US2876763A

US2876763A - Multiple fuel burner and space heater

Info

Publication number: US2876763A
Application number: US515686A
Authority: US
Inventors: Robert H Hunter; Ralph S Damon
Original assignee: Hunter Co Inc
Current assignee: Hunter Co Inc
Priority date: 1955-06-15
Filing date: 1955-06-15
Publication date: 1959-03-10
Anticipated expiration: 1976-03-10

Description

R. H- HUNTER ET AL 2,876,763

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15. 1955 March 10, 1959 4 Sheets-Sheet 1 ATTOQNEYS March 1 1959 R. H- HUNTER ETAL I 2,876,763'

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15, 1955 4 Sheets-Sheet 2 50 55' FLE-E. EE-E INVENTORS POBEE'T Hulk/TEE AND BY Pa /4 5. DAMON {JTTOQNB S March 10, 1959 R, HUNTER IEI'AL 2,876,763

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15, 1955 4 Sheets-Sheet 3 INVENTORS P019527 H HUNTEE M0 BY Paw 5. DAMo/v Mm Mr s aw.

ATTOENEYfi "Mamh 1959 R. H. I-VIUNTER ET AL 2,876,763

MULTIPLE FUEL BURNER AND SPACE HEATER Filed June 15, 1955 4 Sheets-Sheet 4 Q filil/ENTOR. 0 55/27 UNTEE AND FIE A By QALPH 5. DAMON Bow-011%, 5W

#0144150; MW ATTOEA/EYi United States Patent MULTIPLE FUEL BURNER AND SPACE HEATER Robert H. Hunter, Gates Mills, and Ralph 5. Damon, Cleveland, Ohio; said Damonassignor to said Hunter Application June 15, 1955, Serial No. 515,686

8 Claims. (Cl. 126-110) This invention relates to atomizing liquid fuel burners, more particularly to such burners designed for use with fuels of different viscosities. It has been recognized that liquid hydrocarbon fuels can be efliciently burned by spraying them into combustion supporting atmospheres. Various arrangements have been devised to improve the characteristics of the spray, to provide turbulence and specialized rotary and spiral movements of the air or ent .invention to provide a fuel burning method and a metal fuel burner which are adapted to the use of liquid fuels of different viscosities, weights and values. In accordance with this aspect of the invention the fuel is projected from a nozzle under pressure in an expanding spray pattern into one end of a helically rotating air mass, the spray entering the air mass in a plane normal to the spray axis and spaced axially from the spray nozzle. The cross sectional area of the spray in the plane at which it enters the air mass represents only a small fraction of the cross sectional area of the air mass, so that the spray is completely surrounded by, and its outer portions entrained in, the rotating air to maintain the liquid fuel particles in suspension during burning. As a refinement of the process the rotating, helically advancing air mass into which the fuel spray is projected constitutes the secondary air for combustion, the primary air being mixed, as in asuitable nozzle, with the liquid fuel at or prior to the instant the fuel is sprayed into the rotating airmass. As a further refine spaced axially along the length of the rotating mass and distributed about its outer periphery or circumference. In a specialized version concerned with this aspect of the invention the combustion chamber is defined by inner flame shield and outer shroud combustion tubes of circular section disposed in coaxial relation and separated by an annular air supply chamber. The inner flame tube is formed with a plurality of distributed openings through which air introduced under pressure into the annular chamber is admitted, preferably tangentially, into the interior of the flame tube, the tangentially entering air effecting the desired rotation of the air mass inside the flame tube, such a structural arrangement being a further object of the invention.

Another object is to provide a burner of the character mentioned in which the fuel projecting nozzle is maintained during operation at a temperature sufiiciently low to eliminate objectionable carbonization while the sprayed fuel is prevented from contacting relatively low temperature components of the structure until after combustion is complete, elimination of objectionable carbon deposits that. would interfere with the continued eflicient functioning of the burner being thus obtained. This objective is achieved by the projection of the fuel in an expanding spray pattern through a matching opening in a control plate which delineates the hot burning zone from a relatively low temperature non-burning zone or chamber spacing the nozzle from the burning zone. This aspect of the invention contemplates an elongated combustion tube or tubes disposed in coaxial relation to the projection axis of the nozzle. The aperture control plate is disposed transversely across the interior of the tube or tubes to divide such interior into the low temperature normalizing chamber adjacent the nozzle and the high temperature flame chamber remote from the nozzle, the flame chamber preferably being much longer and larger than the normalizing chamber. In the arrangement mentioned, wherein an inner flame tube and an outer shroud tube are disposed in coaxial relation in the provision of an annular air chamber, secondary air is introduced tangentially into one end of such annular air chamber and,

in circulating between the combustion tubes, cools the latter while being heated. The air and fuel receiving ends of the combustion tubes are closed by a metal plate to which they are rigidly attached, this plate desirably constituting the apertured control plate through which the fuel spray is projected. A hollow member,

also of metal, is secured against the outside of the closure plate and carries the fuel projecting nozzle. The metal nozzle body'is rigidly secured to the hollow mountingmember in a wall of the latter which is spaced from 'the apertured control plate so that the spray from the nozzle is projected across the chamber of the mounting member before passing through the aperture of the control plate into the combustion chamber of the flame tube. The cooling effect obtained by introduction of the secondary air spirally into the receiving end of the combustion tube or tubes is thus effective by reason of the heat conducting characteristics of the rigidly connected together metal components in keeping the nozzle body at a sufliciently low temperature to prevent carbonization of the fuel in or on the nozzle. As a refinement of this aspect of the invention the nozzle body and the related components are made of heavy sectioned brass or similar metal of high heat conductivity, and primary air is led through such heavy sectioned components and into a mixing chamber in the nozzle to provide localized cooling ofthe nozzle structure. As a further refinement of the nozzle arrangement there is provided a protective cap or-shield, which desirably takes the form of a hollow cup disposed in embracing relation over the nozzle. The cup is mounted in heat conducting air receiving relation to "the'nozzle supporting member and is formed with an opening through which the received air mixed with the expanding spray is projected, these being further objects of the invention.

Other objects and advantages relate to certain novel features of construction and combinations and arrangements of parts devised to achieve simplicity in construction, service and repair and economy in manufacture and operation. These and the preceding objects and advantages are apparent in the following detailed description of the invention made in connection with the accompanying drawings forming a part of the specification.

In the drawings:

Figure 1 is a side elevational view partly in section with parts broken away and removed and partly diagrammatic showing a space heater incorporating the burner out the top opening 5.

heat exchanger and control principles of the present invention;

Fig. 2 is an elevationaldetail of the rear end of the nozzle mounting member showing the nozzle and the ignition electrodes, this-'viewbeing enlarged with respect to Fig. 1;

Fig. '3 is a fragmentary side'elevational detail partly in section and with parts broken away and removed showing the nozzzle mounting member and related parts of part broken away, taken transversely through'the heater of Fig. l and enlarged with respect to that figure.

The space heater shown in the drawings and representing the best known mode of practicing the invention comprises 'a generally rectangular casing having top 1, bottom 2, end walls3 and 4, and side walls, one of which -is removed in Fig. 1 and the other of which is behind the illustrated components and is parallel to the plane of the drawing. The casing is formed with sheet metal bolted, welded or riveted together and provided with suitable openings through which the fuel and electrical conduits and conductors are admitted. One or bothof the side walls are formed with louvers or grills'to admit atmospheric-air into the casing for circulation through the heatexchanger and to supply combustion airfor the burner. -An openings in the casingtop 1is covered by ascreen 6, this opening constituting the exit through which-heated air is discharged after'passing through-the heat'exchanger. The burner and-heat exchanger are suspended;as-a-unitfrom thfecasing top -1 and -occupy-the upper-half'of the casing. The heatexchanger is'enclosed between spaced parallel side partition panels 7 and 8 of sheet metal flanged along their upper'edges for securement as by screws 9 against the underside of the casing top panel 1 along the margins of the opening 5. A bottom panel 10, also sheet metal, has parallel edge flanges 11 and 12 which lap the bottom edges of the Side panels 7 and 8 and are welded to the latter in the provision of a shelf on which the heat exchanger and burner are supported.

The-heat exchanger comprises a pair of hollow sheet metal headers 15 and 16, each of generally rectangular configuration and constructed of heat -resistant sheet metal, such'as stainless steel, suitably formed and welded together. These'headers have approximately the-same dimensions and are of such size that they 'have'easy-slid- --ing fits onto the supporting shelf -and --between-the spacedsidespanels 7 and 8. each spaced inwardly from the side walls of the'heater casing to permit the circulation of air between the. panels The panels 7 and 8 are '7 and 8 and the casing walls which they confront, thereby preventing excessive and localized heating of the casing walls. 7 p

By making the headers and 16 so that they closely changer so that'air forced into the bottom'of the heat exchanger is confined to flow upwardlytherethrough and It is apparent, of course, that tight sealing between the headers and the walls and bottom of the'internal shell or casing of the heat exchanger is unnecessary since-air which escapes into the interior of the main casing-is merely recirculating through the heat exchanger.

The header 15 thus includes inner and outer walls 17 and 18 disposed in spacedparallel relation to one another and connected by top and bottomwalls 19 and 20. This ---into the header walls.

4 header also includes side walls one of which, shown at 21 (Fig. 5), is disposed against the inside of the panel 7 and the other of which isdisposed against the inside of the panel 8. Extending through chamber 22 of the header 15 is a cylindrical sleeve 23 the ends of which are received in flanged openings in the header walls 17 and 18 by circular welded joints 24'which seal the sleeve ends Thisslecve receives and accommodates outer combustion tube or shroud 25 of the burner in a sliding fit.

The'header-16 comprises inner and outer walls 27and 28 corresponding-to the heat resistant stainless steel walls 17 and'1 8 of the header 15. Top and bottom walls 29 and 30 correspond -to the walls 19 and 20 previously described and the header 16 has side walls corresponding to the side walls of the header 15, one side wall of the header 16 being indicated at 31.

The end of the combustion tube or shroud 25 projects through a flanged circular opening'inthe inner wall 27 of the header 16 and iswelded to the wall flange in the provision of a circularseal 33 that secures the tube to the header wall. As will appear, hot gases projected into chamber 32 of the'head'er 16 through the discharge end of the combustion tube "25 are circulated between the headers arid ultimately discharge to atmosphere through a suitable exhaust tube or conduit (not shown)connected tubes 35 which areof stainless steel or other heat resistant ine'tal.

These tubes are made from cylindrical tube'blanks of uniform circular cross section. At spaced points along its length each tube blank is partially collapsed orcrushed by the application of localized radial -forces actingtowardoneanother on a common diameter 50 as to impart to the tube an ovoid cross section (Fig.

5). The deforming of the tubes 35 may be accomplished,-for example, in a press 'or stamping machine provided with opposed jaws represented diagrammatically at-36'and 37 (Figs. 1 and 5). The jaws have elongated narrow working faces or edges 38 arranged in parallel relation and movable toward and away from one another. As the jaws are brought toward one another under power in a'working-stroke'the walls of the cylindrical tube blank are forced toward one another forming wide angled generally V-shapedcreases 39 which confront and are parallel to one another.

In making successive deformations along the length of the tube blank the latter is rotated approximately -between the crushing operations so that the long axis of -each-of the ovoid-sections is angularly disposed relative {to-the co'rrespondingaxes of the adjacent ovoid sections.

The tube blanks of which the exchanger tubes 35 are formed are undisturbed at their endsso that such'ends -remain ofcircular section andare inserted'into'the inner walls '17 and 27 of the headers through circular flanged openings, each tube end being welded to the embracing fianges'in the-openings in the provision of circularseals cation with the outlet tube or nipple 34. The gases or fluid heatingmedium entering the lower portion of the header 16"are'thus constrained by the diagonal partition or baffle '42 fto flow through the lower tubes 35 to the header 15. Inthe chamber 22 of the header 15 the 'hot' gases receivedthroughthe lower tubes flow upwardly about the sleeve 23 and into the upper portion of the header chamber- 22. The gases from the iup per portion ofthechamber22 return to-the"header 16 throughthe upper tubes 35 of the heat exchanger entering the. chamber 32 above the baflle partition 42.

Circulation of atmospheri: air through the heat exchanger is induced by a blower, or fan 44 carried on a shaft 45 journaled in bearings which support the fan in a sheet metal scroll 46. The outlet of the fan scroll, indicated at 47, is of rectangular shape and registers with an opening 48 in the bottom panel or shelf of the heat exchanger. An integral flange 49 on the fan scroll outlet is disposed flatwise against the underside of the bottom panel 10, being secured to the latter as by screws 50 which support the entire fan assembly. An electric motor 52 mounted in the casing drives the fan 44 by belt 53 trained around pulleys on the motor shaft and the shaft 45 of the fan assembly. The motor 52 is controlled conventionally to operate the fan to force air into the chamber defined by the heat exchanger panels 7, 8 and 10 and the headers and 16 in response to heat demand registered by thermostat or other suitable indicator. If desired, the motor circuit may be con nected in parallel with the burner control circuit, to be later described, so that the burner and fan are started and stopped simultaneously. Alternatively the fan motor may be controlled separately from the burner to provide a preliminary period of burner operation during which the heat exchanger is brought up to temperature and subsequently the fan is started and to provide, if desired, a terminal period during which the fan is continued in operation after the burner is shut down so that movement of air through the heat exchanger is continued for sufficient time after the burner stops to cool the heat exchanger tubes and headers and thereby reduce stack losses in the over-all operation of the space heater. It is apparent, of course, that since the fan scroll 46 is located within the casing walls, the latter must be formed with openings through which the air to be forced through the heat exchanger is first drawn into the interior of the casing.

The combustion chamber of the present burner is defined by the cylindrical outer tube and by a shorter inner flame shield tube 55. This inner tube is of cylindrical shape and is mounted within and coaxial to the outer tube 25, the two tubes being separated 'by an annular chamber 54 into the left end of which, as viewed in Fig. l, secondary air is introduced tangentially through a pipe 59. Both the inner flame tube 55 and the outer tube 25, which constitutes a shroud for the inner tube, are constructed of heat resistant sheet metal such as stainless steel in order to withstand the high temperatures to which they are subject. The inner flame tube 55 extends outwardly an appreciable distance beyond the outer Wall 18 of the manifold 15 and it is desirable that the annular air chamber 54 be coextensive in length with the inner flame tube. To achievesuch an arrangement it is feasible, of course, to extend the'outer tube 25 to the left end of the inner tube 55. To facilitate manu- -facture and assembly, however, it is contemplated to utilize a supplemental cylindrical tube 56 which extends as a continuation of the tube 25, the two tubes being held together in end to end relation by a joint comprising outwardly projecting radial end flanges 57 and 58 secured as by bolts or screws (not shown).

Across the outer end of the supplemental tube 56 is secured a closure and control plate 60 to the inside of which the inner flame tube 55 is secured as by means of radially inwardly directed flange 61. The plate 60 is formed with a central circular opening 62 through which the fuel spray is projected from a nozzle assembly, indicated generally at 63. The nozzle and control plate opening 62 are centered on the axis of the burning

tubes

25, 55 so that the fuel spray is centered in the opening 62 and is projected into the center of the air mass within the combustion tube.

A nozzle structure or assembly 63 is carried by a circular plate 64 disposed across the end of a hollow cylinthe parts snugly together.

drically shaped mounting member 65 which issecured against the outer face of the control plate and constitutes a continuation of the combustion tube component. The parts are conveniently located and held in place as by screws68 (Fig. 3) which extend through aligned holes in the plate 64, the body of the hollow mounting member 65, and the end closure and control plate 60, the inner ends of the screws being threaded into the circular flange 61 of the fiame tube 55 so as to draw The cross sectional area of chamber 66 in the mounting member is larger than that of the circular control opening 62 so that, in effect, the control plate 60 constitutes a partition dividing the interior of the combustion tube structure (which comprises the inner flame tube 55, the outer shroud 25, the supplemental tube 56, and the circular sectioned mounting member 65) into the outer or normalizing chamber 66 of relatively short axial length and the inner combustion chamber located within the inner and

outer tubes

55 and 25.

The nozzle structure 63 comprises a body 70 which may take the form of a turning of brass or similar machinable metal of high heat conductivity. It is formed with a central axial fuel passage 71 and a number of primary air passages 72. The central fuel passage 71 is reduced adjacent the outlet orifice of the nozzle in the provision of a tapered or frustoconical valve seat. The air passages 72 open into an annular chamber 73 which is provided by a hollow cap 74 fitted over the end of the nozzle body and held by a shouldered sleeve 75 threaded onto the outside of the body. The cap 74 is formed with a central orifice 76 through which air is discharged from the nozzle tip chamber 73. An axial projection 77 on the nozzle body 70 extends into the opening of the orifice 76 with a surrounding clearance to provide the desired annular air escape passage of the nozzle orifice 76. The projection 77 is formed with the aforementioned small diameter extension of the axial fuel passage 70 through which the liquidfuel under pressure is projected into the center of the air stream issuing through the circular nozzle 76.

The nozzle body 70 is formed with an externally threaded extension of small diameter which is screwed into one end of an internally threaded transverse passage 79 of a mounting block 80. The fuel passage 71 is continuous through the threaded extension of the nozzle body and opens into the chamber provided by the threaded passage 79 in the block 80. An elongated stem 81 of a needle valve structure extends axially through the threaded passage 79 and the fuel passage 71, this stem having a tapered end'82 which is movable toward and away from the frustoconical valve seat in the fuel passage in regulating the rateof fuel flow or to seal the passage. The stem 81 has a portion intermediate its ends threaded through an axial threaded passage in a fitting 83 screwed into and constituting a closure for the threaded passage 79 in the mounting block 80. Rotating the valve stem 81 as by thumb wheel 84 on its outer end shifts the stem axially in adjusting the valve. Suitable packing in an annular chamber provided in the outer end of the fitting 83 in surrounding relation to the stem 81 is held in place by a cap 85 threaded onto the fitting 83 to provide a fiuid tight seal around the valve stem. Fuel is supplied to the nozzle assembly through a tubular conduit 86 the end of which is connected as by threaded fitting 87 to a chamber 88 in one end of the nozzle mounting block 80. The nozzle block chamber 88 receiving fuel under pressure from the conduit 86 communicates with the transverse threaded passage 79 through a longitudinal drill hole so that the fuel flows freely into the fuel passage 71 and, when the needle valve is open, into the reduced diameter nozzle passage from which the fuel is projected through the orifice and mixed with the air in an expanding conical spray pattern.

"nozzle orifice. and related nozzle components are contemplated to pro- Air is' supplied to the nozzle steamin block80 through a co'uduit ortube 9 threaded into a socket in the end of-the bl'oek 80opposite the socket which receives the threaded fuel'tube fitting '87. From chamber 91 in the right-hand end oftlie nozzle block 80, as viewed in Fig. 4,

the primary air 'un'der'pressure enters an annular passage '92 which surrounds the previously mentioned threaded 92 in the attaching block'sll to receive air from "the latter. The oblique air passages 72 communicate with "the channel 95 to receive air therefrom which is conducted thence into the nozzle tip chamber 73, as previously mentioned. The base end of the nozzle body 70 and the face of the mounting block boss 93 are machined and finished with matching faces which come together in the provision of a fluid tight-seal which eliminates the loss -of.pressuriz'ed air from the

annular channels

92 and 95.

In mounting the nozzle assembly 63 on the circular supporting plate 64 a central circular opening 96 formed in the plate is received over the circular boss 93 of the mounting block and the parts are brazed together before the nozzle body 70 is screwed into the mounting block 80. The nozzle body and other components of the nozzle assembly are then assembled with the mounting block'80. Received over the nozzle body and also over the nozzle end member 74 and threaded collar 75 is a protective cap or shield 97 which is cupshaped and has relatively thick cylindrical walls and a relatively thin end wall 98. The end of the cup 97 is abutted against the supportingiplate 64, being received through a circular opening 99 in a web or partition 100 adjacent the end of the mounting member 65. The partition 100 is separated from the end plate 64, which carries the nozzle assembly by annular insulating air space 101 which surrounds the nozzle assembly. In addition to being abutted strongly against themounting plate 64 and being fixedly body 70 in the provisionof good heat conducting relationship between the protective cap and the mounting plate '64, iioz'zle mounting body 80 and the mounting member 65. The end wall 98 of the protective cap 97 is separated from the endelement 74 ofthe nozzle as- "senibly by a clearance space or chamber 104 which serves as an insulator and prevents the absorption of radiant heat energy by the nozzle tipmember 74 directly from "the 'fla'r'neburnin'g in the tube 55. A central opening lilo in'the'thin endwall 98 of the'protective cap 97 is axially 'alig'nedwith' and is 'suiiicien'tly larger than the discharge orifice 76 to clear the conical spray issuing from the Various designs of the nozzle orifice 76 vide a suitable expanding spray pattern. In one ar- 'ra'nge'in'e'nt 'which' is satisfactory for the relationships il- 'lu'stratedfthe liquid fuel and primaryair issue from the nozzle orifice in a conical spray pattern having an include angle of approximately l30. The diagrammatic repl'res'entation of the spray shown in Fig. ldoes not represent the "true spray angle but is merely shown to indicate the "direction and location of the expandingspray. The arr'anger'nent of the 'parts is such, with reference to the epeningms in jtheprotective cap '97 and the opening 62 "in 'tlieebnt'rolplateftifi, that the expanding conical spray is rojected frohtthenozz'lebrifice 76 across the norobservedthat the opening 106 in the circular attaching flange 61 of'the flame-tube is appreciably larger than thecontrol plate opening 62.

Ignition is effected by a hi h tension electricalspark produced across a gap between the ends of electrodes 10 108 and 109 mounted in insulators 110. The insulators are held in externally threaded metal tubular fittings 111 secured in-the circular supportplate 64. Openings 112 are, provided in the partition 10% in alignment with the tubular fittings 111 to accommodate the electrodes and insulators. As shown in Fig. 1 the outer ends of the electrodes are connected as by wires 114 and 115 to secondary of a transformer 116. The primary of the transformer is connected to the electrical circuit which energizes the burner so that whenever the burner is energized to supply heat the transformer is likewise energized to maintain continuous ignition spark across the

electrodes

108 and 109.

One of the refinements of the primary air supply system is concerned with the by-passing of a portion of the primary air around the chamber 73 at the end of the nozzle body and through the cap chamber 104. This supplemental air supply is obtained through a hole 103 drilled through the nozzle mounting blockand the circular mounting plate 64 from the primary air chamber 91 in the nozzle block to the annular air space or chamber 101 located between the partition and the circular nozzle mounting plate 64. A number of radial holes 107 are drilled through the cylindrical side walls of the cap 97 at the base end of the latter so as to place the interior of the cap in communication with-the chamber 101. The supplemental air fed into the chamber 101 through the drilled passage 103 thus flows into the base of the cap 97 ata plurality of points and thence flows axially inside the cap to the chamber 104 located between the internal nozzle structure and the end wall 98 of the protective cap. This supplemental air flows across the flats of the hex portion 102 of the nozzle body 70 and through an annular clearance space between the shouldered sleeve 75 and the internal surface of the cap 97. The supplemental air cools both the cap 97, which is subjected to the radiant heat energy from the flame, and the internal nozzle structure to prevent these parts becoming heated to temperatures which cause carbonizationof the fuel. In flowing radially across the face of the cap 74 of the internal nozzle structure the supplemental air moves radially into the air stream issuing through the nozzle orifice 76. The commingled primary air and the supplemental air together constitute the vehicle which carries the fuelreleased through the central fuel orifice. Some of the 'air forcedinto the chamber- 101 escapes --into the normalizing chamber 66 through the openings 112 for the electrodes, thereby keeping such openings clear of soot and other objectionable deposits.

Both primary air and secondary air are supplied to the burner by a centrifugal blower suitably supported within the casing of the heater and driven by an electrical motor (not shown) connected to-shaft 121 of the blower. The motor for the blower 120 is connected in parallel with the transformer 116 so that the blower, like the transformer, is energized whenever the thermostat or other control or indicator device demands heat ed tangentially into the rad tlly narrow annular chamber 54 which separates the inner flame tube 55 and the outer shroud tube 25. The entering secondary air is thus induced to a helical flow in the annular chamber and at points spaced along its helical path the advancing secondary air is released, preferably tangentially, into the interior of the flame tube 55 through apertures distributed both longitudinally along and circumferentially about such flame tube. These secondary air inlet apertures may be arranged in various patterns, preferably so that the ratio of inlet aperture area to flame tube area increases progressively from left to right in Fig. 1, this being the general direction of flow of the air in the annular chamber 54 and also, of the helically rotated air mass within the flame tube. In the arrangement shown the apertures are distributed in accordance with a geometric pattern. The apertures are arranged in circumferentially extending rows, the rows being located in parallel planes spaced along the length of the inner combustion or flame tube. To obtain the desired increasing ratio of aperture opening area to tube area the circumferential rows may be spaced progressively closer together toward the outlet end of the flame tube or, as shown, the aperture rows may be uniformly spaced with the apertures increasing in diameter or area from left to right, this being the direction of air flow in both the annular air chamber which surrounds the flame tube and the interior combustion chamber. For example, in a burner having an outer combustion tube 25 of about 4 inch inside diameter and a tributed openings 125 are inch diameter and are located in a transverse plane parallel to and spaced approximately 2 inches from the circular opening 62 in the control or partition plate 60 which separates the combustion chamber from the normalizing chamber 66 of the composite combustion tube structure. Apertures 126 of the next succeeding row are distributed about the flame tube in a plane spaced in the direction of air and flame travel approximately 1 /2 inches from the plane of the apertures 125, the apertures 126 being approximately inch diameter. Aperturer 127 comprising the third row are in a transverse plane spaced approximately 1 /2 inches from the plane of the apertures 126 and are inch in diameter or slightly larger but less than inch in diameter. Apertures 128 of the fourth row and 129 of the fifth row are in transverse planes each spaced approximately 1% inches from the plane of the preceding row of apertures and are inch in diameter or larger. The

apertures

128 and 129 may be of the same diameter or, preferably, the apertures 129 are slightly larger than the apertures 128. Each group or circumferential row consists of eight apertures uniformly distributed, the apertures of each row being offset circumferentially with respect to the apertures of adjacent rows.

The secondary air supply tube 59 projects the air into the annular chamber 54 through an opening 130 which is located intermediate the plane of the control or partition plate 60 and the plane of the first group of apertures 125. Thus is insured circumferential flow of the secondary air in the chamber 54 so that such air approaches the plane of the apertures 125 as well as the succeeding apertures in a helical flow pattern. In this manner the secondary air is induced to enter the combustion chamber within the flame tube 55 in a multiplicity of tangential jets which cause the mass of air in the combustion chamber to rotate about the axis of the combustion tube structure and to advance helically as a column from left to right as viewed in Fig. 1. When the expanding fuel spray is projected axially into the center of the receiving end of the rotating air mass and ignited, the resulting flame and combustion products are likewise induced to rotate by reason of their entrainment in the secodnary air mass. Augmentation of the secondary air mass by tangentially directed airjets distributed along its length and about its circumference maintains the fuel particles in suspension while they are being raised to ignition temperature and burned. The depositing out of fuel and carbon on the walls of the combustion chamber is thus minimized with resulting improvement in efliciency and elimination of frequent cleaning and servicing of the combustion tube, structure. This is a specially desired feature in connection with the burning of fuel oil of the type used in domestic oil burners or aircraft jet engine oil which are liquid fuels of relatively high viscosity compared to gasoline. By reason of the heating of the combustion tubes from the internal flame, the heat being conducted along the tubes toward the supplemental outer tube 56 and the tubular mounting member 65, these components of the combustion tube structure at the nozzle end become hot and preheat the secondary air which flows circumferentially about that portion of the annular chamber 54 inside the supplemental outer tube 56 before being projected into the combustion chamber through the apertures 125. Thus, the entering secondary air cools the end of the combustion tube structure which carries the nozzle assembly 63 so that objectionable overheating of the nozzle is avoided.

Adjacent the outlet end of the flame tube 55 the latter is embraced by a centering ring 123 which is in circumferential contact With the inside walls of the outer combustion or shroud tube 25. This ring, in addition to supporting the flame tube 55 in coaxial relation to the shroud tube 25 so as to maintain concentricity and uniformity in the radial dimension of the annular air chamber 54 constitutes a closure for the end of such annular air chamber. By thus sealing off the end of the annular air chamber that surrounds the flame tube the secondary air forced tangentially into one end of the annular air chamber by the blower feeding through the conduit 125 and the tangential inlet tube 57 is forced to flow into the combustion chamber within the flame tube 55 through the openings distributed along and about the flame tube. To insure tangential flow of the secondary air into the interior of the flame tube 55 from the annular chamber 54 the sheet metal of which the flame tube is formed is deformed or bent around some, preferably all, of the distributed apertures 125-129 in the manner shown in Fig. 5 with respect to one each of the

apertures

127, 128 and 129. This deformation is accomplished by suitably formed dies which shape the metal so that the openings face toward the oncoming helically advancing air and, in effect, scoop the air so that it flows tangentially into the internal combustion chamber. The deformation or bending of the flame tube 55 may also be accomplished by inserting a tapered metal bar into the openings one at a time and, with the bar wedged in the opening mov ing or swinging the bar in a plane transverse to the axis of the tube and in a direction reverse to the flow direction that the helically advancing air moves in the annular chamber. For example, a tapered bar inserted in one of the

openings

127, 128 or 129, Fig. 5, would be rotated counter-clockwise in the plane of the drawing to produce the scoop formations illustrated.

To augment the spiral motion of the advancing air column as it is released from discharge end 131 of the innerflame tube 55 the latter is formed with a number of inwardly bent tabs or deflector vanes 132. These vanes may be made by cutting a number of relatively short circumfere'ntially spaced axial slits in the end of the tube 55 and bending inwardly corresponding ends of the tabs so formed along diagonal lines 133. The swirl imparting vanes 132 not only augment the helical motion of the advancing air column, but by deflecting outer peripheral portions of the advancing air column to flow diagonally across the column the turbulence of the flame in and beyond the discharge end of the flame tube is enhanced with resultant improvement in combustion efliciency. In the case of relatively high viscosity fuels the combustion is'initiated in the perforated flange tube 55 and continues as the spirally advancing column of air flame combustion products and fuel and suspension moves forward through thatportion of the outer combustion tube 25 which extends beyond the discharge end 131 of the inner combus- "tion or flame tube 55. The outer combustion tube may, if desired, extend beyond the discharge end of-the inner combustion tube a distance equivalent to several times the length of the latter. Such an arrangement results in a heater of awkward and impractical length. For operation with fuels over the viscosity range represented by gasoline, jet engine fuel and No. 1 fuel oil, it is satisfactory if theouter combustion tube 25 be no more than about twice the length of the inner flame tube 55.

Upon being discharged from the outlet end of the outer combustion tube 25 the flame and hot gases received in the header 16 are deflected by the partition '42 into the'lower part of the header chamber 32 where they enter the lower group of exchanger tubes 35. From these lower exchanger tubes the hot gasesand flame, if

;any, are released into the chamber 22 of the headerlS,

flowing upwardly in such header and thence into and through the upper group of the exchanger tubes 35. From the latter tubes the products of combustion are discharged into the :upper portion of the header 16 and flow thence out the discharge 34. The circulation of air upwardly through the heat exchanger chamber between andaround the tubes-35 and the outer combustion tube 25 heat such air so that it is discharged through the screen 6 at an elevated temperature to provide the desired space heating.

The liquid fuel for the burner is received through a main supply conduit 135, a conventional motor driven pump 136 drawing the fuel from the supply line 135 and forcing it under pressure into a conduit 137 which is connected to the fuel inlet conduit 86 through adjustable pressure reducing valve 138 and a solenoid operated or other electric valve 140, a conduit 139 connecting the reducing valve 138 to the electric valve 140.

The electrical power forenergizing the several electrical components of the space heater is supplied to the de leads141,142'so that the supply of fuel to the burner is initiated" by the pump in response to the heat demand transmitted through the thermally responsive control.

Alternatively the pump 136 can be continuously operated with a suitable by-pass which functions when the electrical valve 140 is closed. In lieu of the pump 136 the fuel may be contained in an elevated tank withgravity feed into' the fuel system.

Sothat the air mass within the combustion tube structure is properly conditioned to receive a fuel spray without objectionable deposit of liquid fuel on the walls of the tube structure and without excessive smoking on starting, provision is made for establishing spiral air flow in the combustion tube structure before the fuel spray is released. 'This is accomplished by a delayed action in the opening of the solenoid valve 140. The electrical "valve '140 is of the type which is normally biased to closed position by a spring loaded valvebody and 1S opene'cl by electromagnetic action of a solenoid coil or 1 the" like when such coil is energized. The electrical enei'gy forthe valve 140 is obtained from the power leads "141, 142 through an interposed pressure responsive switch 143' 'vei'nedb'y" the pressure ofthe'airin the secondary difiiit betweenthe blower120and the annular chamber e 154. The pressure switch 143 may, for example, -be

connected by a tube 149 to the flexible hose 148 which joins the blower takeoff 124 and the inlet tube59 that feeds the secondary air into the annular chamber 54 of the combustion tube structure.

In operation in response to a demand for heat which causes the control unit to energize electrical power leads 141, 142, the

spark ignition electrodes

108, 109 are immediately energized through the transformer 116 toproduce-aspark infront of the nozzle structure 63. The pump 136 is energized simultaneously with the transformer-116 to feed the fuel into the conduit system leading into the nozzle assembly 63. However, the electric valve 140 being closed prevents the fiow offluid through the nozzle system, since the electrical circuit through the solenoid coil of the valve 140 remains de-energized While the pressure switch is in its normally openedcondition. The electrical motor 52 driving the blower 120 is energized as through the power leads 141, 142 simultaneously with the energization of the spark ignition transformer'116 and starts the flow ofair through the

primary supply tubes

147 and 90 and through the secondary

air supply tubes

148 and 59. When the pressure in the secondary tube 143 is built up to a predetermined minimum which corresponds to the normal operating condition so that the air mass within the combustion tube structure is rotating helically, the pressure switch 143 responding to the pressure in the tube 148, is actuated to close the electrical contacts to complete the circuit through the solenoid coil of the electrical valve 140.

Upon such energization of the electrical valve the fuel supply line is opened and the fuel is projected from the orifice 76 of the nozzle structure into the combustion chamber through the circular opening 62 of the control plate 60, the combustible mixture being ignited by the continuous spark maintained between the

electrodes

108, 109. While these electrodes are shown to be wholly within the normalizing chamber 66, the spark being carried into the combustion zone by the fuel and primary air spray, it is apparent that they may be extended into or through the opening 62. Besides conventional gasoline, plain or leaded, and the No. 1 fuel oil of 132,000

B. t. u. per gal, the present burner operates on JP-4 jet fuel. It burns fuel at a rate as low as about .65 gal per hour delivering about 75,000 B. t. u. per hour and is capable of instant starting at temperatures as low-as F.

In operation the blower 120 delivers air which in the primary supply line into the nozzle chamber 73 is-at a pressure of from about 4 inches to about 12 inches of water, preferably, in the range of from about 8 inches to about 10 inches of water. In the secondary supply line feeding air into the annular air chamber 54a much lower pressure is maintained, pressures as low as about2- inches of water being satisfactory.

On operation with fuel of relatively low viscosity, such, for example, as gasoline, the tendency of the-flame is to burn-close to the nozzle structure 63 relative to the posichamber into the normalizing chamber 66, the flame produced by low viscosity fuel is apparently heldaway from 'close proximity to the-nozzle structure 63 and overheating of the latter is avoided.

' While the combustion tube structure of the present-invention comprises a number of components, being the :inner and

outer tubes

55 and 25, the supplemental. tube that a unitary outer tube maybe employed. "case the nozzle structure63 is supported in the centerof "the end closure for such unitary outer tube and the controliblatebfl takes'the form of a. partition spacedxaxially from such end closure, the flame tube 55 being then a 5 6 and the tubular mounting member 65, it is apparent In such 13 separate tube located wholly on the combustion chamber side of the partition and suitably supported and centered in the unitary outer tube.

In accordance with the patent statutes the principles of the present invention may be utilized in various ways, numerous modifications and alterations being contemplated, substitution of parts and changes in construction being resorted to as desired, it being understood that the embodiment shown in the drawings and described above and the particular method set forth are given merely ing being deformed and bent out of the surface of revolution and so shaped that air admitted to the interior through such opening moves with a tangential component, means closing one end of the tube whereby air admitted through the openings advances to and is discharged from the other end of the tube, said advancing air moving helically under the influence of the tangential components, the other end of the tube being axially slotted at circumferentially spaced points, corresponding portions of the metal of the tube adjacent the end slots being bent inwardly and disposed in angular relationship to the longitudinal axis of the tube in the provision of a plurality of integral air deflecting vanes symmetrically spaced about the tube axis at such other end of the tube to intercept and deflect radially inwardly air being discharged through such other end of the tube and to direct such intercepted air to flow tangentially relative to the tube in augmentation of the circumferential component of the helical flow produced by the deformed metal liquid fuel to the nozzle under pressure.

2. A liquid fuel burner comprising an elongated metal combustion tube in the form of a surface of revolution and having a multiplicity of axially and circumferentially spaced openings for admitting air to the tube interior, 1

that portion of the metal of the tube surrounding each opening being deformed and bent out of the surface of revolution and so shaped that air admitted to the interior through such opening moves with a tangential component, means closing one end of the tube whereby air admitted through the openings advances to and is discharged from the other end of the tube, said advancing air moving helically under the influence of the tangential components, the other end of the tube being axially slotted at circumferentially spaced points, corresponding portions of the metal of the tube adjacent the end slots being bent inwardly and disposed in angular relationship to the longitudinal axis of the tube in the provision of a plurality of integral air deflecting vanes symmetrically spaced about the tube axis at such other end of the tube to intercept and deflect radially inwardly air being discharged through such other end of the tube and to direct such intercepted air to flow tangentially relative to the tube in augmentation of the circumferential component of the helical flow produced by the deformed metal openings, a nozzle supported and adapted to project a spray of liquid fuel into the tube at said one end, a shroud of circular section surrounding the combustion tube in spaced relation in the provision of an annular air supply chamber, an air delivery tube disposed to release air tangentially into the annular chamber,'means supplying air under pressure to the delivery tube whereby air released into the annular chamber first advances helically therein, is then admitted to the interior of the combustion tube through the openings in the latter, and then moves helically to the'discliarge end of the tube, and means supplying liquid fuel to the nozzle under pressure.

3. A liquid fuel burner comprising an elongated metal combustion tube in the form of a surface of revolution and having a multiplicity of axially and circumferentially spaced openings for admitting air to the tube interior, that portion of the metal of the tube surrounding each opening being deformed and bent out of the surface of revolution and so shaped that air admitted to the interior through such opening moves with a tangential component, means closing one end of the tube whereby air admitted through the openings advances to and is discharged from the other end of the tube, said advancing air moving helically under the influence of the tangential components, the other end of the tube being axially slotted at circumferentially spaced points, corresponding portions of the metal of the tube adjacent the end slots being bent inwardly and disposed in angular relationship to the longitudinal axis of the tube in the provision of a plurality of integral air deflecting vanes symmetrically spaced about the tube axis at such other end of the tube to intercept and deflect radially inwardly air being discharged through such other end of the tube and to direct such intercepted air to flow tangentially relative to the tube in augmentation of the circumferential component of the helical flow produced by the deformed metal openings, a nozzle supported and adapted to project a spray of liquid fuel into the tube at said one end, a tubular shroud of greater axial length than the combustion tube surrounding the latter in spaced relation in the provision of an annular air supply chamber, the shroud projecting axially beyond said other end of the combustion tube and defining an expansion chamber for receiving flame and hot gases discharged from the combustion tube, means supplying air to the annular chamber under pressure to force such air into the combustion tube through the tangential component openings, and means supplying liquid fuel to the nozzle under pressure.

4. A liquid fuel burner comprising an elongated metal combustion tube in the form of a surface of revolution and having a multiplicity of axially and circumferentially spaced openings for admitting air to the tube interior, means closing one end of the tube whereby air admitted through the openings advances to and is discharged from the other end of the tube, a nozzle supported and adapted to project a spray of liquid fuel into the tube at said one end, a tubular shroud of greater axial length than the combustion tube surrounding the latter in spaced relation in the provision of an annular air supply chamber, the shroud projecting axially beyond said other end of the combustion tube and defining an expansion chamber for receiving flame and hot gases discharged from the combustion tube, an air delivery tube disposed to release air tangentially into the annular chamber adjacent said one end of the combustion tube, said delivery tube constituting the sole means supplying air to the annular chamber, means supplying air under pressure to the delivery tube whereby air released into the annular chamber first advances helically therein is then admitted to the interior of the combustion tube through the openings in the latter, and then moves helically to the discharge end of the tube, the other end of the combustion tube being axially slotted at circumferentially spaced points, corresponding portions of the metal of the combustion tube adjacent the end slot being bent inwardly and disposed in angular relationship to the longitudinal axis of the combustion tube in the provision of a plurality of integral air deflecting vanes radially inwardly air being discharged through such other end of the combustion tube and to direct such intercepted air-to flow helically in the shroud whereby the air deflecting vanes augment the circumferential component of the spirally moving air and means supplying liquid fuel to the nozzle under pressure.

5. In a liquid fuel burner of the type in which a spray comprising a mixture of liquid fuel and primary air is projected into a combustion chamber and there commingled with secondary air, the combination of a nozzle structure comprising a metal mounting block, a metal body and cooperating metal parts formed with a discharge orifice and separatepassages extending from the mounting block for conducting fuel and air to such discharge orifice, mounting plate means of metal, the plate means having an opening and the nozzle structure being received through such opening and supported by the mounting plate means in heat conducting relation, the mounting block being generally on one side of the mounting plate means and the metal body being generally on the other side of the mounting plate means, the plate 1means being formed with an annular chamber surrounding the nozzle structure, a cup shaped metal cap, the cap being disposed over the nozzle body and supported by the mounting plate means in heat conducting relation, the cap having an opening in alignment with the discharge orifice of the nozzle structure, the cap and the nozzle body :being formed to provide an air circulating chamber therebetween, means defining another air passage from said first mentioned air passage in the nozzle structure to the annular chamber, duct means for the flow .of air radially from the annular chamber into the air circulating chamber between thenozzle structure and the cap, vthe air circulating chamber being continuous with the cap opening so that air flowing into such air chamber .is discharged through the cap opening to commingle with the projected fuel and primary air mixture, the nozzle structure being adapted to project the spray in an expanding .pattern through the cap opening for burning in spaced relationto the cap and the nozzle structure, whereby radiant heat energy directed toward the nozzle structure from the burning spray is intercepted by the .cap in the elimination of excessive heating of the nozzle structure.

.6. A heater comprising in combination a hollow casing havingside, end, top and bottom panels,'a heat exchanger in the casing, the heat exchanger having spaced h'ollow headers and tubes connected between the headers for the circulation of hot gases through, the tubes and the headers, a flue outlet tube extending from one of the headers through one of the'panelsof the casing, partitions means secured-to the top panel of the casing in de- -tachablerelation and including spaced parallel side elements and a bottom element connecting. the side elements, the side elements of 'the partition being spaced-from and parallel torcorresponding-side panels of the casing, the bottonr element :being spaced above the bottom panel of the casing,said partition means defining an :open ended 1: vpocket to receive the heat exchanger for facile removal "and replacemenhthe pocket open end being substantially closed by one of said headers, the partition means and said one'header dividing the interior of the easing into a heat exchanger chamber and-a blower chamber, one of --"the casing panels being formed with an outlet opening communicating directly with the heatexchanger chamber, the casing being formed with an inlet opening communicating directly with the blower chamber, a blower secured *to the partition means and solely supported thereby in suspended relation within the casing, the heat exchanger -being removable from andreplaceable into the pocket in- :dependently of the blower, a motor within the casing and drivingly connected to the blower, the blower having -aninletopening within the blower chamber to receive air ;-from;' such chamber and having anoutlet opening into atheheat exchanger: chamber: so that: actuation. :of the blower draws air into the blower chamber through said 16 inletopeningrin the casing and forceslair. into thez heat exchanger chamber and out of the casing through said outletopening, a burner assemblycomprising .a combustion tube'having anend for receiving fuel and air and another endfor discharging hots products of combustion, a mountingmember secured across said oneend :ofzthe combustion tube,.a nozzle carried by:the mounting memher, the combustion tube extending through said one header across the heat exchanger chamber and-having connection at its other end with the other header todischarge hot gases into the latter, the one receiving end of air and burn in suspension, the combination'of a fuel nozzle, means defining a combustion chamber, means mounting the; nozzle to direct a fuel spray into the chamber, and ignition means for igniting the fuel; the mountl ing means including plate means formed with a central apertureto receive the nozzle and with an annular chamber surrounding the receivednozzle, the plate means includingone wall element interposed betweenithe combustion chamberand the annular chamber and another wall element spaced-from theone wall element byirthe annular chamber, the one wall element of the plate means being formedtwith an opening accommodating the electrode, said opening constituting a discharge orifice through which air from the annular chamber :is discharged into the combustion chamber, the ignitionmeans including an electrode supported by said other wall element of the platemeans and projecting therethrough and also projecting through the chamber in the plate means and in insulated relation through the orifice opening :in the one wall element, said orifice opening being; sufficiently large to provide clearance space surrounding: the electrode andseparating it from the one wall, and means supplying air under pressure to the annular chamber in itherplate means-continuously during operation OfLthG burner for circulation of the supplied air through-such .annular chamber about the nozzle and release:through the clearance space of the orifice opening.

8. In a liquid fuel burner of the type in which a spray comprising a mixture of liquid fuel and primary .air is projected into a combustion chamber; a nozzle structure fice and separate fuel and air passages extending from. and

continuous with the corresponding passages of the mounting block for conducting pressurized fuel and air'tov-such discharge orifice; mounting plate means of metal,.1the

. ,plate means having an opening and the nozzle structure being receivedzthrough such opening, the plate. means being formed with an annular chamber surrounding the nozzle structure, a cup shaped metal cap, the. cap being disposed over the nozzle body and supported bywthe mounting plate means, the cap having. anqopeninghin alignmentwith the discharge orifice of the nozzle structure, the cap and the nozzle body beingv formed to provide an air circulating chamber therebetween, means defining another air passage from said first mentioned1air passagexin the nozzlerstructure to the annular chamber, rneans providing a passage for the flow of air radially from the annular chamber into the air circulating chamber between thenozzle structure and the cap, the air circulating chamber being continuous with the capopening .so' thatrair flowing, intosuch air chamber is discharged through rthe cap opening to-commingle with the projected ,fueliand primarytair; mixture, the nozzle structureabeing adapted to project the spray in an expanding pattern 17 through the cap opening for burning in spaced relation to the cap and the nozzle structure, whereby radiant heat energy directed toward the nozzle structure from the burning spray is intercepted by the cap in the elimination of excessive heating of the nozzle structure.

References Cited in the file of this patent UNITED STATES PATENTS 18 Arnold Oct. 10, 1939 McCollum Dec. 4, 1945 Holthouse Jan. 15, 1946 Meyer et a1 June 17, 1947 Arnhym July 20, 1948 Logan et al July 18, 1950 Caracristi Dec. 23, 1952 Schumann Mar. 16, 1954 FOREIGN PATENTS France Nov. 1, 1950 Germany Nov. 15, 1913 Great Britain June 13, 1951