US2325442A - Pulverized fuel burner - Google Patents

Description

lJuly 27, 1943. n R. c. vRooM l 2,325,442

yPULVERIZED FUEL BURNER Filed March' 1o, 1941 2 Sheets-sheet 1 75??? :'r"r*| lv." "'1 "T" 10 1w 4s A Y O i 43 45 Filed March lO 1941 2" Sheets-Sheet 2 TTORNEY throat, is'assure'd.

Patented July 27, 1943 PATENT s'irjed.

Fig. 2 is a transverse section, taken along'z't'fie illustratingy a still. furtherf embodiment anthem-' ventiomnand i Ytirereoffifs efteted.

` 9 is axlgngitudinal section-:takenaalong .the linea- Sor E isr. In :thefoilowins descriptiQn :and in the icleinis certain :specific tems @are used foi-1 contenan@ in 'ref erririgto Marinus details offthe invention. 'Iheseiterms howeyersareto'begivnambroaiian interpretation as the state ofthe art f penmii. Referring fno the drawings more inidetail, the inventioniis yslfiovvn in Eiss- 1 :1:03 as applied 'Stora burner --comprising an elongated' burner tu b e L0 which y:is muntedlin registration with@ bnrner opening For throat fl'Lfin @furnace wall 1,2 rand is open at itscoutletiend 19ato the .combustion chamberof .theiuriia Tdhezburrierttiibe is Shown as :provided with@ aliange :I which cured Joy` any :suitahieinennssaginst im Miter surfacef-of ti1e :fu r nace wal1 t2. llieiinletgerd ib of #the :burneritube i0 zistiprovided si flange il@ secured against the :.Wall 15 0I a\vgind Wallerthezbnrnertuberl tiirough-anrinlet-.opena telesceping sleeve 32 which may be adjusted axially to vary the effective length of the cylinder Si) as desired. The inlet duct i8 and the inlet opening l are shown as extending axially over a substantial portion of the length of the burner tube Iii so as to supply the fuel stream thereto in the form of an extended layer which rotates and advances along the inner surface of the wall of the tube ,it in a uniform manner.

Secondary air may be supplied to the cylinder 30 by any suitable means, shown as an air register 35, mounted in the windbox l between the Wall i and a forward wall 35 and having a plu- Operation Y furnace and the helical ribs 28 cause the layer rality of peripheral air doors 3?. which are adapt- Y ed to admit a controlled quantity of air to the register and to cause the Same to advance axially with a rotary motion. The air register 35 is provided with an axial air discharge opening 33 registering with the open end of the cylinder 3B. The air register 3d may be of any standard type and is accordingly. not set forth herein in detail.

The cylinder Sii and the sleeve 32 .are shown asprovided. with a plurality -of peripherally spaced slots il@ and li respectively through which a portion of the stream of carrier air and fuel flows from the annular passage 3i into the interior 'of the cylinder 35 and is mixed therein with thesecondary air received from the air register. By rotating thesleevei 372 with respect to thefcylinder Billthe effective size of the slots 4Q may be varied, thereby regulating the quantity of carrier air and fuel admitted therethrough. One of 'the'slots El is preferably disposed in-registration with the inlet opening i9 whereby a portion of the fuel stream received from the inlet duct i8 is caused to pass directly into the interior of the cylinder 3Q Where it is-mixed with the secondary air. .The remainder ofvthefuel, sus

pended in primary air, flows around-the burner tube l in the annular passage 3l wherein it is caused to Vrotate and'advan'ce, asabovementioned. I f

`.incertain instances it may be desired toburn gaseous or liquid fuel in addition to or in place of the solid fuel above mentioned orfto use suchl gaseous. or liquid fuel for ignition purposes. For this purpose',l the vburner is shown as 'provided with a iiuidfuelsupply barrel 42 which extends axially of .the-burner tube lil and is provided at its inner fend with `an atomizer tip d3 -of any desired type. VHA diffuser lift is likewise mounted on the barrell Il?. but may be withdrawn into the air register, as indicated at ida by dotted lines, when pulverized fuel is burned; The barrel '2 extends outwardly thro-ugh the Aair register 35 and may bel lconnected vto any suitable' source of fluid fuel`,not shown. Y

l The centrifugal force produced by the rapidly rotating fuel mixture in the burner tube iii causes a substantial portion of the heavier fuel lparticles to hug'the surface of the tube. In or-V der toy increase turbulence and to throw such fuel toward theaxis of the burner, thus distributingV it acrossthe burner throat area, a plurality of curved varies may ybe providedwhich may be positioned closely. adjacent the wall ofthe burner 'tube iii.v In Ythe embodlmentshown the vanes'zi are adjacent ybut do not touch, the ribs 23. Thel vanes [i5 are shown as mounted on a spider-d6 having, a hub 'l'l which is secured to the atomizer barrel vigrby suitable means, such as a set screw'll.. The 'vanes i5 may thus be adjusted axially or angularly'to the optimum position. f

of fuel and carrier air to advance through the passage 3i helically toward the burner opening .i and to be discharged uniformly around the entire periphery of the burner throat. At the same time the secondary air for combustion is received from the discharge opening 38 of the air register and advances axially on the inside of the cylinder Sii. Upon leaving the cylinder 3% it mixes with the fuel and carrier air from the passage Si to form a combustible mixture.

A controlled portion of the fuel may be permitted to pass through the slots it into the in terior of the tube 37E? where it is immediately mixed with the secondary air.

Shortly after the fuel and carrier air have advanced past the end of the cylinder 3i! in the orm of a rotating mass, a complete mixture with the secondary air takes place and a uniform mixture of fuel and air is advanced to the burner throat forfcornbustion. The desired turbulence and distribution across the burner throat may be aided by the varies l5 which act as scoops to pick up the rotatingV mass of fuel and air and to throw the same inwardly toward the axis of the burner, and by the premixing of the secondary air with the portion of the fuel which has passed through the openings d into the tube Bil. The diffuser fifi may be adjusted in position to assist in controlling the opening of the burner throat and the direction of the air-fuel mixture issuing therefrom or the diffuser may be removed or withdrawn into the air register when desired. The direction of flow of carrier air and fuel supplied to the passage Si from the duct i3 may be controlled by suitable adjustment of the dampers 2l. Thedegree of rotationV of the secondary air may likewise be controlled by making a suitable adjustment of the air doors 37 of the air register 35. The point of direct contact between the carrier and secondary air and the proportion of fuel supplied through the slots 4t to the secondary air stream within the cylinder Si? for premixing may be regulated by suitable axial and rotary adjustment of the sleeve 32. Such adjustment is preferably made by experiment in order to obtain the optimum burner characteristics.

' Figs. 4 and 5 The embodiment Vshown in Figs. 4 and 5 is generally similar to that above described and the description of corresponding parts will not be repeated. In this embodiment the cylinder 50, corresponding to the cylinder lili of Fig. 1, is shown asY provided with a plurality of deflectors 5| which may be stamped out of the cylinder 5i? to form slots 52.4 The purpose of the deflectors 5I is to create an inward flow of fuel and carrier air from the passage 3i to the interiorrof the cylinder 5d, thereby causing a predetermined quantity of fuel to be withdrawn from the passage 3l into the central stream of secondary air. It is to* be understoodv that the deectors 5l may be varied in shape or position as desired-and may be made adjustable for the purpose of controlling the amount of fuel supplied Vthrough the wall of the cylinder to the stream of secondary air.

The cylinder 5,3 of Fig. 4 is also shown as provided with a set ofV peripherally spaced apertures 53 at the inlet end 59D thereof to permit a fur-` ther control of the distribution of the fuel and primaryl and secondary air. The apertures 53 may be made of any desiredv size or the end of the cylinder 5i) may be spaced inwardly from the end of the burner tube IG to obtaina similar effect. The apertures 52 and 53 may be used separately or in combination.

IThe lembodiment shown4 in Figs. 6 and '7,Y is generally similar to the embodiment shown in Fig. l, 4In this embodiment, however, the cylinder 55 is'made of smaller'diameter than the cylinder 3d ofFig. 1 and provides an annular passage 58 of greater crossfsectional area than the passage 3|. The cylinder 55 is shown as secured to theair register 35 by brackets 5 7 and is of smaller'diameter than the air register opening 38 so as to afford. access for secondary air from the air register opening intorthe passage 56 as well as into the interior of the` cylinder 55.

l In this embodiment a portion of the secondary air is admitted directly fromthe register into the annular passage 5S and is mixed therein with the fuel stream received from the inlet duct iS. This portion of the secondary air alsoassists in causing the rotating fuel stream to advance axially.

Figs. 8 and 9 In the embodiment shown in Figs. 8 and 9, the influence of the secondary air on the flow of fuel and carrier air is regulated by centrifugal means.` ln this embodiment, which is generally similar to that above described, the inlet duct 60 is provided with a wall El which is positioned beyond the opening 38 of the air register `35 and beyond the burner tube i0 in a radial direction toV form a fuel inlet chamber S2 out of the directl pathV of the secondary air from -the air register open'- ing. The wall El may be made of an axial length such that it registers with all or a portion only of the inlet duct G and joins the burner tube if] tangentially at a suitable point such 'as at 63 (Fig. 8). i

A fuel inlet chamber E4` is formed by awall of the duct E@ which joins the burner tube I0 tangentially at a point 66. The chambers 62A and 64 constitutea pair of fuel supply chambers receiving fuel from the inlet duct 6i) and delivering the same tangentially to the burner tube Iii.

The fuel inlet chambers 62 and G4 are joined by 63. The secondary air stream supplied from the air register 35 near the axis of the burner tube Iii does not make contact with the rotating mass of fuel in the chamber 62 until the air stream has been expanded from the diameter of the air register opening 38 to the diameter of the tube IU. n this embodiment, the portion of the fuel admitted to the chamber 62 and the portion supplied to the chamber 64 maybe controlled by adjusting the angular position of the bafes 2l. AV plurality of fuel inlet chambers of different and graduated diameters may be used if desired, two such chambers 62 and 54 having been shown for purposes of illustration only; l

When the fuelis deflected toward the chamber 62 by vanes 2l as in Fig. 9, a greater portion thereof is caused to rotate in said chamber E2 before being brought into contact with the stream of secondary air for combustion. When the Vanes 2|,are shifted to the right (as seen in Fig. 9) a greater portion of the fuel stream is deflected to the'chamber 64 and comes into contact with the stream of secondary air from the register 35 at a dierent zone. By a suitable adjustment of ,these above mentioned elements, improved distribution and mixing characteristics may bey obtained.

It will be noted that in all of the embodiments above described, a controlled portion of thefuel streamY is caused to assume a rotating motion and to travel axially a predetermined distance before it is brought into direct contact with the secondary air for combustion, This'permits con'- trol of the relative distribution of the fuel and carrier air and the secondary air, therebi7 livro-l viding a more uniform fuel and air distribution at the burner throat.

It is to be understood that the atomizer barrell 42, the vanes 45, and the ribs 28 may be utilized with any of .the embodiments above described; alsothat the helical ribs 23;. may be made of various forms as desired. i

The present invention, as above described, pro,-

vides a dependable and efficient burner of theV type above indicated, which is well suited for commercial o-peration. The flame produced thereby is extremely stable and uniform. `Although certain embodiments thereof have been shown and described for purposes of illustration,r it is to be understood that the invention is not; to be limited thereto, but that various changes and modifications may be made therein as will be readily apparent to a person skilled in the art. The invention is only to be limited in accordance with thescope of the following, claims.

What is claimed is:

1. A pulverized fuel burner comprisingv a burner tube having an open outlet end adapted to connect with a combustion chamber, means includ ing an inlet portin the peripheral wall of said burner tube supplying to said burner: tube in a, direction tangential to. the inner surface thereof l astream of pulverized fuelsuspended in carrier air, means causing said suspended fuel to advance helically in a peripheral layer in said burner tube to the outlet end thereof, a central axial air admission means including an air register admitting a secondary air stream at the inlet end of said burner tube out of the main path of the peripherally rotating layer of fuel, said air register having peripheral doors to irnpart a rotary motion to said secondary stream, and means preventing direct contact between at least the main portion of the rotating stream of secondary air and the main portion of said fuel stream at the inlet end of said burner tube.

2. A pulverized fuel burner comprising a burner tube havingan open outlet end adapted to connect with a combustion chamber, an inner tube in said burner tube having walls spaced therefrom to form an annular fuel passage therebetween, tangential fuel inlet means including an inlet port in the peripheral wall of said burner tube communicating with said annular passage to supply thereto a stream of pulverized fuel suspended in carrier air under conditions to cause said stream to rotate peripherally in said annular passage, means causing said layer of suspended fuel to advance helically in saidburner tube, and a central axial Vair admission means including an'air register admitting a secondary air stream :at the axis of said inner tube to advance axially therein, said air register having peripheral'doors to impart a rotary motion to said secondary air stream, said inner tube preventing contact between said peripherally rotating fuel stream and said rotating secondary air stream at the inlet end of said burner tube.

3. In a pulverized fuel burner as set forth in claim 2, means for adjusting the axial length of said inner tube for thereby controlling the point of contact between said streams.

. 4. In a pulverized fuel burner as set forth in claim 2, a'telescoping sleeve on said inner tube for adjusting the axial length thereof so as to control the point of contact between said streams.

5. A pulverized fuel burner as set forth in claim 2 in Vwhich said inner tube is provided with spaced slots to pass a portion of the fuel from the pe ripherally rotating fuel stream into the secondary air stream within said inner tube for pre-mixing.

6. A pulverized fuel burner as set forth in claim 2 in which said inner tube is provided with spaced slots to pass a portion of the fuel from the peripherally rotating fuel stream into thesecondary air stream within said inner tube for pre-mixing, and deflectors carried byrsaid inner tube adjacent said slots to directvthe flow of fuel inwardly therethrough.

7. A pulverized fuel burner as set forth in claim 2 in which said inner tube is provided with spaced slots to pass a portion of the fuel from the peripherally rotating fuel stream into the secondary air stream within said inner tube for pre-mixing, and means for adjusting the effective opening of said slots'.

8. In a pulverized fuel burner as set forth in claim 2, a set of Yaxial vanes mounted within said burner tube near the periphery thereof and beyond the end of said inner tube, said vanes being positioned to deflect the fuel stream toward the axis of said burner tube so as to distribute the fuel across the outlet end of said burner tube.

9. A pulverized fuel burner comprising a burner tube having an open outlet end adapt-ed to con- `nect with a combustionchamber, a central axial air admission means at the inlet end of said tube including an air register having an air discharge opening supplying a'secondary air stream to said tube to advance axially therein, said air register having peripheral' doors to impart a rotary motion to said secondary air, a fuel inlet duct carrying a stream ofpulverized fuel suspended in carrier air, a peripheral fuel inlet chamber at the inlet end of said tube receiving a stream of fuel from said duct and having an outer wall spaced radially beyond said air discharge opening and beyond the peripheral Wall of the burner tube to form an annular fuel passage out of the direct path of the secondary air stream, said outer wall becoming tangential to the wall of said tube to supply said stream of fuel thereto under conditions to cause the stream to rotate peripherally in a layer in said tube, means causing said layer of suspended fuel to advance helically toward the outlet end thereof, whereby at least the major portion of the stream of fuel suspended in carrier air is caused to advance in said tube beyond said inlet chamber before being mixed with the secondary air stream.

l0. A pulverized fuel burner comprising a burner tube having an open outlet end adapted to connect with a combustion chamber, tangential fuel inlet means, including an inlet port in the peripheral wall of said tube, supplying to said tube a strearnof pulverized fuel suspended in carrier' air under conditionsto cause said stream to rotate peripherally in said tube, means causing said layer o-f suspended fuel to advance helically therein, a central axial air admission means admitting a secondary air stream to said tube to advance axially therein and to mix with said fuel stream to form a combustible mixture, and a set of axial vanes mounted in said burner tube near the periphery thereof and positioned to deliect the fuel stream toward the axis thereof so as to distribute the fuel across the outlet end of said tube. Y 'Y 11. A pulverized fuel burner comprising a burner tube with a burner throat at its outlet end adapted to open into a combustion chamber, means supplying to said burner tube, in a direction tangential to the inner surface thereof, a stream of pulverized fuel suspended in carrier air, means causing said suspended fuel to advance helically in a peripheral layer in said tube to the outlet end thereof, and elongated tubular means of a diameter at least as small as the diameter of said burner throat extending into said burner tube from the inlet end thereof for supplying secondary air thereto.

ROBERT C. VROOM.

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