US3493180A - Oil burner combustion head swirl means - Google Patents

Description

Feb. 3, 1970 I ,w H 3,493,180

OIL BURNER COMBUSTION HEAD SWIRL MEANS Filed Nov. 6, 1968 2 Sheets-Sheet 1 INVENTOR. 542/65 R. WALSH B. R. WALSH OIL BURNER COMBUSTION HEAD SWIRL MEANS Feb. 3, 1970 2 Sheets-Sheet 2 Filed Nov. 6, 1968 IN VENTOR. Abel/c5 4. W449 United States Patent Ofiice 3,493,180 (NIL BURNER CQMBUSTION HEAD SWIRL MEANS Bruce R. Walsh, Pittsburgh, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Continuation-impart of application Ser. No. 556,339, June 9, 1966. This application Nov. 6, 1968, Ser.

Int. 'Cl. F23d 11/38 US. Cl. 239406 12 Claims ABSTRACT OF THE DISCLOSURE This invention relates to oil burner combustion heads, particularly to such an apparatus for use with gun-type oil burners, and more particularly to an improved air swirl means for such an apparatus.

The invention provides apparatus of the character described wherein the flame produced from the combustion head is short and compact, whereby the apparatus is particularly suitable for use in conversions, that is, converting heating equipment which may have been built to burn other fuels and which may have relatively small fireboxes, or, in effect, no fireboxes, to burn oil.

Another object of this invention is to provide apparatus of the charatcer described comprising exit orifice means forwardly of the nozzle, whereby the swirling air is forced into a. vena contracta, which is formed forwardly of the nozzle, to cause more intimate intermixing between the air and the oil mist issuing from the nozzle. After passing through the vena contracta the air forms itself into a diverging cone, and this cone may approximate the shape of the diverging cone of oil mist or droplets issuing from the nozzle, whereby the oil droplets are constantly surrounded with the air required for cmplete burning.

Still another object of this invention is to provide improved air swirl means for use in apparatus of the character described, comprising air spinners of relatively simple construction to improve the economics surrounding burners including the apparatus of the invention.

A further object of this invetnion is to provide improved air swirl means comprising a plurality of swirl passageways around the periphery thereof, which passageways are inclined forwardly and inwardly towards and at an angle to the oil burner air blast tube axis. The invention provides an improved air swirl means wherein said passageways are formed by vanes formed on the outer periphery of a swirl plate. Both embodiments of the swirl plate are of relatively simple construction, lending themselves to manufacture from a simple flat blank, with the vanes and other openings being formed by means of simple stamping and bending operations.

Still another object of this invention is to provide apparatus of the character described wherein the advantages of thorough mixing of oil and air are achieved both when firing a burner embodying the invention into a furnace 3,493,180 Patented Feb. 3, 1970 or the like heating equipment combustion chamber, and when firing the burner without such a chamber.

The above and other advantages of the invention Will be pointed out or will become evident. in the following detailed description and claims, and in the accompanying drawing also forming a part of the disclosure, in which: FIG. 1 is a side elevational view of the front end of an oil burner air blast tube having a combustion head including a first embodiment of the air swirl means of the invention mounted therein, with some parts broken away and some parts in cross-section; FIG. 2 is a rear elevational view of the first embodiment of the swirl means of the invention; FIG. 3 is a side elevational view thereof; and FIGS. 4 and 5 are views similar to FIGS. 1 and 2, respectively, showing a second embodiment of the swirl means of the invention.

Referring now in detail to the drawing, 10 designates the front end of a gun-type oil burner embodying a first embodiment of the invention. Apparatus 10 comprises an air blast tube 12 of conventional construction in guntype oil burners. Tube 12 is open at its front end and comprises a. front annular surface 14.

Removably mounted in the front open end of air blast tube 12 is a combustion head 16 comprising swirl means 18 and an end member 20. End member 20 may be a casting or may be fabricated in any other suitable manner. End member 20 comprises a front surface 22, having an outer peripheral head 24 which bears against annular surface 14 of air blast tube 12. Extending axially rearwardly from head 24- is an axial, cylindrical surface 26 which is in close fitting contact with the front inside surface of tube 12.

Means are provided to removably mount end member 20 within the front open end of tube 12, and may conveniently comprise a set screw 28 threadedly mounted in a suitable threaded opening in tube 12 to bear against surface 26. Bead 24 and surface 26 may be notched out, not shown, to provide an oil drain. As is well known in this art, the blast tubes of gun-type oil burners are tilted or canted slightly forwardly and downwardly, an angle of three degrees is common, for purposes of safety, so that any raw unburned oil will drain out of the front end of the blast tube, and not collect therein, which could create a fire or explosion hazard. The end member 20 is illustrative of many different kinds of front end air handling apparatuses that may be used with the invention. The end member need not be removably mounted in the front end of the blast tube, but could be made integral therewith, as will be evident from the following description.

End member 20 is formed with a central opening 30. As is well known in this art, the heat output capacity of a burner is determined in part by the oil output capacity of the nozzle and the air output of the blower, not shown, in combination with the diameter of opening 30. It is within the scope of the invention to be used with a wide range of sizes of burners and nozzle capacities, the physical dimensions of the parts being adjusted accordingly, when necessary.

Extending rearwardly and radially outwardly from opening 30 is a conical surface 32 defining a largest diameter substantialy equal to the inside diameter of tube 12 so as to fit snugly therein. It is desirable that the swirl means 18 of the invention cooperate with an end member having a smooth conical surface analogous to surface 32 for a reason that will be explained below.

However, many conventional gun-type oil burners end members are formed with internal vanes. When it is desired to add the swirl means of the invention to such a burner, it is most economical to leave the existing end member, rather than change it, and tests have shown that satisfactory though slightly less than optimal operation results. Such conventional end members formed with internal vanes may provide a direction of air swirl in either direction. Tests were performed when the direction of swirl of the end member vanes and the swirl means of the invention were in the same direction and were opposite to each other. When these directions were the same, then the above mentioned satisfactory though slightly less than optimal operation results. However, when these two directions of swirl are opposite to each other, then totally unsatisfactory operation results, characterized by low efiiciency and an unstable flame. In certain prior apparatuses wherein swirl means are provided both in the end cone and at another location upstream of the end cone, and the directions of swirl are opposite to each other, this disadvantage does not result, or at least it not so marked, because a substantial axial space between the two swirl means is also provided. In the present invention there is no such space, and therefore such prior apparatuses cannot achieve the advantages of the present invention if these two opposite direction swirl means in such apparatuses were brought into contact with each other, which would have to be in accordance with the teachings of the present invention.

Referring to FIGS. 2 and 3, swirl means 18 comprises a body portion 34 which is formed with a plurality of openings for different purposes. Body 34 is formed with a pair of relatively large openings 36 to receive conventional oil burner ignition means 38, FIG. 1. Ignition means 38 comprise a pair of insulated electrodes, electrically connected to the oil burner ignition circuit, not shown, in such a way as to create an electrical are between the two electrode tips, which are ignites the air-oil mist, in the usual manner.

Body 34 is formed with a plurality of smaller openings 40 provided to bleed air into the swirling air vortex, for a reason that will appear more clearly below. Finally, body 34 is formed with a central opening 42 in which is afiixed a mounting collar 44.

Along the outer periphery of body 34, swirl means 18 comprises a plurality of swirl vanes 46. Vanes 46 are preferably integral with the body 34 and may be conveniently formed during one series of stamping and bending fabrication steps. The embodiments of swirl means 18 which have been successfully built and used were made from a single metal plate having a thickness of about of an inch.

Referring back to FIG. 1, the space between swirl means 18 and opening and defined by conical surface 32 comprises an air swirl and air and oil mixing chamber 48. A nozzle and adapter assembly 50 has its exit end positioned in chamber 48, and the swirl means 18 is fixed to nozzle assembly 50 by means of a set screw 52 passing through collar 44. The nozzle is mounted on a conventional oil supply pipe 54. Thus, the swirl means 18 with the ignition means 38 and nozzle 50 may be removed for servicing and the like, from the rear end of the oil burner, not shown, without disturbing the end member 20, by removing the service plate, transformer or other assembly at the back of the burner, and pulling the entire above-mentioned assembly backwardly outwardly through the blast tube by pulling on the oil supply pipe 54. This simplifies maintenance because the oil burner need not be removed from the furnace or the like with which it is associated to allow servicing of the ignition means, nozzle, or the swirl means. Suitable clamping devices, not shown, are pro vided to hold the ignition means 38 in spaced relation to oil supply pipe 54.

Each swirl vane 46 is of generally trapezoidal shape, comprising a bottom edge 56, a rear side edge 58 and a front side edge 60. The side edges 58 and 60 are formed by radial lines on body 34. As shown in FIG. 1, the plane of body 34 is co-extensive with the largest diameter de in d by con cal surface 32. h ch i th d a t r of the air blast tube 12. Each vane 46 is twisted or canted out of the plane of the body on a central portion 61 on bottom edge 56 on which portion 61 each vane is attached to the body 34. Thus, the rear part of the outer edge of each vane 46 contacts the inside of air blast tube 12 and the front part of each vane contacts the rear portion of conical surface 32. Accordingly, the outer periphery of each vane comprises a rear edge portion 62 and a front edge portion 64.

Theoretically and geometrically, each of the edge portions 62 and 64 are curved because they contact a cylindrical and a conical surface, respectively. However, because of the relatively small thickness of the blank from which body 34 is formed, these two edges may be fiat across their thickness only, which will result in a s-ulficiently tight fit. Front edge portion 64- is theoretically a compound curved surface formed by the angle of twist of each vane out of the plane of body 34 and the intersection of that angled line with conical surface 32. Rear edge portion 62 is also theoretically a compound curved surface, because it is generated by the intersection of the plane of the vane with cylindrical surface 26 of the blast tube 12.

Each pair of vanes defines a swirl slot or passageway in that the air under pressure from the oil burner air blower, not shown, upon passing between each pair of vanes simultaneously has its direction changed from axial of the blast tube, to tangentially and radially inwardly of the blast tube axis, i.e., a spiral path.

Referring now to FIGS. 4 and 5, a second embodiment of the swirl means of the invention is shown. The mode of operation and all essential features of this second embodiment are the same as the first embodiment described above, with the differences residing in structural changes. Parts of this second embodiment identical to those described above are indicated by the same reference numerals.

The second embodiment of the swirl means are generally indicated by reference numeral 70, and comprises a body 72, analogous to body 34 described above with the exception that body 72 is of annular configuration. At its outer periphery, body 72 carries a plurality of vanes 46 identical to those described above. At its inner periphery, body 72 carries three lugs 74 which are turned perpendicular to the plane of the body.

The swirl means 70 furthercornprise a mounting plate 76 formed with a plurality of openings 78 adapted to snugly receive and pass the lugs 74. The parts are joined together by means of the lugs 74 and openings 78, by passing each lug through an opening, and then twisting the lug, see FIG. 5.

Thus, this second embodiment of the swirl means of the invention 70 has the added feature of increased versatility, in that by merely unfastening the lugs 74 and removing the body 72 from mounting plate 76 and then attaching a different size body to the mounting plate, various sizes of air blast tubes 12 and burners can be accommodated.

Means are provided to secure swirl means 70 to the oil supply pipe 54. To this end, a spider assembly 80 is swagged or otherwise fixed to a suitably formed central opening in mounting plate 76. Spider 80 comprises a central collar 82 carrying a set screw 84 by means of which the spider is removably fixed to the oil supply pipe 54. Extending from collar 82 is a web 86 which carries a pair of bifurcated adjustable ignitor holding collars 88. Between the collars 88 on Web 86 there is mounted a spring 90 by means of a screw 92. On the opposite side from collar 82, web 86 carries a pair of locating fingers 94. The fingers 94 and the spring 90 are spaced approximately around the axis of the spider to provide a solid three-point contact against the inside of tube 12.

Mounting plate 76 is formed with a plurality of opene ings 41 analogous in structure and function to openings 40, as will be described below.

All of the air passing between the vanes 46 is changed from its axial flow in the tube to a flow which is both swirling and conical, converging towards opening 30, simultaneously. This is an advantage over prior apparatuses which have two separate means spaced from each other in the blast tube to impart first swirl and then conical flow or vice versa, since the direction component imparted by the first means is dissipated by the time the air reaches the second means to have the second component imparted to it. The vanes cause the air to swirl and create a blanket of swirling air against conical surface 32 within chamber 48. The centrifugal force of the air in combination with the decreasing cross-sectional area of chamber 48 further increases the speed of the blanket of air causing it to compress itself against surface 32. A semi-evacuated or low-pressure zone is thus created by said swirling blanket of air within chamber 48 because the spinning blanket of air tends to draw the air at its vortex or center region into itself. When the swirling blanket of air reaches positions on surface 32 forwardly of the front end of the nozzle 50, it will also draw the oil mist produced from the nozzle into itself, thus causing intimate intermingling of the oil and the air, to result in eflicient burning of the oil.

When the air blanket and the oil mist reach the vena contracta in the region of orifice 30, the centrifugal force will thereafter tend to throw the air-oil mist outwardly, thus creating a compact short flame. This short flame is advantageous particularly in conversion applications, that is, when using the apparatus of the invention to convert a furnace which was designed for some other fuel to burn oil, which furnace may have a small firebox or, in certain applications, no effective firebox.

In addition to the above-mentioned advantages of economy of manufacture, the present invention provides improved air swirl means in that a relatively large quantity of air passes through the vanes 46. The total annular crosssectional area between the outer edge of the body of either embodiment and the circular line of juncture between surface 32 and the inside of tube 12 in the plane of the body is almost completely open in that the only restriction therein is the sum of the cross-sectional areas of the rear side edges 58 of the vanes. In fact, because such a relatively large quantity of air is caused to swirl, the semi-evacuated condition created by the swirling air blanket in chamber 48 has been found to have such a reduced pressure that provision of the openings 40 and 41 was required in order to raise said pressure somewhat closer to atmospheric to prevent the semi-evacuated or low pressure condition from interrupting the outward flow of the oil mist from the nozzle 50. The total open crosssectional area provided by the Openings 40 and 41 is predetermined to somewhat reduce the vacuum condition in chamber 48, but not to raise it so close to atmospheric pressure that proper intermixing of the oil mist and the swirling air in the chamber 48 between the plane of the exit face of nozzle 50 and the region of the exit orifice 30 is interrupted. The sizes and locations of the openings 40 and 41 are not critical, so long as the total crosssectional area provided by them is predetermined to yield the above desideratum.

Conical surface 32 of the end member 20 shown in the drawing has an included angle of about sixty degrees, and both swirl means comprise eighteen vanes. These two values for these parameters have been more or less randomly chosen based on experience with oil burners, are illustrative only, and have been used in the successfully built and tested embodiments of the invention, but are not to be construed in a limiting sense. For example, a larger or smaller number of vanes could be used in an air blast tube having a larger or smaller diameter, respectively.

Because of the relatively large volume of air in the swirling blanket of air in chamber 48 provided by the swirl means of the invention, burners embodying the invention have the additional advantage of increased versatility. A burner apparatus embodying the invention may be used with more than one capacity nozzle. That is, one set of air handling equipment embodying the invention permits a burner so equipped to be operated with different nozzles of differing fuel flow capacities.

While the invention has been described in detail above, it is to be understood that this detailed. description is 'by way of example only, and the protection granted is to be limited only within the spirit of the invention.

I claim:

1. Air swirl means comprising a body; said body consisting of a substantially flat sheet member having a substantially circular periphery, a plurality of swirl vanes and an equal number of connecting portions along the periphery of said body each connected. to a swirl vane, each of said swirl vanes being substantially flat and disposed at an angle to the plane of said body by turning each of said vanes on each of said connecting portions, each of said vanes comprising an outer edge having a rear portion adapted to closely contact a cylindrical surface such as the inside of an oil burner air blast tube and a front portion adapted to closely contact a conical surface such as means to form a conical swirl chamber, said swirl means being formed with a central opening, and separate mounting means of fixed in said central opening.

2, The combination of claim 1, said swirl means body being of substantially circular shape, said swirl means central opening being formed in said body, and said separate mounting means comprising a mounting collar.

3. The combination of claim 1, said swirl means being formed with at least one pressure relief opening having a predetermined cross-sectional area.

4. The combination of claim 1, said swirl means body comprising an annular plate, said swirl means further comprising a mounting plate, means to removably join said mounting plate to said annular plate, said swirl means central opening being formed in said mounting plate, and said separate mounting means comprising a spider fixed to said mounting plate central opening.

5. In a combustion head, the combination comprising means forming an orifice disposed substantially perpendicular to the combustion head axis, means extending rearwardly from said orifice means to form a swirl chamber of truncated conical configuration, swirl means in said chamber at the location of the largest diameter of said chamber and extending forwardly therefrom towards said orifice means, said swirl means comprising a plurality of peripheral passageways inclined forwardly towards and at an angle to said axis, the portions of said swirl means between said passageways being in closely abutting relation to said conical swirl chamber, said swirl means comprising a body formed with a plurality of vanes at the periphery thereof, said swirl means body consisting of a substantially flat sheet member having a substantially circular periphery, the outer edges of said vanes comprising said abutting portions of said swirl means, each of said outer edges of said vanes having a rear portion adapted to contact a cylindrical surface such as the inside of an oil burner air blast tube and a front portion closely contacting the conical surface of said swirl chamber forming means, and each of said vanes being joined to said body by a connecting portion and turned out of the plane of said body about said connecting portion to form said inclined passageways.

6. The combination of claim 5, in combination with the air blast tube of an oil burner, said swirl chamber forming means having a rearmost largest diameter substantially equal to the inside diameter of said blast tube.

7. The combination of claim 6, said body comprising means to receive a nozzle positioned with its front end located within said swirl chamber in spaced relation to said orifice, and means to mount said swirl means on said nozzle.

8. The combination of claim 7, said swirl means body comprising a plate formed with a central opening, and said swirl means mounting means comprising a mounting collar joined to said central opening.

9. The combination of claim 7, said swirl means body comprising an annular plate, said swirl means further comprising a mounting plate, means to removably join said annular plate to said mounting plate, said mounting plate being formed with a central opening, and said swirl means mounting means comprising a spider joined to said mounting plate central opening.

10. The combination of claim 6, said swirl means being formed with a plurality of openings communicating said swirl chamber with the inside of the air blast tube upstream of said body.

11. The combination of claim 7, in combination with oil burner ignition electrodes, said swirl means comprising means adapted to receive said ignition electrodes, whereby UNITED STATES PATENTS 2,663,365 12/1953 DeLancey 239-406 X 3,007,515 11/1961 Furdock 239-406 FOREIGN PATENTS 164,037 12/ 1933 Switzerland.

M. HENSON WOOD, Primary Examiner MICHAEL Y. MAR, Assistant Examiner US. Cl. X.R. 239-4345, 495

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,493,180 D t d February 3, 1970 Inventofls) Bruce R. Walsh It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, column 6, line 29, "of fixed in should be --fixed to--.

SIGNED 'KND SEALED JUN 3 01970 Meat:

Edwin! M. member.

ffi .a I. m Atteaimg 0 Oomissioner of Pet-Ont:

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