US 3750302 A
Description (OCR text may contain errors)
nited States Patent 11 1 Smith 1' Aug. 7, 1973 1 1 JET DEVICE Drexel Kermit Smith, Hendersonville, Tenn.
 Assignee: E. 1. du Pont de Nemours and Company, Wilmington, Del.
 Filed: Apr. 23, 1971  Appl. N0.: 136,866
 US. Cl 34/154, 34/160, 28/1.4
 Int. Cl. F26b 13/00  Field of Search 34/154, 155, 156, 34/160; 28/1.4
 References Cited UNITED STATES PATENTS 3,659,350 5/1972 McCullough 23/155 3,587,177 6/1971 Overly et al. 34/160 3,422,510 1/1969 Livingston et al. 28/1.4 2,645,031 7/1953 Edwards 34/156 X 3,583,048 6/1971 Gutmann 28/1.4 3,316,657 5/1967 Haywood... 34/111 3,431,602 3/1969 Appel 19/66 FOREIGN PATENTS OR APPLICATIONS 758,398 10/1956 Great Britain 1,218,009 1/1971 Great Britain Primary Examiner-Carroll B. Dority, Jr. Attorney-Howard P. West, Jr.
 ABSTRACT An apparatus for heat treating a plurality of filaments arranged in a ribbon-like array that includes a base having a planar surface, a pair of upstanding walls attached to the base between which the filaments pass for treatment and a transverse slot through the planar surface in communication with a source of heated pressurized fluid, improves uniformity and efficiency of heat transfer to the filaments. A particular relationship between the slot, the planar surface of the base and the walls enables the fluid stream issuing from the slot to first pass upwardly through the filaments then turn'downwardly and attach to the planar surface at a point downstream of the slot where it flows parallel to the filament array to provide an extended heating zone.
8 Claims, 5 Drawing Figures PATENIEDAUB 11w 3.750.302
' sum 1 0r 2 INVENTOR DREXEL KERMIT SMITH ATTORNEY minnow: 1 ma FIG-4 JET newer:
This invention relates to an apparatus for the fluid treatment of filamentary material. More particularly, it relates to a jet device for providing uniform treatment across a plurality of filaments arranged in a ribbon-like array with improved uniformity of treatment and accessibility for stringup.
Many devices are known for treating ribbon-like arrays of filaments in a confined channel by impinging hot fluid on the array from one or both sides to reduce the drawing tension and localize the draw point. However, those devices whichare not completely sealed on all sides except the filament entrance and exit have given nonuniform heat treatment to some portion of the array, whereas those which are sealed must be provided with means for opening the devices to introduce filaments. Whenever such a device is opened for stringup, the temperature of the device itself is changed and requires some time to return to normal. If only a portion of the filament array needs to be restrung, those filaments undergoing treatment when the jet is opened will receive substandard heating. On the other hand, the heating efficiency is usually low in unenclosed devices which are easy to string up as, for example, where the filamentary material spends only a very brief time in the hot fluid stream which passes perpendicularly through the filament array. Such an arrangement is disclosed by Jones and Wakerly in British Patent No. 758,398.
SUMMARY OF THE INVENTION It has now been found that ease of stringup can be provided in a jet device having good heating efficiency and uniformity where the apparatusincludes a base parallel to the array of filaments, side walls connected to the base and extending above the array in the zone of heat treatment and a narrow slot orifice in the base extending transverse to the array for the full distance between the side walls. The downstream surface of the orifice intersects the planar surface of the body near one end at an angle between about and 45. A Coanda surface may be provided at the opposite end of the body to divert spent fluid away from the filament array. The narrow slot orifice preferably defines successive converging and diverging walls with a divergence angle of from about 1 to about 7. Most preferably, the surface constituting the downstream surface of the slot orifice is a flat plane intersecting the planar surface of the body at an angle between and and a converging, parallel and diverging character is provided entirely by the shape of the opposite upstream surface. In jets having the above configuration when operated at fluid pressures sufficient to give sonic or supersonic flow at the slot exit, the fluid stream separates from the body, rises a certain distance above the body forming a low pressure zone between the body and the fluid stream and then turns downward, attaches to the body beyond the low pressure zone and flows parallel to the body to the end. Since the heat transfer coefficient is higher when hot fluid flows transversely across filaments than when it flows parallel to the fiIaments, heat transfer is improved when the filaments are positioned in a fluid stream which first passes transversely through the filaments as it issues from the slot orifice and then turns downward and flows parallel to the body to provide an extended heating zone. The side walls should extend above the array at least as high as the fluid stream issuing from the slot orifice rises above the body before turning downward.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a device of this invention.
FIG. 2 is a cross sectioned elevation taken along 2-2 of FIG. 1 showing details of a typical narrow slot orifice and the desired fluid flow condition.
FIGS. 3, 4 and 5 are enlarged views representing the slot orifice of FIG. 2 showing alternative slot configurations.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Although slot orifices of various shape and impingement angle may be employed in enclosed jets where the fluid is forced to flow in contact with the filaments, design criteria are critical in jets of the present invention which are open on the side opposite the fluid slot orifice. The first critical requirement is that at least a portion of the surface constituting the downstream surface of the slot orifice be a flat plane directed downstream and intersecting the planar surface of the body at an angle between 15 and 45. At smaller angles, the flow separation at this intersection, is reduced and reattaches to the body in a short distance, minimizing the filament spreading action and transverse flow which are necessary to provide improved heat transfer. At greater angles, the flow will separate completely from the body, will be unable to maintain a low pressure zone at the separation point and will not reattach to the body.
The next critical requirements'are the presence of side walls and the slot orifice extending for the full distance between the side walls. If there are no side walls or if the slot orifice does not extend the full width of the distance between the walls, air at ambient pressure and temperature will flow into the region between the fluid stream and the body and will prevent the development of a stable low pressure zone which is essential for uniform reattachment of the fluid stream across the full width of the device. Mixing of ambient air into the hot stream at the edges, introduces temperature nonuniformities.
Referring to FIGS. 1 and 2, an array of filamentary material 1 passes over guides 12 which maintain the filamentary material at a desired distance 3 above the planar surface 4 of the jet body base 5. Heated fluid enters the body at port 6 and leaves the body at slot orifice 7, where it impinges on the filamentary array. Upstanding side walls 8 are attached to the base 5 on both sides of the filamentary array. Coanda surface 9 having side walls 10 may be attached to the downstream end of the body to divert spent fluid away from the filament array. Hot pressurized fluid l3 flows through slot orifice 7 which is bounded by upstream surface 14 and downstream surface 15, both oriented in a downstream direction. The latter intersects the planar surface 4 of body 5. at angle 16. Edges l7 and l8-must have'no substantial radius, that is, none greater than about 0.005 inch. Side walls 8 must extend along the length of planar surface 4 from at least point 18 to point 21 and preferably along the full length of surface 4.
The fluid exiting from orifice 7 continues at first in a more or less straight line and passes upward through the filamentary array 1 to separate the filaments for maximum heat transfer. Low pressure zone 19 forms below the fluid stream. Ambient air pressure 20 then acts on the opposite side of the fluid stream, bending it toward the body so that it passes through filamentary array 1 a second time and reattaches to planar surface 4 of body 5 at point 21, heating the yarn again. Hot fluid also circulates in low pressure zone 19, further heating the yarn and finally the fluid which is flowing parallel to planar surface 4 downstream of point 21 maintains the filaments at elevated temperature, although the average temperature of the fluid stream in this region' will be reduced by mixing with ambient air. This cooling effect may be minimized by locating the entire apparatus of this invention in a partial enclosure, which permits recirculation of hot gas within the enclosure but which does not appreciably impede stringup. Coanda surface 9 may be used to retain the heated gas within such an enclosure and prevent it from leaving with the filamentary material through the exit opening which must be provided.
Although high exit velocity might be expected to detach the flow from planar surface 4, it has been found, surprisingly, that for a given impingement angle 16 expanding the flow in the nozzle actually improves attachment because the pressure at zone 19 is lowered so that ambient air pressure 20 is more effective in bending the flow. It has been found that Mach numbers at the orifice exit of between 1.5 and 2.0 are optimum for heating which may be obtained by fluid supply pressures between 50 and 115 psig and with divergence angles between 3 and 7 degrees.
In a wide jet, the requirements for temperature uniformity side-to-side may require that hot fluid be brought into the body through two ports on opposite sides, as described by Gutmann in the copending U.S. application Ser. No. 858,921, filed Sept. 18, 1969 and now U.S. Pat. No. 3,583,048. However, in narrow jets where temperature uniformity is more easily achieved, the hot fluid may be brought in through a single passage 6 into plenum chamber 22 ahead of first distribution plate 23 and second distribution plate 24, which give temperature and velocity uniformity to flow 13 as it approaches slot orifice 7. Slot orifices may be employed instead of distribution plates 23 and 24, in which case the open area of second distribution slot 24 should be roughly twice that of first distribution slot 23.
FIG. 3 shows a preferred slot orifice design. Heat transfer coefficient to the filaments is at maximum when the velocity of the impinging fluid is at or above the speed of sound. To provide high heat transfer rates, it is desirable to increase the fluid velocities to supersonic at the orifice exit. This can be done by using a converging-diverging nozzle form. One convenient means of fabricating such a nozzle is to have downstream wall 15, a single plane surface and to shape the upstream wall so that surface length 26 forms a converging passage with and surface length 14 forms a diverging section. The transition between surfaces 26 and 14 may be radiused. In order that the emerging fluid stream be as coherent as possible, divergence angle 25 should be between 1 and 7 and not greater than 18. Furthermore, the shortest surface length of the diverging section, in this case 14, should be no less than three times the minimum dimension of throat 27.
FIG. 4 shows slight modifications to the design of FIG. 3. A flat surface length 29 parallel to wall 15 is provided at throat 27. The length 29 should be at least twice the minimum dimension across the throat at 27 to provide adequate flow guiding. If it is desired for safety to eliminate a very sharp corner at 18, a small flat 30 can be provided, making an angle of approximately with plane 14. The length of flat section 30 should be no greater than the minimum throat dimension at 27.
FIG. 5 shows another slot orifice with converging, parallel and diverging shape. In this case, the downstream surface of the orifice consists of section 15 making an angle 16 with the planar surface of the body 4 and an additional surface 31 making a somewhat larger angle with 4. The upstream surface of the slot orifice is formed by surface 14 making an angle 28 with surface 4, angle 28 being the same as the angle between surfaces 31 and 4 and section 26 forming the converging portion of the orifice. A section of parallel sides 29 is formed by the overlap between surfaces 14 and 31.
The advantage of jets having configurations which cause the fluid flow to separate from the body and reattach is illustrated in the following example.
EXAMPLE Three jets similar to FIG. 4 having slightly different dimensions are compared with one similar to FIG. 5 which was modified to prevent flow separation from the body by providing a radius of 0.10 inch at edge 17 so that flow following surface 15 will flow smoothly onto surface 4. superheated steam at 245C. and psig is fed to each jet, all of which have a minimum throat dimension 27 of 0.010 inch so that the amount of steam used in treating the filaments is the same. Eight ends of denier 34 filament polyethylene terephthalate are fed to'the jet apparatus at 688 yards per minute and taken away at 2,890 yards per minute, giving a draw ratio of 4.2. The distance 3 of the filaments 1 from the planar surface 4 is 0.008 inch. The eight yarn ends of each run are wound up into eight separate packages and a portion of each package is used as the filling yarn for weaving a plain weave fabric, 80 picks in warp and 48 picks in the filling, 50 inches by 6 inches long. The fabrics are dyed with Latyl Brilliant Blue FLW to a critical shade. They are then inspected and the total numbers of undrawn sections (flashes) in the eight sections woven from the yarns of each example are totaled. It can be seen from the data in Table I that the jet having no flow separation gave more than 10 times the number of undrawn sections than the least effective of the preferred jets. Counting the number of undrawn sections in a fabric made from a yarn has been found the most meaningful measure of the ability of the draw jet to localize the draw point and is correlated with heat transfer efficiency.
Fluid flow patterns are confirmed by the Shadowgraph technique. A short duration burst of highintensity light from a source such as a spark gap is directed across the jet as in the viewing direction of FIGS. 2 through 5. Transparent side walls 8 are used. A sheet of photographic film is placed behind the jet in a darkened room. Because the speed of light changes with the density of the medium, density gradients in the flow pattern refract the light beam. The patterns registering on the photographic film are proportional to the second derivative of the fluid density (the first derivative of the density gradient). The uniformity of the flow pattern across the width of the jet may be observed by taking Shadowgraph pictures from either the leftor right-hand ends of the jet.
stream wall comprising a flat surface terminating at an angle of from about to about 45 with said planar surface, said upstream wall comprising, with respect to said downstream wall, converging and diverging TAB LE ii Length Length Total un- Jet design. lmpinge- (inches) (inches) Flat 30 Divergence drawn sec- Run Figure ment angle surface parallel Angle 28 (inches) angle tions in test Fluid flow pattern 1 14 section fabrics l 4 0073 0.030 33 None 3 6 Separates from body and reattaches. 2 4 30 0.073 0.096 33 0.004 3 1 Separates from body and reattaches. 3 4 30 0.073 0.] 13 33 None 3 0 Separates from body and reattaches. 4 5 27 0.073 0.1 12 30 None 3 65 No separation from body.
What is claimed is:
l. A filament treating apparatus comprising: a base having a planar surface; a pair of spaced upstanding walls attached to the base to form with said base an open channel through which filaments pass for treatment; said base having therein a transverse slot extending the distance between said walls, said slot terminating at said planar surface and being oriented in a downstream direction with respect thereto at an angle of from about 15 to about 45; and a source of pressurized fluid connected to said slot.
2. The apparatus of claim l, said slot being defined in part by walls approaching said planar surface at a diverging angle of from about l to about 7.
3. An apparatus for treating a plurality of filaments arranged in a ribbon-like array comprising: a base having a planar surface with a slot therethrough; a pair of spaced upstanding walls fastened to the base to form with said planar surface an open channel through which the array passes for treatment; said slot extending the distance between said walls and being defined in part by upstreamand downstream walls, said downlengthswith said diverging length terminating at said planar surface at an angle of from about 1 to about 7 with said downstream surface; and a source of heated pressurized fluid connected to said slot.
d. The apparatus as defined in claim 3, said upstream wall including length parallel to said downstream wall between said converging and diverging lengths.
5. The apparatus as defined in claim 3, including a smoothly contoured surface attached to the downstream end of said base sloping downwardly away from said planar surface.
6. The apparatus as defined in claim 3, said upstanding walls being parallel to each other.
7. The apparatus as defined in claim 3, said downstream wall terminating at an angle of from about 20 to about 40 with said planar surface.
0. The apparatus as defined in claim 3, said downstream wall terminating at said planar surface in an edge having a radius of less than 0.005 inch and at an angle of about 30", said diverging length terminating at said planar surface and being at an angle of about 3 with respect to said downstream surface.