GB2256175A

GB2256175A - Thrust reverser for high bypass ducted fan gas turbine engine.

Info

Publication number: GB2256175A
Application number: GB9111691A
Authority: GB
Inventors: Norman Roberts
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1991-05-31
Filing date: 1991-05-31
Publication date: 1992-12-02
Also published as: GB9111691D0

Abstract

A thrust reverser comprises a plurality of blocker doors 26 disposed circumferentially about a cowl 18 which defines a duct 22 of a gas turbine engine. The blocker doors 26 are pivotally mounted to actuators 32 attached to an upstream portion 17 of the cowl 18. The blocker doors 26 are displaced between a retracted position, in which they form a continuation of the cowl 18 and do not impede the flow of air through the duct 22, to an operative position in which the blocker doors 28 are substantially transverse to the duct 22 to redirect the flow of air forwards. The inner surface 25 of the blocker doors 26 are provided with a plurality of recesses 28 which extend in a direction parallel to the flow air therethrough. The recesses 28 increase the surface area of the blocker doors 26 increasing the effective flow area of the thrust reverser. A deflector plate 30 at the forward edge 29 of each blocker door improves the forward deflection of air when the doors are operative. <IMAGE>

Description

THRUST REVERSER The present invention relates to a thrust reverser and in particular to a thrust reverser for a gas turbine engine.

Ducted fan gas turbine engines are well known and typically comprise a core engine having an exhaust duct, through which the exhaust gases from the core engine flow. A bypass duct is located concentrically about the core engine and is defined by a cowling which is spaced from the core engine by a plurality of struts. A large diameter fan typically mounted on the front of the core engine directs air through the bypass duct to increase the performance characteristics of the engine.

With engines which have a high bypass ratio ie. the quantity of air flowing through the bypass duct is large compared to the quantity of gas flowing through the exhaust duct of the core engine, it is sufficient to apply a thrust reverser to the flow in the bypass duct. The thrust reverser acts to redirect the flow of air from the fan forwards, thus applying a deceleration force to the engine. It is not necessary to reverse the flow of exhaust gases from the core engine as the majority of the engine thrust is derived from the flow through the bypass duct.

A typical thrust reverser arrangement comprises a number of blocker doors pivotally mounted to an upstream portion of the cowling. The blocker doors can be displaced between a retracted position in which they form a continuation of the cowling and do not impede the flow of air through the bypass duct, to an operative position in which the doors block the bypass duct to redirect the flow of air forwards.

A problem with this type of thrust reverser is that when the blocker doors are deployed to the operative position it is difficult to provide sufficient surface area to redirect the gas from the bypass duct. The effective flow area of the thrust reverser is limited by the surface area of the door which is available to redirect the air flowing through the bypass duct.

The present invention seeks to provide blocker doors which increase the operating effective flow area of the thrust reverser then they are deployed into the operative position.

According to the present invention a thrust reverser for a gas turbine engine having an at least one duct through which exhaust gases operationally flow comprises a plurality of doors disposed circumferentially about an outer wall of the duct, each door having an inner and an outer surface, the doors being mounted for pivotable movement from a retracted position in which the outer surface of the doors form part of the outer wall of the duct, the doors causing substantially no blockage to the flow of gas through the bypass duct, to an operative position in which the doors lie substantially transverse to the duct to cause substantially complete blockage of the duct, the inner surfaces of the doors deflecting the exhaust gases forwards, said inner surfaces being provided with a plurality of recesses which extend in a direction parallel to the flow of gas therethrough so as to increase the effective flow area of the thrust reverser when the doors are in the operative position.

The thrust reverser may be provided with deflector plates which are attached to the upstream edges of each of the doors, a portion of each of the deflector plates extends radially inward beyond the inner surface of the door to direct the gas flow in a more forward direction, the recesses in the inner surface of each of the doors are arranged to direct the gases to impinge upon the deflector plates.

The present invention will now be described with reference to the accompanying drawings in which, Figure 1 is a diagrammatic view of a gas turbine engine incorporating a thrust reverser in accordance with the present invention.

Figure 2 is a cross sectional view of part of a thrust reverser in accordance with the present invention, showing a blocker door in the retracted position during normal operation.

Figure 3 is a cross sectional view of part of a thrust reverser in accordance with the present invention, showing a blocker door in the operative position when thrust reversal is required.

Figure 4 is a pictorial view of a blocker door in accordance with the present invention.

Figure 5 is a cross sectional view of the blocker door in figure 4 along line I-I Referring to figure 1 a gas turbine ducted fan engine 10 comprises a core gas turbine engine 12 having an exhaust duct 14 and a stage of fan blades 16 mounted at its upstream end. A cowl 18 is located concentrically about the core engine 12. The cowl 18 is spaced from the core engine 12 by a plurality of struts 20 to define an annular duct 22, known as the bypass duct through which a flow of air from the fan blades 16 passes.

A plurality of openings 24, shown in figure 3, are provided in the cowl 18, through which the bypass air is redirected when thrust reversal is effected. A number of blocker doors 26 , one for each of the openings 24 are provided for effecting thrust reversal. The blocker doors 26 are pivotally mounted from actuating mechanisms 32 which are attached to the upstream portion 17 of the cowl 18. In the preferred embodiment of the present invention the actuating mechanisms which move the blocker doors 26 are hydraulic actuators 32. The hydraulic actuator 32 may be of conventional type such as a power cylinder having an extensible and retractable piston rod connected to the blocker doors 26 in known fashion. The blocker doors 26 and the actuating mechanism 32 are integral with the cowl 18.

In normal operation, referring to figure 2, the blocker doors 26 obstruct the openings 24 in the cowl 18. The outer surface 27 of the blocker door 26 is flush with the outer surface 19 of the cowl 18 to provide continuity of the cowl 18. Air passes through the bypass duct 22 in the direction of arrow A. The air exhausts adjacent the exhaust duct 14 of the core engine 12 to increase the performance characteristics of the engine.

When thrust reversal is required the doors 26 are pivoted to the position shown in figure 3 in which they lie substantially transverse to the bypass duct 22. The inner surface 25 of the blocker door 26 deflects the fan air flow passing through the bypass duct 22 in the direction of arrow A. The air flows to atmosphere through the opening 24 in the cowl 18. The air is directed forwards by the inner surface 25 of the blocker doors 26 to give a deceleration force.

The inner surface 25 of each of the blocker doors 26 are provided with a plurality of recesses 28 shown in figure 4. The recesses 28 increase the surface area of the inner surface 25 of each of the blocker doors 26 so that more of the fan air is redirected through the openings 24 in the cowl 18 when the blocker doors are deployed to the operative position. The recesses 28 extend in a direction parallel to the flow of air passing through the bypass duct 22 to minimise the disturbance to the flow of air through the bypass duct when in the stowed position whilst giving the redirected flow a forward component of velocity when deployed to the operative position.

In order to further increase the effectiveness of the thrust reverser deflector plates 30 may be attached to the upstream edges 29 of the blocker doors 26. The deflector plates 30 protrude radially inwards beyond the inner surface 25 of the blocker door 26 so as to direct the air flow in a more forward direction when in the operative position. The recesses 28 in the inner surface 25 of the blocker doors 26 are arranged to direct the air so that it impinges upon the deflector plates 30.

Although the present invention has been described with reference to a thrust reverser in a ducted fan engine it will be appreciated to one skilled in the art that it is applicable to any thrust reverser which utilises blocker doors.

Claims

Claims:

1. A thrust reverser for a gas turbine engine having at least one duct through which exhaust gases operationally flow, the thrust reverser comprising a plurality of blocker doors disposed circumferentially about an outer wall of the duct, each blocker door having an inner and an outer surface, the blocker doors being mounted for pivotable movement from a retracted position in which the outer surface of the blocker doors form part of the outer wall of the duct and the blocker doors cause substantially no blockage to the flow of gas therethrough, to an operative position in which the blocker doors lie substantially transverse to the duct to cause substantially complete blockage of the duct, the inner surfaces of the blocker doors deflecting the exhaust gases forwards, said inner surfaces being provided with a plurality of recesses which extend in a direction parallel to the flow of gas therethrough so as to increase the effective flow area of the thrust reverser when the doors are in the operative position.

2. A thrust reverser as claimed in claim 1 in which deflector plates are attached to the upstream edges of each of the blocker doors, a portion of each of the deflector plates extending radially inward beyond the inner surface of the blocker doors to direct the gas flow in a more forward direction, the recesses in the inner surface of each of the blocker doors being arranged to direct the gases to impinge upon the deflector plates.

3. A thrust reverser as claimed in any preceding claim for use in a ducted fan gas turbine engine.

4. A thrust reverser as hereinbefore described by way of example and with reference to figures 1-5.