US3240433A - Burner construction having casing with tangentially arranged air inlet and swirl chambers - Google Patents

Description

J. P. KEATING 3,240,433 BURNER CONSTRUCTION HAVING CASING WITH TANGENTIALLY March 15, 1966 ARRANGED AIR INLET AND SWIRL CHAMBERS 2 Sheets-Sheet 1 Filed April 8, 1963 INVENTOR' JAMES P. KEA 7'//v6 March 15, 1966 J. P. KEATING 3,240,433

BURNER CONSTRUCTION HAVING CASING WITH TANGENTIALLY ARRANGED AIR INLET AND SWIRL CHAMBERS Filed April 8, 1963 2 Sheets-Sheet 2 INVENTOR.

JAMES 1 K154 TING ATTOR Y United States Patent C) 3 240,433 BURNER CONSTRUCT ION HAVING CASING WITH TANGENTIALLY ARRANGED AIR INLET AND SWIRL CHAMBERS James P. Keating, Rockford, Ill., assignor to Eclipse Fuel Engineering Co., Rockford, 111., a corporation of Illinois Filed Apr. 8, 1963, Ser. No. 271,309 1 Claim. (Cl. 239-400) The present invention relates to burners and has particular reference to a burner casing construction which, by the simple expedient of nozzle substitution, is capable of use either as a gas burner or as a liquid fuel burner. Whether employed as a gas or liquid fuel burner, the burner casing of the present invention is admirably well adapted for use in connection with the internal heating of small diameter radiant tubes and in one illustration thereof, it is shown as being provided with a gas-burning nozzle and in operative association with such a tube. The burner casing is, however, suitable for use in firing a combustion block, and in another illustration thereof, it is shown as being provided with a liquid fuel-burning nozzle and in operative association with a combustion block. It will be distinctly understood, however, that the casing may be employed for tube-heating purposes when equipped with a liquid fuel-burning nozzle and that it may similarly be employed for combustion blockhea'ting purposes when equipped with a gas-burning nozzle. Irrespective, therefore, of the particular type of nozzle employed, the fuel involved or the use to which the burner casing may be put, the essential features of the invention are at all times preserved.

Inasmuch as the principles of fuel and air introduction into the burner casing, of fuel and air conduction and distribution through the casing, of fuel mixture at the outlet region of the casing, of flame establishment, and of flame conduction and distribution in a direction forwardly of the burner casing remain substantially the same whether the fuel involved be fuel gas or a liquid will be discussed in detail herein on the basis of a gas burner used for tube-firing purposes. Thereafter, when a full understanding of the principles involved has been had, the burner casing will be briefly described in association with a liquid fuel-burning nozzle with the burner as a whole being employed for combustion block-firing purposes.

A conventional present-day gas burner which is designed for the same purpose as the burner of the present invention is possessed of numerous limitations, principal among which is the inability of such a burner to transfer the heat that is generated thereby to the wall of a tube undergoing heating in proportion to the B.t.u. input of the burner. This limitation is attributed to lack of turbulence at the burner nozzle and axially along the tube undergoing heating. Without such turbulence, the generated heat of the burner flame travels centrally along the tube and is insulated from the tube wall by a layer of relatively cool gases which travel along the wall and hug the same for appreciably long distances from the burner. At regions close to the burner nozzle, before these cool gases assume their encompassing position, there is a tendency for overheating.

Efforts to overcome the above-noted limitation of localized overheating near the burner and insuflicient heating at points remote from the burner have not proven altogether satisfactory. These efforts have been predicated upon attempts to secure increased turbulence within the tube, as, for example, the creation of obstructions in the path of gas flow, by corru-gating or dimpling the tube wall, or by the use of ceramic targets in the path of gas flow, not only to break up the even flow of gases, but also to create radiant heat for direct application to the tube wall. Not only are such expedients costly from .a manufacturing and servicing standpoint, because they involve tube modification or internal support within the tube, but the uniformity of the attained heat leaves much to be desired inasmuch as the amount of turbulence established for any given obstruction varies in proportion to its distance from the burner.

The present invention is designed to overcome the above-noted limitation that.is attendant upon the construction and use of a conventional present-day radiant tube heating burner and, accordingly, the invention contemplates the provision of an extremely simple nozzlemixing burner which requires no modification whatsoever of the tube undergoing heating or internally-mounted tube obstructions or baflles, yet which will establish a high degree of turbulence within the tube, both. in the vicinity of the burner and at points remote therefrom. The provision of such a burner constitutes one of the principal objects of the invention.

Another and equally important object of the invention is to provide a tube heating nozzlefmixing burner of the type under consideration and in which uniform heating of the associated tube takes place throughout an appreciably long longitudinal extent of the tube wall.

The provision of a burner which is comprised of but two principal parts, namely, a burner casing and a gas nozzle, and, therefore, may be manufactured of a relatively low cos-t; one which is rugged and durable and has no intricate parts and, therefore, is possessed of a comparatively long life without requiring servicing; one which is comparatively smooth and silent in its operation whether the same be used for tube or combustion block firing; one which requires no manual adjustment; and one which, otherwise, is well-adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

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

In these drawings:

FIG. 1 is a sectional view taken substantially centrally and longitudinally through a gas burner that is constructed according to the present invention and showing the same in operative association with a tube undergoing firing;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1 and in the direction indicated by the arrows;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1 and in the direction indicated by the arrows; and FIG. 4 is a sectional view similar to FIG. 1 but showlng a liquid fuel burner that is constructed according to the invention, the burner being in operative association with a combustion block undergoing firing.

Referring now to the drawing in detail and in particular to FIGS. 1 to 3, inclusive, the burner 10 that is illustrated therein is essentially a nozzle-mixing gaseous fuel burner and comprises two parts, namely, a burner casing 12 and a gas nozzle 14. The burner casing 12 preferably is in the form of a casting, while the gas nozzle 14 is in the, form of a short length of tube stock and is press-fitted into the casing in a manner that will be described presently.

The burner casing 12 is generally of tear-drop configuration in transverse cross section as shown in FIGS. 2 and 3, and includes spaced apart front and rear walls 16 and 18 of tear-drop design and a connecting continuous or peripheral marginal wall 20 of relatively short axial extent.

The rear Wall 18 ,of the burner casing is provided with an inlet opening 21 for one of the two gaseous constituents of combustion, preferably air, and an inlet opening 22 for the other gaseous constituent, preferably fuel gas. The air inlet opening 21 is established by reason of an integral attachment flange 24 which threadedly receives one end of an air supply conduit 26. The gas inlet opening 22 similarly is established by reason of an integral attachment flange 28 which threadedly receives one end of a gas supply conduit 30. The front wall 16 of the casing 12 is provided with an air discharge opening 32. The latter is surrounded by an integral cylindrical flange 34 which constitutes the burner discharge nozzle. The air inlet opening and the air discharge opening 32 are of approximately the same diameter, while the diameter of the gas inlet opening 22 is reduced.

As best seen in FIGS. 2 and 3, the peripheral wall 20 of the burner casing 12 is provided with a relatively large diameter, semi-cylindrical end wall section 40, a relatively small diameter, semi-cylindrical end wall section 42, and two generally tangential interconnecting side wall sections 44 and 46. The side wall section 44 is substantially flat anad merges gradually with the end wall sections 40 and 42, while the side wall section 46 is provided with an inwardly bowed portion 48. An inwardly extending curved vane 50 is formed on the inwardly bowed portion 48 and constitutes a continuation of the curvature of the cylindrical end wall section 40 of the casing. The curved vane 50 divides the interior of the easing into a relatively large swirl chamber 52 and a relatively small air inlet chamber 54, the two chambers being in communication through a throat port 56 which exists by reason of the spacing of the extreme or distal edge 58 of the vane 50 from the side wall section 44. The crosssectional area of the throat port 56 is at least as great as the cross-sectional area of the air inlet opening 21, it being shown in the illustrated form of the invention as being somewhat larger than such air inlet opening so that air admitted to the air inlet chamber 54 will not be restricted in its flow to the chamber 52. The character and disposition of the curved vane 50 are such that a tangent plane atthe distal edge of the vane extends at a small angle to the plane of the side wall section 44.

The gas inlet opening 22 is offset from the longitudinal axis of the generally cylindrical swirl chamber 52, the direction of offset being such that the vane 50 extends between the air inlet opening 21 and the gas inlet opening 22. The air inlet opening 21 is substantially centered ,with respect to the generally cylindrical confines of the air inlet chamber 54. The short length of tube stock which forms or COl'lS'Eltutes the gas nozzle 14 has one end thereof press-fitted as at 60 (see FIG. 1) in the forward end of the gas inlet opening 22, and the nozzle extends forwardly across the swirl chamber 52 and terminates in coaxial relationship within the medial region of the flange 34 which forms or constitutes the burner discharge nozzle.

As shown in FIG. 1, in the operation of the above described burner 10, the front wall 16 is welded or otherwise secured as at 62 to the proximate end of a radiant tube, such as the tube T to be heated, and a ring 64, which is comprised of a suitable heat-resistant ceramic or other material, is disposed between the wall of the tube T and the cylindrical flange 34. The forward end region of ring of material is preferably flared outwardly in frusto-conical fashion as indicated at 66, tapering to a thin edge 68 'where it merges with the tube wall.

When the burner is fired, the air which enters the burner casing 12 through the air inlet opening 21 passes through the throat port 56 and is forced against the end wall sec-- tion 40 surroundingt'he swirl chamber 52 and is constrained to follow the curvature of this end wall section due to the centrifugal force involved. The axis of the flange 34 which forms the discharge, nozzle being offset as preyicusly glesg libcd from the center of curvature of the end wall 40, the centrifugal forces involved as the air swirls inwardly toward the air discharge opening in involute fashion become increasingly greater so that the air is discharged through the flange 34 in a stable or even manner. Stated otherwise, the air which passes outwardly across the rim of the discharge opening 32 has the same velocity at all points along such rim. The resulting discharge of air from the discharge nozzle 34 which is formed by the high rotative velocity with practically no forward velocity other than that imparted to it by reason of the pressure of back-up air emerging from the swirl chamber 52. This escaping air is thus caused closely to hug the frusto-conical wall surface 66 of the ceramic material 64 with a large component of circumferential velocity and a small component of forward velocity.

As the air passes forwardly through the aforementioned burner discharge nozzle, gas is picked up from the forward rim of the gas nozzle 14 and is constrained to follow the swirling motion of the air. At this initial region of gas entrainment within the burner discharge nozzle, the mixture is incomplete and little or no combustion takes place. However, as the two gaseous fluids move forwardly and are thrown radially outwardly into contact with the frusto-conical surface 66 of the ring 64, the intermixture improves and a more thorough mixing takes place to support combustion. At a region just forwardly of the frusto-conical surface 66 substantially stoichiometric conditions obtain, and because of'the fact that during travel of the mixed gaseous fluids forwardly along an appreciable length of the tube .T, there is a tendency for the same to hub the cylindrical wall of the tube and establish a continuation of the initial rotating swirling velocity of the products of combustion, thus yielding heat evenly to the tube wall for an appreciable distance forwardly. of the burner 10.

In FIG. 4, the burner that is illustrated is essentially a nozzle-mixing liquid fuel burner and comprises a burner casing 112 and a liquid fuel nozzle 114. The burner casing 112 is identical in every respect to the burner casing 12 described in connection with the gas burner 10 of FIGS. 1 to 3, inclusive, and, therefore, to avoid needless repetition of description, corresponding reference numerals but of a higher order have been applied to the corresponding parts as between FIGS. 1 and 4.

The liquid fuel nozzle 114 which has been substituted for the gas nozzle 14 of FIG. 1 is in the form of a composite tube and a horizontally extending liquid fuel tube 123. The composite tube embodies a horizontally extending part the inner or forward end portion of which extends through the swirl chamber 152 in the same manner as the nozzle 14 extends through the swirl chamber 52 of the burner construction of FIGS. 1 to 3, inclusive. The composite tube also comprises an externally disposed, laterally extending or depending leg 115 through the upper end of which there projects in sealing relationship the liquid fuel tube 123. Such liquid fuel tube extends longitudinally and centrally through the horizontal part of the composite tube of the nozzle 114 and its forward end terminates at the forward end of the nozzle.

Liquid fuel is adapted to be supplied to the nozzle through the tube 123 while gas (air) is adapted to be supplied to the nozzle through the lateral leg 115, the two constituents of combustion being discharged into the central regions of the cylindrical flange 134 which constitutes the burner discharge nozzle. The gas is supplied under pressure so that an atomizing effect on the liquid fuel takes place at the region of fuel discharge.

The burner casing 112 is shown as being operatively associated with a combustion block B which is installed within a furnace wall 125. The combustion block B is formed with the usual tapered combustion tunnel 166 in register with the burner discharge nozzle 134.

The operation of the burner assembly 110 is substantially the same as the operation of the burner assembly 10 so that a detailed description thereof is unnecessary,

it being deemed sufficient to state that atomized liquid fuel and the gas within which it is entrained are introduced into the combustion tunnel at the base of the throat region thereof and combine with the swirling air issuing from the swirl chamber 152 in substantially the same manner that the gas is combined with the air issuing from the swirl chamber 52 in the previously described burner 10. The swirling products of combustion are thus carried a considerable distance forwardly of the combustion block B where substantially stoichiometric conditions are prevalent.

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 or scope of the invention. For example, while the rear ends of the lengths of tube stock which constitute the fuel nozzles 14 and 114 are shown as being press-fitted into the fuel inlet openings 22 and 122, respectively, obviously the parts may be threaded and thus connected together if desired. Such minor details may be resorted to within the scope of the appended claim.

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

A burner comprising, in combination, a unitary, vertically elongated burner casing embodying a front wall, a rear wall, and a continuous peripheral wall extending between and connected to the front and rear walls and consisting of a relatively large diameter, semi-cylindrical upper end Wall section, a relatively small diameter, semicylindrical lower end wall section, a substantially straight first side wall section having its end regions connected to, and merging gradually and tangentially with, the adjacent end regions of the upper and lower end wall sections, and a second side wall section having its end regions connected to, and merging gradually and tangentially with, the adjacent end regions of said upper and lower end wall sections, and provided with an inwardly bowed central region, a curved vane disposed between and connected to the central portions of the front and rear walls, having one end thereof connected to the inwardly bowed central portion of the second side wall section, extending upwards and inwards at a small angle to the first side wall section and having its other end terminating a small distance short of said first side wall section in order to form therewith a throat port, said vane being curved complementally to the upper end wall section and having the upper side thereof defining with the upper end wall section and the upper portions of the first and second side wall sections a comparatively large, substantially circular, free-flow, unrestricted swirl chamber, the lower side of said vane forming with the lower end wall section and the lower portions of the first and second side wall sections a comparatively small free-flow, unrestricted air inlet chamber of pear shape in outline, said swirl chamber and said air inlet chamber being in communication with each other through the throat port, the lower portion of the rear wall of the casing being provided with a single central air inlet opening in communication with the air inlet chamber and coaxially positioned with respect to the lower end wall section, the upper portion of the casing front wall being provided with an air discharge tube in communication with the swirl chamber, the upper portion of the casing rear wall being provided with a fuel inlet opening in axial alignment with the air discharge tube, and a horizontally disposed tubular fuel nozzle having its rear end sealingly connected to the fuel inlet opening, projecting across the swirl chamber, and having its front end terminating within said air discharge tube, said rear wall of the casing being imperforate except for said air inlet opening and said fuel inlet opening and the casing front wall being imperforate except for the communication with said air discharge tube.

References Cited by the Examiner UNITED STATES PATENTS 2,215,272 9/1940 OBrien 15876 2,433,317 12/1947 Carter 158-1.5 2,456,930 12/1948 De Lancey 15876 2,500,344 3/1950 Carter 15876 2,796,118 6/1957 Parker et al 1269l 3,088,681 5/1963 McCutcheon 158-76 FOREIGN PATENTS 178,509 4/ 1922 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

MEYER PERLIN, JAMES W. WESTHAVER,

Examiners.

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