US3050112A - Radiant gas burner - Google Patents

Description

Aug. 21, 1962 Filed Sept. 2, 1960 J. A. SAUNDERS ETAL RADIANT GAS BURNER 2 Sheets-Sheet 1 By EDWARD E cone llg- 21, 1962 .1. A. sALJNDERs ETAL 3,050,112

RADIANT GAS BURNER 2 Sheets-Sheet 2 Filed Sept. 2, 1960 INVENTORS SAuNus aan A.

owARo E. Moons ATTY.

United States Patent O 3,050,112 RADIANT GAS BURNER John A. Saunders and Edward E. Moore, Rockford, lil., assignors to Eclipse Fuel Engineering Co., Rockford, Ill., a corporation of Illinois Filed Sept. 2, 1960, Ser. No. 53,744 3 Claims. (Si. 158-109) The present invention relates to gas burners and it Ahas particular reference to a radiant gas Iburner of novel design capable -of producing a flame of low forward Velocity over a wide expanse with the ilame being developed within a comparatively short combustion zone. l

There are many industrial applications in which it 1s desirable to develop a large expanse of 'heat radiation which may be directed towards an object to be heated with the flow of gases proceeding at a relatively `low velocity. `For example, in glass annealing furnaces, it 1S necessary to uniformly heat a large area of glass with no localized heating or hot spots resulting from direct flame impingement. The burner requirements for such furnaces therefore are the production of a flame of large expanse which produces an appreciable amount of radiant heat and which may be directed against the work 1n close proximity thereto, uniformity of flame temperature throughout the entire liame area, and negligible forward velocity of the products of combustion. Where a single burner furnace is concerned, it is obvious that such a large radiant area is a necessity. Uniformity of temperature must be maintained throughout the flame area to prevent localized heating of the work. Minimum forward velcity is a requirement for the reason that with a high forward velocity, flame length is increased at the expense of accurate heat control within the vicinity of the work undergoing heating.

Radiant burners constructed in accordance with the above-mentioned requirements are by no means limited to use in connection with glass annealing furnaces and they may nd wide industrial application in iields such as the heating of galvanizing kettles, for firing melting furnaces, flat roof rotary heat treatment furnaces, forge furnaces, billet heaters, cover-fired ladles, process tubing heaters and a wide varieyt |of other installations too numerous to mention.

There are, at the present time, on the market and in current use, burners which meet the above requirements of a large area and low forward velocity llame and which, furthermore, depend for their eliiciency upon a large measure of radiant heat generation. These burners, in general, consist of concave refractory shapes of cup-shape design and through which premixed gas and air is delivered -for combustion purposes and then deflected along the inside walls of the refractory cup. Such burners require some method of premixing the `gas and air as, for example, the use of a fuel proportioning apparatus, such arrangements being subject to frequent back-firing. The present invention is designed to overcome the abovenoted limitations that are attendant upon the use of such burners as use premixed gaseous constituents for combustion purposes. Toward this end, briefly, it contemplates the provision of a burner assembly including a relatively simple burner casting of novel design capable of developing a highly radiant surface by means of gas combustion and incorporating Athe advantages of a nozzle mixing burner in that it has a wider range of heating capacity, is not subject tok back-firing, and is extremely simple to control.

The provision of a burner construction of the type briefly outlined above is among the principle objects of the invention and, in carrying out this object, the invention contemplates the provision of a composite burner assembly and a cooperating refractory combustion block,

3,50,l12 Patented Aug. 21, 1962 ICC the arrangement being s-uch as to provide an inner swirl chamber at the rear of the assembly into which air is admitted through a series of tangentially arranged ports which give to the air a swirling motion within the chamber. The chamber is provided with a restricted forward exit opening Ihaving associated therewith a forwardly extending lip. The air within the chamber picks up a considerable amount of circumferential velocity causing it to hug the cylindrical Wall of the chamber as it passes forwardly toward the exit opening and lip. As it leaves the lip, this swirling mass of air has injected into it gas which is introduced through a series of circumferentially arranged gas ports. The air and the thus injected gas travel still further forwardly within the burner construction, while at the same time the swirling action continues with :both the air and gas being thrown outwardly by centrifugal force and thus caused to hug the cylindrical wall surrounding it. As the gas and air mixture continues thus forwardly, intermixing thereof is progressively elfected until such time as there has been sul'licient intermixing to support effective combustion. Combustion is initiated at this point and, due to the high velocity spin of the mixture, the forward motion of the same is very materially reduced and is, in fact, maintained at a rate which is dependent only upon the crowding action of the oncoming gaseous constituents. At this p region of extremely low forward velocity, the surface of the combustion block spreads outwardly in radial fashion so .that the flame, still affected strongly by centrifugal forces, tends to follow the radial surface of the block with little or no forward motion. The net result of this phenomena is the provision of a wide flat expanse of llame with the necessary turbulence for intimate mixing of the gas and air, and consequent complete combustion taking place in a circumferential path rather than in an axial path so that an extremely short flame characteristic is attained for heat application over a wide area, while at the same time, the radial faces of the combustion block and furnace -wall become incandescent and olfer a large amount of substantially static radiant heat.

The provision lof a burner construction of the character ybrieiiy outlined above being among the principal objects of the present invention, it is a further object to provide a composite burner assembly which is comprised of a minimum number of parts and each of which is 0f relatively simple design which readily lends itself to straightforward casing operations, thereby resulting in a burner assembly which is simple in its construction and which may be manufactured at a relatively low cost.

A further object of the invention is to provide a burner assembly of this sort in which the operation thereof is not vaffected by the direction of firing. Stated in other words, the burner assembly of the present invention is capable of Vertical firing, either upwardly or downwardly, of horizontal tiring, or of firing at any in-between angle.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood in the light of the following description.

In the accompanying two sheets of drawings forming a part of this specification, yone illustrative embodiment of the invention has been shown.

In these drawings:

FIG. l is a front elevational view of a burner assembly constructed in accordance With/the principles of the present invention;

FIG. 2 is avsectional View taken substantially along the line 2 2 of FIG. 1 and schematically illustrating certain flame and radiant heat characteristics which are associated with the use of the present burner;

FIG. 3 is a sectional view taken substantially along the line 3-3 of FIG. 2; and

FIG. 4 is a sectional view taken substantially along the line 4-4 of FIG. 2.

Referring now to the drawings in detail, the burner assembly of the form of the invention selected for illustration herein involves in its general organization three principal parts including a main burner casting 1t), a front tube 12 which in effect constitutes a forward extension of the main casting 1), and a rear cover casting 14 which constitutes an air connection for the main casting 10. These three parts, when assembled upon one another, are associated with a cooperating combustion block 16 and a block holder 18.

The main burner casting is of cylindrical design and it is also of cup-shaped or dished configuration. The casting 1i? is provided with a substantially flat circular rear wall 20 and a cylindrical side wall 22 having a forward cylindrical extension 24. The side wall 22 and its forward extension, in combination with the circular rear wall 20, dene therebetween a substantially cylindrical inner air chamber 26 which, because of the peculiar motion of air owing through this chamber, will hereinafter be referred to as the swirl chamber. The forward end of the swirl chamber is open and is provided with an inwardly directed rib 27 defining a gradual restriction and terminating in a relatively thin circular lip 2S, the nature and function of `which will be set forth presently. Air is adapted to be admitted to the interior of the swirl chamber 26 through a series of circumferentially spaced and tangentially directed air ports 30, the nature and function of which also will be explained subsequently. The rear lwall 28 may be formed with a threaded hole 31 adapted to receive a conversion plug 33 therein. The hole and plug have no signicance in connection with the present invention other than to provide a convenient means whereby the burner may be converted to oil operation.

The side wall 22, at its juncture with the extension 24, is formed with a radial web 32 which is joined to an outer cylindrical wall 34 spaced from and concentric with the extension 24. The outer wall 34 projects a short distance forwardly of the extension 24 and has an inturned open rim 36 provided with a reentrant portion 38 which is interiorly threaded as at 40. The outer wall 34, in combination with the side wall extension 24, Web 32 and inturned rim 36, provides a jacket-like gas chamber 42 which surrounds the swirl chamber 26.

The front tube 12 is of cylindrical design and it is externally threaded in the medial regions thereof as at 44 forrthreaded reception in the reentrant portion 38 so that, in etect, it constitutes a further extension of the side wall 22. Forwardly of the threaded portion 44, the tube 12 is thickened as at 46 and projects into the block holder 18 and combustion block 16. Rearwardly of the threaded portion 40, the tube 12 has a thin lip portion 48 which spans the distance between the reentrant portion 38 and the lip 28 and closes the otherwise open annulus between these two parts. The tube 12 is provided with an inner cylindrical wall surface 50 which, except for the interruption provided by the lip 28, aiords a cylindrical continuation of the inner cylindrical wall surface 52 of the side wall 22. The lip 48 seats within a recess 53 provided at the rim of the extension wall 24 and it is spaced slightly from the lip 28 so that the two lips dene therebetween a small annular pocket S5 immediately behind the lip 28. The lip 4S is formed -With a series of circumferentially spaced gas ports 57 therethrough which function to admit gas from the gas chamber 42 to the annular pocket 55 for purposes that will be.

made clear presently.

The web 32 terminates a radially extending bolting flange S4 designed for attachment to a similar bolting flange 56 provided on the cover casting 14, suitable clamping bolts S8 being provided for attachment purposes.

The cover casting 14 is of cup-shape design and includes a rear Wall 60 and a cylindrical side wall 62 having the previously mentioned bolting flange 56 associated CII therewith. The rear wall 6i? is formed with a relatively large central opening 64 therethrough and designed for threaded reception of an air supply pipe 68. It will be seen therefore that the cover casting 14, in elfect, constitutes a manifold casting which, in combination with the rear portion of the main casting 10, provides a preliminary or manifold chamber 66 for air and from which chamber air is admitted through the air ports 30 to the swirl chamber 26. The lower region of the outer cylindrical wall 34 is thickened as at 69 and is provided with an opening '76 therethrough which is threaded as at 72 for threaded reception of a gas supply pipe 74.

As best seen in FIGS. l and 4, the rim region 36 of the outer cylindrical wall 34 is for-med with a pair of radially extending diametrically disposed attachment ears 8@ by means of which the entire assembly, including the main casting 18, and the rear cover casting 14, as a whole may be secured to the combustion block holder 18. A gasket 81 may be interposed between the rim 36 and the block holder 18.

The combustion block holder 18 is in the `form of a generally flat dish-shaped casting including a rectangular plate-like portion `82, provided with a marginal ange 84 which extends forwardly therefrom and which encompasses the extreme rear portion of the combustion block 16. The combustion -block is conformably shaped to the holder 18 and it may be formed of various materials capable of heat absorption and radiation as, for example, a refractory or ceramic material, asbestos block, metal alloy, etc. The block 16 is generally rectangular and it is formed with a relatively large central horn-shaped opening 86 therethrough which is ared forwardly and outwardly as best seen in FIG. 2. The opening 86 registers at its rear end with a conformably shaped opening 88 provided in the block holder 18 and the rear end of the opening 86 encompasses the forward open rim 90 of the front tube 12. The rear region of the opening 86 is generally cylindrical as indicated at 92 but in the medial regions of the opening, a gradual flaring thereof as shown at 9'4 causes the opening to terminate in a radial face 96 which constitutes the forward face of the combustion block.

The block holder 18 and its attached combustion block 16 are adapted to be projected in the usual manner through a suitable opening 97 provided in a furnace wall, a fragment of which has lbeen shown at 98, suitable mounting clamps or straps 101) being provided to retain the assembly in position on the furnace Wall.

Referring now to FIG. 3, the side wall 62 of the cover casting 14 is shown as having nine of the tangentially disposed air ports 30, but it is to be distinctly understood that a greater or lesser number of such ports may be employed if desired. The various port-s 30 have their axes arranged tangentially with respect to a circle which is cnocentric with the longitudinal axis of the main burner casting 10, the circle having a diameter only slightly smaller than the diameter of the inner cylindrical wall surface 102 of the side Wall 62. The gas ports 57 in the front tube 12 have been shown purely for illustrative purposes, as being nine in number, Aand these latter ports are truly radial. It will be understood, of course, that the size and inclination of the ports of either series may be varied at will to accommodate varying installations.

The essential and operative elements of the improved burner assembly of the present invention have been described above and certain alternative or auxiliary instrumentalities, such as peep sight, piloting and electrode devices 104, 106 and 108, respectively (FIG. l), are believed to require no detailed description. It is deemed sufficient to state that provision is made for these devices by affording a thickened region 110 in the body of the combustion block holder 18 in the upper regions thereof and providing tapped holes therein yfor removable reception of the same.

In the operation of the burner assembly air entering the manifold chamber 66 from the supply pipe 68 causes an appreciable pressure to be built up within this chamber so that it -will pass through the tangentially disposed air passages or ports 30 and enter the swirl chamber 26 in a generally circumferential direction. Since the axes of all of the ports lie in a common transverse plane of the burner, each jet produced by the por-ts 30 will intersect the next adjacent jet in the direction of air swirl near the base of such jet. The net result of this is that the various jets are forced against the cylindrical wall surface 52 of the side wall 22 in the immediate vicinity of the common transverse plane of the jets and the various jets pick up, so to speak, considerable velocity. The rear wall 20 provides a reaction surface for the forward impelling of the swirling mass of air under the inlluence of the oncoming air issuing from the ports 30 and the mass of -air tends to move slowly forwardly while at the same time closely hugging the cylindrical wall 52.

Due to the restriction afforded by the lip 28, the component of forward velocity remains small in comparison with the component of circumferential or swirling velocity and, at the lip 28, sucient air pressure is built up to draw gas inwardly through the radially disposed ports 57 by a modified venturi action. This venturi action, unlike conventional venturi phenomena wherein the motivating fluid rushes axially past a secondary opening, relies -for its venturi effect upon the relatively high velocity circumferential sweep of air around the rim of the lip 28 and in front of the pocket 55 into lwhich the various ports 57 discharge their gas streams. The gas is picked up at this region and is constrained to follow the swirling motion of the air and move forwardly with the latter. At this initial region of gas entrainment intermixture of the air and gas is incomplete so that there will be little or no combustion. However as the two fluids move forwardly in the swirl chamber 2.6 along the inside of the front tube 12, the mixture is improved gradually until the same reaches the forward rim of the front tube, at which time the gas and air are thoroughly intermixed and will support combustion. As a region just forwardly of the front tube 12, stoichiometric conditions obtain and, because of the fact that during the entire travel of the Itwo iluids through the front tube 12 there is a tendency for the gas and air to hug the cylindrical inner wall surface of the tube, an ignition ring is created immediately forwardly of the front rim of the tube 12 at the region where the mixture iirst contacts the bore 86 of the combustion block. The now burning mixture, i.e., the products of combustion, retain a high velocity spin and as lthe diameter of the bore 86 becomes larger the forward velocity of these products of combustion is reduced practically to nothingness so that the ame hugs the forwardly and outwardly flared wall of the bore 86 and spreads out, so to speak, across the iiat radial face 96 and travels radially outwardly considerably beyond the forward rim of the combustion block 16 and into the interior of the furnace chamber.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. Only insofar as the invention has particulraly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what we claim as new and desire to secure by Letters Patent is:

1. In a gas burner assembly, in combination, Ia burner casing comprising a cylindrical cup-shaped body having a rear wall anda cylindrical side wall dening a forward open circular rim, said walls defining a substantially cylindrical swirl chamber, said side wall being provided with a series of circumferentially spaced air passages therethrough at a region spaced slightly forwardly of said rear wall, said air passages having their longitudinal axes extending substantially tangent to a circle which is coaxial with the side wall and which is of a diameter slightly less than the internal diameter' of the swirl chamber, said passages'being disposed in a common transverse plane of the cylindrical swirl chamber, said side Wall being further provided with a series of circumferentially spaced gas passages 'therethrough at a medial region spaced still further forwardly of said rear wall and rearwardly of said open circular rim, said gas passages being disposed in a common trnsverse plane of the cylindrical swirl chamber, the medial region of said side wall being provided with a continuous internal annular inwardly and forwardly directed rib which lies insideA and is spaced radially inwardly from said gas passages `and which, in combination with the inside face of the side wall, defines an annular pocket which opens forwardly and into which gas is discharged from said gas passages, said rib providing a restriction within the swirl chamber for inhibiting the forward dow of air in the latter to thus enhance thes'wirl characteristics of such air prior to passage thereof forwardly of said rib, means for supplying air to said -air passages, and means for supplying gas to said gas passages.

Z. In a gas burner assembly, in combination, a burner casing comprising a cylindrical cup-shape body having a rear wall and a cylindrical side wall deiining a forward open circular rim, said walls dening a substantlally cylindrical swirl chamber, said side wall being provided with a series of circumferentially spaced air passages therethrough at a region spaced slightly forwardly of said rear Wall, said air passages having their longitudinal aXes extending substantially tangent to a circle which is coaxial with the side wall and which is of a diameter slightly less than the internal diameter of the swirl chamber, said air passages being disposed in a common transverse plane of the cylindrical swirl chamber, said side wall being further provided with a series of circumferentially spaced gas passages therethrough at a medial region spaced still further forwardly of said rear wall and rearwardly of said `open circular rim, said gas passages being disposed in a common transverse plane of the cylindrical swirl chamber, the medial region of said side wall being provided with a continuous internal annular inwardly and forwardly directed rib which lies inside and is spaced radially inwardly from said gas passages and which, in combination with the inside face of the side wall, denes an annular pocket which opens forwardly and into which gas is discharged from said gas passages, said rib providing a restriction within the swirl chamber for inhibiting the forward flow of air in the latter to thus enhance the swirl characteristics of such air prior to` passage thereof forwardly of the rib, means encompassing the rear end region of said side wall and defining therewith a manifold air chamber common to said air passages, means encompassing the medial regions of said side wall and defining therewith a manifold gas chamber common to said gas passages, an air supply pipe in communication with said manifold air chamber, and a gas supply pipe in communication with said manifold gas chamber.

3. A gas burner construction for producing a low forward velocity flame of wide expanse, said burner construction comprising a burner casing comprising a cylindrical cup-shape body having a rear wall and a cylindrical side wall dening a forward open circular rim, said walls defining a substantially cylindrical swirl chamber, said side wall being provided with a series of circumferentially spaced air passages therethrough at a region spaced slightly forwardly of said rear wall, said air passages having their longitudinal axes extending substantially tangent to a circle of relatively large radius which is coaxial with the side wall, said air passages being disposed in a common transverse plane of the cylindrical swirl chamber, said side wall Ibeing further provided with a series of circumferentially spaced gas passages therethrough at a region spaced still further forwardly of said rear wall but rearwardly of the forward open rim of the side wall, said gas passages being disposed in a common transverse plane of the swirl chamber, said side wall immediately rearwardly of the series of gas passages being formed with an internal rib defining a restriction within the swirl chamber and terminating in a forwardly extending lip spaced inwardly of the side Wall and dening in combination therewith an annular pocket -which opens forwardly and with which said gas passages communicate, the restriction afforded 1by said rib serving to inhibit the forward velocity of air issuing from said air passages and passing spirally forwardly toward the restriction and to enhance the swirl characteristics of such air prior to passage thereof forwardly of the rib, a combustion block of refractory material capable of heat-assimilation and of heat-radiation and having a at forward face and a central lliore therethrough in register with the forward open end of said side wall, said Ibore presenting an internal surface of circular crosssection throughout, the rear region of which is substantial- 1y cylindrical and constitutes in eiect a cylindrical extension of the inner surface of the side wall, and the forward region of which is ared gradually outwardly and forwardly soas to merge gradually with the forward at face of the combustion block, means for supplying air to said air passages whereby the swirling mixture of air and gas which moves forwardly in the swirl chamber from said restriction will, under the inuence of centrifugal force, closely hug the flared forward region of said internal surface and increase its radial velocity while at the same time decreasing its forward velocity, and means for supplying gas to said gas passages.

References Cited in the le of this patent UNITED STATES PATENTS 1,893,533 Barber Jan. 10, 1933 1,918,397 Jesler July 18, 1933 2,439,554 Anderson Apr. 13, 1948 FOREIGN PATENTS 476,721 Germany May 28, 1929

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