US3511589A

US3511589A - Gas burner

Info

Publication number: US3511589A
Application number: US690299A
Authority: US
Inventors: Charles W Rothhaar; Guy Richard Harter
Original assignee: Maxon Premix Burner Co Inc
Current assignee: Maxon Premix Burner Co Inc
Priority date: 1967-12-13
Filing date: 1967-12-13
Publication date: 1970-05-12
Anticipated expiration: 1987-05-12
Also published as: DE1751483A1; BE713431A; DE1751483C3; NL6806789A; DE1751483B2; GB1196338A

Description

May 12, 1970 c. w. ROTHHAAR ETAL v 3,511,589

GAS BURNER med nec. 1s. 19s? s sheets-sheet 2 May 12, 1970 c. w. RoTHHAAR ETAL 3,511,589

GAS BURNER 3 Sheets-Sheet 5 Filed Dec. 13, 1967 j@ Z2 Z0 gw/Z727?? f United States Patent O 3,511,589 GAS BURNER Charles W. Rothhaar, Muncie, and Guy Richard Harter, New Castle, Ind., assignors to Mason Premix Burner Company Inc., Muncie, Ind., a corporation of Indiana Filed Dec. 13, 1967, Ser. No. 690,299 Int. Cl. F23d 13/26 U.S. Cl. 431-350 7 Claims ABSTRACT OF THE DISCLOSURE A gas burner for combustion of air-gas mixtures and for operation in either a static environment or a moving -air stream. A manifold, which denes an interior fuel conduit, is provided with burner face means having ports communicating with the conduit. The ports and the face means are cooperatively oriented to establish an interlaced flame pattern. A pair of aerodynamic projections on the manifold upstream of the burner face means serve to pre- `vent the formation of a fluid barrier about the face means when the burner is operated in a moving air stream.

BACKGROUND-SUMMARY-DRAWINGS This invention concerns gas burner systems and, more particularly, an improved burner unit adapted to burn airgas fuel mixtures. It is a primary purpose of the invention to provide a burner unit capable of uniformly high performance under a wide range of operating conditions and in a variety of Iapplications, either in a moving air stream or in a static environment.

Gas burners are used in a variety of applications including, for example, the heating of make-up air in industrial and commercial structures, supplying heated air for ovens and other recirculating industrial facilities, supplying heated air for non-recirculating drying systems, and ordinary direct heating applications. These typical applications ideally require a burner characterized by, among other things, a wide range of heat output (high turndown), good llame retention and ignition control, high maximum heat output with short flame length, system flexibility (i.e. the ability to satisfy many different industrial, commercial and institutional heating needs), and operating flexibility (i.e. the ability to provide satisfactory performance under adverse environmental or operational conditions).

Accordingly, the principal objective of the invention lies in the provision of a gas burner having -means for establishing a self-sustaining interlaced flame pattern, and aerodynamic means for improving operating performance. These novel structural features result in a burner unit possessing numerous advantages over prior burner designs, including the following beneficial characteristics:

(l) Ability to operate at atmospheric pressures in a static environment or above or below atmospheric pressures in a moving air stream.

(2) Positive ilame retention without the need for ignition rails, external flanges, flame targets and other mechanical contrivances.

(3) Smooth operation over a wide range of firing rates, without impairment by adverse environmental factors, and without the need for external shielding and the like.

(4) High heat output per unit burner length, and low cost and weight per unit heat output.

(5) Cool and quiet operation with no need for special materials and components.

(6) Complete control over the point of ignition and positive cross ignition Iwith minimal risk of pre-ignition or hash-back within the burner.

(7) Adaptability for use in a wide variety of applications with no modification to the basic burner unit.

ice

(8) Ease and low cost of manufacture, installation and maintenance, with a minimum of parts, and compatibility with existing installations.

These and other advantages are achieved by providing a basic burner unit comprising a manifold which defines a conduit for the gas-air mixture. Associated with the manifold are burner face means having essentially opposed surface areas which are convergently inclined toward the center of the conduit. Each of the surface areas includes one or more rows of ports communicating with the conduit, with the ports in one area being longitudinally staggered from those in the other area-to provide an interlaced flame pattern. The ports in adacent rows may lbe of different dimensions to assist in reducing burner noise level. Certain ports may have concentric counterbore depressions to assist in llame retention and sustain ignition. The invention lalso contemplates the use of aerodynamic means to prevent formation of a uid barrier or seal about the combustion area, in moving air stream environments. The basic burner unit may be fabricated in a variety of shapes and sizes to promote system flexibility.

The foregoing and other advantages and features of the invention will be more fully appreciated by considering the remainder of the specification, with illustrative reference to the drawings, in which:

FIG. 1 is a somewhat diagrammatic sectional view of an air heating installation employing an exemplary burner 'assembly constructed in accordance with the invention;

FIG. 2 is an enlarged view of a portion of the installation depicted in FIG. 1;

FIG. 3 is a view taken on the line 3 3 of FIG. 2, lsjlliowing a front elevation of the exemplary burner assemy;

FIG. 4 is a somewhat diagrammatic view of an exemplary burner assembly in a direct heating application;

FIG. 5 is a sectional View taken on the line 5 5 of FIG. 3;

FIG. 6 is a Vview similar to that of FIG. 2, showing a modified burner assembly;

FIG. 7 is a sectional View taken on the line 7 7 of FIG. 6;

FIG. 8 is a sectional view similar to that of FIG. 5, taken on the line 8 8 of FIG. 7;

FIG. 9 is a perspective View of a perforated baffle member designed for use in accordance with the invention;

FIG. 10 is a top plan view of a portion of the burner assembly taken on the line 10-10 of FIG. 8, showing a straight burner unit and yassociated components;

FIG. 11 is an enlarged view of a portion of the burner unit depicted in FIG. 10;

FIG. 12 shows a transverse section of the burner unit taken on the line 12 12 of FIG. 11; and

FIG. 13 is an enlarged fragmentary sectional View of a portion of a burner unit constructed in accordance with the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENT The air heating installation depicted in FIG. 1 is illustrative of arrangements wherein a burner assembly 10` is used to heat an air stream flowing in a duct 12. The air stream may be a fresh air stream, in which case the duct might be connected to a fresh air inlet grille; or the duct 12 may be part of the recirculating duct-work of an industrial oven 14 or the like, as shown in FIG. 1. The air stream is propelled through the duct 12 by a blower 16 which may, depending upon the nature of the installation, be located downstream of the burner assembly 10, or upstream as shown in FIG. 1.

Included in diagrammatic form in the air heating installation of FIG. l is one of several types of air-gas mixers, e.g. a mixer 18, which may be employed to supply air-gas mixtures to the burner assembly 10. (The air may be ordinary fresh air, or any other gas containing oxygen in suilicient amounts to sustain combustion when mixed with the fuel gas.) A thermostat 20 is provided downstream of the burner assembly to regulate its firing rate in accordance with the sensed temperature.

As best shown in FIG. 2, the illustrated mixer 18 includes a fuel gas supply line 22 and an air inlet shutter 24. A controller 26 is responsive to signals from t-he thermostat to actuate a valve in the mixer 18, thus regulating the volume rate of flow of mixed fuel from the mixer to the burner assembly 10 through a suitably supply line 28. In FIG. 2", the moving air stream is assumed to be flowing through the duct 12 in the general direction shown by the arrows, thus passing the burner assembly 10 from left to right.

Although the burner assembly 10 will, for purposes of illustration, be discussed herein as operating in a moving air stream, it should lbe understood that the burner assembly is equally suitable for use under static or quiescent conditions in which little or no air Ilows past the burner assembly. For example, FIG. 4 depicts a typical burner assembly I0 as it might be used in a direct heating application, as for example, the heating of a vessel. Also illustrated in FIG. 4 is an alternative form of mixing apparatus 19, comprising a gas inlet line 23, an air inlet line 25, a chamber 27 and a proportional mixing tube 29, the latter being connected to the supply line 28.

As shown in FIG. 3, the burner assembly 10 constitutes an interconnected array of individual burner units, including a centrally located straight burner unit 30 having a back inlet portion 32 for connection with the supply line 28. Also included in the array are a pai-r of T-shaped burner units 34 and four L-shaped burner units 36. Each of the L-shaped -unts 36 has its free end closed with a generally hemispherical end cap 38.

As best seen in FIG. 5, each of the

burner units

30, 34 and 36 is provided at each of its open ends with an attachment flange 40, so that it can be attached to neighboring burner units or closed by the end cap 38 by means of suitable fasteners 42. Also as shown in FIG. 5, the air-gas mixture enters the back inlet portion 32 of the straight burner unit 30 and is dispersed by a generally rectangular baille plate 44 and smoothly and uniformly distributed throughout the remaining

burner units

34 and 36 in the burner assembly 10. FIG. 5 likewise shows the somewhat Y,

unusual cross sectional shape of the burner unit 30, the purpose and function of which will be considered in greater detail hereinafter.

FIGS. 6 and 7 are similar to FIGS. 2 and 3, and depict several alternatively-shaped burner units arrayed to form a modified burner assembly 50. As in the case of the burner assembly 10, the assembly S0 is shown mounted for operation in a moving air stream flowing in a circular duct 12, with an air-gas mixture entering through the supply line 28. The modified burner assembly is made up of an X-shaped back inlet burner unit 52, a pair of X-shaped burner units 54 and a pair of straight burner units S6. Again, as in the case of the burner assembly 10, the

burner units

52, 54 and 56 in the burner assembly 50 are bolted together at the attachment flanges 40, and the end caps 38 are employed to close the free, ends of the burner units 54 and S6.

FIG. 8 shows in more detail the manner in which the air-gas mixture enters the array of burner units comprising the burner assembly 5t). The mixture from the supply line 28 enters an inlet portion 58 which is integrally formed on the back of the burner unit 52. A modified form of perforated baflle member (shown in perspective in FIG. 9) is mounted in the burner unit 52 in front of the inlet portion S8. As in the case of the baille member 44 mounted in the straight inlet burner unit 3d (FIGS. 3 and 5), the baille member 60 serves to disperse the entering stream of fuel mixture and distribute it smoothly through le array of burner units comprising the burner assem- As can be seen, burner units constructed in accordance with the present invention can be made in any number of shapes and sizes, thus permitting them to be easily and flexibly arrayed to produce a burner assembly of any desired size and configuration.

FIGS. I0 through l2 illustrate in greater detail an exemplary burner -unit embodying the features of the present invention. The burn-er unit shown is the straight unit 56 illustrated in FIGS. 7 and 8, but it should be understood that all of the

units

30, 34, 36, 50, 54 and 56 are constructed in accordance with the inventive features, and are merely differently shaped, some having inlet sections.

The burner unit 56 includes a manifold 70 which defines an interior fuel conduit 72. Associated with the front of the manifold are face means having suitable surface areas for accommodating burner ports. In this instance, the face means comprise a pair of bumer faces 74 which are convergently inclined toward the center of the fuel conduit 72. The manifold 70, the burner faces 74 and the attachment ilanges 40 may be advantageously fabricated in a single casting of iron or other suitable material. Each of the burner faces 74 includes two rows of

ports

76 and 78 with the ports 76 being arranged in the rows adjacent the line of convergence between the burner faces 74 (the inner rows), and the ports 78 being arranged in the outer rows. The

ports

76 and 78 are preferably of circular cross section and are disposed with their longitudinal axes substantially normal to the burner faces 74, extending therethrough to communicate with the fuel conduit 72. Associated with each of the ports 78 in the outer rows are concentric counterbore depressions 80 in the burner faces 74.

Although the illustrated embodiment employs the convergently inclined burner faces 74, it should be understood that the burner face means may assume other coniigurations. For example, the face means might be curved, or might comprise a series of planar surface elements, In this regard, it is contemplated that the face means include at least a pair of essentially opposed surface areas (eg, the faces 74), and that the face means and ports be cooperatively oriented to establish an interlaced llame pattern.

The manifold 70 also includes a pair of integrally formed longitudinally extending aerodynamic projections 82 which function to prevent the formation of a fluid barrier or seal about the burner face means when the burner unit 56 is operated in a moving air stream, as will be described in greater detail hereinatfer.

In operation, the air-gas mixture enters the burner assembly 50 through the back inlet portion S8 of the X-shaped burner unit 52, and strikes the perforated baille member 60 (FIGS. 7 and 8), thus being distributed through the remaining units including the straight burner unit 56. The mixture then passes from the conduit 72 of the burner unit 56 through the

ports

76 and 78 in standing jets, where it is ignited and burned in the space adjacent the burner faces 74. The hemispherical end caps 38 serve to absorb turbulence beyond the ported portion of the conduit 72, thereby inhibiting flash-back, i.e., ignition of the mixture within the conduit.

It will be noted that the ports in one of the burner faces 74 are longitudinally staggered with respect to the ports in the other burner face. As best shown in FIG. ll, this staggered relationship results in a llame pattern which is interlaced. The flame pattern shown (in somewhat idealized form) is that which might be produced with the burner unit 56 being operated at a low to medium tiring rate. As can be seen, the llames issuing from the

ports

76 and 78 on one of the burner faces 74 make slight Contact `with the llames issuing from the other burner face. This aids in establishing cross ignition, and in maintaining ignition and flame retention.

The counterbore depressions 80 also serve to maintain ignition, as best illustrated in FIG. 13. As shown therein, the increased -volume of the counterbore depression 80 surrounding the port 78 permits the formation of a negative-pressure pocket in the form of an annular space 84 disposed concentrically about the main jet of mixture 86 issuing from the port 78. Flow in this volume 84 is turbulent and relatively slow, thus permitting easy ignition of the gas therein. In this manner a ring of ame is maintained about the main jet of mixture 86, and the ring in turn sustains ignition of the main jet. Although the depth and diameter of the depression 80 may vary with respect to the diameter of the port 78, in practice it has been found that ignition is maintained most satisfactorily when the diameter of the depression 80 is from about two to about three times the diameter of the port 78, and when the depth of the depression is from about 75 to about 200% of the port diameter.

As an alternative to the single counterbore depressions 80, a pair of concentric counterbore depressions could be concentrically associated with each of the ports 78. In such an arrangement, the depth of the inner counterbore is greater than that of the outer counterbore (but preferably still within the range of 75% to 200% of the diameter of the port 78), and the diameter of the inner counterbore is approximately one-half the sum of the diameters of the outer counterbore and port 78. As a further alternative, instead of providing counterbore depressions individually associated wtih each of the ports 78, each of the burner faces 74 might include a longitudinal slot or depression running the length of the row of ports 78'. In this arrangement the width of the slot is about one and one-half to about three times the diameter of the ports 78, and the depth f the slot is again preferably in the range of 75% to 200% of the port diameter.

The ports 76 are preferably of a different diameter than the ports 78, so as to substantially diminish a condition of resonance, and the attendant increase in burner noise level or tone, which might result from identically sized ports. Moreover, the ports 76 in the inner rows are preferably larger than the ports 78 in the outer rows, so as to assist the aerodynamic projections 82 in preventing the formation of a fluid barrier or seal about the burner faces 74. In practice it has been found that these objectives will be achieved most successfully by maintaining the total area of the ports 76 in the range of from about one and one-half to two times the total area of the ports 78 (exclusive of the counterbore depressions 80).

Thus, in a typical 12-inch straight burner unit constructed in accordance with the present invention, each of the burner faces 74 might include, for example, an inner row of 24 ports 76 each having a diameter of about 0.154 inch and an outer row of 24 ports 78 each having a diameter of about 0.125 inch. In such a burner, and further by way of example, the counterbore depressions 80 associated with the ports 78 in the outer rows might have a diameter of about 6 inch and a depth of about 1/s inch, with the thickness of walls of the manifold 70 and the burner faces 74 bein-g about 1A inch and 'M6 inch, respectively. Of course, it will be understood that the number and spacing of the rows, the number, size and spacing of the

ports

76 and 78, the diameter and depth of the counterbore depressions 80, and the thickness of the manifold 70 and burnerV faces 74 can vary over wide limits, and will depend upon such factors as the desired heat release per linear foot of burner, the mixture supply pressure, the velocity of ignition, the amount of space available in each face for drilling and counterboring, etc. In this connection, it will be noted that a single port 78a at one end of the outer row in each of the burner faces 74 does not have a counterbore depression associated therewith, due to the fact that, in the construction illus- 6 trated in FIG. 10, the staggering of the ports does not permit sufficient space.

When the burner unit 56 is operated in a moving air stream, the projections 82, which in such case are upstream from the burner face means, operate aerodynamically to prevent the moving air stream from for-ming a fluid barrier or seal about the burner faces. It has been found that elimination of this barrier reduces the burner noise or tone and enhances heat release from the space between the burner face means.

The included angle of convergence between the burner faces 74 may also be significant in this regard. It has been found that, for most satisfactory operation this angle should be in the range of from about to about 100, and preferably about Larger angles result in increased suction in the flame area between the faces 74, and also render the burner faces more vulnerable to adverse elements in the moving air stream, thus impairing flame retention. On the other hand, smaller angles substantially reduce the potential heat release per foot of burner and likewise impair flame retention. Where other face means configurations are employed, the angular relationships may be adjusted accordingly.

It should be noted that the open configuration of the face means exposes the

ports

76 and 78 and the depressions 80 for easy inspection and cleaning and, moreover, provides more space for drilling and counterboring than would a single fiat face. In addition, the interlaced flame pattern produces a benecial scrubbing action on the face surfaces.

It should be apparent that the aerodynamic projections 82 could be omitted if it were desired to construct a burner unit for use only in a static environment. Conversely, similar aerodynamic means could be advantageously employed to enhance the performance of ordinary prior burner units operating in moving air streams. In this connection, it should be understood that the precise shape and size of the projections 82 are not critical, so long as they serve to break the streamline ow of air past the sides of the manifold 70 and prevent the formation of a fluid barrier downstream of the burner face means.

Although an embodiment constructed in accordance with the present invention has been described with the requisite particularity, the disclosure is of course only exemplary. Consequently, numerous changes in details of construction, in size, configuration and arrangement of components and materials, and in modes of application will be apparent to lthose familiar with the art and may be resorted to without departing from the scope of the invention as set forth in the following claims.

What is claimed is:

1. A burner comprising: a manifold defining a fuel conduit; burner face means associated with said manifold including a pair of essentially opposed surface areas; and two rows of ports defined in each of said surface areas, the axes of the ports in one of said surface areas being essentially parallel to one another and to the other of said surface areas, the ports in one of said surface areas being spaced in longitudinally staggered relationship to those in the other of said areas, said spaced relationship being such that a full flame issuing fro-m a port in one of said areas makes no more than slight contact with adjacent flames issuing from ports in the other of said areas, the ports in the innermost row in each face being larger than those in the outermost row.

2. A burner comprising: a manifold defining a fuel conduit; a pair of burner faces on the exterior of said manifold convergently inclined to include an angle of about 90; and two rows of ports defined in each of said faces essentially normal thereto, the ports in one of said faces being staggered with respect to the ports in the other of said faces to form an interlaced but only slightly contacting ame pattern, the ports in one row in each face being of different diameter than the ports in the other row, the ports in the outer row in each face having associated therewith a depression formed in said face.

3. A burner as defined in claim 2, wherein said manifold includes a pair of aerodynamic projections on the outer surface thereof for preventing the formation of a fluid barrier about said faces.

4. A system for obtaining heat from premixed gaseous fuel, including mixing means for mixing said fuel, an array of connected burner units, inlet means for passing said fuel from said mixing means to said array of burner units, and end cap means for closing unconnected ends of said burner units, wherein each of said burner units cornprises: a manifold defining a fuel conduit; attachment means at each end of said manifold permitting attachment thereof to similar burner units or said end cap means; a pair of burner faces on the exterior of said manifold 'convergently inclined to include an angle of about 90; and two rows of ports defined in each of said faces essentially normal thereto, the ports in one of said faces being staggered with respect to the ports in the other of said faces to form an interlaced but only slightly contacting iiame pattern, the ports in one row in each face being of different diameter lthan the ports in the other row, the ports in the outer row in each face having associated therewith a depression formed in said face.

5. A system in accordance with claim 4, wherein said end cap means consists of substantially hemispherical hollow members having a cross section essentially congruent with the cross section of said manifolds.

6. A system in accordance with claim 4, including perforated baie means associated with said inlet means for evenly distributing said fuel throughout said array of burner units.

'7. A system in accordance with claim 4, wherein the outer surface of said manifold includes areodynamic means for preventing the formation of a fluid barrier about said burner face means.

References Cited UNITED STATES PATENTS 366,780 7/1'887 Love Z39-553.3

697,235 4/ 1902 Claybourne 431-350y XR 702,873 6/ 1902 Holland 23 9-544 817,750 4/ 1906 Carroll 239-544 1,695,587 12/1928 Harris 239-544 XR 1,859,961 5/1932 Dodd et al 239-544 1,907,734 5/1933 Butz 431-349- 2,061,561 11/1936 Cartter 431-350XR 2,150,819 3/1939 Brurnbaugh 239-544 3,051,464 8/1962 Yeo et al 263-19 3,202,203 8/ 1965 Reed 431-175 XR FOREIGN PATENTS 1,026,899 4/ 1966 Great Britain.

521,772 5 1940 Great Britain.

DONLEY J. STOCKING, Primary Examiner H. B. RAMEY, Assistant Examiner U.S. Cl. X.R. 239-544