US3057611A - Burner-blower combination for grain dryers - Google Patents

Description

Oct. 9, 1962 T. J. BJERKAN BURNER-BLOWER COMBINATION FOR GRAIN DRYERS Filed Feb. 15, 1960 3 Sheets-Sheet l INVEN TOR. 7776000/6 J dyer/fa Affamey Get. 9, 1962 T J. BJERKAN 3,057,611

BURNER-BLOWER COMBINATION FOR GRAIN DRYERS Filed Feb. 15, 1960 3 Sheets-Sheet 2 JNVENTOR. 771600'0/2 J fijrr/Esw Affarnay Oct. 9, 1962 r 'r. J. BJERKAN 3,057,611

BURNER-BLOWER COMBINATION FOR GRAIN DRYERS I Filed Feb. 15, 1960 Y 3 Sheets-Sheet 3 I INVENTOR. 726002,? J @Pr/fan QMdM A ffarncy.

United States Patent U 3,057,611 BURNER-BLOWER COMBINATION FOR GRAIN DRYERS Theodore J. Bjerkan, Prairie Village, Kans., assignor to Bjerkan Engineering Service, Inc., Prairie Village, Kans., a corporation of Missouri Filed Feb. 15, 1960, Ser. No. 8,542 8 Claims. (Cl. 263-19) This invention relates to new and useful improvements in burner-blower combinations for use in connection with grain dryers and the like, and has as its principal object the provision of means for automatically proportioning the primary and secondary air supplied to the burner for maximum efiiciency of fuel combustion despite variations in the static pressure head against which the blower may be operating.

In a common form of grain dryer, heated air is forced through a bed of grain disposed in a grain bin or the like, the air being propelled by a blower disposed in a conduit interconnected with the bin, and heated by a burner also disposed in said conduit and supplied with gas or other fuel. The blower also supplies the air for combustion, and the large amount of air delivered by the blower when operating against a low pressure head is such that little or no primary mixture of air and fuel before the fuel leaves the burner is required. However, when the grain bed is thicker or the grain is wetter and denser, greater pressure is required to force the air therethrough, and the blower must operate against a greater static head. As a result, less air is drawn through the conduit, and poor combustion of the fuel will result, causing an expensive waste of fuel, and carboning of the burner parts. Under such conditions the efliciency of combustion may be maintained if a greater proportion of primary air is delivered to the burner. The present invention contemplates means for delivering primary air to the burner automatically in proportion to the static head against which the blower is operating. That is, the greater said static pressure, the more primary air will be delivered to the burner.

Another object is the provision, in a burner-blower combination of the character described, of -a burner and baffle arrangement for producing good flame retention characteristics despite the high velocity of air adjacent thereto, that is, for causing the flame to burn directly adjacent the burner face. Separation of the flame from the burner face causes excessively noisy operation, may cause the flame to be blown or snuffed out, and may cause pulsation of the flame with vibration which may be injurious to the structure.

A further object is the provision of a device of the character described wherein the blower and the burner are disposed in independent and separable casings, and the further provision of means whereby a single burner casing may be mounted selectively on blower casings of several different diameters without loss of burner efficiency. Thus a plurality of bins of diflerent sizes, wherein the blower diameter is determined by the bin size, may be serviced by a single burner.

Other objects are simplicity and economy of construction, efficiency and dependability of operation, and adaptability for use in applications other than grain drying.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the drawing, wherein:

FIG. 1 is a side elevational view, partially broken away, of a grain bin having a burner-blower combination embodying the present invention disposed in operative relationship thereto,

Patented Oct. 9, 1962 FIG. 2 is an enlarged fragmentary sectional view taken on line II-II of FIG. 1 with parts left in elevation,

FIGS. 3 and 4 are slightly reduced sectional views taken respectively on lines III-III and IVIV of FIG. 2,

FIG. 5 is a sectional view taken on line VV of FIG. 2, and

FIG. 6 is an enlarged sectional View taken on line VI-VI of FIG. 2.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies to a grain bin having a cylindrical vertical wall 4, a roof 6 spaced above wall 4 by brackets 8 to provide a ventilating opening 10 therearouud, a floor 12, and a perforated false bottom 14 spaced above floor 12 to form a plenum chamber 16 therebetween. Grain 18 to be dried is supported on the false bottom. Communicating with chamber 16 is a conduit 20, to the open outer end of which is attached, successively, a blower housing 22 and a burner housing 24, said burner and blower housings in conjunction constituting single tubular housing. Details of the blower and burner construction are shown in FIGS. 2-6.

Blower housing 22 is cylindrical in form, being open at both ends, and is interconnected at one end to conduit 20 by a bolted flange connection 26, or any other suitable connecting means. At its opposite end, housing 22 is also provided with a flange 28, and the end of the housing is covered by a wire screen 30, said screen being secured against the face of flange 28 by means of an annular face plate 32 and rivets 34. Disposed concentrically in housing 22 is an electric motor 36, said motor being mounted on a shelf 38 extending across and welded at its ends to said housing. The shaft 40 of said motor is coaxial with the housing, and has a fan or blower 42 keyed thereto. Said fan is operable when actuated to deliver air through conduit 20 into plenum chamber 16, thence upwardly through the perforations of false bottom 14 and through the bed of grain 18, and finally out of the bin through opening 10. Housing 22 is also fitted with a small pipe 44 fixed in the wall thereof so as to communicate with the interior of the housing just ahead of, that is at the delivery side of, fan 42. Said pipe supplies primary air to the gas burner, as will be described below.

Burner housing 24 is also cylindrical in form and open at both ends, being disposed in coaxial relation with blower housing 22 and in end-to-end relationship therewith. It is attached to the blower housing by means including a plurality of radially extending fins 46 affixed to the external surface thereof at angularly spaced intervals. A hook 48 engaging flange 28 of housing 22 is secured to each of said fins by a bolt 50 which is inserted selectively in any one of a series of radially spaced apart holes 52 formed in said fin. It will be apparent that by mounting bolts 50 in different holes 52, the burner housing may be mounted on blower housings of different diameters.

Supported in housing 24, co-axially therewith is a burner ring 54. Said burner ring is annular in form, having an external diameter smaller than that of housing 24, whereby 'to leave an annular lair passage 56 there-between (see P16. 5 Said burner ring is provided at angularly spaced intervals with integral lugs 58 (see FIG. 5) which extend radially outwardly and are securedto housing 24 by screws 60. Said burner ring has a circular gas passage 62 which is adapted to direct the primary air-gas mixture forwardly from the face 64 of the burner through a ring of holes 66 and through an annular opening 68, the major portion of the mixture passing through opening 68. The ring is provided with an integral cylindrical extension 70 which forms the inner wall of annular opening 68 and which projects somewhat forwardly of face 64 of the ring. Disposed in the forward portion of housing 24, coaxially form an air passage 73 therebetween (see FIG. 2).

therewith, is a cylindrical tube 72, of smaller diameter than the internal diameter of the burner ring. The forward end of said tube extends nearly flush with the forward end of housing 24, and is supported concentrically therein by tie rods '74 connected to the housing. The rearward end of said tube extends within the burner ring and is fitted with a forwardly divergent conical baffle 76. The rearward edge of said baflle is joined to tube 72 around the entire periphery thereof, and the forward portion of the bafiie extends forwardly of extension 70 of the burner ring in spaced relation therefrom, whereby to Said baffle is connected to and supported by the burner ring, by means of a plurality of Welded brackets 30 which do not appreciably affect the flow of air through passage 78.

The primary air-gas mixture is supplied to passage 62 of the burner ring through a pipe 82 interconnected therewith through the rearward face of the burner ring. Said pipe is interconnected at its outer end with one of the end outlets of a T-fitting 84. A gas supply pipe 86 is interconnected in the side inlet of said T-fitting, and is fitted with the usual gas orifice member 88. The other end inlet of said T-fitting has connected therein a short pipe 90 in which is installed a flow-regulating butterfly valve )2. As shown in FIG. 6, said valve constitutes a flat circular plate mounted on a stem 94 which extends through a bushing 96 aflixed to the pipe and which may be turned manually by a handle 98 aflixed thereto. A flexible hose 100 is connected at one end to the outer end of pipe 90 by a hose clamp 102, and is connected at its opposite end to theouter end of pipe 44 by hose clamp 104. The hose is preferably disposed externally to the blower and burner housings, as shown. It will be understood also that the burner may be provided with the usual control and safety devices, such as a main valve, a pilot burner, and means for shutting the main valve if the pilot burner or the blower should fail. However, such devices form no essential part of the present invention, and are therefore not shown.

In use, it will be apparent that when motor 36 is started and the burner is lighted, the fan 4-2 will draw air into the rearward end of burner housing 24, and that the air will then flow through passages 56 and 78 to supply secondary air for complete combustion of the primary mixture emerging from the burner ring. The hot gaseous products of combustion, and air heated thereby, will then be forced by the fan through conduit and through the bed of grain 18 as previously described, whereby said grain is dried. The fan will necessarily operate against a static pressure in conduit 29, the degree of this pressure depending primarily on the depth and density of the grain bed. This static pressure forces air through hose 100 to supply primary air to T-fitting 84, wherein it is intermixed with the gas before it enters the burner ring. When the static pressure is low, as is the case when the grain bin is only partially filled, very little primary air is required, since the volume of air being drawn through the housings is relatively large and will be sufficient for eflicient combustion. It will be seen that at this time the low static pressure will deliver only a small amount of air through hose 1%. Correspondingly a high static pressure head on the fan, as when the bin is more nearly full, will decrease the amount of air drawn through the housing by the fan, to the point where ineflicient combustion and carboning of the burner parts could occur. This higher static pressure causes more air to be delivered through hose 100, whereby the air-gas ratio for efficient combustion is maintained. In other words, the primary air delivered varies directly with the static pressure against which the blower is operating, and the proper air-gas ratio is maintained automatically.

Butterfly valve 92 serves to initially regulate the primary air flow for optimum operation. However, once this setting has been determined for a given installation, it need not be further adjusted, since in all subsequent operation the primary air flow will be regulated by variations in the static air pressure ahead of the blower fan, as described.

The relationship of conical baffle member 76 to the burner ring has been found to produce a burner having good flame retention characteristics, in that the flame commences at or very close to the burner face 64. As has been pointed out, separation of the flame from the burner face causes ineflicient combustion, noisy operation, and possibly damaging pulsation or vibration. The provision of a special flame retention means is of peculiar and special importance in a grain dryer device as shown, or other similar applications, in that for efficient drying a great excess of air over that actually required for combustion is necessary. The resultant high velocity of the air flowing past the burner would tend to cause flame separation it special provision were not made to prevent it. In the present structure, baffle 76 directs a conical wall of air forwardly so as to intersect angularly the substantially cylindrical wall of the air-gas mixture emerging from burner opening 68, and also the substantially cylindrical wall of secondary air flowing past the burner through annular passage 56. This angular relation causes an extreme flow turbulence, which produces rapid and thorough inermixture of the secondary air and primary air-gas mixture, with the result that the flame burns evenly from the face of the burner ring. The extension 70 of the burner ring prevents the conical Wall of air delivered by battle 76 from inhibiting the actual exit of the primary airgas mixture from the burner. Also, it will be seen that air drawn forwardly through tube 72 is substantially unheated, and since the tube is in alignment with electric motor 36, it envelopes said motor at all times with relatively cold air, whereby to protect said motor from damage by overheating by the burner flame.

Another advantage of my structure is that it permits a single burner assembly to be mounted interchangeably on blower housings of various sizes, so long as the blower housing is at least as large as the burner housing, without loss of blower capacity or burner efliciency. When the burner housing is smaller than the blower housing, the blower intake includes the annular portion of the rearward end of its housing which surrounds the burner housing. Therefore the blower intake is not restricted nor its capacity reduced by the small burner housing. At the same time, the burner housing passes substantially the same quantity of air as it would if it were the same size as theblower housing, so that the large blower does not increase the air velocity in the burner housing, which otherwise would interfere with the burner efliciency. In other words, changes in the diameter of the composite conduit formed by the two housings, caused by the fact that the burner housing may be smaller than the blower housing, will not effect the efficiency of the device so long as the burner housing does not appreciably obstruct or restrict the intake end of the blower housing.

While I have shown and described a specific embodiment of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention as defined by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent is:

1. In combination, a substantially tubular housing having an air inlet end and an air outlet end, a blower mounted in said housing intermediate its ends and operable to impel a current of air through said housing from its inlet end to its outlet end, a fluid fuel burner mounted in said housing intermediate said blower and the inlet end of said housing and operable to eject fuel into said housing whereby when said fuel is ignited said air will be heated, said air supplying secondary combustion air for said burner, and means for mixing primary combustion air with said fuel prior to its ejection from said burner, said means comprising a conduit interconnected at its one end to said burner, and interconnected at its opposite end into said housing intermediate said blower and the outlet end of said housing, said conduit opening into said housing at right angles to the axis thereof, so that air flowing through said conduit to said burner varies generally in direct proportion to the static air pressure in said housing.

2. The combination as recited in claim 1 with the addition of an adjustable flow regulating valve in said conduit.

3. The combination as recited in claim 1 with the addition of baflle means mounted in said housing and operable to direct a portion of the air flowing through said housing in angularly intersecting relationship to the primary air-fuel mixture emerging from said burner, closely adjacent its point of emergence therefrom.

4. The combustion as recited in claim 1 wherein said burner is ring shaped and directs the primary air-fuel mixture forwardly therefrom, in a substantially cylindrical configuration, and with the addition of a conical baflle plate mounted in the open center of said burner ring concentrically therewith and diverging forwardly, said baflle plate terminating at its forward edge forwardly of said burner, whereby to direct a conical wall of air in angularly intersecting relation to the primary air-fuel mixture emerging from said burner.

5. The combination as recited in claim 1 wherein said burner is disposed intermediate said blower and the inlet end of said housing and is driven by an electric motor mounted centrally in said housing, and wherein said burner is ring-shaped, has an open central portion, and is coaxial with and of larger diameter than said motor, whereby the heat of the flame of said blower will tend to pass around said motor in a cylindrical sheath, and whereby said motor will be blanketed at all times with relatively unheated air drawn through the central opening of said burner.

6. The combination as recited in claim 5 with the addition of an open-ended tube of smaller diameter than the internal diameter of the ring-shaped burner and mounted coaxially with said burner, said tube extending from a point substantially within said burner to a point substantially forward of said burner and adjacent said motor.

7. The combustion as recited in claim 5 with the addition of an open-ended tube of smaller diameter than the internal diameter of the ring-shaped burner and mounted coaxially with said burner, said tube extending from a point substantially within said burner to a point substantially forward of said burner and adjacent said motor, and a frustro-conical baffle plate secured around its smaller diameter to the rearward end of said tube and diverging forwardly to a diameter substantially equal to the internal diameter of the burner ring, and terminating forwardly of said burner ring.

8. The combination as recited in claim 1 wherein said housing is composite and comprises a tubular blower housing in which said blower is mounted and a tubular burner housing in which said burner is mounted, said blower and burner housings being disposed in end-to-end relation with the burner housing at the intake end of said blower housing, and means for connecting said housings together, said connecting means comprising a plurality of radially extending fins secured to said burner housing and a fastener secured to each of said fins and engaging said blower housing, said fasteners being radially adjustable along said fins whereby said burner housing may be selectively mounted on blower housings of various diameters.

References Cited in the file of this patent UNITED STATES PATENTS 1,629,253 Breese May 17, 1927 2,174,663 Keller Oct. 3, 1939 2,432,525 Kruse Dec. 16, 1947 2,460,983 Hess Feb. 8, 1949 2,604,312 Andersen et a1 July 22, 1952 2,606,014 Baumann Aug. 5, 1952 2,654,219 Zaba Oct. 6, 1953 2,703,706 Bishop Mar. 8, 1955 2,836,409 Harrison May 27, 1958 2,966,347 Wolfiradt Dec. 27, 1960 FOREIGN PATENTS 323,458 Switzerland July 31, 1957

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