US 3161257 A
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Description (OCR text may contain errors)
Dec. 15, 1964 A. D. YOUNG 3,161, 57
JET PIPE NOZZLE SILENCERS Filed April 25. 1960 3 Sheets-Sheet 1 lNveN-roR AT TOQN EYS Dec. 15, 1964 A. D. YOUNG 3,161,257
JET PIPE NOZZLE SILENCERS Filed April 25. 1960 3 Sheets-Sheet s 24.4 244 HG 24A 24A 248 7 ,3}. 3 Lax 2 24a j 3;; \v 24- y 244 :45 24A FIG 245 24A 24B INVENTOR Alec Day/'4 y j ATTORNEYS United States Patent Ofilice 3,l6l,257 Patented Dec. 15, 1964 3,161,257 JET lllE NGZZLE SILENGERS Alec Eavi- Young, The Sycamores, Whitehall Lane, Buckhurst Hill, England Apr. 25, 196i), Ser. No. 24,553 Claims priority, application Great Britain May 1, 1959 ll (Ilaims. (iii, l3l33) This invention relates to apparatus for partially inhibitthe generation of noise created by a high velocity jet issuing from a nozzle into ambient fluid.
The noise generated by such a high velocity jet is created to a large extent by the intense vortices of annular shape existing in an annular zone near to and beyond the nozzle exit where there is a steep velocity gradient across the boundary of the jet and the ambient fluid. This zone known as the mixing region of the jet. If the regularity of the pattern of these vortices can be broken up and their intensity reduced, the overall noise level can be correspondingly reduced. It can be inferred that by controlling the jet how in such a way as to produce irregular formations of large but weak vortices, rather than regular small vortices of strong intensity, a useful reduction of noise level will result and this reduclion should be most marked in the higher frequency ranges which are found to be particularly unpleasant to the human car. it is also desirable that the mixing region should be reduced in length by increasing the rate of mixing immediately downstream of the nozzle exit.
The present invention provides apparatus for partially inhibiting the generation of noise created by a high velocity fluid jet issuing from a jet pipe nozzle ending into ambient fluid, the jet pine having mounted thereon a plurality of vanes, which in an operative position are inclined along their length with respect to the general flow direction through the nozzle, and in non-stalled relationship to the liow over the vanes.
The vanes may be mounted on the inner periphery of the jet pipe. In addition, or alternatively, vanes may be mounted on the outer periphery of the jet pipe. When vanes are mounted both on the inner and outer periphery of the jet pipe, the inner and outer vanes in an operative position may be inclined with respect to one another, in non-stalled relationship to the fluid flow over the vanes. The outer vanes may be provided with shrouds and the shroud provided with apertures.
The apparatus may incorporate means for adjusting the inclination of the vanes with respect to the general flow direction through the nozzle and the inclined vanes may be of twisted form in cross-section.
In an alternative arrangement according to the invention, the vanes may be attached to the jet pipe by means which permit oscillation between inclination angles of a different sense. The inner vanes may oscillate out of pi see. The vanes may be positioned downstream of the jet pipe nozzle ending and means may be provided for the locking of the vanes in alignment with the general flow direction through the nozzle.
The invention will now be described with reference to the accompanying diagrammatic drawings, in which:
FIGURE 1 shows an end View of a jet nozzle provided with vanes on the inner periphery of the nozzle;
FIGURE 2 shows a nozzle provided with vanes on the outer periphery of the nozzle as well as with vanes on the inner periphery of the nozzle;
FIGURE 3 shows a modified form of the nozzle shown in FIGURE 2;
FIGURE 4 shows a developed view on an enlarged scale of the downstream end portion of the nozzle shown in FIGURE 3, the tubular-like part of the downstream end of the nozzle being cut in an axial direction, unfolded and shown viewed from the outer periphery;
FIGURE 5 shows on an enlarged scale a perspective View of the nozzle shown in FIGURE 3;
FIGURE 6 shows in a developed view a nozzle similar to that shown in FIGURES 3 and 5 but including means for adjusting the position of the vanes;
FIGURE 7 shows on an enlarged scale a nozzle similar to that shown in FIGURES 3 and 5 but with the outer vanes shrouded;
FEGURE 8 shows a nozzle similar to that shown in FIGURE 7;
FIGURE 9 shows a nozzle with vanes which are mounted for oscillation;
FIGURES 10 and 11 show a developed view taken in the some Way as the development of FIGURE 4, of a nozzle similar to that shown in FIGURE 9witli alternative vane mounting arrangements.
FTGURE 1 shows the rear end of a nozzle 2, the inner periphery of which is provided with vanes 1, which project into the jet flow. These vanes are inclined along the whole of their length with respect to a plane 3 which passes through the longitudinal axis of nozzle.
The general direction of how through the nozzle 2 is substantially axial as shown by the heads of arrows C in FIGURES 1, 2 and 3 and more clearly by the arrows C- in FIGURES 46 and 9l1 inclusive.
The vanes l in FIGURE 1 of the drawings serve to deflect the jet flow away from the general direction of flow through the nozzle 2. The vanes produce flows inclined with respect to the flow in the central region of the jet. These deflected flows interact with the how in the central region of the jet and as a consequence are induced to swirl. The swirling flows effect more rapid mixing between the jet and the ambient fluid surrounding the nozzle 2, as well as inhibiting the formation of rcgu lar annular vortices otherwise formed in the mixing region of the jet. Furthermore, the vanes also assist in reducing the axial extent of the mixing region downstream of the exit of the nozzle 2.
FIGURE 2 shows a nozzle 2. provided. with inner vanes l, the nozzle also having around its outer periphery vanes 4. The inner and outer vanes 1' and 4 are substantially opposite one another and inclined along th whole of their length with respect to the plane 3 but in a difierent sense.
In FIGURE 2, the outer vanes 4 dellect the flow of surrounding ambient fluid from what would have otherwise been its direction of flow in an anti-clockwise direction (as viewed from the downstream end of the nozzle). The jet ilow flowing over the inner vanes 1 is deflected in a clockwise direction. The flows deflected by the inner and outer vanes 1 and 4 interact with one another and the flows deflected by the vanes 1 also interact with the flow in the central region of the jet. This interaction induces contra-rotating swirls in the flows over vanes 1 and 4. The contra-rotating swirls thus formed inhibit the formation of the regular annular "ortices in the mixing region of the jet and also tend to increase the rate of mixing between the ambient and jet flows.
In FIGURE 3 the vanes l and 4 are displaced relatively to each other and this arrangement of vanes is shown more clearly in the developed view of the nozzle shown in FIGURES 4 and S.
The nozzle arrangement shown in FIGURE 3 operates in a similar manner to that shown in FIGURE 2.
The developed view of the nozzle 2 shown in FIGURE 6 has vanes 20 and 21 which are each mounted on a pivot pin 7. The upstream end of each of the vanes 29 is pivotally joined to a linkage 9. The linkages 9 are in turn joined to a connecting rod 19 which is provided with an operating rod 11. Similarly the upstream end of each of the vanes 21 is pivotally joined to a linkage 12. The linkages 12 are in turn joined to a connecting ring 13, provided with an operating rod 14. Operating rods ill and 14 respectively are each provided with a locking mechanism 11A and 14A.
The nozzle apparatus shown in FIGURE 6 of the drawings incorporates means for adjusting the inclination of the vanes with respect to the general flow direction through the nozzle. Movement of the operating rod 11 in the direction shown by arrow A displaces the connecting ring in the same direction and consequently pivots each of the vanes 20 from the position shown in broken line to a position in which the vanes 29 lie normal to the nozzle exit. Similarly the vanes 21 may pivot to a position 21A shown in dotted line by movement of the operating rod 14 in the direction of arrow B. Thus when the vanes 2d and 21 are brought to lie normal to the nozzle exit little or no noise suppression effect is obtained. In an aircraft application, during take-off of an aircraft the vanes will be inclined at an angle relative to the plane 3 through the longitudinal axis of the nozzle as shown in FIGURE 1. The vanes Ztl and 21 can be locked in either the inclined position or the normal position by placing the operating rods 11 and 14 in the appropriate slot in the locking mechanisms 11A and 12A. Such an arrangement of adjustable vanes has the advantage that any thrust loss due to the inclination of the vanes only occurs when the vanes are in their operative position. When the aircraft has climbed to a height at which the noise is no longer a problem, the vanes can be pivoted into the position in which the vanes 20 lie normal to the nozzle exit, and the aircraft will not incur any additional thrust loss penalty.
In FIGURE 7, the outer vanes 23 are provided with a shroud 5 which is provided with a series of apertures 6, and in FIGURE 8 the inner and outer vanes 22 and 23 respectively are of twisted form. The twist on the inner vanes 22 is in the opposite direction to the twist on the outer vanes 23.
Ambient air surrounding the nozzle 2 is either entrained between the spaces defined between adjacent pairs of vanes 23 and the shroud 5 or the ambient air in these spaces is passed out through the apertures 6, depending on pressure conditions obtaining in the space. Such an arrangement will further assist mixing between the jet flow and the ambient fluid surrounding the nozzle 2. The arrangement shown in FIGURE 8 in which the outer and inner vanes are twisted in opposite directions further assists this mixing process.
FIGURE 9 shows a nozzle 2 with an outer fairing 2A. Spacing members are provided between the nozzle 2 and the outer fairing 2A. In order to show the nozzle arrangement more clearly both the nozzle 2 and the fairing are shown in cross-section but in practice the fairing 2A would be smoothly joined to the nozzle 2 downstream of the plane shown in cross section. Pivot pins 7 are firmly mounted between the nozzle 2 and the fairing 2A through the spacing members 15. Each of the pivot pins 7 projects inwardly towards the longitudinal axis of the nozzle. Vanes 24 are each provided at their upstream ends with a pair of lugs 8 which are mounted on pivot Pins 7 50 t at t e'vanes .24 are free to pivot. A coil spring 8A surrounds each of the pivot pins 7 and is attached at each end to the lugs h of the vanes 24.
In FIGURE 9 the vanes 24 are pivotally mounted and thus the vanes can oscillate between inclined angles on either side of the position of equilibrium of the vanes as shown in full lines. The frequency of the oscillation is dependent on the resilience of the spring, the velocity of the jet and ambient flows, the turbulence in the jet flow and the vane inertia. The coil springs 8A control the amplitude of the oscillation of the vanes 24. The oscillation of the vanes 24 induces corresponding oscillation in the flow direction of the jet gases and consequently inhibits the formation of the regular annular vortices as well as reducing the extent of the mixing region.
FIGURE 10 shows an arrangement similar to that shown in FIGURE 9, but in which the use of coil springs is avoided. Each of the pivot pins 7 is attached to one end of a crank member 15. The other end of the crank members 15, which are associated with adjacent pairs of vanes 24' are linked together by a pin 16, which is free to move both in a slot 17 in the wall of the nozzle 2 and in slots in the crank members 15. Flates 18 are pivotally mounted about their upstream ends on the outer surface of the wall of the nozzle 2, each adjacent a slot Eli. The plates lit; are each connected at their upstream ends to an operating rod 19. The pins 16 in their most upstream position abut the upstream end of the slot 17 in the nozzle wall. In this position of the pins 16 the vanes 24 are in a position shown in full line at 24A. Under the influence of the jet stream the vanes commence to oscillate and the pins 16 are displaced by the crank members 15 to abut the downstream ends of the slots 17. Thus the vanes 24- assume the position 248 shown in broken line. When the operating rods 19 are moved in the direction shown by the arrows A the plates 1% are pivoted so that their normally downstream ends abut the pins 16 and prevent the pins from moving in the slots 17.
FIGURE 11 shows an arrangement in which the vanes 24 are pivotally mounted on pins 7 and, at a point downstream of the pivot pins 7, the vanes 24 are pivotally interconnected by a linkage 25 which causes all the vanes 24- to oscillate in phase, e.g. all vanes 24 are in position 24A or all vanes in position 243 as shown respectively in full and broken lines.
1. A jet pipe nozzle for partially inhibiting the generation of noise by a high velocity fluid stream issuing from the nozzle exit into ambient fluid, the nozzle including a boundary wall, a plurality of vanes mounted on the boundary wall and extending lengthwise upstream from the nozzle exit, some of said vanes projecting widthwise from one side of the boundary wall into the high velocity fluid stream and the others projecting widthwise away from the opposite side of the boundary wall into the ambient fluid, said vanes in their operative position being inclined lengthwise with respect to the general direction of fluid flow with all said vanes on either one of the boundary wall sides inclined in the same sense.
2. A jet pipe nozzle according to claim 1, wherein the vanes on one side of the nozzle boundary wall are inclined in the opposite sense from those on the opposite side of the nozzle boundary Wall.
3. Apparatus as claimed in claim 1, in which the vanes are provided with shrouds.
4. Apparatus as claimed in claim 3, in which the shrouds are provided with apertures.
5. Apparatus as claimed in claim 1, further incorporating means for adjusting the inclination of the vanes with respect to the general direction of flow through the nozzle.
6. Apparatus as claimed in claim 1, in which the vanes are of twisted form.
7. Apparatus as claimed in claim 6, in which the outer vanes are twisted in a different sense from that of the inner vanes.
8. Apparatus as claimed in claim 5, in which means are provided fer locking the vanes in alignment with the jet axis.
References Cited in the file of this patent 5 UNETED STATES PATENTS 2,648,192 Lee Aug. 11, 1953 2,664,700 Benoit Jan. 5, 1954 2,696,709 Oulianoff Dec. 14, 1954 2,878,643 FOX Mar. 24, 1959 6 Hawkins Mar. 15, 1960 Tylei- Mar. 29, 1960 Glenn Apr. 5, 1960 Poulos May 3, 1960 Bodine July 12, 1960 Keen Apr. 4, 1961 Tyler et a1 May 8, 1962 FOREIGN PATENTS Australia Sept. 26, 1955 France Dec. 1, 1958