US 3263417 A
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Aug. 2, 1966 s. G. HOOKER JET PROPULSION NOZZLE 5 Sheets-Sheet 1 Filed Sept. 24, 1964 I Inventor ffl/VAEV ames Hus/(5E ByM) W WA ltorney;
1966 s. e. HOOKER JET PROPULSION NOZZLE 5 Sheets-Sheet 2 Filed Sept. 24. 1964 g- 2, 1966 s. G. HOOKER 3,263,417
JET PROPULSION NOZZLE Filed Sept. 24, 1964 5 bheets-Sheet 5 Inventor $374 46) (awe M A tlofneys United States Patent 3,263,417 JET PROPULSION NOZZLE Stanley George Hooker, Brimol, England, assignor to Bristol Siddeley Engines Limited, Bristol, England, a British company Filed Sept. 24, 1964, Ser. No. 398,862 Claims priority, application Great Britain, Oct. 2, 1963, 38,830/ 63 7 Claims. (Cl. 60--35.6)
The invention relates to jet propulsion nozzles for aircraft comprising a jet pipe and at least one flap hinged at its front end to the jet pipe and having an external surface which is exposed during flight to the free airstream past the aircraft and an internal surface exposed to flow through the nozzle and terminating in a rear edge defining part of the periphery of the outlet end of the nozzle, with means for varying the inclination of each flap to the general direction of the free airstream 'for the purpose of varying the area of the outlet end of the nozzle.
If, in the course of progressively restricting the outlet area of the nozzle, the inclination of the external flap surface to the general direction of the free airstream exceeds a certain value, the adjacent part of the free airstream will cease to follow the external flap surface, and a reduced pressure eddy zone will be formed, which causes drag. I
The invention consists in the provision of means for discharging gaseous fluid rearwards over the external surface of at least one of the flaps from a position adjacent to the front end of that flap, when that flap is inclined to the direction of the free airstream. By this means the formation of a drag-producing eddy zone adjacent to the exposed external flap surface may be opposed, so that steepe'r flap inclination can be used. The invention is illustrated by the examples shown in the accompanying drawings. In the drawings:
FIGURE 1 is a perspective view of a jet propulsion nozzle of circular cross section with a ring of flaps, which are shown adjusted to give a small outlet area;
FIGURE 2 is a similar view with the flaps shown adjusted to give a large outlet area;
FIGURE 3 is a longitudinal section on a larger scale on the line 3-3 in FIGURES 4 and 6, through a flap and an end part of the wall of a jet pipe to which it is hinged;
FIGURE 4 is a transverse section on the line 4-4 in FIGURE 3;
FIGURE 5 is a transverse section on a still larger scale, on the line 5-5 in FIGURE 3;
FIGURE 6 is a fragmentary section on the line 6-6 in FIGURE 3, showing operating mechanism;
FIGURE 7 is a longitudinal section similar to part of FIGURE 3, but taken on the line 77 in FIGURE 6;
FIGURE 8 is an enlargement of a fragment of FIG- URES 3 and 7, but showing a modification; and
FIGURE 9 is a perspective view of a jet propulsion nozzle of rectangular cross section, with two opposed flaps and a centre-body.
The principal components of the nozzle shown in FIG- URES l to 7 appear in FIGURE 3. The nozzle is of circular section, with a ring of narrow flaps 1 hinged to jet pipe structure 2, the jet flow being on the side and in the direction indicated by an arrow J in FIGURE 3, and the free airstream on the other side as indicated by an arrow A. The jet pipe is connected at its up stream end to a jet propulsion power plant, not shown, for example a turbojet or ramjet engine. The flaps are shown in full lines in a position inclined to the free airstream for restricting the outlet area of the nozzle (as also shown in FIGURE 1), and may be moved outwards "Ice to the position shown in chain dotted lines for the purpose of increasing the outlet area (as also shown in FIGURE 2).
Each flap comprises an outer member 5 and an inner member 6, the two being hinged together or resiliently interconnected at 7 near the rear end of the flap. As may be seen from FIGURE 4, both members are generally channel-shaped in section, and decrease in Width and thickness rearwards so as to allow for movement to and from the inclined position. The inner member is inverted with respect to, and nests in, the outer member, while one side flange of the outer member has an extension 5a which underlaps the adjacent inner member to provide an adequate gas seal in all positions of adjustment. To avoid confusing the showing; of other parts, the extensions 5a, and the flanges of the members 5 and 6, are not shown in FIGURE 3.
At its front end each outer flap member 5 has an inward extension 8 by which it is hinged at 19 to an extension 9 which projects from a portion 26 of the rear wall of a manifold 11. This manifold encircles, and forms part of, an outer wall of the jet pipe and nacelle structure. Each portion 26 of the rear wall has a partcylindrical surface centred on the axis of the hinge 19 of the respective flap, and is in sliding engagement with a part-cylindrical surface on a forward portion 10 of the outer flap member 5, leaving a slot 15 between the por tion 10 and an outer wall 13 of the jet pipe. A pipe 12 (FIGURE 3) connected to the manifold 11 serves for admission of air or hot gas under pressure, a suitable shut-off valve 27 being interposed. From the manifold, the air or gas issues through theslot 15 and flows over the external surface of the outer flap members 5.
The air or gas can be derived from the power plant with which the nozzle is associated.
The inner member 6 of each flap is hinged at its forward end 16 to one or more radius arms 17 and to a sleeve 18 forming a prolongation of an inner wall 20 of the jet pipe structure. The radius arms 17 are pivoted to the extension 9 at 19, while the sleeve 18 slides axially 0n the outside of the inner wall 20 and carries short radial pins 21 on each of which is mounted a roller 22 engaging a cam slot 29 (FIGURE 6) in a channel-sec- .tion cam ring 23. There may be, for example, three sets of pins 21 and rollers 22 spaced around the sleeve 18 at equal angular intervals. One of the flanges of the cam ring 23 is provided with one or more toothed portions 28 each of which meshes with a pinion 24 driven by an actuating motor 25. The ring 23 is also adequately supported, and located axially, by rollers 30 (FIGURES 6 and 7) engaging one or both of its flanges at suitable angular intervals. Operation of the motor 25 from the setting shown in FIGURE 6 turns the cam ring 23 and forces the rollers 22 and the sleeve 18 rearwards so that the flaps 1 are turnedoutwards to the position shown in chain dotted lines in FIGURE 3 (i.e. to the position shown in FIGURE 2). The radius arms 17 prevent the sleeve 18 from rotating.
The valve 27 for admission of air or gas under pressure to the manifold 11 may, as shown, be operatively connected to the cam ring 23 by a rack and pinion 31, 32, so that admission takes place when the inclination of the external surface of the flaps to the free airstream exceeds a predetermined value.
An equivalent effect may be obtained, as shown in FIGURE 8, by making the arcuate forward portion 10a of the outer flap member 5 tapered in thickness, so that the slot 15 is progressively opened as the flaps are inclined inwards.
FIGURE 9 illustrates the application of the invention to another type of nozzle, namely one of rectangular cross section. This nozzle is divided by a centrebody 57, and has two opposed flaps, each consisting of an upstream portion 54 hinged to the jet pipe 50 at 53, and a downstream portion 55 hinged to the upstream portion 54 at 56. The nozzle may be of considerable lateral extent, and may be subdivided by fixed partitions 58, and limited by end walls (not shown), similar to the partitions. The upstream edge of each portion 54- is spaced from the downstream edge of the outer wall 51 of the jet pipe, so as to define a slot 52 through which air or hot gas under pressure may be discharged rearwards over the external surfaces of the flap portions 54 and 55.
The range of inclination of the flaps to the external airflow over which blowing is useful is approximately :12 to 40. Blowing is mainly of advantage during flight at a speed lower than that for which the nozzle is primarily designed, i.e. for so-ca-lled off-design operation when a strongly convergent nozzle is required. In particular, blowing is useful in subson-ic/transonic offdesign operation of nozzles designed for flight speeds in excess of Mach 2. 1
The velocity of the blowing air is of the order of two to three times the eight velocity. The magnitude of the blowing is best expressed by a blowing coefficient CM defined as:
C: WBVB 1/2PV02AN where: 7
W is the mass flow of the blowing air, V is the velocity of the blowing air, p is the density of the ambient air, V is the flight speed, and A is the nozzle external cross-section area.
This blowing coefficient C, lies within the range 0.02
The position from which the air or gas is discharged may be a little downstream of the upstream edge of a 'flap. The considerations governing this are that the effect of ejecting fluid into the boundary layer will be felt a short distance upstream of the point of ejection. Also, once flow separation has started, the point of separation is likely to move upstream. It is therefore not strictly necessary to eject the fluid at a point upstream of where the separation would stabilise when operating without it. Alternatively the position from which air or gas is discharged may be a little upstream of the upstream edge of a flap.
1. A jet propulsion nozzle for an aircraft, comprising an assembly of a jet pipe and at least one flap hinged at its front end to'the jet pipe and having an external surface which is exposed during flight to the free airstream past the aircraft and an internal surface exposed to flow through the nozzle and terminating in a rear edge defining part of the periphery of the outlet end of the nozzle, with means for varying the inclination of each flap to the general direction of the free airstream v for the purpose of varying the area of the outlet end of the nozzle, and means for discharging gaseous fluid rearwards at a velocity at least about twice the flight velocity over the external surface of at least one of the flaps from ,a position adjacent to the front end of that flap, when that flap is inclined to the direction of the free airstream, the means for discharging fluid including a rearward-facing slot defined externally by a rear portion of a member of the jet pipe and internally by a forward portion of the flap and means forming a passage within the jet pipe leading to said slot, means closing off said passage from the interior of the jet pipe-flap assembly, and means responsive to movement of the flap to a position corresponding to the largest nozzle opening to close-said passage.
2. A nozzle according to claim 1, in which the flap is hinged to the jet pipe on an axis offset inwards from the slot, and the forward portion of the flap includes a part-cylindrical surface centred on that axis and making sliding engagement with a part-cylindrical surface fixed to the jet pipe.
3. A nozzle according to claim 2, in which the forward portion of the flap is tapered in thickness.
4. A nozzle according to claim 1, in which the jet pipe comprises an outer wall and an inner wall, and each flap comprises an outer member hinged to the outer wall, and an inner member connected to the outer member at their trailing edges, and the means for varying the inclination of the flap is means for axially displacing the forward edge of the inner member relatively to the inner wall of the jet pipe.
5. In a nozzle as claimed in claim 1, said passage clos ing means comprising a valve in the passage, a ring part carried by the jet pipe for rotation about the longitudinal axis thereof, means op'erativcly connecting the valve to the ring part for operation by rotation of the ring, means to turn said ring part, and means operatively connecting the ring part to a flap operating part for tilting the flap in response to turning of the ring part.
6. In a nozzle as claimed in claim 5, said last connecting means comprising pins carried by one of the parts engaging in oblique slots in the other part.
7. In a nozzle as claimed in claim 1, said passage closing means comprising cooperating surfaces on the jet pipe and flap movable into engagement with one another to close the passage.
References Cited by the Examiner UNITED STATES PATENTS MARK NEWMAN, Primary Examiner. RALPH D. BLAKESLEE, Examiner.