A blocker door for a gas turbine engine thrust reverser having a tray with a base and sidewalls extending about the base to define a volume, the volume being closed by a cover that extends beyond the periphery of the tray. The extension of the cover beyond the periphery provides a sealing feature.

TECHNICAL FIELD OF INVENTION

The invention relates to thrust reverser arrangements for a gas turbine engine and in particular a cascade thrust reverser.

BACKGROUND OF INVENTION

Thrust reversers are provided on a gas turbine engine to selectively alter the direction of the fan flow from the engine. The thrust reversers are typically deployed on landing to decelerate an aircraft.

One type of thrust reverser is known as a cascade thrust reverser that has an array of cascade boxes downstream of a fan casing that are deployed by an axial rearward translation of a cowl that causes blocker doors to rotate from a stowed position to their deployed position and direct the engine air through the cascade.

Engine efficiency is driven partly by the amount of air loss that could otherwise be used to generate thrust and it is an object of the invention to seek to provide an improved thrust reverser arrangement that limits these losses when the thrust reverser is not deployed.

STATEMENTS OF INVENTION

According to a first aspect of the invention there is provided a blocker door for a gas turbine engine thrust reverser having a tray with a base and sidewalls extending about the base to define a volume, the volume being closed by a cover that extends beyond the periphery of the tray, wherein the extension of the cover beyond the periphery provides a sealing feature.

The tray may be rectangular, trapezoidal or combination with chamfered sides, in plan and is preferably formed of a metal or more preferably a composite, made up of a plurality of resin impregnated plies of carbon or glass fibres.

Preferably the tray further comprises a flange extending from the sidewalls to which the cover is joined, the cover extending beyond the periphery of the flange. The flange may extend outwardly or inwardly from the sidewalls. Preferably the flange is integral with the sidewalls.

The cover which faces the bypass duct is preferably a moulded rubber directly bonded or mechanically fastened to the flange or sidewalls. The rubber offers the advantage that it can have a flexibility that can be used to seal with another part of the engine when the blocker door is stowed or deployed.

The cover may be perforated for acoustic lining purpose. Preferably the volume contains an acoustic liner. Preferably the acoustic liner is a honeycomb.

Preferably the sealing feature is a flat (“lip”) seal, or a P or omega seal.

According to a second aspect of the invention there is provided a thrust reverser unit for a gas turbine comprising a cowl having an inner surface and a blocker door according to any of the preceding seven paragraphs, wherein the sealing feature seals against the inner surface of the cowl when the blocker door is in a stowed position.

Preferably the inner surface has a land and a depression, the tray being located in the depression and the sealing feature sealing against the land.

The inner wall may have a plurality of depressions, each depression locating a respective tray. The inner wall may have a land between adjacent depressions.

Preferably the cowl is translatable from an axially forward stowed position to an axially rearward deployed position.

The thrust reverser may further comprising a linkage connecting the blocker door with the cowl, the linkage arranged such that translation of the cowl from the stowed position to the deployed position effects employment of the blocker door from a stowed position against the inner surface of the cowl to a deployed position across a gas turbine bypass duct.

In a deployed position the sealing feature of a first blocker door may abut a sealing feature of a second blocker door.

DETAILED DESCRIPTION OF INVENTION

Referring toFIG. 1, a ducted fan gas turbine engine generally indicated at10has a principal and rotational axis11. The engine10comprises a propulsive fan13and a core engine9having, in axial flow series, an air intake12, an intermediate pressure compressor14, a high-pressure compressor15, combustion equipment16, a high-pressure turbine, an intermediate-pressure turbine18, a low-pressure turbine19and terminating with a core exhaust nozzle20. A nacelle21generally surrounds the engine10and defines the intake12, a bypass duct22and an exhaust nozzle23.

The compressed air exhausted from the high pressure compressor15is directed into the combustor16where it is mixed with fuel and combusted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low-pressure turbines17,18,19before being exhausted through the nozzles20to provide additional propulsive thrust. The high, intermediate and low pressure turbines17,18,19respectively drive the high, intermediate pressure compressors15,14and the fan13by suitable interconnecting shafts.

A centre plug29is positioned within the core exhaust nozzle20to provide a form for the core gas flow A to expand against and to smooth its flow from the core engine. The centre plug29extends rearward of the cone nozzle's exit plane27.

The fan is circumferentially surrounded by a structural member in the form of a fan casing24which is supported by an annular array of outlet guide vanes28. The fan casing24comprises a rigid containment casing25and attached rearwardly thereto is a rear fan casing26.

The gas turbine engine10is installed under an aircraft wing7via a pylon8. The nacelle21comprises an axially forward cover35(fan cowl) and a translatable cowl37. Both the cover and the cowl are provided by C-shaped openable doors with each door being separately hinged to the aircraft pylon8. The nacelle has a thrust reverser unit31which is formed from a number of cascade panels arranged sequentially around the circumference of the engine10. The hinged doors permit access to the engine core for maintenance or inspection purposes.

FIG. 2depicts the open nacelle21has hinges positioned at the top of the engine or on the pylon and which permits each part of the C duct defined by the cover35, the translating cowl37and inner fixed structure40to rotate away from the engine to permit access thereto. Both the cowl and the cover35can pivot away from the engine. The thrust reverser unit31is mounted to the cover and can pivot away from the engine with the cover.

The cowl37is provided with an axially forward tongue60which is formed of two parts60aand60bextending from each of the two doors forming the translatable cowl. The cover35has a recess which engages the tongue when the cowl and cover are closed to provide a streamlined external surface for the nacelle.

This is shown inFIG. 3where the nacelle is closed in an in-flight position. The translatable cowl is in its stowed position such that the cowl abuts the axially forward cover. translatable thrust reverser unit is in an axial forward position in contrast toFIG. 4, where the unit has been deployed rearwardly to open the cascades41. As shown inFIG. 4the tongue60in the deployed position of the cowl is aligned with the axial position of the cascade. Advantageously, this negates the need for a blanking cascade panel to be provided in the cascade in order to inhibit the flow of thrust reverser air radially towards the ground. However, it is possible to provide an appropriate cascade panel with or without the use a cowl that does not have a tongue arrangement. Where a tongue is used it can be provided with a radially inner form that turns the air towards the front of the engine. In both these figures the tongue60is located 180 degrees from the pylon (not shown) and is located on the underside of the engine.

FIG. 5is a partial cross section through the cascade and cowl arrangement ofFIG. 3. The cowl37has a bifurcated fairing that has a radially outer wall62that forms an airwashed surface for the external surface of the nacelle and a radially inner wall64that forms an airwashed surface for the bypass duct22. A blocker door39is located against the radially inner surface of the radially inner wall64in the stowed position with the inner wall of the fairing providing additional support for the blocker door against the pressures of the flow through the bypass. The inner wall is stepped66to enable the blocker door to be recessed in the stowed position in order to provide a streamlined surface. A frame68joins the radially inner and outer walls (64,62).

Between the inner and outer walls there is a cavity70within which the cascade41is located. When the cowl is in the stowed position ofFIGS. 3 and 5the cascade is isolated from the main flow through the bypass duct by the blocker door39and the radially inner wall64of the fairing. In addition, any leakage flow through either of these parts is inhibited from leaving the engine by the radially outer wall62of the cowl which seals against the cover35. Any parasitic air flows inside the cavity70reduces the performance of the powerplant and therefore it is imperative to reduce them to minimum.

The cascade41comprises an arrangement of vanes that are designed to turn a flow of air from the bypass duct when the cowl is translated to its open position towards the front of the engine to provide the reverse thrust relative to the normal direction of thrust generated by the engine. The cascade is assembled as a series of panels each of which provides a segment of the circumference of the thrust reverser.

InFIG. 6the cowl37is shown in its deployed position which is axially rearward of the stowed position. The blocker doors39are connected to the trans cowl via hinges (for axial translation of the blocker doors) and by linkages to the inner fixed structure (for rotation of the blocker doors) to direct the bypass flow through the cascades where the flow is turned in a forward direction and through a passage opened in the outer wall of the nacelle by the axially rearward movement of the outer wall. The flow of air through the cascade is shown by the arrows B and C.

FIG. 7is a perspective view of the blocker doors39arranged in their stowed position. Each door has a generally trapezoidal form which is mounted within a correspondingly shaped depression in the inner wall64of the translatable cowl. By locating the blocker doors in respective depressions it is possible to the blocker doors and inner wall to together provide a streamlined outer wall for the bypass duct22.

InFIG. 8the blocker doors are deployed following translation of the cowl. The axially rearward and narrower end of the door rotates inwards till the edges abut the edges of the adjacent and neighbouring doors to provide the barrier that deflects the air flow from the bypass duct through the thrust reverser cascade.

The leakage, parasitic flow in cavity70, past the stowed blocker panels can reduce the overall efficiency of the engine and it is desirable to minimise this leakage. The blocker panels are formed as an assembly including a backskin100, an internal support material102(honeycomb) and an air-washed facing sheet104.

As shown inFIG. 9, the backskin is moulded or otherwise formed into a tray having a base106, side walls108, and a flange110which protrudes from the side walls. The backskin is formed of metal or, more preferably, a composite material which may be formed of a laminate of individual plies of carbon or glass fibres held within a resin matrix. The flange extends around the periphery of the tray and provides a surface to which the facing sheet can be joined.

The tray is filled with the internal support material that provides rigidity to the blocker doors so that on deployment into the gas flow when reverse thrust is required the doors can withstand the high force of the flow. The support material is preferably in the form of a honeycomb, which, when combined with perforated facing sheet104, contributes to a noise insulation lining as well as providing the required strength.

The tray is closed with a facing sheet104, bonded or otherwise secured to the flange110. The facing sheet has some flexibility and is preferably formed of a rubber or other elastomeric material that can be perforated to allow a small flow of air into and out of the tray that assists with the acoustic damping.

By making the facing sheet104from elastomeric material or rubber and making the rubber sheet protrude beyond the periphery of the flange to provide a “lip” seal portion112and in the stowed position seals against the inner wall64of the translatable cowl and against the cascade support structure43along its and beneficially all edges. The pressure of the air in the bypass duct forces the seal against a land on the inner wall of the cowl.

In the deployed position the flexible rubber sheet seals against the core engine fairing40at its radially inner edge, against abutting blocker doors along its side edges.

The seal is enhanced by the pressure in the bypass duct which presses the seal against the inner wall of the cowl in use to further limit the parasitic flow of air past the seal.

Although the seals have been depicted and described here as flat (“flip”) seals it will be appreciated that other forms of seals e.g. P or Omega seals that have a shaped end may also be used.FIG. 10depicts an alternative arrangement, where the inner wall64has a step to provide a ledge114that supports the seal. The “omega” seal116has an elongate portion117and as bulbous portion118integrally moulded together. Advantageously, sealing is improved by providing two seal locations: the first against the ledge on the land, the second against the side of the depression120in the inner wall64. The choice of material, material thickness and/or shape112&118and its programmed hardness for the facing sheet can also be selected to achieve the desired functionality for the seal. Additionally, because the cover is formed of a thermoplastic or thermosetting resin or rubber material it is possible to provide this as a moulded construction with graded material and/or functional properties. Advantageously, the periphery of the cover that seals against the outer wall of the bypass duct may therefore be formed to be more rigid or more flexible than the inner section of the cover which secures the cover to the tray.

If the facing sheet is formed of a fire resistant material the use of the blocker doors as a fire barrier is enhanced.

Access to the core engine and associated accessories is achieved by deploying the thrust reverser unit and/or rotating open the translating cowls. The core fairing40, which is hinged independently, is then rotated open. Alternatively, individual panels may be provided and readily removed.