US3278125A - Oil burner structure - Google Patents

Description

Oct. 11, 1966 DOE-LUNG ETAL 3,278,125

OIL BURNER STRUCTURE 4 Sheets-Sheet 1 Filed July 24, 1 964 11, 1966 R. P. DOELLING ETAL 3,

QIL BURNER STRUCTURE 4 Sheets-Sheet 2 Filed July 24, 1964 Oct. 1966 R. P. DOELLING UETAL 3,278,125

OIL BURNER STRUCTURE 4 Sheets-Sheet 5 Filed July 24, 19.64

1966 R. P. DOELLING ETAL 3,278,125

OIL BURNER STRUCTURE Filed July 24, 1964 4 Sheets-Sheet 4 TJELHE.

BZADEAFMI 71/554554 :77 Z70 0L l l l TJEHZ- PM 5 OF United States Patent 3,278,125 OIL BURNER STRUCTURE Ralph P. Doelling, Beacon, and Julius J. Lorzing, Jr., Wiccopee, N.Y., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware Filed July 24, 1964, Ser. No. 384,936 9 Claims. (Cl. 239-405) This invention relates generally to fuel burning apparatus, and specifically to oil burners of the gun type wherein air and fuel are mixed properly to produce a combustible mixture. More particularly, the invention is concerned with an improved means for stabilizing air flow and directing the stabilized air into the combustion chamber of a furnace.

Many standard gun type oil burners have unsatisfactory air handling and fuel mixing characteristics. Since the manufacture of such burners is simple, and so relatively inexpensive, resulting in a highly competitive market, various mechanical devices have been promoted to increase the efiiciency of combustion and so reduce fuel cost. Also, the widening use of competitive fuels for home heating provides additional incentive for improved oil burning equipment.

Accordingly, it is an object of the present invention to provide gun type oil burners with structure designed to produce an improved at flow pattern leading to more efficient combustion.

Another object of the invention is to provide an improved air swirler or stabilizer and end cone combination operating with a minimum of turbulence and pressure loss.

Still another object of the invention is to provide for better mixing of the stabilized air with sprayed fuel for more efficient combustion.

These and other objects, advantages and features of the present invention will become apparent from the following description of the invention and by reference to the accompanying drawings wherein:

FIG. 1 is a plan view of the discharge end of an oil burner gun or air blast tube, partially in section;

FIG. 2 is a cross section view through the air blast tube looking upstream at the air swirler or stabilizer positioned therein, with the electrode insulators shown dotted for purpose of clarity;

FIG. 3 is an elevation view of the air swirler or stabilizer in the air blast tube, taken along line 33 of FIG. 2;

FIG. 4 is an elevation view looking downstream at the air swirler or stabilizer as it would be positioned in the air blast tube;

FIG. 5 is an orthographic presentation of an unmounted air swirler taken in the direction of the arrow indicated in FIG. 4;

FIG. 6 is an end view of the swirler vane or blade taken along line 66 of FIG. 5;

FIG. 7 is a view of the end cone, looking upstream, taken along line 77 of FIG. 1;

FIG. 8 is a view of the end cone, looking downstream,

taken along line 8-8 of FIG. 1;

FIG. 9 is a partial section view taken along line 99 of FIG. 7;

FIG. 10 is a development showing the several planar upstream surfaces of the end cone in linear representation;

FIG. 11 is a generalized velocity pattern showing the effect on air flow due to increased effective blade areas;

FIG. 12 is an air flow pattern of a burner system utilizing the improved air swirler and end cone; and

FIG. 13 is a graphical showing of the improved operation of a burner system using the disclosed invention.

In accordance with the illustrated embodiment of the invention, there is shown an air swirler or stabilizer of improved design for stabilizing the unsymmetrical flow pattern of air in the blast tube of a gun type oil burner to provide an air flow pattern having a more uniform mass How, and an end cone to direct the stabilized air for intimate mixture of fuel and air.

Referring to FIG. 1, there is disclosed a blast tube at 10 with an air swirler or stabilizer at 11 and an end cone structure disclosed generally at 12. An oil line or conduit at 13 passes through the air swirler and ends in the fuel nozzle at 14, with electrodes comprising the electrical ignition means at 15 projecting from the insulators 16 extending through the upper pair of vanes or blades 11a, 11a of the air swirler and supported in position on the hub extension 17 by clamp 18 and fastening means 19.

Referring to FIGS. 2 to 6 inclusive, the air swirler per se comprises a plurality of vanes centered in each quadrant and positioned upstream the fuel nozzle. The upper pair of vanes 11a, 11a has openings for the passage therethrough of the insulators 16 but otherwise their structure is essentially the same as that of the lower pair of vanes 11b, 11b. With particular reference to FIG. 5, each of the vanes is shaped to present an angular entrance to the air flow with respect to the longitudinal axis of the blast tube of the burner, extending from an upstream hub 17a, which may be either conical or pyramidal as shown with a vertex angle of 40, although other vertex angles are not excluded, to provide for the gradual entrance of the pressurized air onto the curved vane surface, whence it is guided to the periphery of the blast tube while imparting a spiral motion to the air, in this case, a clockwise rotation. Adjacent edges of the vanes are coincident in longitudinal alignment as shown at 20 in FIGS. 2 and 4. The outermost edge of each vane with respect to the axis of support is formed preferably about a cylindrical mandrel positioned at the desired swirl angle to form substantially a semi-cylindrical surface. However, other geometrical surfaces can be used to pro vide the desired air mass flow. The swirl angle is defined as the angle between the center line or longitudinal axis of the blast tube and the direction in which the'air is deflected by the swirler vanes, indicated as a and shown as approximately 50 in FIG. 5, with an operating range from 30 to 60, while the semi-cylindrical surface indicated as B in FIG. 6 is shown as being approximately in extent, other curved surfaces not being precluded. In addition, each of the vanes or blades presents an effective area to the flowing air, large enough to pick up most of the air directed thereagainst but not so large to act as an undue restriction or choke. This is shown eifectively in FIGS. 2 and 4, while FIG. 11 clearly demonstrates the effect on the air pattern in the combustion zone of the larger ratio of the sum of the blade areas to the blast tube cross section area. Interference effects arising from the presence of the electrode insulators are more than offset by the large vane areas and the positioning of the electrode clamp and fastening means in the shadow of the swirler on the downstream hub extension 17. Positi-oning supports on the lower pair of the vanes of the air swirler are shown at 21, 21, and another support at 22, although all the vanes may be provided symmetrically with the same type positioning supports. The lower pair of vanes also defines an opening 20a for passage of flame detector means therethrough.

The end cone structure is disclosed in FIGS. 7, 8, 9 and 10, to which reference is made now. A series of intersecting planar surfaces define a plurality of open end, pyramidal cowls, shown at 39, spaced equally around the opening 31, to form a substantially star shaped configuration, the size of the opening being dependent on the rate of fuel combustion. These cowls are shown as generally angled roof-like protuberances and shaped so that each ridge line at 30a extends downstream and is pointed eccentrically with respect to the longitudinal axis of the blast tube, i.e., skewed. The end cone also includes a peripheral collar at 32 thereby defining an annular member, which is fitted into the discharge end of a blast tube. Another modification could dispense with such a collar and appropriate means for fastening the end cone to the blast tube could be used.

The upstream face of the end cone is exposed to the stabilized air leaving the air .swirler as a rotating mass with substantially uniform mass flow and comprises a plurality of a series of surfaces, preferably planes, which serve to guide and direct the rotating mass of stabilized air into a tight swirl for intimate mixture with the fuel in the form of a spray from the fuel nozzle 14. These surfaces include a series of guiding planes indicated at A, a series of directing planes indicated at B, and a series of bounding planes indicated at C, all in FIG. 10. The lines of intersection of adjacent guiding and directing planes are indicated by the lines 33, parallel to the ridge lines at 30a, and inclined downstream and ecoentrical-ly of the axis of the blast tube, with the same angularity as the line 30a, so that there is a skew angle made with the radius, as indicated at X in FIGS. 7 and 8, this angle being dependent on the opening in the end cone and varying from 8 to 16 for use with burners in commercial use presently. The lines of intersection of adjacent directing and bounding planes are indicated at 34, all of these lines of intersection laying in a common plane normal to the blast tube axis, and the lines of intersection of adjacent bounding and guiding planes are indicated at 35, each of the bounding planes being directed tangent to an imaginary cylinder coaxial with the discharge opening of the end cone and of slightly lesser diameter than that of the opening. In this manner, the air is directed in a solid cone air pattern, as a highly contracted swirl about the longitudinal axis of the blast tube, which is shown as leaving the planar surfaces C in a clockwise downstream spiral-like manner, and a series of jet-like currents from the planar surfaces A and B behind the protuberances. This pattern of rotating air cuts through the cone of the fuel spray to produce the desired combustible mixture downstream the face of the end cone. It is important to note that the angle of the swirler blades and the angle made by the guiding planes A with respect to the flow axis must be coordinated in view of the boundary layer effect as the stabilized air moves down the blast tube. This type of solid cone air pattern is best suited for universal utilization in various shaped fire boxes or furnace combustion chambers.

Although the upstream face of the end cone is shown as comprising a plurality of planar surfaces and dihedral angles, when the matter of thermal expansion can be overlooked or compensated for, it is feasible to modify the guiding, directing and bounding planes into a smooth streamlined configuration so as to discharge a mass of swirling air in a similar solid cone air pattern and with the surface behind the protuberances on the end cone increasing the air swirl at the axis of the fuel nozzle.

Studies have shown that in most gun type oil burners, due to the characteristics of the fan which provides air to the :last tube, the air leaves the fan and flows down the blast tube in an unsymmetrical manner. The improved air swirler or stabilizer redistributes the air so that it now fills the tube and moves forward with a uniform mass fiow. Thus, when the air with uniform mass flow reaches the end cone, the guiding and directing planes in combination with the bounding planes produces a tight swirling mass of air with eccentric air currents to provide for excellent mixture with the sprayed fuel.

The five star end cone structure defined by the protuberances causes the airstream to enter the combustion chamber in a solid air pattern having a five-lobe shape, as shown in FIG. 12, the dotted arrows in the section of the vertical traverse plane indicating the jet action induced by the surfaces beneath the protuberances, the nomenclature thereon being self explanatory of this figure. Thus, at any given position downstream the fuel nozzle, the' peripheral area of this air flow pattern is greater than that of the usual solid cone pattern of air streams. This increased area aids in transferring heat from the recirculating combustion gases and surrounding hot fire box to the cooler incoming fuel-air mixture thereby improving fuel vaporization, the five currents of rotating air from under the protuberances cutting across the cone of the fuel spray providing good mixture, as opposed to the smooth flow obtained from conventional solid cone air patterns. Further, the lobe air flow pattern is characterized by higher velocities in the center of the air mass.

The stabilized air upon leaving the end cone induces a sweep back flow effect to provide a recirculation of hot combustion gases toward the end cone. Thus, not only is there an intimate mixture of the fuel spray and air resulting from the swirling action of the air directed from the planar surfaces on the upstream face of the end cone, but the recirculation of the air passing through the opening to sweep back on itself provides for further mixture of fuel with air which has been preheated by being adjacent the combustion zone in the fire box of the furnace.

Ina series of forty field tests, the average oil fired home heating unit was found to be 67% eflicient and operating with a Bacharach smoke number of 3.5. Adjustments of these home heating units to the best values of draft, smoke and fuel pressure decreased the smoke to an average value of 2.2 and did not materially effect the efficiency of the units. The application of the elements of the disclosed burner system in these test units produced an average efficiency of 76.4%, at a Bac-harach smoke number of 1.0, not previously obtainable with available test units. In addition, the quantity of excess air Was reduced by approximately 50%. Thus, this improved burner system increased the efficiency of the average home unit by approximately 9 /2% or an increase of 14%, and would reflect a calculated average fuel saving of 12%, together with a considerable reduction in smoke. Tables I and II are tabulations of the test results, and FIG. 13 is a graphical showing of a typical test.

TABLE I.RANGE OF UNIT EFFICIENCIES Etliciency, Percent; As Found Best Ad Improved justment System TABLE IL-RANGE OF BACHARACH SMOKE NUMBERS Bacharach Smoke No. AsFound Best Adjustment Improved System 9 (Heavy Soot) 2 (Light; Soot)- 1 (Trace) 0 (N 0 Soot) Because of the spray characteristics of fuel nozzles, the downstream face of the individual fuel nozzle must be accurately positioned so that the cone of the fuel spray will not impinge on the upstream face of the end cone, and yet not be far enough downstream in order that the air merging from the opening in the end cone provide a conical zone without having fuel admixed thereinto. In addition, the angularity of the swirl axis of the vanes of the stabilizer and that of the guiding and directing sur faces of the end cone to provide for the same directional rotation, and the distance between the downstream edge of the stabilizer and the upstream face of the end cone must be coordinated so that the discharged air can rotate with stability for proper mixture with the fuel. Thus, a fuel oil burner equipped with the improved air stabilizer and end cone achieves an optimum mixing of fuel spray and air, discharged with stability and a high velocity, to produce efiicient combustion at a low noise level, the solid cone air flow pattern having a large peripheral surface area to absorb a maximum amount of heat through radiation :and convection of the recirculating hot gases induced by the improved end cone, to insure complete vaporization of fuel.

Further, although the swirler blades have been shown in FIGS. 2, 3 and 4 as centered in each quadrant, a central positioning of the blades along the horizontal and vertical axes is not precluded, considering the requirement that the electrodes for ignition are not located in a quadrant directly underneath the nozzle.

Obviously, other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. An exit structure for the air blast tube of a gun type oil burner comprising an end cone with a discharge opening having a plurality of adjoining planar surfaces defining channels on the upstream face between the periphery of said end cone and said opening and with a general downstream inclination for directing air tangent to an imaginary cylinder coaxial with said opening and of slightly less diameter thereof in a highly contracted swirl about the longitudinal axis of the blast tube and downstream and closely eccentric to said longitudinal axis in the form of jet-like currents flowing from said channels whereby intimate mixture of fuel spray and air is obtained, said planar surfaces comprising a series of relatively elongated guiding planes inclined downstream with respect to said longitudinal axis, a series of directing planes inclined downstream with respect to said axis and intersecting the respective adjacent guiding planes to define a dihedral angle along each line of intersection, each line of intersection being directed downstream and closely eccentric to said longitudinal axis, and a series of bounding planes extending tangent to an imaginary cylinder coaxial with said discharge opening and of slightly less diameter thereof and interconnecting the respective adjacent guiding and directing planes, each line of intersection of adjacent directing and bounding planes lying in a plane normal to said longitudinal axis, each line of intersection of adjacent bounding and guiding planes being directed downstream closely adjacent the edge of said discharge opening.

2. In the exit structure as defined in claim 1, the downstream face of said end cone having a plurality of dihedral cowls thereon extending from the periphery and ending at the opening thereof and defined by planar surfaces parallel to the upstream guiding and directing planes and intersecting at a dihedral angle substantially equal to that defined at the line of intersection of each adjacent upstream guiding and directing planes.

3. In the exit structure as defined in claim 2, said series of guiding, directing and bounding planes and said plurality of dihedral cowls being five each in number, said cowls extending between the intersections of said series of bounding planes with said opening, said dihedral angle at the intersection of adjacent guiding and directing planes being in the range of 70 to 120, the lines of intersection between adjacent directing and bounding planes and between adjacent bounding and guiding planes lying in the common bounding plane.

4. Flow stabilizing means for an air blast tube in a gun type oil burner comprising a support axis, with a plurality of blades spaced equally thereabout adjacent edges of said blades lying in the same plane and being aligned longitudinally, said blades flaring outwardly from said support axis in a generally downstream direction to provide a spiral flow to fluid in the air blast tube, the outer edges of said blades with respect to said support axis being curved to form a surface of a volume of any cross section such that the straight line generatrix thereof is parallel to the angle of swirl with respect to said support axis, the blade area in normal projection to said support axis exposed to the fluid flow substantially completely occupying the blast tube without undue restriction to a fluid flow therein.

5. The flow stabilizing means of claim 4 wherein the upstream surfaces of said blades are inclined to said support axis, said outer edges being curved slightly less than semi-cylindrical, and the angle of swirl being in the range from 30 to 60 with respect to said support axis.

6. An air swirler having a plurality of vanes comprising means for supporting said vanes in equally spaced relationship in each quadrant of a fluid flow cylinder, said vanes having a generally downstream spiral inclination and an area exposed to fluid flow to direct substantially all of said fluid flow without undue restriction thereof, the outer edge of each of said vanes defining a semi-cylindrical surface having a straight line axis defining the angle of swirl of each of said vanes, adjacent edges of said vanes lying in the same plane and being aligned longitudinally.

7. In the air swirler as defined in claim 6, said angle of swirl being in the range of 30 to 60, said swirler having means for support within the cylinder.

8. In a gun type oil burner having an air flow tube with an oil line therein ending in a fuel nozzle adjacent the opening in the discharge end thereof, said discharge end having polyhedral surfaces on the upstream face thereof for directing air having a uniform mass flow with a minimum of turbulence in a tight swirl with jetlike currents around the longitudinal axis of said tube, an air flow stabilizer structure having blade areas defining the angle of swirl of the air in said tube and matched to each other and to the angular orientation of said polyhedral surfaces and comprising a support axis with a plurality of curved surfaces extending angularly therefrom for providing rotational motion to air in said flow tube, adjacent edges of said curved surfaces being in longitudinal alignment in the same plane, the edges of said curved surfaces adjacent the inner wall of said flow tube having a shape to define a surface to improve the air flow pattern in said flow tube, said polyhedral surfaces comprising a series each of relatively elongated guiding planes and of directing planes, both series being inclined downstream with respect to said longitudinal axis, the respective adjacent guiding and directing planes intersecting to define a dihedral angle along each line of intersection, each line of intersection being directed downstream and closely eccentric to said longitudinal axis, and a series of bounding planes extending tangent to an imaginary cylinder coaxial with said opening and of slightly less diameter thereof and interconnecting the respective adjacent guiding and directing planes, each line of intersection of adjacent directing and bounding planes lying in a plane normal to said longitudinal axis, each line of intersection of adjacent bounding and guiding planes being directed downstream closely adjacent the edge of said opening.

9. In combination in a pressurized fluid flow chamber for a gun type oil burner having a fuel conduit positioned therein and ending in a fuel discharge nozzle adjacent the discharge end of said chamber, fluid flow control means comprising a stabilizer positioned within said chamber and having angled blades with an effective area exposed to fluid flow to direct substantially all thereof without undue restriction of fluid flow, and an end cone structure having a central opening at the discharge end of said chamber, control surfaces on the upstream face of said end cone for directing air with a downstream swirling motion about the longitudinal axis of said chamber with jet-like currents closely eccentric to said axis, said control surfaces comprising series of guiding, directing and bounding planes, said guiding and directing planes being inclined downstream with respect to said longitudinal :axis with adjacent guiding and directing planes intersecting to define a dihedral angle along each line of intersection, each line of intersection being directed downstream and closely eccentric to said axis, said bounding planes extending tangent to an imaginary cylinder coaxial with and of lesser diameter than said chamber and interconnecting the respective adjacent guiding and directing planes, each line of intersection of adjacent directing and bounding planes lying in a plane normal to said longitudinal axis, each line of intersection of adjacent bounding and guiding planes being directed downstream closely adjacent said discharge end.

References Cited by the Examiner UNITED STATES PATENTS 2,146,250 2/1939 DElia 15876 2,347,594 4/1944 De Lin 15876 2,570,996 10/1951 Walshin 158-76 2,657,741 11/1953 Brierly 1581.5

FOREIGN PATENTS 183,874 8/1922 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

E. G. FAVORS, Assistant Examiner.

Claims (1)

1. AN EXIT STRUCTURE FOR THE AIR BLAST TUBE OF A GUN TYPE OIL BURNER COMPRISING AN END COME WITH A DISCHARGE OPENING HAVING A PLURALITY OF ADJOINING PLANAR SURFACES DEFINING CHANNELS ON THE UPSTREAM FACE BETWEEN THE PERIPHERY OF SAID END CONE AND SAID OPENING AND WITH A GENERAL DOWNSTREAM INCLINATION FOR DIRECTING AIR TANGENT TO AN IMAGINARY CYLINDER COAXIAL WITH SAID OPENING AND OF SLIGHTLY LESS DIAMETER THEREOF IN A HIGHLY CONTRACTED SWIRL ABOUT THE LONGITUDINAL AXIS OF THE BLAST TUBE AND DOWNSTREAM AND CLOSELY ECCENTRIC TO SAID LONGITUDINAL AXIS IN THE FORM OF JET-LIKE CURRENTS FLOWING FROM SAID CHANNELS WHEREBY INTIMATE MIXTURE OF FUEL SPRAY AND AIR IS OBTAINED, SAID PLANAR SURFACES COMPRISING A SERIES OF RELATIVELY ELONGATED GUIDING PLANES INCLINED DOWNSTREAM WITH RESPECT TO SAID LONGITUDINAL AXIS, A SERIES OF DIRECTING PLANES INCLINED DOWNSTREAM WITH RESPECT TO SAID AXIS

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