the interior of the body 8, the result is that, by shifting the tube 4 axially by rotating the gear 13, the rate of flow of the atomizing air, which is just the air flowing through the gap 11, can be varied without varying the feeding pressure and thus maintain its outflow speed, and also its atomizing efliciency, virtually unaltered.

It is also possible to cause said variation of the rate of flow of atomizing air to be in a preselected relationship with the rate of flow of the fuel oil fed by the valve 15 by properly adjusting the gear ratio obtained with the

linkage

17, 18, 19 which bounds the tube 4 axially, and thus the piece 8 relative to the piece 3, to the position of the regulator 16 which controls the valve 15.

It is thus possible to adopt the optimum ratio of oil to atomizing air through a wide range of rates of flow of fuel oil. The central jet of secondary air which flows in the interior of the piece 8, conversely, is kept at a substantially constant rate of flow and speed, and thus also its shape remains virtually the same irrespective of the variations of the jet of surrounding air which contains atomized fuel.

The adjustment of the rate of flow of oil and atomizing air can, if desired, be servoed to certain factors which are inherent in the combustion run, for example by a thermometric member such as diagrammatically shown at 22.

It is understood that the exemplary embodiment shown herein can be variously modified: for example the position of the tube 4 and of the piece 8 could be maintained unvaried and the piece 3 could be made axially displaceable within the part 2.

I claim:

1. A burner for liquid fuels comprising a tube with an inner surface having a cross-section which is variable along the axis of said tube, a tubular piece within said tube and coaxial therewith, with an outer surface having a cross section which is variable along said axis, a gap between said tubular piece and said tube, a conduit for the fuel within said tubular piece terminating into a plurality of perforations on the region of greatest crosssection of the outer surface of said tubular piece, means for conveying compressed air to one end of said tube, whereby said air passes through said tubular piece and through said gap, and means for displacing said tubular piece axially with respect to said tube.

References Cited UNITED STATES PATENTS 2,531,538 11/1950 Smith 239-417 X 3,091,283 5/1963 Kidwell 239-4l7 X M. HENSON WOOD, JR., Primary Examiner M. Y. MAR, Assistant Examiner U.S. Cl. X.R. 239-4173 F'YiB'ZBARZANO8cZANARDO( G SBORLINO 668, 892 )N5WG2hn7O age T NEED STATES PATENT OFFICE CERTEFECATE OF CORRECTEQN Patent No. 3, 5, 452 Dated December 23, 1969 Inventor(5) GinO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification column 1 1ine'3 for oraflfi Parisini" I r eedwfl arisini S.p.A. e

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WILLIAM E- SOHUYLER, JR.

A Officer uesnng Commissioner of Patents