US2747657A - High capacity oil burner with impeller hub air jet ring - Google Patents

Description

May 29, 1956 J. F. HARVEY ETAI.

HIGH CAPACITY OIL BURNER WITH IMPELLER HUB AIR JET RING 2 Sheets-Sheet 1 Filed April 25, 1952 f ,PH 3 fn RFQM mam. N fl m ww n mwJ Jmm 2 m F WW- ATTORNEY May 29, 1956 J. F. HARVEY ET AL 2,747,657

HIGH CAPACITY OIL BURNER WITH IMPELLER HUB AIR JET RING 2 Sheets-Sheet 2 Filed April 25, 1952 FIG? F G. 6 INVENTORS c/bbl? FflarI ey flnfizzrfifrmandor/r BY $605 fl/Vzson MM ATTORNEY United States Patent HIGH CAPACITY OIL BU inn wrrrr WELLER HUB AIR JET n ne John F. Harvey, Akron, and Arthur W. Hermandorfer, Barberton, Ohio, and Jacob A. Mason, Mapleweod, a s n t The ab-r els .& W tte Germany, NewYork, N. Y., acorporation of New .lfiersey Application April 25, 1952, Ser ial No.-284,26 11 C im (c Ass s-vs) The present invention relates in general to the construction and operation of fluid fuel burners, and more particularly, to improvements in the construction and the operation of high capacity, wide range, return flow liquid fuel burners utilizing a conical spray of atomized fuel discharging through a burner port'into a swirling stream of air.

Modern fluid fuel burners ofthe return flow type are designed to operate over a wide range of capacities, for example, from 200-500 lb. of fuel per hour, and at supply pressures ranging, for example, from 300 p. s. i. to 1000 p. s. i. The lower supply pressures are generally better for low capacity operation, and the higher supply pressures for the higher capacities.

In such return flow burners, fluid fuel is delivered inwardly to a whirl chamber in an atomizer through slots tangential to the chamber periphery, and all or a portion of the fuel is discharged through an orifice as a conical whirling spray. At less than full load, some of the fuel thus delivered to the whirl chamber is withdrawn therefrom and returned to storage or to the input of a fuel delivery The rate of fuel discharge depends upon the supply pressure, the return pressure, the constants of the atomi zer, and the interrelation of these factors. Gontrol of the discharge rate over the burner range may be effected by varying the supply pressure, the return flow pressure, or b th, Optimum results have been obtained when the supply pressure, the return pressure, and the ratio of the supply pressure to the return pressure are changed in accordance with load.

An oriented air flow is provided immediately embracing the atomizer. nozzlev discharge by a varied impeller at the discharge end of the nozzle. However, the major portion of combustion air is supplied through an air re er, whi m y compr se n or mo e of a d cones, mounted in the burner port concentric with the atomizer nozzle. Air is supplied under pressure to the burner port for controlled delivery through the impeller and air register and generally with suflicient whirl to provide rapid and effective admixing of the entering air with the cone of fuel particles, thereby promoting ignition and combustion of the fuel.

T e Pre u e n a e f fl w of he c mbu t on air is varied in accordance with load variation, as is also the supply pressure of the fuel delivered to the atomizer. While the pressure differential across the tangential slots, which determines the angular velocity in the whirl churnber, is reduced with a decrease in load or in burner delivery, the angular velocity is not reduced sufficiently to appreciably narrow the spray angle. The reduced secondary air flow through the register, concurrent with the reduced fuel delivery, may be insufficient to keep the apex angle of the fuel spray cone narrow enough to avoid impingement of fuel spray particles on the adjacent brickwork of the burner throat. Such fuel impingement on 2,747,657 Patented May 29, 1-956 B the brickwork is aserious operating difliculty and involves a great reduction in burner efliciency.

Furthermore, at the lower capacities, it has been found that thesuction effect of the air flowing through the impeller creates a fuzz or fog of fuel particles around .the atomizer nozzle. This fuzz settles on the nozzle and is carbonized, requiring frequent removal of carbon to assure optimum mixing and combustion. Various means have been proposed to correct this condition, such as frequent scraping of the carbon from the atomizer tip or nozzle, adjustment of the burner position in the port with load changes, etc. None of these expedients has been found satisfactory.

In accordance with the present invention, the foregoing difficulties are preventedby directing air under pressure toward the rear of the spray cone and in an annular zone parallel to the burner axis and located radially between the nozzle periphery and the air stream through the impeller. To this end, an air chamber is provided in embracing relation with the atomizer nozzle and having a circular group of circumferentially adjacent air ports in a forward wall located approximately at the discharge end of the nozzle. Air under pressure is supplied to the chamber, and the ports are arranged to discharge air parallel to the nozzle axis.

This additional pressure air discharge immediately around the atomizer orifice tends to narrow the apex angle of the fuel spray cone, particularly at reduced burner rates, so that the fuel particles do not impinge .on the brickwork of the burner throat. Furthermore, :the suction eflfeet of the impeller air is counteracted so that a fuel mist doe n t form n he a miz r nozzle.

For a more th eugh understandin of the principles of the invention, referen e is made to the following description of typical embodiments of the invention as illu t in the aeesmpanying dr wi n he d awing;

Fig. 1 is a part sectional and part elevational view of a liquid fuel burner and an associated burner port air admission arrangement embodying the. invention;

Fig. 2 is an enlarged elevation view, partly in section, of the atomizer, impeller, and associated .air chamber;

Fig. 3 is a transverse sectional view on the line 3.-3 0f is- 2;

Fig. 4 is an inside elevation view, with some parts omitted, of the burner port closure and burner mounting plate;

Fig. 5 is a. transverse sectional view on the line 5--5 of Fig. l, with the louver blades closed;

Fig. 6 is a view, similar to Fig. 2, of a modified form of the invention; and

Fig. 7 is an axial sectional view through the atomizer.

The invention is illustrated as incorporated in a wide range return flow liquid fuel atomizer burner which may generally be constructienally of the type shown in U. S. Patent No. 2,369,046, The atomizer assembly is mounted in a circular burner port 15 formed in one of the vertical walls 11 of a liquidfuel, burning furnace. The port 10 converges inwardly to. an intermediate. circular throat, and then diverges to the inner or furnace side of wall 11. A- metallic p rt ring 2, ,v sub antially shaped as; a truncated cone, defines the outer section of the burner port, and has a. flange 21 secured to. then-retail. casing 1 :2 of the furnace wall' 11 by bolts 13 which also secure the flange 14 of a spoolmember 15' to the cone 2% and casing 12. A second or inner port ring'30, likewise shaped as a truncated cone, issupported within and in spaced relation tocone 20 by studs 16' extending through tubular spacers 17. Exteriorly spaced from-casing 12 is an outer casing '18, the casings 12 and 18- forming a passageway 19 for the flow of combustion air from a forced draft fan (not shown) to burner port 10.

A circular cover plate 41 closes an access opening in wall 18 arranged coaxially of and of larger diameter than the burner port 10. Plate 41 is provided with a heat protective covering of insulating material 42 held in place by a metallic sheet 43, and is rigidly connected by struts 44 to the outer circumference of an air register ring 45 carried by spool member 15, the parts and forming a continuation of outer cone 20.

Cover plate 41 supports a central hub member through which extends a distance piece or tube 47 embracing an atomizer assembly having a fuel supply assembly 48 on its outer end and an atomizer head 49 on its inner or furnace end. The atomizing head 49 is preferably of a type producing a conical spray of atomized liquid fuel with the axis of the spray coaxial with the cones 20 and 30.

Referring to Fig. 7, liquid fuel is delivered under pressure from an annular supply passage 125 formed between an inner tube 122 and an outer tube or barrel 121. The furnace end of tube 122 is threaded into a cylindrical primary nozzle or plug member 123 having a sealing contact with the furnace ends of the two tubes. Nozzle 123 has an annular slot 124 in its furnace face connected by a circular series of passages 126 to fuel inlet passage 125. This furnace face also has a small diameter annular slot 127, defining a central protuberance 128 and connected by a circular series of apertures 129 to the central fuel return passage 120 in tube 122.

The furnace face of nozzle 123, when atomizer 49 is assembled, contacts the outer face of a secondary nozzle or intermediate plate 132. The latter has a central passage therethrough defined by forwardly and rearwardly flaring frusto-conical surfaces connected by a short throat. The forward frusto-conical surface, with protuberance 128, constitutes a substantially frusto-conical portion of a whirl chamber 135. The rearward frusto-conical surface is radially spaced from the lateral surface of protuberance 128 to form an annular passage 136 connecting chamber 135 to slot 127. An annular slot 137 is formed in the furnace face of plate 132 in alignment with slot 124 and connected therewith by a circular series of apertures 138.

The furnace face of plate 132 contacts the outer face of a sprayer or orifice plate 140, which is peripherally cut away to provide a seat for an end cap 141 screwed on tube 121 to hold the parts assembled. Sprayer plate 141) has a central cylindrical passage 142 coaxial with the central aperture of plate 132 to form the main section of whirl chamber 135. Passage 142 is connected by a frusto-conical passage to a discharge orifice 144 of smaller diameter than passage 142. The outer face of sprayer plate 140 is formed with a plurality of slots 146 each tangential to the periphery of passage 142 and communicating, at their outer ends, with slot 137 of plate 132, to receive liquid fuel from slot 137 and deliver the same substantially tangentially to the central portion of the whirl chamber.

With the foregoing construction, liquid fuel under a substantial pressure is delivered through inlet passage 125, holes 126, slot 124, holes 138 and slot 137 into tangential slots 146. Due to the tangential arrangement of slots 146, the fuel follows a spiral path in the whirl chamber toward the discharge orifice. In such return flow atomizers, a portion of the fuel is bypassed and returned to the reservoir or fuel pump inlet to vary the burner capacity. In the illustrated atomizer head, the return fuel is drawn off near the outer end of whirl chamber 135, passing through passage 136, slot 127, and holes 129 into the return fuel passage 120. The illustrated atomizer nozzle is the same as that shown and described in the copending application of Lewis W. Heller, Serial No. 115,013, filed September 10, 1949.

Concentric with distance piece 47 and exteriorly surrounding the atomizer head 49 is an impeller plate shaped as a truncated cone with the base toward the furnace chamber. The conical surface of impeller plate 50 has a series of equally spaced air openings and corresponding air deflector plates 51 associated therewith.

A circular series of segmental louver blades are pivotally mounted within the annular space between ring 45 and distance piece 47 by pins 52 and 53. The rotational axis of each louver blade is at an oblique angle to the axis of distance piece 47, and the blades are adjustable about their axes by means of pinions 54 engaging a ring gear 56 on a rotatable sleeve 57. Sleeve 57 is rotated by suitable external mechanism 58 (Fig. 4) such as shown in U. S. Patent No. 2,260,062, to position the louver blades 55 to control the flow of air from passageway 19 into cones 20 and 30.

The primary and secondary air admission arrangements, and their relation to impeller 50 are, in the illustrated example, the same as those disclosed in the copending application of Thomas B. Stillman, deceased, and Jacob A. Mason, Serial No. 167,992, filed June 14, 1950, for Burner Throat with Air Inlet Annulus Defined by Internally Bladed Cone, now Patent No. 2,669,296, issued February 16, 1954. Accordingly, these arrangements will be described only generally, and reference is made to said copending Stillman et al. application for details of construction.

Inner cone 30 defines the primary air passage through the burner port. The secondary air passage is defined by outer cone 29 and inner cone 30. The cones 2i) and 30 are provided with special vanes and 70, respectively, for imparting a whirling motion to the primary and secondary air streams, the whirling motion being about the axis of burner tube 47 and in the same angular direction as the whirl produced by the impeller deflectors 51.

In the operation of the described burner, the minor portion of the secondary air passing through impeller 50 has a swirl imparted thereto for effective mixing with the whirling conical spray of liquid fuel directed from atomizer 49. The major portion of the air stream through the burner port passes through the primary air passages formed by cone 30 and blades 70, being mixed therein with the primary air entering cone 20 beyond the periphery of impeller 50. A whirling motion is imparted to the air passing through cone 30, for effective mixing of the air with the fuel stream. At the same time, the secondary air passing through the secondary air passages, formed by cones 20 and 30 and vanes 60, has a large degree of swirl imparted thereto. The secondary air entering these passages has its pressure somewhat reduced and its velocity increased as it passes from the relatively large cross sectional entrance areas of the secondary air passages into the gradually constricted secondary air passage portions formed by convergence of outer cone portion 23 toward cone 30. The high velocity whirling motion of the secondary air leaving the furnace end of cone 20 results in a further effective mixture of the secondary air with the mixed primary air and liquid fuel cone.

As previously explained, in the operation of Wide range, high capacity, return fiow fluid fuel atomizers, the air flow is reduced concurrently with the oil discharged with reduction in output of the atomizer. However, the velocity imparted to the fuel in flowing through the tangential slots into the whirl chamber is still sufficient to produce a fuel spray cone with a relatively wide apex angle. Due to reduced air flow through the register, the spreading of the spray cone causes fuel to impinge on the brickwork of the burner port, greatly reducing the burner efiiciency. This effect is accentuated by the relatively small openings through impeller 56 which inhibit sufficient flow of air, at reduced loads, to narrow the apex angle of the spray cone. In addition, the suction effect of the air passing through the impeller openings amines causes a mist to form on the outer end of the atomizer nozzle.

In the present invention, these undesirable elfects are prevented by directing air under pressure against the back of the spray cone and in embracing relation with the outer end of the atomizer nozzle, to partially collapse the spray cone and narrow its angle so that the spray cone will not impinge on the burner port brickwork, and simultaneously destroying the suction efiect of the air passing through the impeller openings.

In the arrangements of Figs. 1 through 5, the air delivery arrangement is provided by modifying distance piece 47 for cooperation with a sleeve member 65 to form an air chamber. Distance piece 47 is externally threaded outwardly of its inner end as indicated at 61. Inwardly of threaded portion 61, the outer diameter of distance piece 47 is of reduced diameter as at 62.

Member 65 has a thick walled outer end internally threaded, as at 63, to engage threads 61. Inwardly of threads 63, the wall of member 65 is substantially thinner, as at 64, and has an inner diameter substantially greater than the outer diameter of distance piece 47. This wall portion 64 has diametrically opposite apertures 66, 66' in which are seated nipples 67, 67. At its inner end, wall 64 has a radially inwardly directed flange 68 having an inner diameter substantially equal to that of distance piece 47. When member 65 is threaded onto distance piece 47 until flange 68 tightly engages the reduced distance piece end, an annular air chamber 75 is formed. An outwardly directed frusto-conical flange 69 on the inner end of member 65 serves as a mounting for impeller 50.

Air is controllably discharged from chamber 75 through a circumferential series of apertures 80 in flange 68. It will be noted that apertures 80 are in surrounding or embracing relation to atomizer nozzle 49. The air discharged from chamber 75 is under pressure, such as, for example 1 /2 p. s. i., and at a rate of, for example, 25 C. F. M. The pressure of the air delivered through ports 80 is generally equal to the pressure of the secondary air through the register.

The low pressure air is delivered to chamber 75 in the following manner. A coupling 71 is mounted through wall 41, 42, 43 for attachment to a suitable pipe connection from a controlled source of air under pressure. Just inside the wall, coupling 71 is connected to a T 72. From T 72, two branch connections 73, 73' extend outwardly, downwardly, and then inwardly for connection to nipples 67, 67', respectively. It will be noted that the inwardly extending sections of the two branches are each aligned with the closed mating edges of a pair of louvers 55, these mating edges being suitably arcuately recessed to accommodate the branches, as best seen in Fig. 5.

The air supply is thus branched and delivered in substantially uniform supply to, and distribution of theair in chamber 75 for substantially uniform discharge through the apertures 80. This provides a uniformly distributed enveloping air stream around the projected outer surface of nozzle 49, which impinges on the back of the fuel spray cone and collapses the cone at least sufficiently to prevent impingement of fuel on the burner port brickwork. The enveloping air stream through the apertures 80 also destroys the suction effect of the air flowing through the impeller openings to prevent the mist formation.

Fig. 6 shows an alternative air delivery arrangement removably mounted on a burner 81 having an atomizer 49' at its furnace or inner end. Burner 81 extends through a distance piece or inner sleeve 82, which has a loose fit over nozzle 49', being held in concentric relation with burner 81 by a spacer ring 83. The furnace end of distance piece 82 is reduced in wall thickness and threaded, as at 84, to receive an internally threaded extension 86 on a flat annular port plate 85 formed with a circumferential series of air delivery ports 87. The

inner diameter of plate is substantially equal to that of distance piece 82 and the plate outer diameter is substantially equal to that of an outer sleeve 88. The latter is held with its furnace end in tight engagement with plate 85 by a cap 91 threaded onto the furnace end of sleeve 88 and having a lip 92 overlying the peripheral margin of plate 85.

A ring 93 is welded or otherwise secured to sleeve 82 near its outer end, and holds the inner ends of the sleeves in concentric spaced relation to form an air chamber 90, cap 91 and plate 85 holding the inner sleeve ends in concentric spaced relation. A clamping ring 94 is threaded into the outer end of sleeve 88, compressing a packing 96 against ring 93, ring 94 having an annular flange 97 fitting closely over burner .81 to properly position the air chamber thereon in cooperation with ring 83. It will be noted that the chamber assembly is relatively adjustable longitudinally of the burner.

Air under pressure is delivered to chamber 96 through one or more nipples 9.9 secured in ports 98 in outer sleeve 88, these nipples being suitably connected to a sourceof air at low pressure. Ring 9.1 may be suitably modified in the same manner as member 65 (Fig. 2) to support the impeller. The arrangement of Fig. 6 operates in the same manner as that of Figs. 1-5, so that detailed description of its operation is believed unnecessary.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

We claim:

1. In combination with a furnace wall having a fuel burn r port therein, a burner arranged in operative relation to such port and including a tubular distance piece; a fluid fuel burner nozzleconst ructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; a supply of fluid fuel under pressure connected to said nozzlej means mounted in embracing relation on the nozzle'end of said distance piece having an inner surface spaced from the distance piece outer surface and end wall means'engaged with the end of said distance piece to form, with said distance piece, an air chamber embracing said nozzle; a bladed aperture conical impeller mounted on the discharge end of the air chamber for directing a whirling air stream into admixture with the fuel spray cone; air register means embracing said impeller to direct the major portion of the combustion air through said burner port; said end wall means having a series of apertures therein forming air discharge ports around said nozzle periphery inwardly of said impeller;

and a supply of air under pressure connected to said chamber for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means 2. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; a supply of fluid fuel under pressure connected to said nozzle; means mounted in embracing relation on the nozzle end of said distance piece having an inner surface spaced from the distance piece outer surface and end wall means engaged with the end of said distance piece to form, with said distance piece, an air chamber embracing said nozzle; a bladed aperture conical impeller mounted on the discharge end of the air chamber for directing a whirling air stream into admixture with the fuel spray cone; said end wall means having a series of apertures therein forming air discharge ports around said nozzle periphery; and a supply of air under pressure connected to said chamber for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

3. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; and sleeve means mounted in embracing relation on the nozzle end of said distance piece and including an end portion firmly secured on said distance piece, a radial end flange abutting the nozzle end of said distance piece, and an intermediate surface portion spaced from the distance piece outer surface, all cooperating to form, with said distance piece, an air chamber embracing said nozzle; a bladed aperture conical impeller mounted on the discharge end of the air chamber for directing a whirling air stream into admixture with the fuel spray cone; said end wall means having a series of apertures therein forming air discharge ports around said nozzle periphery inwardly of said impeller; said sleeve means being constructed and arranged for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

4. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; and sleeve means mounted in embracing relation on the nozzle end of said distance piece and including an end portion firmly secured on said distance piece, a radial end flange abutting the nozzle end of said distance piece and an intermediate surface portion spaced from the distance piece outer surface, all cooperating to form, with said distance piece, an air chamber embracing said nozzle; a bladed aperture conical impeller mounted on the discharge end of said sleeve means for directing a whirling air stream into admixture with the fuel spray cone; said end Wall means having a series of apertures therein forming air discharge ports around said nozzle periphery inwardly of said impeller; and nipple means mounted through said intermediate surface portion for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means. 5. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; a sleeve embracing said distance piece and having an inner diameter greater than the distance piece outer diameter; means supporting one end of said sleeve in spaced fluid tight relation on an intermediate portion of said distance piece; and means, including a radially extending wall, supporting the opposite end of said sleeve in spaced fluid tight relation on the nozzle end of said distance piece to form, with said distance piece, an air chamber embracing said nozzle; and a bladed aperture conical impeller mounted on the discharge end of said sleeve means for directing a whirling air stream into admixture with the fuel spray cone; said wall having a series of apertures therein forming air discharge ports around said nozzle periphery inwardly of said impeller; said sleeve being constructed and arranged for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

6. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; a sleeve embracing said barrel and having an inner diameter greater than the distance piece outer diameter; a bladed aperture conical impeller mounted on the discharge end of said sleeve means for directing a whirling air stream into admixture with the fuel spray cone; a member secured on the nozzle end of said distance piece and having a radially extending wall peripherally contiguous with the inner surface of said distance piece and the outer surface of said sleeve; said wall having a series of apertures therein forming air discharge ports around said nozzle periphery inwardly of said impeller; means securing the nozzle end of said sleeve in fluid tight engagement with said wall; and means supporting the other end of said sleeve in spaced fluid tight relation on an intermediate portion of said distance piece; said sleeve being constructed and arranged for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

7. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; a sleeve embracing said barrel and having an inner diameter greater than the distance piece outer diameter; a bladed aperture conical impeller mounted on the discharge end of said sleeve means for directing a whirling air stream into admixture with the fuel spray cone; a member secured on the nozzle end of said distance piece and having a radially extending wall peripherally contiguous with the inner surface of said barrel and the outer surface of said sleeve; said wall having a series of apertures therein forming air discharge ports around said nozzle periphery inwardly of said impeller; means securing the nozzle end of said sleeve in fluid tight engagement with said wall; and means, including a fluid tight packing, an abutment on said distance piece, and a packing unit engaged in said sleeve, supporting the other end of said sleeve in spaced fluid tight relation on an intermediate portion of said distance piece; said sleeve being constructed and arranged for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

8. In combination with a furnace Wall having a fuel burner port therein, a wide range return flow mechanical atomizing liquid fuel burner arranged in the port and including a tubular distance piece, a nozzle mounted through said distance piece and having a fuel supply line and a fuel return line connected thereto, the nozzle being constructed and arranged to discharge at least a portion of the fuel supplied thereto in the form of a whirling spray cone from discharge means at the discharge end of the burner, and a bladed aperture impeller embracing the discharge end of the burner and operative to direct a whirling air stream through the port for admixture with the fuel spray, the fuel discharge pressure and the air flow rate being varied in accordance with load and the angle of the spray cone remaining sufliciently Wide under the lowered air flow conditions at low load to impinge fuel particles upon the burner port surface due to the restrictions on air flow by the impeller aperture; means for collapsing the spray cone sufliciently to prevent such impingement comprising means mounted in embracing relation on the nozzle end of said distance piece having an inner surface spaced from the distance piece outer surface and end wall means engaged with the end of said distance piece to form, with said distance piece, an air chamber embracing said nozzle; said end wall means having a series of apertures therein forming air discharge ports around the periphery of said nozzle; said chamber being constructed and arranged for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

9. In combination with a furnace wall having a fuel burner port therein, a wide range return flow mechanical atomizing liquid fuel burner arranged in the port and including a tubular distance piece, a nozzle mounted through said distance piece and having a fuel supply line and a fuel return line connected thereto, the nozzle being constructed and arranged to discharge at least a portion of the fuel supplied thereto in the form of a whirling spray cone from discharge means at the discharge end of the burner, a bladed aperture impeller embracing the discharge end of the burner and operative to direct a whirling air stream through the port for admixture with the fuel spray cone, and an air register in the port embracing the burner and operative to direct the major portion of the combustion air through the port for admixture with the fuel spray cone, the fuel discharge pressure and the air flow rate being varied in accordance with load and the angle of the spray cone remaining sufficiently wide under the lowered air flow conditions at low load to impinge fuel particles upon the burner port surface due to the restrictions on air flow by the impeller aperture; means for collapsing the spray cone sufficiently to prevent such impingement comprising means mounted in embracing relation on the nozzle end of said distance piece having an inner surface spaced from the distance piece outer surface and end wall means engaged with the end of said distance piece to form, with said distance piece, an air chamber embracing said nozzle; said end wall means having a series of apertures therein forming air discharge ports around the periphery of said nozzle; said chamber being constructed and arranged for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

10. In combination, a fluid fuel burner including a tubular distance piece and a fluid fuel burner nozzle constructed and arranged to discharge a stream of fluid fuel in the form of a whirling spray cone from discharge port means at the discharge end of the nozzle, said nozzle being mounted through said distance piece; and sleeve means mounted in embracing relation on the nozzle end of said distance piece and including an end portion firmly secured on said distance piece, outer end wall means including a radially inwardly extending flange portion abutting the nozzle end of said distance piece to limit axial movement of said sleeve means relative to said distance piece and a radially outwardly extending flange portion in substantially the same diametric plane as said inwardly extending flange portion, for mounting an impeller, and an intermediate surface portion spaced from the distance piece outer surface, all cooperating to form, with said distance piece, an air chamber embracing said nozzle; said radially inwardly extending flange portion of said outer end Wall means having a series of apertures therein forming air discharge ports around said nozzle periphery; and nipple means mounted through said intermediate surface portion for connection to a supply of air under pressure for discharge through said air discharge ports in impinging relation on the spray cone of fluid fuel discharged through said nozzle discharge port means.

11. Sleeve means as claimed in claim 10 in which said outer end Wall means are integral with said sleeve means.

References Cited in the tile of this patent UNITED STATES PATENTS 468,589 White Feb. 9, 1892 1,817,470 Adams Aug. 4, 1931 2,066,806 Smith et a1 Jan. 5, 1937 2,206,070 Andler July 2, 1940 2,219,696 Mueller et a1 Oct. 29, 1940 2,260,062 Stillman Oct. 21, 1941 2,369,046 Harvey et a1 Feb. 6, 1945 2,396,867 Mason et a1. Mar. 19, 1946 2,414,459 Fletcher Jan. 21, 1947 2,458,541 Urquhart Jan. 11, 1949 2,502,664 Nest Apr. 4, 1950 FOREIGN PATENTS 465,691 Great Britain May 13, 1937

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