US3049172A

US3049172A - Gas burner

Info

Publication number: US3049172A
Application number: US387770A
Authority: US
Inventors: Labino Dominick
Original assignee: Johns Manville Fiber Glass Inc
Current assignee: Johns Manville Fiber Glass Inc
Priority date: 1953-10-22
Filing date: 1953-10-22
Publication date: 1962-08-14
Anticipated expiration: 1979-08-14

Description

Aug. 14, 1962 D. LABlNO 3,049,172

GAS BURNER Filed 001;. 22, 1955 FIG-l INVENTOR.

DOMINICK LABINO BY fizdwwmw ATTORNEYS United States Patent 3,049,172 GAS BURNER Dominick Labino, Toledo, Ohio, assignor, by mesne assignments, to Johns-Manville Fiber Glass Inc, Cleveland, Oh o, a corporation of Delaware Filed Oct. 22, 1953, Ser. No. 387,770 3 Claims. (Cl. 15899) This invention relates to burner apparatus in which combustible gases are burned within a chamber and the gases of combustion are caused to be passed therefrom at high velocity and high temperature through a narrow slot or mouth. More particularly the invention relates to the arrangement of the slot or mouth of such a burner.

The burners generally referred to above find particular utility in fibrous glass production; to produce fine fibers molten glass may be formed into streams and the streams may be attenuated into filamentary form as the glass cools; these filaments when subjected to a hot gaseous blast of a burner may be then blown into very fine diameter staple fibers. Fibers having diameters of less than one micron have been produced in this manner.

To produce such fibers in uniform diameters it is essential not only that the primary filament diameter be closely controlled but that the blast itself as to velocity and temperature be maintained within narrow limits.

The burners customarily employed have a relatively large chamber in which the gases are burned and the expanding gases issue through a relatively narrow slot defined by lips in the wall of the chamber, thereby attaining a high gaseous velocity at an intense heat.

The portions of the burner, including the lips, which are contacted by the hot gases of combustion are of a refractory material, usually Corundum, which is approximately 96% aluminum oxide. The long narrow slots formed in this refractory in the cold have heretofore been rectangular in shape as formed.

It has now been found that under the influence of the heat which generally is above 3000 F. that the rectangular lips, even of a highly refractory material such as Corundum, tend to close centrally early in service life. This tendency is accentuated by the impracticability of supplying a support centrally to the upper lips and also by the tendency for the refractory to shrink under service conditions.

That the central closure in whole or part of the lips is highly important in the production of uniform fibers is clearfor the velocity of the gases will vary materially over the length of the lips, increasing as the spacing therebetwen decreases, occasioning a vary velocityas well as varying heat effects-on the filaments to be blown to the fiber form; this results in non-uniformity thereof.

A complete closing of the lips about the central portion of the length of the slot has been found to exist in some burners upon their removal from service. Such condition does not permit the attainment of the substantially planar gaseous blast which is required for optimum production of thin blown material. I

The height of the slots employable is so slight that detection of closure or partial closure under operating conditions is diificult due to the several factors which influence burner operation. It has now been determined experimentally however that closure or tendency to close centrally upon initial heating as well as over the life of the burner may be avoided by so constructing and arranging the refractory of the burner lips as to provide a uniform opening across the mouth of the burner under operating conditions.

It is therefore a primary object of this invention to describe an improved burner apparatus for the blowing of glass fibers in which the slot of the burner will be of uniform rectangular cross-section under the most severe of operating conditions.

It is a particular object of the invention to describe an improved arrangement of a burner slot which permits of long, trouble-free operation at maximum blast velocities and blast temperatures.

These and other allied objectives of the invention are attained by providing the cold refractory of both the upper and lower lips of the burner with an arcuate form, the lips each being curved outwardly with respect to the slot. This effectively provides in the cold burner a wider mouth or slot at the central portion and when placed in service the arcuate refractory lips tend to straighten out providing a rectangular operating opening capable of delivering a gas flow of improved uniformity of velocity across the mouth of the burner.

The specific degree of are which is required in the lips is dependent upon the particular refractory material which forms the lips; the degree to secure materially improved results is surprisingly slight however as will be noted from the specific example which follows hereinafter. In general the degree of curvature is principally dependent on the shrinkage of the refractory under service conditions, the service temperature and the lip length, and the desired width of the slot itself.

The invention will be more fully understood by reference to the following detailed description and accompanying drawing wherein:

FIGURE 1 schematically illustrates apparatus useful in the practice of invention and which apparatus incorporates the burner having the lip arrangement of invention;

FIGURE 2 is an elevational view of the burner particularly illustrating the contour of the burner lip; and

FIGURE 3 is a view illustrating a portion of the burner appearatus including the lip arrangement.

Referring to the drawing the numeral 10 indicates one embodiment of fiber-forming apparatus in which a supply pot 12, constructed of platinum for example, for retaining molten glass, is surrounded by insulating material 13. The glass is made molten and retained in the molten state by the application of heat energy through induction heating coils indicated at 14 supplied from a high frequency source (not shown).

Solid glass in the form of marbles 15 is fed automatically from the hopper 16 to the pot 12 through a trap door mechanism 18 which is suitably controlled to permit feeding of the marbles in response to the level of the liquid in the pot 12. By this means glass is fed into the pot at the same rate at which it is withdrawn through the apertures 20 in the base of the pot.

As the glass exudes from the apertures 20 and cools primary filaments 22 are formed and as they solidify they are passed over guide roll 24 to drawing rolls 26; the drawing rolls 26' are spaced at a suflicient distance below the pot 12 such that the glass will have hardened before it passes through the rolls themselves. The rolls preferably have surfaces of resilient rubber which frictionally engage the glass and due to the high speed of the rolls feffects a drawing to form fine filaments.

'Ihe filaments passing from the drawing rolls are fed over a second guide 28 and are presented in parallel relation and alignment over the V-shaped edge 29 of the block to a hot high velocity blast of gas issuing from a burner 30; burner 30 is supplied through conduit 33 with a suitable fuel mixture for combustion within the burner in the manner known to the art. The heat of this issuing gas blast softens the material of the filaments and the velocity of the blast causes the softened material to be attenuated still further; the blown material then passes under the influence of the force of the gaseous blast through conduit 32 to be collected at a suitable receiver (not shown) at the remote end of the conduit.

It is essential to uniformity of production that the hot gas blast affect each of the primary filaments 22 uniformly and to this end the burner lips must provide for uniform passage of the gas blast.

In the practice of the invention therefor the burner 30 is provided at 34 with a slot or mouth, the shape of which may be more clearly seen in FIGURE 2. The lateral sides a and b of the mouth 34 are rectilineal, whilethe upper and

lower lips

36, 38, respectively, are slightly arcuate, each being in fact convex outwardly with respect to the slot of burner mouth.

The material within which the lips are formed is usually a suitable refractory such as corundum; whatever the specific material the upper lip 36 is subject to three distinct distortion effects when the burner is placed in operation; that is shrinkage of the refractory material itself, which tends to compact the material, a tendency to expand under heat, which is greatest at the lip surface and consequently results in unequal stresses in the body of material, and the tendency of the substantially unsupported upper lip to bow centrally. The formation of the upper lip in arcuate form turns these effects to advantage for the arcuate lip straightens out to assume in operation the contour shown by dotted line 39 in FIG- URE 2. Similarly the lower lip 38 which is likewise subject to the shrinkage and heat is shortened by these effects and it assumes the straight line or rectilineal form indicated at 40.

The sides a, b are maintained rectilineal to give to the structure as much support as is possible and to maintain a sharp area of blast gases.

In specific application it has been found that a slot, formed rectangular in the cold 'recractory, and having a dimension of A for the sides a, b and a width of about 4" will over a period of service distort and 'close completely. By forming the upper and lower lips in smooth curve extending between the rectilineal sides it, b, which have the same dimensionthe central spacing between the lips need only be to materially improve the burner service conditions and burner life.

Thus the lip arrangement of invention under service conditions provides an issuing blast of gases in rectangular shape which gases contact the filaments passing over "the V-shaped edge 29 of block 28 uniformly. Further over a long period of service life the lips do not close and this permits a material reduction in equipment shutdown time thus increasing productivitya factor which has hitherto been of considerable economic importance in the production of glass fibers.

It is to be understood that while the invention and specific example have been set forth with reference to 'coiunduin the invention is not to be limited to a specific refractory material for the burner lip but is to be considered as applicable to anysuitable refractory or combinanon of refractories the lips of which would be subject to the stresses designated hereinbefore;

'It will be understood that this invention is susceptible to fihodification in order to adopt it to different usages and conditionsan'cl accordingly, it is desired to compreh'ehd such modifications within this invention as ma fall within the scope of the appended claims.

I claim:

1. In a gas burner capable of emitting hot ases bf combustion in planar form for the hot gaseous blowing of thermoplastics into fine fibers, a vertically extending wall formed of corundum, said wall having a transverse slot therein defined by opposed upper and lower lips, said slot having rectilineal sides joining the opposed lips and the lips in the cold inoperative condition of the burner being each arcuate in form and curving uniformly in a vertical plane with respect to the rectilineal sides said rectilineal sides being spaced about 4 inches apart, said lips defining a spacing about A inch larger, at their greatest point of separation, than the dimension of one of said sides.

2. A gas burner, capable of emitting hot products of combustion in planar form and having wall portions which are in direct contact with said products of combustion, comprising a refractory wall portion having a pair of opposed lips and a pair of opposed lateral sides transverse to and joining said lips, said lips and said sides defining an elongated outlet for discharging said products of combustion, said lips in the cold inoperative condition of the burner being each arcuate in form, substantially greater in length than said sides, and defining a spacing at their greatest point of separation larger than the length of one of said sides, said refractory being susceptible to deformation when subjected to elevated temperatures of a predetermined order, said spacing between said lips and the length of each lip being of predetermined magnitudes interrelated with the degree of deformation of said refractory so that each of said lips will assume a substantially rectilineal shape upon subjection to elevated temperatures of said predetermined order, and said lateral sides being of sufficient length to maintain a sharp area of blast when said burner is in operation.

3. A gas burner, cap-able of emitting hot products of combustion in planar form and having wall portions which are in direct contact with said products of combustion, comprising a refractory wall portion having a pair of opposed lips and a pair of opposed lateral sides transverse to and joining said lips, said lips and said sides defining an elongated outlet for discharging said products of combustion, said lips in the cold inoperative condition of the burner being each arcuate in form, substantially greater in length than said sides, and defining a spacing at their greatest point of separation larger than the length of one of said sides, said refractory being susceptible to contraction when subjected to a temperature in the order of 3000 F., said spacing between said lips and the length of each lip being of predetermined magnitudes interrelated with the degree of contraction of said refractory so that each of said lips will assume a substantially rectilineal shape upon subjection to said temperature, and said lateral sides being of sufficient length to maintain a sharp area of blast when said burner is in operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,045,475 Van Zandt Nov. 26, 1912 2,367,119 Hess Jan. 9, 1945 2,614,619 Fuller on. 21, 1 952 2,681,696 Stalego Jun-e 22, 1954 FOREIGN PATENTS 1,631,448 Trance Mar. 18, 1953