US3249413A - Apparatus for producing a propulsion stream adapted to attenuate fibers - Google Patents

Description

y 1966 c. D. SIMMERS ETAL 3,249,413

APPARATUS FOR PRODUCING A PROPULSION STREAM ADAPTED TO ATTENUATE FIBERS 6 Sheets-Sheet 1 Filed Nov. 21, 1962 TM M R u mmo O V G T mMB y 3, 1966 c. D. SIMMERS ETAL 3,249,413

APPARATUS FOR PRODUCING A PROPULSION STREAM ADAPTED TO ATTENUATE FIBERS Filed Nov. 21, 1962 5 Sheets-Sheet 2 IN ENTORS CHARLES D. ammaRs THOMAS R. Gum BY Roam-r C. ANDERSON ATTORNEY y 1966 c D. SIMMERS ETAL 3,249,413

APPARATUS FOR PRbDUCING A PROPULSION STREAM ADAP'I'ED TO ATTENUATE FIBERS Filed Nov. 21, 1962 5 Sheets-Sheet 5 INVENTORS CHARLEQ D. Smmms ATTO RN EY United States Patent APPARATUS FOR PRODUCING A PROPULSION STREAMADAPTED T0 ATTENUATE FIBERS Charles D. simmers, Neshauic Station, Thomas R. Gould,

Martinsville, and Robert C. Anderson, Somerville,

N..I., assignors to .lohns-Manville Corporation, New

York, N.Y., a corporation of New York Filed Nov. 21, 1962, Ser. No. 239,176 4 Claims. (Cl. 65,l6)

This invention relates generally to improvements in forming propulsion streams, as commonly employed in the attenuation of heat softenable materials such as glass fibers, and has particular reference to novel method and burner apparatus for producing ahot gaseous blast to form or attenuate a source of heat softenable material into fibers or filaments.

Glass fibers are produced by subjecting primary filaments to a gaseous blast which attenuates the filaments into fine fibers. The primary filaments may be formed by exuding molten glass through orifices in the base of a melting crucible or by delivering molten glass into engagement with a spinner which through centrifugal forces causes the molten glass to flow through orifices in the sidewall of the spinner.

It has been the common practice in attenuating glass fibers to employ burners which burn a premixed mixture of air and fuel supplied from a central premixing station. This involves certain hazards because the mixture delivered to the burner is explosive in character and the burner must be constructed and operated so that explosion due to flashback will not occur. Due to the necessity of having to provide first checks, combustion grids, etc., in the supply lines and because of the pressure limits prescribed by insurance companies under which the premixed supply may be transported, such premixed burners are relatively inefficient in obtaining the optimum blast characteristics.

It has been previously suggested to employ burners wherein fuel is inspirated by a pressurized air stream and is diffused therewith to form a combustible mixture within the burner.

The present invention embracesmethod and apparatus for accelerating and enhancing the rate of diffusion of the fuel and air streams in an attenuating burner, forming means for producing a gaseous propulsion medium, without the necessity of inspirating the fuel stream with the air stream.

Having in mind the disadvantages of the prior art at tennating burners, it is an object of this invention to provide an attenuating burner wherein the fuel and air are introduced separately under pressure and are rapidly intermixed to form a combustible mixture.

Another object is to provide method and apparatus for forming a gaseouspropulsion medium for attenuating fibers wherein the input energy is converted to blast energy in a more efficient manner.

Before entering a description of the method and apparatus of this invention, it may be helpful to review the concepts involved in the mechanism of combustion and of the physical properties of gases.

A gas is composed of molecules which are in constant motion at relatively high velocities and which constantly collide with one another. The result of the collisions is to produce individual velocities, some of which are faster and some of which are slower than the average. If the molecules collide with sufficient force, a chemical reaction may occur. At room temperatures the average velocities are not great enough to yield collisions of sufficient force to cause chemical reaction. However, if a mixture is heated by external means, the average velocity of the .molecules increases and the collisions increase in fre- 3,249,413 Patented May 3, 1966 quency until the phenomenon of ignition occurs. If a combustible mixture is externally heated to 1100 F., the rate at which com-bustion reaction occurs will be great enough to evolve heat at a greater rate than it may be dissipated. The heat which is not dissipated will serve to raise the temperature of the gaseous mixture and with the increased temperature, greater molecular activity occurs and causes more frequent collisions and consequently a faster rate of combustion.

The most common method for carrying out combustion in industrial applications involves the separate introduction of fuel gas and air into a proportional mixing device. The mixture constantly maintains the correct pro portion of fuel and air and feeds a homogeneous mixture as a stream to 'a burner port where it is ignited and burned. This phenomenon is called premix combustion. In this type of burner the burning and burnt mixture is strongly heated by energy released in the combustion process. conduction forwardly into the unburnt mixture, and as a result the unburnt mixture layer immediately adjacent to the flame is heated to the ignition temperature. In this type of burner the rate of flame propagation is limited by the rate at which heat can be conducted through the mixture. In practice, the mixture is moved in a' stream at the flame propagation velocity with'the result that the flame front is stationary. If the critical velocity of the stream is exceeded, the flame front is caused to move in a direction of the mixture stream and blow-01f occurs. If the mixture stream velocity is slower than the critical velocity, the flame front moves counter to the direction of the mixture stream and flash-back occurs. In order to deter flash-back, orifice plates are usually inserted in the burner. Such orifice plates tend to impart a generally laminar flow to the mixture stream. 7

The common method for producing diffusion combustion involves flowing the gas and air in separate streams at substantially the same velocity, with little or no turbulence between the gas and air streams. Initially, combustion occurs only at the surface of contact between the fuel and air streams since this is the only area where an explosive mixture exists. As the streams advance, molecules of both the fuel and air diffuse from their respective streams into the burning and reaction zone. The rate of combustion in a diffusion burner is dependent not upon the flame propagation velocity as in the premixed burner, but upon the much slower rate of diffusion of the two streams. This phenomenon tends to produce a long, lazy flame.

Significant structural features are incorporated in the elements of the burner forming the gas propulsion means of this invention. The invention uniquely combines the desirable features of premixed and diffusion combustion by introducing the. gas and air as separate streams to the burner and then causing the fuel and air streams to be immediately intermixed in a highly turbulent manner to accelerate the rate of diffusion.

In accordance with a preferred embodiment of this invention, air under pressure is supplied in an axially flowing stream to a confined combustion space through an air supply conduit; fuel under pressure is also supplied to the confined combustion space through a fuel conduit disposed centrally of and coaxial with the air supply conduit in an amount sufiicient to support combustion and preferably to provide a substantially stoichiometric mixture; a spinning vane is provided at the terminus of the air supply conduit to impart initial spin to the air stream and thereby enhance the turbulent motion of the stream as it advances through the confined combustion space; the fuel stream is discharged through ports transverse to the axis of the fuel supply conduit to project the fuel into intimate contact with the air in a highly turbulent manner A portion of the heat energy is transferred by and at the earliest possible moment; the resultant admixture is then burned in the confined combustion space and the resultant products of combustion are issued from the space at the rate at which they are produced. The blast of hot products of combustion are then projected adjacent to a source of heat-softened material to form or attenuate the material into fine fibers.

The invention will be more fully understood and further objects and advantages thereof will become apparent when reference is made to the following detailed description and to the accompanying drawings in which:

FIG. 1 is a cross-sectional elevational view of a burner of the present invention shown in conjunction with a rotary spinner for forming glass fibers;

FIG. 2 is a cross-sectional plan view of the burner shown in FIG. 1 and taken along line 22 of FIG. 1;

FIG. 3 is a cross-sectional elevational view of another embodiment of a burner of this invention;

FIG. 4 is a View of the burner shown and taken along line 44 of FIG. 3; and

FIG. 5 is a cross-sectional elevational view of another embodiment of a burner of this invention shown in conjunction with a rotary spinner.

Referring to the drawing, in FIG. 1 is a rotor or spinner 10, which may be of any suitable type known in the art, to which molten glass is fed through conduit 12 from a suitable source (not shown) such as a forehearth furnace. The upstanding walls 14 are provided with a plurality of apertures or orifices 16 through which the molten glass is exuded or projected outwardly by virtue of centrifugal forces created by the rotation of the spinner 10.

Disposed superjacent to the outermost wall 14a is a confined combustion space or chamber 18 from which hot products of combustion emanate through discharge port 20 preferably in the form of an annular blast to attenuate the glass exuded through orifices 16.

Burner ports 22 are disposed circumferentially of chamber 18 and are adapted to deliver an admixture of fuel and air into the chamber 18 where the admixture is burned.

Each of the improved burner nozzle ports 22 are generally comprised of three parts: an air conduit in the form of tube 24, a fuel conduit in the form of tube 26, and vane 28. The air conduit 24 is in open communication with preheat plenum chamber 30 to which air is introduced under pressure from a suitable source through air supply conduit 32. The terminus 34 of air conduit 24 extending into chamber 18 is open to normally deliver an axial stream of air into chamber 18. Fuel conduit 26 is disposed centrally of and coaxially with air conduit 24. Each of the fuel conduits 26 preferably extends from common manifold 25. The terminus of fuel conduit 26 is closed off; however, adjacent the discharge end there are provided a plurality of fuel ports 36 arranged circumferentially about conduit 26 and disposed to impart components of motion to the fuel transverse, preferably normal, to the axis of the fuel conduit 26 and the air conduit 24.- The vane 28 having diagonal surfaces is disposed intermediate the fuel conduit 26 and air conduit 24 adjacently of the outer end or terminus 35 of air conduit 24 to impart a swirling action to the air discharge therethrough.

This air will have an agitating and mixing action upon the fuel introduced traversely thereof to produce the maximum diffusion of the air and fuel at the earliest moment upon discharge from their respective conduits. The transverse introduction of the fuel serves to augment the diffusion and enhance combustion.

To further enhance combustion, as indicated previ ously, the combustion air supply is preheated in chamber 30. Chamber 30 is defined by sidewall 38, which also forms a sidewall for combustion chamber 18 and by sidewall 40, topwall 42, and bottom wall 44. Vanes 46, preferably helical in form, may be optionally provided in chamber 30 to faci iiate distribution of the air to the various burner ports 22 and to form extended surface heat exchange means for increasing the heat transfer to the air as well as reinforcing wall 38.

It is to be noted that the walls 42, 44 and 48 are covered with refractory material 50 to protect the metal from deterioration due to heat in the combustion chamber 18. Wall 38 is not covered with refractory material since the air circulating through chamber 30 will wipe heat from the wall 38 that would normally be lost.

' Another feature of this invention is the configuration of the port 20 and its relation with the spinner 10. The port 20 is defined by outer plate member 52 and inner plate member 54 which members are provided with corresponding beveled peripheral sides 56 and 58. The angle of the beveled sides 56 and 58 is suflicient to project the blast from the combustion chamber slightly away from the spinner 10 and in a manner to compensate for the tendency of the fibers as they are attenuated to whip back into contact with the outer rotor wall 14a because of the vacuum beneath spinner 10 created by the rotation of the spinner 10. Of course, the angle will vary depending upon such parameters as the size of the rotor wall 14a and the position of the port in re- The efficiency of the burner of this invention has been demonstrated in connection with a unit similar to that shown in FIG. 1. Fuel and air were delivered from the burner ports 22 to the combustion chamber at 40 oz./in. static pressure and discharged from the combustion chamber at 32 oz./in. through port 20 indicating an efficiency of percent. By comparison, in amore conventional design of burner and combustion chamber using a premixed supply of fuel and air delivered at 48 oz./in. the developed impact pressure was only 12 oz./in. indicating an efficiency of 25 percent. With equal amounts of fuel and air, the burner of this invention can develop about twice the velocity (700 ft./sec.)

as the conventional burner can in the issuing blast. The

velocity of the issuing blast is one of the most critical factors in developing the attenuating force or propulsion medium in forming fine diameter filaments.

FIG. 3 shows a burner 122 that may be employed to attenuate fibers emanating from orifices in the base of a glass melting crucible such as shown in Patent No. 3,049,172. The burner nozzle 121 of F-IG. 3 corresponds substantially to the burner nozzles 22 of FIGS. 1 and 2. However, a single nozzle 121 is provided to fire axially of the combustion chamber 118 and the products of combustion are discharged through port 120 into contact with primary glass filaments. The port 120 is preferably substantially rectangular in cross section when viewed in a plane normal to the longitudinal extent of the burner 122. Pressurized air is introduced through air supply conduit 132 to preheat chamber and passes to combustion chamber 118 through air conduit 124 shown to be a separate element inserted within wall 138 defining the combustion chamber 118. However, it will be, apparent that the rear terminus 125 of wall 138 may form the air. conduit leading to the zone where combustion occurs. Air conduit 124 is also shown to have a frusto-conical terminal portion 123 which forms a restricted orifice and also assists in promoting mixing of the fuel and air. Fuel conduit 126 is disposed centrally and coaxially with air conduit 1 24 and delivers fuel under pressure through a plurality of orifices or ports 136. Vane 12 8 is also provided to impart a spinning component to the air passingthrough conduit 124. Optionally, fluid coolant passages may be provided to increase the life of orifice defining plate member 152.

Additionally, vane-s (not shown) may be provided in the fuel conduits 26 and 126 to augment the transverse flow of the fuel into the air stream and enhance the admixing in either of the burners as disclosed in FIG. 1 and FIG. 3. It will also be apparent that in the burner of FIG. 1 the vane in the air conduit of one burner nozzle may be ar anged to impart spin in a clockwise direction and the vane in the air conduit of an adjacent burner nozzle may be arranged to impart spin in a counterclockwise direction. However, the nozzles should be arranged so that each discharges the combustible admixture in the same direction in relation to the combustion chamber.

An alternate form of burner is illustrated in FIG. 5 wherein a portion of the air is conducted from the air preheat chamber for discharge adjacent to and intermixing with the main blast of products of combustion from the burner. Heated air from chamber 18 is conducted through a series of orifices 70, as defined by bottom wall plate 52A, to annular pass-age 72, as defined by plate'52B,-and is discharged at port 20 through orifice 94, preferably in angular relation with the blast emanating through port 20. The air diverted from chamber 30 passing through passage 72 serves to recover a substantial portion of the heat that normally would be lost by conduction through wall plates 52 and to add mass and heat to the main blast from combustion chamber 18 to enhance the attenuating force thereof. The passage of preheated air through the bottom wall plates 44 also serves to equalize and more uniformly distribute the heat across the bottom of the combustion chamber and consequently throughout the circumference of the annular port 20. While this feature has been described in particular connection with the form of burner illustrated in FIG. 1, it will readily be apparent that it may also be employed in connection with the type of burner illustrated in FIG. 3.

Although the burners of this invention have been described in detail as to their component parts, it will be apparent that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

What we claim is:

1. A burner for producing a propulsion stream adapted to attenuate fibers, comprising: first -=wall means defining a confined combustion space about a longitudinal axis; second wall means circumposing said first wall means and having a longitudinal :axis extending in the same direction as the longitudinal axis of said first wall means, said first and second wall means defining a preheat chamber zone for combustion air; means for introducing combustion air under pressure to said preheat chamber adjacent one end thereof; air conduit means for directing air from said preheat chamber to said combustion space,

said air conduit means being positioned adjacent the end of said preheat chamber opposite to that where the combustion air is introduced to said preheat chamber; fuel conduit means for directing fuel to said combustion space, said fuel conduit means and said air conduit means being disposed in the same direction and one within the other; and port means positioned about the periphery of one of said fuel conduit means to impart to the fiuid issuing therefrom a component of motion substantially normal to the axis of the path of fluid travelling through the other of said conduit means and entering said combustion chamber.

2 Fluid propulsion apparatus adapted to attenuate fibers, comprising: an annular combustion chamber; a plurality of air inlet tubes extending through the upstanding side wall of said combustion chamber introducing combustion air under pressure into said combustion chamber; a fuel inlet tube for each of said air inlet tubes, said fuel inlet tube being disposed centrally of the corresponding air inlet tube and having at least one outlet port arranged to discharge fuel under pressure and substantially normal to the path of the combustion air and for combustion with said combustion air in said combustion chamber; a preheat chamber circumposing the lateral side of said combustion chamber and being interconnected therewith, said preheat chamber preheating said combustion air prior to delivery to said combustion chamber; an annular port disposed in the bottom wall of said combustion chamber to discharge the products of combustion in a path diverging away from the central axis of said combustion chamber.

3. Apparatus as described in claim 2, wherein a vane is provided within and adjacent the terminus of each of said air inlet tubes for imparting spin to the air passing therethrough.

4. Apparatus as described in claim 2, which further comprises:

means for diverting a portion of the air from said preheat chamber and discharging said portion adjacent to and for mixing with the blast emanating from the discharge port means of said combustion chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,609,566 9/1952 Slayter et al -14 X 2,626,484- 1/ 1953 Stalego 65-16 X 3,049,173 8/1962 Costello et a1. 158-110 3,140,155 7/1964 Cull et al 23-155 X DONALL H. SYLVESTER, Primary Examiner. C, VAN HORN, G, R. MYERS, Assistant Examiners.

Claims (1)

1. A BURNER FOR PRODUCING A PROPULSION STREAM ADAPTED TO TO ATTENUATE FIBERS, COMPRISING: FIRST WALL MEANS DEFINING A CONFINED COMBUSTION SPACE ABOUT A LONIGTUDINAL AXIS; SECOND WALL MEANS CIRCUMPOSING SAID FIRST WALL MEANS AND HAVING A LONGITUDINAL AXIS EXTENDING IN THE SAME DIRECTION AS THE LONGITUDINAL AXIS OF SAID FIRST WALL MEANS, SAID FIRST AND SECONDWALL MEANS DEFINING A PREHEAT CHAMBER ZONE FOR COMBUSTION AIR; MEANS FOR INTRODUCING COMBUSTION AIR UNDR PRESSURE TO SAID PREHEAT CHAMBER ADJACENT ONE END THEREOF; AIR CONDUIT MEANS FOR DIRECTING AIR FROM SAID PREHEAT CHAMBER TO SAID COMBUSTION SPACE, SAID AIR CONDUIT MEANS BEING POSITIONED ADJACENT THE END OF SAID PREHEAT CHAMBER OPPOSITE TO THAT WHERE THE COMBUSTION AIR IS INTRODUCED TO SAID PREHEAT CHAMBER; FUEL CONDUIT MEANS FOR DIRECTING FUEL TO SAID COMBUSTION SPACE, SAID FUEL CONDUIT MEANS AND SAID AIR CONDUIT MEANS BEING DISPOSED IN THE SAME DIRECTION AND ONE WITHIN THE OTHER; AND PORT MEANS POSITIONED ABOUT THE PERIPHERY OF ONE OF SAID FUEL CONDUIT MEANS TO IMPART TO THE FLUID ISSUING THEREFROM A COMPONENT OF MOTION SUBSTANTIALLY NORMAL TO THE AXIS OF THE PATH OF FLUID TRAVELLING THROUGH THE OTHER OF SAID CONDUIT MEANS AND ENTERING SAID COMBUTION CHAMBER.

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