US3490858A - Flame retention burner head assembly - Google Patents

Description

Jan 20, 1970 FLETCHER 3,490,858

FLAME RETENTION BURNER HEAD ASSEMBLY Filed Dec. 19, 1967 INVENTOR HERBERT R. FLETCHER ATTORNEY United States I Patent 3 490,858 FLAME RETENTION liURNER HEAD ASSEMBLY Herbert R. Fletcher, Lebanon, Ind., assignor to Stewart- Warner Corporation, Chicago, 111., a corporation of Virginia Filed Dec. 19, 1967, Ser. No. 691,810 Int. Cl. F23q 3/00 US. Cl. 431-265 3 Claims ABSTRACT OF THE DISCLOSURE It is conventional to mount nozzle assemblies including the liquid fuel nozzle or nozzles and the ignition means within a blast tube carrying combustion air which moves at some velocity relative to the nozzle assembly. The liquid fuel exits from the nozzle nose under high pres sure cone in atomized form and readily mixes with the high velocity combustion air. Upon ignition, a flame front is created downstream of the nozzle assembly. Ordinarily, the blast tube opens up into a combustion chamber since the flame front does not remain stationary relative to the burner assembly, but rather, moves axially away from and back toward the nose cone. In the ordinary burner,

this movement of the flame front creates a sound wave and if the combustion space is in tune with the sound wave, a resonant sound (pulsation) results.

It is, therefore, a primary object of this invention to provide flame. retention means within a burner head of the nozzle assembly and blast tube type which eliminates the need for a combustion chamber allowing the flame to radiate directly upon heat exchange surfaces with resulting increased thermal efficiency.

It is a further object of this invention to provide an improved burner head assembly of this type which ensures maximum mixture of atomized fuel oil and combustion air.

It is a further object of this invention to provide flame retention means which may be easily and cheaply applied to existing burner head assemblies, involving simplified construction without moving parts.

Other objects of this invention will be pointed out in the following detailed description and claims and illustrated in the accompanying drawings which disclose, by way of example, the principle of this invention and the best mode which has been contemplated of applying that principle.

In the drawings:

FIGURE 1 is a sectional elevational view of the flame retention means of the present invention as applied to a burner head assembly including a nozzle assembly carried centrally of a blast tube carrying combustion air.

FIGURE 2 is a front elevational view of a portion of the assembly shown in FIGURE 1 taken about lines 2-2.

FIGURE 3 is a front elevational view of a portion of the assembly shown in FIGURE 1 taken about lines 33.

In general, the apparatus of the present invention comprises an improved liquid fuel burner head assembly in the form of a blast tube carrying a nozzle assembly in the Patented Jan 20, 1970 path of incoming combustion air. The present invention is directed to flame retention means, positioned downstream of the nozzle assembly nose cone, which directs a portion of the moving combustion air at relatively low velocity axially of and generally in line with the nozzle assembly, and another portion of combustion air at higher velocity in a vortex path around the central low velocity air. The flame retention means consists of an annular ring assembly fixed to the inner periphery of the blast tube, generally at right angles to the tube axis. The assembly comprises an annular plate having openings formed by spaced, radially directed deflector vanes with the axis of each vane being inclined with respect to the tube axis to cause some of the combination air to swirl at high velocity in an annular path. The annular ring assembly further includes an inner air ring coupling the inner ends of the vanes and forming a central opening in axial alignment with the nozzle assembly, allowing the low velocity air to move past the nozzle assembly. The annular, perforated plate, preferably concave in crosssectional configuration in the downstream direction, cooperates with a diverging flame hood downstream of the annular ring assembly to maintain the flame front longitudinally positioned relative to the nozzle assembly. A thin disk is carried by the nozzle assembly, upstream of the nose cone, coaxial therewith and generally at right angles to the tube axis with the disk being of a diameter smaller than the internal diameter of the tube for ensuring that a major portion of the air, in moving through the blast tube, strikes the annular ring assembly in the vicinity of the vanes.

Turning to the drawing, there is shown in FIGURE 1 a burner head assembly which comprises two basic components, a blast tube indicated at 10 formed of thin sheet metal and a nozzle assembly indicated generally at 12 which is positioned centrally of the blast tube and in the path of the combustion air. Nozzle assembly 12 comprises dual nozzles 13 and 13', but could comprise a single nozzle or any multiple thereof. The air moves from left to right through the blast tube 10 in the direction indication by arrow 14. In this respect, the burner head assembly of the present invention is conventional. Liquid hydrocarbon fuel is discharged from the nose cones 16 and 16 in atomized form into the combustion air. In conventional fashion, the nozzle assembly 12 is provided with ignition means in the form of spaced electrodes 18, forming a gap therebetween. Upon the application of an electrical voltage across the gap, a spark is created between the spaced electrodes resulting in ignition of the atomized fuel and air mixture.

The nozzle assembly 12 is fixedly positioned with respect to the blast tube and centered coaxially with the tube by means of a static disk assembly 29. The disk assembly includes a thin metal disk member 22 having a diameter somewhat less than the inner diameter of the blast tube 10 to form, with the inner wall 24 of the tube, an annular combustion air passage 26. The disk 22 is supported, as best seen in FIGURE 3, by three supporting strips 28 which are suitably welded at their inner ends to the disk 22 along area 30 and make sliding contact with the inner Wall 24 of the tube. This allows the disk 22 to be longitudinally adjusted relative to flame retention ring assembly 42. The static disk 22 is perforated centrally at 34 and 34 to receive the nozzle fuel delivery tubes or conduits, such as conduit 36, and is further provided with openings 38 about its upper edge which receive the ceramic electrode supports 40, as best seen in FIGURE 1. The static disk 22 restricts combustion air flow along the center of the blast tube 10, forcing the air to move along the inner Wall 24 of the tube. This relatively high velocity air impinges directly upon the flame retention ring assembly, indicated generally at 42, which is positioned downstream of the static disk assembly 20, in fact, just downstream of the nose cones 16 and 16'. The flame retention ring assembly 42 consists of a plurality of radially positioned, inclined deflector vanes 44. The vanes extend from an outer ring 46 which is vertically oriented with respect to the blast tube 10, inwardly toward and in contact with an inner air ring 48 which is horizontally oriented, that is, concentric with the blast tube 10. The vanes may be struck out of a unitary plate to form the perforations and inner and outer rings. This gives the flame retention ring assembly a concave cross-sectional configuration in a downstream direction. Air flowing through the flame retention ring assembly 42 is given a high velocity swirling motion. However, the flame retention ring assembly acts somewhat as a baffle plate causing some of the relatively high velocity air moving along the path indicated by arrow 14 to be diverted through the opening 52 formed by the inner air ring 48, as at 50, this air moving at a lower velocity than that passing through openings 54 formed by the spaced, inclined vanes 44. It is the excess air that cannot pass through the flame retention ring assembly openings 54 that passes through opening 52 formed by the inner air ring 48 at a lower velocity. This lower velocity permits the flame front to remain stable within the flame hood 56. After ignition, the resultant flame created by the burning fuel and air mixture is retained centrally of the blast tube within flame hood 56, the flame front being maintained coaxially of the assembly by the swirling annular air mass exiting from the downstream end of the flame retention ring assembly 42. Further, the vanes 44 in imparting a high velocity swirling motion to a portion of the combustion air causes the combustion air to thoroughly penetrate and mixwith the atomized fuel oil. The mixing of the air with the fuel oil not only reduces excess air and increases burner efliciency, but acting in conjunction with flame hood 56, maintains the flame front within the flame hood and eliminates the need for a separate combustion chamber.

In this respect, the flame hood itself comprises a unitary, tubular member, preferably formed of the same metal as blast tube and having an upstreamrimsection 58 of a diameter slightly in excess of that of the blast tube so that it may be securely attached to the blast tube by welding, etc. The downstream end 60 of the flame hood is of larger diameter than blast tube and is coupled to rim section 58 by a diverging wall portion 62. The diverging flame hood therefore acts in conjunction with the concave flame retention ring assembly to ensure, along with the swirling action given to the combustion air and fuel passing through vane section 44, the retention of the flame front at a location spaced slightly downstream of the flame retention ring assembly, within the flame hood. In fact, the flame retention ring assembly acts as a physical barrier to the movement of the flame front in an in and out manner and defeats the characteristic of prior art burner head assemblies to pulsate as a result of resonant sound propagation. The flame front, being retained within the flame hood 56, eliminates the need for a combustion chamber, since the combustion chamber is used with a conventional burner to retain the flame and pre-' vent the same from directly impinging upon the heat exchange surfaces. Utilizing the apparatus of the present invention, the combustion chamber may be readily eliminated, since the flame can radiate directly onto the heat exchanger surfaces (not shown) downstream of the flame hood, but since the flame front is prevented from movement out of the flame hood, the flame itself will never contact the heat exchanger surfaces.

While the invention has been particularly shown and described with reference to a preferred embodiment there- 4 of, it will be understood by those skilled in the art that various changes in the form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An improved, liquid fuel burner head assembly comprising a blast tube including a nozzle assembly carried thereby in the path of the incoming combustion air with a nose cone for said nozzle assembly located for spraying fuel downstream in said air and adjacent the central axis of said tube, a pair of rings coaxial with said tube positioned downstream of the nozzle nose cone with one of said rings peripherally engaged with said tube and the other ring positioned intermediate said cone and one ring with the'diameter of said'other ring being smaller than said one ring and larger than said nose cone, a plurality of circumferentially' spaced vortex producing deflector vanes fixed to said one and second ring at respective circumferential positions and lying in respective substantially axially extending planes whereby the inner periphery of said second ring defines a relatively low velocity path for a portion of said combustion air. axially of the tube and generally in line with the nozzle assembly, and means for directing another portion of the combustion air between said rings past said vanes at higher velocity than said low velocity path to form a vortex patharound the low viscosity air path.

2. A liquid fuelburner heating assembly including a blast tube for carrying combustion air and having a nozzle assembly with a nose cone located in the path of incoming combustion air for spraying liquid fuel adjacent the axis of said tube, the improvement comprising a pair of axially spaced rings of different diameter with the internal periphery of the smaller of said rings being larger than the periphery of said nose cone and spaced downstream of said nozzle assembly including said nose cone and the larger of said rings having an external periphery corresponding to the diameter of said blast tube and spaced downstream of said smaller ring, a plurality of circumferentially spaced vanes fixed adjacent opposite ends to said rings at respective circumferential positions and lying in respective substantially axially extending planes to provide a high velocity-path for said combustion air between said rings and direct a portion of said combustion air in a low velocity path definedby the internal periphery of said smaller ring, and means to direct air through the high velocity path at a velocity higher than the velocity of the air which passes through the low velocity path.

3. In a liquid fuel burner heating assembly as claimed in claim 2, a flame hood fixed to the downstream end of said tube comprising a portion with an internal periphery diverging radially downstream of said larger ring, and a ring terminating said radially diverging portion having an internal surface at least as great as the maximum diameter of said radially diverging portion.

References Cited UNITED STATES PATENTS 2,357,622 9/1944 Wiser 431----265' XR 2,480,345 8/1949 Watts -L 431265 3,079,981 3/1963 Loebel et al 43 1265 XR 3,285,316 11/1966 Gustafson et al. 43 l265 FREDERICK L. 'MATT'ESON, JR., Primary Examiner H. B. RAMEY, Assistant Examiner US. Cl. X.R.

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