GB2036669A

GB2036669A - Thrust vectoring nozzle

Info

Publication number: GB2036669A
Application number: GB7941449A
Authority: GB
Original assignee: Bayern Chemie Gesellschaft fuer Flugchemische Antriebe mbH
Current assignee: Bayern Chemie Gesellschaft fuer Flugchemische Antriebe mbH
Priority date: 1978-12-07
Filing date: 1979-11-30
Publication date: 1980-07-02
Also published as: IT7927681A0; IT1127663B; DE2852918A1; FR2443586A1

Abstract

A thrust vectoring nozzle assembly for a propulsion unit such as a rocket engine in a missile, with the nozzle part pivotally supported on an end part of the propulsion unit which is adjacent the combustion chamber, four actuator rams (34) being provided to compensate the force which, in use, tends to separate the nozzle from the propulsion unit and also to provide control of the angular position of the nozzle, each ram being double acting and subject on one side (46) through line (48) to a force dependent on combustion chamber pressure and transmitted through a pressure amplifier (52) connected at the low pressure side (56) with the combustion chamber and at the higher pressure output side (50) with the rams, the other side (58) of the rams being connected with control means (60-68) to set the angular position of the nozzle through displacement of the ram pistons. <IMAGE>

Description

SPECIFICATION A thrust vectoring nozzle for a propulsion unit This invention relates to a thrust vectoring nozzle for a propulsion unit with the nozzle pivotally supported in an angularly displaceable manner on the propulsion unit body part closest to the combustion chamber and with one or more actuator means such as a piston and cylinder subject to force in accordance with the forces acting between the nozzle and body part, and an actuating mechanism for the control of the angular position of the nozzle.

In vectored thrust jet propulsion units using a mechanically pivotable thrust nozzle mounted on the tail pipe part of the propulsion unit nearest to the combustion chamber and having a seal formed by a pair of cooperating guide surfaces forming a ball-like joint around a pivot centre it is known to provide means to relieve the mounting of the high forces occurring during operation, and which tend to act to separate the nozzle and body, which means comprise one or more gas chambers connecting the nozzle and the body part. The chambers are subjected to combustion chamber pressure and provide some of the counter-force to overcome the separating force and form a mechanical connecting and mounting system. (DE 1170284 and DE 2334295).

With this method of support using the actual combustion chamber pressure, difficulties arise because in the region of the pivotable thrust nozzle large areas subject to pressure are required for the gas chambers and only limited space is generally available also the remaining forces to be absorbed by mechanical means through the pivot bearing points are still large. Complex and costly mechanical mounting systems are still required for the thrust nozzle to afford free pivoting without the risk of jamming or seizing.

A nozzle assembly is shown in U.S. 3361362 in which the pivotable nozzle has no additional mounting system but is supported against thrust forces on the combustion chamber side of the propulsion unit part by hydraulic means and in an angularly adjustable manner through a number of rams distributed around the periphery of the pivotal nozzle, the working chambers of the units being interconnected in a closed hydraulic system. In such a closed hydraulic system with passive pressure control, the thrust force cannot be completely supported by the pressure medium and the pivot nozzle at the same time accurately secured about the pivot line.Inavoidable intrinsic elasticity and volumetric changes caused by the thermal factors in the hydraulic system also cause difficulties with the separating thrust force and the hydraulic holding force leading to undesirable longitudinal displacements of the nozzle in respect of the main propulsion unit part nearest the combustion chamber. In the event of a failure in the ram securing system the nozzle may become separated from the propulsion unit part. For the control of the pivotal position the hydraulic have to be supplemented by a hydraulic control system with separate hydraulic servo-motors which occupies much space.

This invention seeks to provide a thrust vectoring nozzle arrangement wherein the securing and control hydraulic systems will provide support in the main free from residual forces, with the nozzle being accurately positioned.

According to this invention there is provided a thrust vectoring nozzle assembly for a propulsion unit with the nozzle part pivotally supported in an angularly displaceable manner on an end part of the propulsion unit which, in use, is adjacent the combustion chamber, one or more actuator rams being provided to compensate the force which, in use, tends to separate the nozzle from the propulsion unit and also to provide control of the angular position of the nozzle, the or each ram being double acting and subject on one side to a force dependant on combustion chamber pressure and transmitted through a pressure amplifier connected at the low pressure side with the combustion chamber and at the higher pressure output side with the ram, the other side ofthe ram being connected with control means to set the angular position of the nozzle through displacement of the ram piston.

In such an assembly the supporting or compensating pressure which prevails in the ram and which acts in opposition to the separating force is actively regulated, by the pressure amplifier, to a pressure which corresponds to that prevailing in the combustion chamber at any instant but which is several times greater, this force, despite small dimensions for the hydraulic system, in the region where the pressure acts, is transmitted almost fully by hydraulic means existing between the thrust nozzle and the propulsion unit, with the particular characteristic that the equilibrium between the separating force and the hydraulic holding force is obtained independently of volumetric changes caused in the hydraulic system by thermal factors or compressibility and without deviations in the pivotal locus of the thrust nozzle.The assembly according to the invention therefore ensures a simple, functionally reliable, accurate and hydraulically balanced mounting and control of the pivot nozzle which is necessary for the mechanical thrust vector control of guided missiles having high power density engines.

The arrangement may have one annular hydraulic chamber approximately concentric with the pivot fulcrum, but will preferably have a plurality of piston and cylinder ram units which are distributed around the outer periphery of the thrust nozzle and of which all the hydraulic chambers on the one side, being the piston rod side, are subjected to the output pressure of the pressure amplifier. In this case, and as an advantageous feature the holding hydraulic system is combined with the control hydraulic system for the nozzle in one and the same ram, making it possible to dispense with servo-motors for controlling the position into which the thrust nozzle part is pivoted.For this purpose the piston and cylinder rams are constructed, on the other side of the piston which faces away from the hydraulic chamber as a single-acting hydraulic servo-motor system which is connected through a controllable valve with a pressure supply line and with a return line and which can be selectively connected to control and position the ram and hence the movement of the thrust nozzle part.

To simplify the control movements to be performed by the rams to pivot the thrust nozzle into a desired position, the pivot connection points of the rams at one end are located in a plane perpendicular to the longitudinal axis of the thrust nozzle part and passing through the locus of pivotal movement of the nozzle. Such a geometrical arrangement of the pivot points allows pivotal movement of the thrust nozzle part around a number of main axes, intersecting at the pivotal locus, to be performed without the need to change the setting of the rams lying on an axis intersecting said axis. The control system is thus much simplified.

With a thrust nozzle adjustable about more than one axis in relation to the propulsion unit, the holding and control hydraulic systems are advantageously supplemented to prevent roll movements by using a mechanical connection between the thrust nozzle and propulsion unit in such a way that it cannot roll in relation thereto. In a preferred construction this mechanical connection is designed to prevent roll but to ailow pivot movement in all directions and comprises two diametrically opposed journals rotatable about an axis passing through the locus of pivot movement of the nozzle and through two arms movable in a longitudinal direction and guided on the respective journals in a perpendicular direction to the axis thereof.A mechanical connection of this kind secures the thrust nozzle to the propulsion unit in a pivotably movable but nonrolling a manner as in a full cardan joint or gimbal suspension but with simplified construction means and without high weight and volume.

Preferably two relatively movable guide surfaces form a seal between the propulsion unit and thrust nozzle and are each spherically curved about a locus of pivotal movement, the surfaces extending to both sides of a plane passing through the locus and perpendicular to the longitudinal axis of the propulsion unit and thrust nozzle.These guide surfaces, in the nature of a ball and socket, not only serve to ensure that any residual forces occurring over a short period and before operation of the holding hydraulic system, (when the propulsion unit is being started) are directly transmitted by mechanical means from the thrust nozzle to the propulsion unit and that the joint between the thrust nozzle and propulsion unit is gas-tight but also form an auxiliary mount and supporting system which comes into operation in the event of a failure of the hydraulic system to retain secure the thrust nozzle and the propulsion unit assembly centrally with respect to the pivot locus. A further pair of surfaces can be provided between the propulsion unit and the thrust nozzle and radially nearer the pivot locus to define a gap for all pivot positions of the thrust nozzle.This can ensure that the guide surfaces and particularly the sealing are not directly subject to the affects of the jet exhaust but will be protected therefrom by annular gap which forms a dead space with no flow and which is delimited nearer the pivot by the further pair of surfaces. A more complete protection of the guide surfaces and the seal between them from damage from the exhaust is obtained if that surface of the radially inermost pair of surfaces which is closer to the pivot locus is positioned on the propulsion unit part and arranged so that the gap between the inner pair of surfaces slants in the opposite direction to the flow of gas so that any solid particles cannot pass into the gap. In this arrangement the surface of the innermost one of the pair of surfaces which is nearer to the pivot locus is preferably formed on a centrai exhaust pipe on the propulsion unit.

An embodiment according to the invention will be described in detail in conjunction with the accompanying drawings. In the drawings: Figure 1 shows a schematic view of a thrust nozzle assembly in a jet propulsion unit and partly in section on line 1-1 of Figure 2, Figure 2 shows a view of the nozzle assembly of Figure 1, looking in the direction shown by arrows 2, and Figure 3 shows a simplified circuit diagram of the control and securing hydraulics system for the nozzle arrangement.

The nozzle assembly for a jet propulsion unit shown in the drawings is intended for driving a guided missile and is a unit with high power density.

The assembly comprises a propulsion unit part 2 connected with the combustion chamber (not shown) and a divergent thrust nozzle 4 secured to the propulsion unit so as to be angularly adjustable about central pivotal locus point (or line) S. The mechanical connection between the propulsion unit part 2 and the thrust nozzle part 4 is effected through part spherical surfaces 6 and 8 having origin at S, the inner guide surface 6 is formed on a cylinder 10 threadably engaging the thrust nozzle part 4 while the outer guide surface 8 is a complementary socket 12, formed on the propulsion unit part 2, and a retaining ring 14threadably engaging the socket.

Between the socket 12 and the ring 14 an annular seal 16 is located which sealingly engages the inner surface 6. The surfaces 6 and 8 are curved in a spherical manner on both sides of the pivot S in a longitudinal direction of the nozzle assembly and form a securing system in the nature of a captive ball and socket joint.

The arrangement also includes means to secure the nozzle to the propulsion unit against roll movement and for this two diametrically opposed journals 18A and 188 are positioned between the socket 12 and the ring 14 so that they afford rotation about an axis A-A which is perpendicular to the longitudinal axis of the propulsion unit which passes through the point S. Arms 22A, B are also provided to engage longitudinal channels 20A and B respectively in the journals 18 and are longitudinall displaceable along these channels. The arms are secured to a collar 24 on the nozzle 4. Due to the rotatability of the journals 18 about axis A-A and the longitudinal displaceability of the arms 22 in the channels 20 the nozzle 4 can be swivelled over the permissible pivot range into any required position but is secured against rotation in a roll direction around the longitudinal axis.

To protect the guide surfaces 6, 8, from the hot gas exhaust stream a further pair of cooperating sur faces 26A, B are provided and a curved about the point S to define a gap angled against the gas flow.

That surface 26A which is nearer to the point S is formed on the tail end of a pipe 30 which lines the inside of the propulsion unit part 2 while the other surface 26B is provided by insert 32 which forms the nozzle throat and may consist of an insulating material, as does the propulsion unit end part 2, such as a mixture of phenolic resin and asbestos. By means of the shape of gap 28 and an annular dead zone 34 connecting therewith no gas flow to the guide surface 6,8, occurs and the seal 16 is protected from the thermal effects of the exhaust gas and also, particularly when the gas exhaust is charged with particles, from mechanical erosion effects.

The control and securing hydraulic system for the nozzle 4 comprises four hydraulic piston and cylinder ram units 34A, B, C and D, which are arranged in diametrically opposite pairs around the periphery and 90 apart. The cylinders 36 of each ram are connected, through pivot couplings 38 capable of pivoting in one plane, to the propulsion unit part 2.

The piston rods 40 of each ram are connected, also through pivots 42, with cranks 44 bolted to the collar 24 of the nozzle 4. The pivot points 42 are all located in a plane passing through the point Sand perpendicular to the longitudinal axis through the nozzle 4.

When the nozzle 4 is pivoted about the axis B-B, containing the pivots 42 of the rams 34A and C, only the rams 34B an D have to be adjusted and in opposed senses. When the nozzle 4 is pivoted about the axis C-C, which contain the pivots 42 of the rams 34B and D only the rams 34A and C have to be adjusted and in opposed senses. Since every other positional movement of the nozle 4 can be subdivided into a pivoting movement about these two main axes B-B and C-C respectively, computing and control for the operation of the rams 34 are considerably simplified mainly due to the particular position of the pivots 42.

By application of pressure to the chamber 46 of the rams which are adjacent the piston rods, a hydraulic holding force can be generated which is opposite to the thrust force acting longitudinally during operation and dependant on the combustion chamber pressure, this holding force is controlled in such a way that apart from a few milliseconds when the propulsion unit is being started the nozzle part 4 will be retained to the propulsion unit part 2 without substantial force between the joint parts 6 and 8. For this purpose the chambers 46 of all the rams 34 are connected by a common hydraulic line 48 with one another and, as shown in Figure 3 with the output 50 of a pressure amplifier 52 of which the differential piston 54 is subjected on the larger piston surface, through a line 56, to the instantaneous gas pressure in the combustion chamber (shown in broken lines in Figure 3).The hydraulic pressure in the rams 46 is thus proportional to the combustion chamber pressure but, in accordance with the area ratio of the piston 54 several times higher, so that for hydraulic equalization of forces only comparatively small pressure surfaces are required in the rams 46 so that the dimensions of the piston and cylinder units 34 can be kept small.

To control the position into which the nozzle 4 is pivoted the chambers 58 of the rams 34 are connected through valves 62A, B, C and D electrically actuated through a control device 60, with a pressure supply 64 and a return 66 of a hydraulic supply 68.

When the valves 62 are at rest the chambers 58 are closed-off from the pressure supply 64 and from the return 66. When the thrust nozzle part 4 is to be pivoted those valves 62A, C and 62B, D, which are associated with chambers 58 on axis B-B and C-C respectively, are actuated through device 60, in pairs and in opposed senses such that when the valve 62A connects the associated chamber 58 to the pressure supply 64 the valve 62C opens the associated chamber 58 to the return 66, and vice versa, and when the valve 62B connects the associated chamber 58 to the pressure supply 64, the valve 62D is connected up to the return 66, and vice versa. Thus the rams 34A, C and 34B, D, situated on one of the axes are adjusted with respect to each other in pairs until the nozzle 4 is in the desired angular position. In this operation hydraulic pressure in chambers 48 of the rams 34 is maintained, and the hydraulic medium merely displaced through conduit 48 when the rams are adjusted. As the nozzle 4, owing to the almost complete hydraulic equalization of force, can be pivoted with a very easy movement, the hydraulic medium source 68 for the control hydraulic system need not be especially high pressure. In place of the four piston cylinder units 34 illustrated, it is naturally possible to adopt any other number of appropriately connected cylinder units according to requirements.

Claims

1. A thrust vectoring nozzle assembly for a propulsion unit with the nozzle part pivotally supported in an angularly displaceable manner on an end part of the propulsion unit which, in use, is adjacent the combustion chamber one or more actuator rams being provided to compensate the force which, in use, tends to separate the nozzle from the propulsion unit and also to provide control of the angular position of the nozzle, the or each ram being double acting and subject on one side to a force dependant on combustion chamber pressure and transmitted through a pressure amplifier connected atthe low pressure side with the combustiqn chamber and at the higher pressure output side with the ram, the other side of the ram being connected with control means to set the angular position of the nozzle through displacement of the ram piston.

2. A thrust vectoring nozzle assembly in accordance with Claim 1, wherein a plurality of rams are distributed around the outer periphery of the thrust nozzle and propulsion unit, all the rams having the hydraulic chambers on their one sides subject to the output pressure of the pressure amplifier.

3. Athrustvectoring nozzle assembly in accordance with Claim 2, wherein the rams are on their other sides, arranged as single-acting hydraulic servo-motors and each connected through a controllable valve with a pressure supply line and with a return line which can be selectively connected to control the position of the ram to effect movement of the thrust nozzle.

4. Athrustvectoring nozzle assembly in accordance with Claim 2 or 3, wherein the pivot connection point of the piston of each ram is located in a plane perpendicular to the longitudinal axis of the thrust nozzle and passing through the locus of pivot movement.

5. Athrustvectoring nozzle assembly in accordance with any one of the preceding claims, wherein the thrust nozzle is secured with respect to the propulsion unit against roll movement about the longitudinal axis.

6. Athrustvectoring nozzle assembly in accordance with Claim 5, wherein the thrust nozzle is secured to the propulsion through two diametrically opposed journals rotatable about an axis passing though the locus of pivot movement of the nozzle and through two arms movable in a longitudinal direction and guided on the respective journals in a perpendicular direction to the axis thereof.

7. Athrustvectoring nozzle assembly in accordance with any one of the preceding claims, wherein two relatively movable guide surfaces form a seal between the propulsion unit and thrust nozzle and are each spherically curved about a locus of pivotal movement, the surface extending to both sides of a plane passing through the locus and perpendicular to the longitudinal axis of the propulsion unit and thrust nozzle.

8. Atrustvectoring nozzle assembly in accordance with Claim 7, wherein a further pair of surfaces are provided between the propulsion unit and the thrust nozzle and radially nearer the locus, said surface lying spherically about the pivot locus and defining a gap therebetween for each pivot position of the nozzle.

9. A thrust vectoring nozzle assembly in accordance with Claim 8, wherein that one of the further surfaces which is innermost is formed on the propulsion unit.

10 Athrustvectoring nozzle assembly in accordance with Claim 9, wherein the innermost surface is provided on a centrally positioned jet exhaust pipe associated with the propulsion unit.

11. A thrust vectoring nozzle assembly constructed and arranged to function substantially as herein described with reference to and as shown in the accompanying drawings.