GB2276434A

GB2276434A - Cam-operated valve

Info

Publication number: GB2276434A
Application number: GB9306418A
Authority: GB
Inventors: Philip Anthony Mansfield
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1993-03-27
Filing date: 1993-03-27
Publication date: 1994-09-28
Anticipated expiration: 2013-03-27
Also published as: US5379800A; GB2276434B; GB9306418D0

Abstract

A cam-operated valve mechanism for directing the flow in a fluid flow duct to alternative outlets comprises an annular array of segmented elements (86) which are each pivotally mounted to an axially translatable sleeve (50) disposed coaxially with the duct. In a first axial position the sleeve extends across port and starboard alternative flow outlets (28), and in a second axial position extends downstream thereof. Each valve element comprises a cam follower (90) which engages an axially extending cam track (92a) formed in the duct surface. The profile of the cam track is such that translation of the sleeve from its first to second axial position causes each of the valve elements to rotate from a stowed to a deployed position, and thereby obturate the duct. A second set of valve elements (74) may be provided to close the duct (fig 5), and a third set of valve elements may be provided, linked to a second sleeve (56) upstream of the first sleeve. The valve is used for thrust-vectoring in jet engines. <IMAGE>

Description

2276434 CAM OPERATED VALVE The invention concerns a cam operated valve

mechanism for a fluid flow duct which operates to direct fluid flow to selective alternative flow exits. In particular, the invention concerns a valve mechanism for use in a vertical take-off and landing (VTOL) aircraft powerplant application, in which engine gases are selectively diverted to alternative discharge nozzles.

The present invention relates specifically to a gas turbine engine of the type described in US patent -3,280,560. In general this patent discloses a gas turbine engine having a plurality of side mounted vectorable lift nozzles, and a conventional axial jet pipe propulsion nozzle. In use, the engine gases are either selectively directed to the side nozzles to generate lift, or to the jet pipe nozzle to provide forward thrust.

In known engine applications of this type it is usual to provide diverter valve means to achieve the required flow redirection. An example of such a valve is described in US Patent 4,587,803. Unfortunately, this and other know diverter valve arrangements tend to be mechanically complex, and as such add appreciably to the overall cost and weight of the engine.

An objective of the present invention is, therefore, to provide a simple low cost low weight diverter valve, and in particular a diverter valve suitable for use in a VTOL powerplant application.

According to the invention there is provided a fluid flow duct comprising a generally cylindrical casing having at least one open ended flow passageway defined therein, and at least one valve means for respectively opening and closing the passageway, the valve means comprising an annular array of segmented elements each being pivotally mounted in relation to a moveable cylindrical sleeve member which is disposed coaxially with the casing, there being provided at least one cam means fixed in relation to the casing, whereby translation of the sleeve member from a first to a second axial position effects translation of at least one segmented element over the cam means which causes each of the segmented elements to rotate from a stowed to a deployed position.

The invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a part sectional part fragmentary view of a gas turbine engine employing a valve of the present invention, Figure 2 shows a sectional half view along line I-I of Figure 1, with the valve deployed for VTOL operation, Figure 3 shows a detailed sectional half view along line II-II of Figure 2, Figure 4 shows a detailed sectional half view along line III-III of Figure 2 with the valve in a first configuration, Figures 5, 6 and 7 show the same detailed sectional view as Figure 4 but with the valve in respective second, third and fourth configurations.

Referring first to Figure 1, there is shown a gas turbine engine 10 for a VTOL aircraft application. The engine is shown in part cut-away part sectional form to reveal the internal features of the engine, particularly the diverter valve mechanism.

The engine shown is of the by-pass type which comprises, a front fan assembly 12, and a core engine 14 which is surrounded by an annular bypass duct 16. In flow series the core engine comprises, a compressor section 18 which receives a portion of the fan discharge flow, a combustion section 20, a turbine section 22 which drives both the fan assembly 12 and the compressor 18, and a jet pipe 24 complete with afterburning means 26.

In the embodiment shown, the engine has selectively alternative discharge nozzles in the form of a pair of side mounted rotatable nozzles 28 and a conventional axial nozzle 30. The by-pass duct casing 32 is formed with port and starboard alternative flow outlets 34 which communicate with respective port and starboard side nozzles 28. The side ports 34 are formed in the by-pass duct casing 32 downstream of the turbine exhaust section 22 and confront corresponding port and starboard alternative flow outlets 36 formed in jet pipe 24. Adjacent the side outlets 34 and 36 there is provided a diverter valve means 38 for selectively directing core and by-pass flows, depicted by arrows A and B respectively, either exclusively to the rotatable nozzles 284. or exclusively to the axial nozzle 30.

Referring now to Figure 4 which shows in detail the diverter valve 38 in half sectional view. In the embodiment shown diverter valve 38 comprises a two part sleeve valve 40, a segmented jet pipe blocker valve 42 and a first bypass blocker valve 44.

Sleeve vale 40 comprises a pair of axially moveable sleeve members 48,50 disposed within the bypass duct 16 about engine axis 52. Each sleeve member 48,50 comprises coaxial inner and outer cylindrical wall elements 54,56 which lie adjacent jet pipe 24 and duct casing 32 respectively. Wall elements 54,56 are spaced apart so as to define an annular passageway 58 therebetween. The wall elements are separated by means of a plurality of circumferentially spaced-radial supports 60 best seen in Figure 2.

In the axial thrust configuration shown, sleeve members 48,50 extend in abutting relationship over the side outlet ports 34,36 so as to prevent engine gases discharging to nozzles 28. As shown, the downstream sleeve member 48 has an upstream end portion 62 which has a reduced annular section. In this configuration end portion 62 extends into the downstream end of sleeve 48 to define Inner and outer annular gaps 64,66. A sealing ring 68 is provided to seal the outer annular gap 66 between the overlapping sleeves 48,50, and an annular spring element 70 is similarly provided to seal the inner gap 64. In addition, an annular spring element 72 is provided at the periphery of each side outlet 36 to prevent leakage of jet pipe flow into bypass duct 16.

The jet pipe blocker 42 of diverter valve 38 is of a generally well know type and is best described with reference to both Figures 2 and 4. As shown the valve comprises an annular array of segmented elements 74 which are each pivotally mounted at their wider end 76 to the upstream end of sleeve 48 at pivot 78. Each element 74 Is pivotally connected to a link element 80 at an intermediate position 82. Link elements 80 are themselves each pivotally connected to the jet pipe at 84 about an axis radially offset from pivot 82. The segmented elements 74 and link elements 80 are arranged such that in the stowed configuration of Figure 4 elements 74 lie flat against sleeve 48 and jet pipe 24, whilst in the deployed configuration of Figure 2 they extend radially inwards towards engine axis 52.

Bypass valve 44 of diverter valve 38 also comprises an annular array of segmented elements 86. As shown in both Figures 2 and 4, each of the elements 86 Is pivotally mounted to the downstream end of sleeve 50 at pivot 96. The wider end 88 of each element is provided with a roller element 90 which defines a cam follower means. The roller element 90, which is spaced apart from pivot 96, engages a cam track 92a formed in the inner surface 94 of the bypass duct casing 32. The cam track 92a extends axially along the duct casing 32 between side outlet 36 and apex 96 of inclined surface 98 formed therein. The narrower end 100 of each element 86 is free and is spaced apart from pivot 96 by an amount equal to or greater than the radial depth of annular passageway 58.

In a similar manner to segmented elements 74 of jet pipe blocker 42, elements 86 lie flat against sleeve 50 when in the stowed configuration of Figure 4, and extend radially inwards, towards jet pipe casing 24, when in the deployed configuration of Figure 2.

Preferably, diverter valve 38 further comprises a second by-pass valve 46 which is operative to control the by-pass flow upstream of side outlets 34,36. In this the preferred embodiment, the construction of by-pass valve 46 is identical to that of by-pass valve 44, and as such identical reference numerals have been used throughout.

In this embodiment, the profile of cam track 92b of valve 46 is different to that of cam track 92a of valve 44. In contrast to cam track 92a, cam track 86b extends between apex 102 of inclined surface 104 and apex 106 of inclined surface 108 so as to define a U-shaped cam profile.

Referring now to Figure 3 a plurality of actuator means 110 are provided for effecting independent axial translation of each of the sleeve members 48,50. Actuators 110 are each anchored at one end to bypass duct casing 32 and at the other to the respective sleeve member 48,50. Preferably four actuators are provided per sleeve for effecting even loading when energised. The actuators may be each located within an aerodynamic housing defined by radial supports 60, and thereby minimise pressure losses in bypass duct 16.

In the configuration of Figure 4 the diverter valve 38 acts to maintain separate jet pipe and bypass flows A and B which respectively comprise fan discharge air and turbine exhaust gases. In this configuration the coaxial flows are both discharged to atmosphere by nozzle 30 to generate forward thrust. In this mode additional thrust may be generated by supplying additional fuel to afterburning means 26 for combustion within jet pipe 24.

Figure 5 shows the diverter valve 38 in the VTOL operating configuration. In this configuration sleeve members 48,50 are translated in axially opposing senses from the positions occupied in Figure 4 by energisation of actuators 110. The translation of sleeves 48,50 causes the jet pipe blocker valve elements 74 to rotate about pivot 78 to their respective deployed positions, and thereby obturate jet pipe flow duct 24..

Simultaneously elements 86 of valve 44 are caused to rotate about pivot 96 by translation of the respective cam followers 90 over cam track 92a, and thereby obturate the bypass flow duct 16 downstream of side outlets 34,36. Translation of sleeves 48,50 also uncovers the side outlets 34,36 to provide a continuous flow passage from both the fan discharge and turbine exhaust regions to the side mounted discharge nozzles 28.

Referring to Figure 6 which shows the diverter valve in the VTOL configuration of Figure 5 but with sleeve 48 translated in an upstream direction. This additional axial movement causes elements 86 of valve 46 to deploy to the position shown, and thereby restrict the flow area of the bypass duct upstream of side outlets 34,36. Obviously in other applications It may be desirable to obturate the bypass duct 16 upstream of side outlets 34,36, for example if the bypass flow is to be directed elsewhere. In the present embodiment this could be achieve by altering the angle of inclined cam surface 108 such that elements 86 deploy fully as in valve 44.

Figure 7 show the diverter valve in the axial thrust configuration of Figure 4 but with sleeve 48 translated in a downstream direction. Again this additional axial movement causes elements 86 of valve 46 to deploy. Obviously, the axial movement required to translate elements 86 over inclined cam surface 108 determines the extent of axial overlap between sleeves 48,50 at their confronting ends.

Although the invention has been described with reference to a gas turbine engine, it is to be appreciated that the invention is not restricted to such application, but Is applicable to any type of fluid flow duct. Likewise, it Is to be appreciated that the Invention is not restricted to use in fluid flow ducts having coaxial inner and outer flow passageways.

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Claims

A fluid flow duct comprising a generally cylindrical casing having at least one open ended flow passageway defined therein, and at least one valve means for respectively opening and closing the passageway, the valve means comprising an annular array of segmented elements each being pivotally mounted in relation to a moveable cylindrical sleeve member which is disposed coaxially with the casing, there being provided at least one cam means fixed in relation to the casing, whereby translation of the sleeve member from a first to a second axial position effects translation of at least one segmented element over the cam means which causes each of the segmented elements to rotate from a stowed to a deployed position.
2 A fluid flow duct as claimed in claim 1 wherein the cam means comprises a cam surface inclined relative to the duct axis.
3 A fluid flow duct as claimed in claim 2 wherein the cam surface is formed in the duct casing.
4 A fluid flow duct as claimed in any preceding claim wherein the segmented elements are each pivotally connected to a first end of the sleeve member.
A fluid flow duct as claimed in any preceding claim wherein at least one of the segmented elements is provided with a cam follower.
6 A fluid flow duct as claimed In claim 5 wherein the cam follower is spaced apart from the pivot axis of the segmented element.
7 A fluid flow duct as claimed in claims 5 and 6 wherein the cam follower engages a track which extends along the cam surface.
8 A fluid flow duct as claimed in claims 4 to 7 wherein the duct casing comprises a pair of generally cylindrical coaxial wall members which together define inner and outer coaxial flow passageways.
9 A fluid flow duct as claimed in claim 8 wherein a first of the valve means is provided for opening and closing the outer passageway.
A fluid flow duct as claimed in claim 9 wherein a second of the valve means Is provided for opening and closing or partially closing the outer passageway upstream of the first valve.
11 A fluid flow duct as claimed in claims 10 wherein the outer passageway forms the bypass flow duct and the inner passageway the core gas flow duct of a gas turbine engine.
12 A fluid flow duct as claimed in claim 11 wherein each of the cylindrical wall members include at least one side opening axially disposed between the first and second valve.
13 A fluid flow duct as claimed in claim 12 wherein each sleeve member comprises inner and outer cylindrical elements which cooperate with the or each side opening in respective inner and outer wall members to provide a sleeve valve mechanism therebetween for opening and closing the side openings.
14 A fluid flow duct as claimed In claims 11 and 12 wherein in respective first and second axial positions the upstream and downstream sleeve members are respectively in abutment and spaced apart relation.
A fluid flow duct as claimed in claims 10-14 wherein the upstream valve means is provided with a first of the cam means for rotating the segmented elements when the sleeve member is in its first axial position, and a second of the cam means for rotating the segmented elements when the sleeve member is in its second axial position.
16 A fluid flow duct as claimed in claim 15 wherein in respective first axial positions the upstream and downstream sleeve members overlap in sealing engagement, the overlap being sufficient to accommodate the relative axial movement of the upstream member required to move the upstream segmented elements over the first cam means.