GB2311968A

GB2311968A - Gas turbine jet pipe blocker valve

Info

Publication number: GB2311968A
Application number: GB9607677A
Authority: GB
Inventors: Robert Geoffrey Marshall
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-12
Filing date: 1996-04-12
Publication date: 1997-10-15
Also published as: GB9607677D0

Abstract

There is provided a valve arrangement 1 for jet engines comprising annular series of rotatable vanes (2)(fig. 1), an outer duct (4) and an inner shroud (6) to support the vanes (2) at outer and inner spindles (3). The whole arrangement is such that the vanes (2) can be rotated to two predetermined end positions, open or closed (figures 1 and 3) The valve 1 is mounted upstream of a jet pipe 10 and downstream of a jet engine 9 and vectoring lift nozzle off-take valves 11. In certain engine configurations and applications, valve (2) actuation effects a transition from wing borne flight to thrust balanced hover mode. Various arrangements are disclosed including valves fitted to twin engine configurations (figure 9), valves with sealing arrangements and valves with blades incorporating fuel passages and having trailing edges shaped to form reheat fuel gutters to facilitate afterburning (figs. 10-11).

Description

GAS TURBINE JET PIPE BLOCKER VALVE This invention relates to jet pipe flow blocker valves for Short Take-Off and Vertical Landing (STOVL) aircraft engines.

Certain STOVL propulsion engine concepts require gas turbine engine exhaust gasses to be blocked, by blocker valves1 from exhausting through a conventional jet pipe and to be diverted to lift nozzles that direct the exhaust gas thrust downwards to support the aircraft in hover.

The nozzles can be vectored from downwards to aft, giving a resultant forward thrust component and thus effecting a transition from thrust balanced to wing borne flight.

Once in wing borne flight, the flow of exhaust gas to the vectoring nozzles is closed and the jet pipe blocker valve is opened, thus ducting the engines exhaust directly aft through the conventional jet pipe as in normal gas turbine engine/jet pipe arrangements. The engine is then in forward wing borne flight mode.

The low aero-thermodynamic losses of the straight through gas flow gives improved forward thrust, increased flight velocity and aircraft performance. A jet pipe fitted with reheat and a variable area convergent-divergent exhaust nozzle will enable still higher forward thrust and flight velocity to be achieved.

For vertical landing the transition from wing borne flight mode to hover mode is achieved by closing the jet pipe blocker valve and directing the exhaust gas flow through aft pointing vectoring nozzles. The vectoring nozzles are then vectored downwards to effect the transition from wing borne flight to thrust balanced hover.

Engine thrust is then reduced to effect the vertical landing.

Short rolling take-off may be carried out by vectoring the nozzles slightly aft thus giving both a forward and vertical thrust component at the point of lift-off.

In certain arrangements auxiliary lift devices, such as main engine driven lift fans or separate lift engines1 also supply lift in the hover mode.

Variable Inlet Guide Vanes (VlGVs) are well known devices, common to many gas turbine engines, that are used to modulate engine air mass flow by reducing or increasing engine intake area from typically 100% open to 50% open or visa versa.

According to the present invention there is provided a jet pipe blocker valve, similar to a VIGV arrangement, that is placed between the gas turbine engine exhaust and the front of the jet pipe. The device differs from a VIGV arrangement in that the geometry allows the flow area to be completely closed thus blocking the jet pipe.

When closed the engine is in the hover mode and other valves located between the gas turbine engine exhaust and the jet pipe blocker valve are open to direct the exhaust gases to vectoring lift nozzles as previously described. These other valves may be of various types.

The jet pipe blocker valve consists of a number of radial vanes, that are circumferentially spaced, that can be rotated about there radial (spindle) axis. The vanes are supported at their outer and inner spindles by bearings in a valve duct casing (at the outer spindle) and in an inner shroud casing (at the inner spindle).

When the vanes are aligned co-planar with the engine axis the jet pipe blocker valve is open and the engine is in forward flight mode. By rotating the vanes in unison, about their spindle axis, the throat area between adjacent vanes reduces and the valve begins to close. Further vane rotation gives a further reduction in jet pipe flow area. The profile of each vane is a truncated sector of a circle of diameter equal to that of the valve duct casing. As the rotation of each vane reaches 900, such that they lie normal to the engine axis, the leading and trailing edges of adjacent vanes come together to form an obstruction, thus blocking the jet pipe. Hence when the vanes lie normal to the engine axis the jet pipe blocker valve is closed and the engine is in hover mode.

Reversing the vane rotation will open the flow area into the jet pipe thus changing back to flight mode.

Embodiments of the invention will now be described by way of example with reference to the accompanying diagrams in which: Figure 1. shows an open jet pipe blocker valve according to the present invention.

Figure 2. shows the vane of a jet pipe blocker valve with spindles supported in bearings according to the present invention.

Figure 3. shows a closed jet pipe blocker valve according to the present invention.

Figure 4. shows a vane mounted on circular buttons at the inner and outer spindle interface.

Figure 5. shows a gas turbine engine fitted with a jet pipe blocker valve according to the present invention. The valve is open and the engine is in wing borne flight mode.

Figure 6. shows a gas turbine engine fitted with a jet pipe blocker valve according to the present invention. The valve is closed and the engine is in thrust balanced hover mode.

Figure 7. shows how vane sealing may be achieved by the use of overlapping vanes with deformable leading and trailing edges.

Figure 8. shows a pair of gas turbine engines fitted with jet pipe blocker valves according to the present invention. The valves are open and the engines are in the wing borne flight mode.

Figure 9. shows a pair of gas turbine engines fitted with jet pipe blocker valves according to the present invention. The valves are closed and the engines are in the thrust balanced hover mode.

Figure 10 shows how jet pipe blocker valve vanes can perform the function of reheat fuel injection.

Figure 11 shows how a jet pipe blocker valve vane can perform the function of a reheat fuel gutter/flame holder.

Referring to the drawings the gas turbine jet pipe blocker valve 1 comprises of a number of rotatable vanes 2 as shown in figure 1. The vanes 2 are mounted for rotation on spindles 3 as shown in figure 2.

In preferred arrangements the vane spindles 3 are radially positioned and circumferentially spaced from one another in a cylindrical duct casing 4 as shown in figure 1. The vane spindles 3 are supported in bearings 5 at an inner casing shroud 6 and at the outer duct casing 4 as shown in figure 2.

Figure 1 shows the valve 1 open, wherein the vanes 2 are aligned co-planar with the duct axis such that the vanes 2 present the minimum obstruction to gas flow through the duct 4.

The valve 1 is closed by rotating the vanes 2, in unison, until the leading edge 7 and trailing edge 8 of adjacent vanes 2 meet such that an annular blockage is formed as shown in figure 3. This annular blockage and the inner casing shroud 6 form a complete circular blockage thus preventing gas flow through the valve duct 4.

In a preferred embodiments each vane 2 plan form is a truncated sector of a circle or altematively each vane 2 plan form is a trapezium as shown in figure 4. Other embodiments may incorporate many other shapes of vanes 2 provided that they can be rotated to form an annular or circular blockage.

In a preferred arrangement the valve 1 is mounted downstream of a gas turbine engine exhaust 9, and upstream of a jet pipe 10.

Vectoring lift nozzle off-take valves 11 are positioned between the gas turbine engine exhaust 9 and the jet pipe blocker valve 1 as shown in figure 5. In this preferred arrangement the jet pipe blocker valve inner casing shroud 6 is formed by an extension of the gas turbine engine's exhaust thrust bucket 12.

Figure 5 shows the configuration in the wing borne flight mode, wherein the jet pipe blocker valve 1 is open and the vectoring nozzle off-take valves 11 are closed such that the engine exhaust gasses exhaust aft through the jet pipe 10.

Figure 6 shows this same arrangement in the thrust balanced hover mode, wherein the jet pipe blocker valve 1 is closed and the vectoring nozzle off-take valves 11 are open such that the engine exhaust gases are prevented from passing aft through the jet pipe blocker valve 1 and are diverted through the open off-take valves 11 into ducts and on to vectoring lift nozzles (not illustrated). In further embodiments the vectoring lift nozzles (not illustrated) may be adjacent to the off-take valves 11 thus eliminating the ducts shown in figure 6.

Valve 1 rotationlactuation can be achieved by a number of well known mechanisms.

In preferred embodiments seals 13 are incorporated to minimise gas leakage. In one such arrangement the leading edge 7 andlor trailing edge 8 of each vane 2 is deformable such that uneven contact between adjacent vanes 2 can be accommodated and an effective seal formed. In such an arrangement the vanes 2 may be arranged to overlap one another in the closed position as shown in figure 7.

In such arrangements gas sealing may be improved, and the risk of valve 1 jamming minimised.

In a preferred arrangement vanes 2 are mounted on circular buttons 14 at the interface between vane root 15 and spindle 3 as shown in figure 4. in such arrangements button seals 16 may be incorporated to minimise gas leakage and shield bearings 5 from hot exhaust gases.

In a preferred arrangement two parallel gas turbine engines 17 may be fitted with jet pipe blocker valves 1, according to the present invention, as shown in figure 8. In such an arrangement the two gas turbine engines 17 exhaust through a 2 to 1 bifurcation to a common plenum chamber 18 where the lift nozzle off-take valves 11 are located.

Figure 8 shows such an arrangement in the wing bome flight mode wherein the offtake valves 11 are closed and the jet pipe blocker valves 1 are open. In the wing bome flight mode flow from the plenum chamber 18 passes through a 1 to 2 splitter bifurcation and on through two separate jet pipe blocker valves 1 into two separate jet pipes 10 and is finally exhausted to atmosphere through two separate thrust nozzles 19. With such an arrangement an aircraft can benefit from twin engine 17 survivability. In the event of an engine 17 failure in the wing borne flight mode the exhaust flow from the remaining engine 17 can be well matched to jet pipe 10 and thrust nozzle 19 flow areas thus minimising the loss of thrust.

Figure 9 shows this same twin engine 17 configuration in the thrust balanced hover mode wherein the two jet pipe blocker valves 1 are closed and the vectoring nozzle off-take valves 11 are open thus diverting the exhaust gasses to the vectoring lift nozzles (not illustrated). With such an arrangement an aircraft, in thrust balanced hover mode, is relatively insensitive to variations in thrust balance, caused by variations between left and right gas turbine engine 17 output, due to the equalising effect the plenum chamber 18 has on the left and right off-take valve 11 flows.

Furthermore, the configuration illustrated in figure 9, shows a central off-take valve 20 and duct 21, equi-spaced between the two engines 17, which is particularly insensitive to a thrust imbalance.

In configurations, such as that illustrated in figure 9, that have a number of individual off-take valves 11 and 20 that could all be operated independently, it would be possible to modulate the gas flow to individual vectoring lift nozzles (not illustrated), by individually varying the valve 11 and 20 openings, thus enabling the aircraft to be controlled in pitch and roll.

In still further embodiments the vanes 2 may incorporate internal fuel passages 22 such that, in the wing borne flight mode, they may perform the function of jetpipe 10 reheat fuel injectors as shown in figure 10.

In still further embodiments the trailing edges 8 of the vanes 2 may be shaped such that they may perform the function of reheat fuel guttersiflame holders as shown in figure 11.

Claims

1) A valve arrangement for jet engines which valve arrangement comprises an annular series of spaced vanes mounted for rotation on spindles, an outer duct supporting said vanes at their outer spindles, and an inner shroud supporting said vanes at their inner spindles, the whole arrangement being such that the vanes can be rotated to two predetermined end positions.

2) A valve arrangement as claimed in claim 1 wherein at one end position ,the open position, the vanes are aligned so as to allow free gas flow through the duct, and at the other end position, the closed position, the vanes and shroud form an obstruction to gas flow through the duct.

3) A valve arrangement as claimed in claim 1 or 2 wherein the vane spindles are radially positioned and circumferentially spaced from one another in a cylindrical duct.

4) A valve arrangement as claimed in claim 1, 2 or 3 wherein the vane plan form is a truncated sector of a circle, or a trapezium, or other shape that can be rotated to form an annular, circular, or other shaped blockage in the closed position.

5) A valve arrangement as claimed in any one of the above claims wherein seals are incorporated to minimise gas leakage between adjacent vanes in the closed position.

6) A valve arrangement as claimed in claim 5 wherein the vanes are arranged to partially overlap one another in the closed position.

7) A valve arrangement as claimed in claim 6 wherein overlapping vane edges are deformable such that uneven contact between adjacent vanes, in the closed position, can be accommodated 8) A valve arrangement as claimed in any one of the above claims wherein the vane spindles are supported in bearings at the inner shroud and at the outer duct.

9) A valve arrangement as claimed in any one of the above claims wherein seals are incorporated to minimise gas leakage between the vanes and the duct or between vanes and the shroud.

10) A valve arrangement as claimed in any one of the above claims wherein vanes are mounted on buttons at the interface between vane root and spindle.

11) A valve arrangement as claimed in any one of the above claims wherein seals are incorporated to shield bearings from hot exhaust gases.

12) A valve arrangement as claimed in any one of the above claims wherein said valve is mounted downstream of a jet engine and upstream of a jet pipe.

13) A valve arrangement as claimed in claim 12 wherein the duct section, upstream of said valve and downstream of said jet engine. is equipped with lift nozzle off-take valves.

14) A valve arrangement as claimed in claim 12 or 13 wherein the valve shroud is an extension of a jet engine turbine exhaust thrust bucket.

15) A valve arrangement as claimed in any one of claims 12 to 14 wherein a pair of said valves are mounted downstream of a pair of jet engines and upstream of a pair of jet pipes.

16) A valve arrangement as claimed in claim 15 wherein the duct sections, upstream of said valves and downstream of said jet engines, are joined to form a common plenum chamber connecting with the lift nozzle off-take valves.

17) A valve arrangement as claimed in claim 16 wherein said valves can be operated independently to match total jet pipe flow area with jet engine mass flow should one jet engine fail.

18) A valve arrangement as claimed in claim 16 wherein said lift nozzle off-take valves can be operated independently to modulate the gas flow to individual vectoring lift nozzles.

19) A valve arrangement as claimed in any one of the above claims wherein the vanes incorporate internal fuel passages that perform the function of jet pipe reheat fuel injectors.

18) A valve arrangement as daimed in claim 19 wherein vane trailing edges are shaped to form reheat fuel gutters or flame holders.

19) A valve arrangement as claimed in any one of the above claims wherein the valve arrangement is fitted to any number of jet, rocket or similar propulsion engines.

20) A valve arrangement substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.