WO2015101758A1

WO2015101758A1 - Thrust reverser of a turbofan engine nacelle comprising sliding and pivoting gratings

Info

Publication number: WO2015101758A1
Application number: PCT/FR2015/050001
Authority: WO
Inventors: Patrick Gonidec; Olivier Kerbler
Original assignee: Aircelle
Priority date: 2014-01-02
Filing date: 2015-01-02
Publication date: 2015-07-09
Also published as: FR3016006A1

Abstract

A thrust reverser of a turbofan engine nacelle, comprising movable covers (4) that retract relative to a fixed front structure (10) to expose openings radially towards the outside, and rotary gratings (12) linked to the front structure by pivots (48) which, when said covers open, pivot in the annular passage, partially closing it and returning the flow, via the openings, towards the front, characterised in that, when the covers (4) are closed, the rotary gratings (12) are at least partially contained in the front structure (10), the reverser comprising guide means (44) that move said gratings backwards, in addition to the pivoting of same, when the covers are opened.

Description

Turbojet engine nacelle thrust reverser comprising sliding and pivoting grilles

The present invention relates to a thrust reverser for an aircraft nacelle receiving a turbojet, and an aircraft nacelle equipped with such a thrust reverser.

The motorization assemblies for the aircraft generally comprise a nacelle forming an outer envelope generally of revolution, comprising inside a turbojet arranged along the longitudinal axis of this nacelle. The turbojet engine receives fresh air from the upstream or front side, and rejects on the downstream or rear side hot gases from the combustion of fuel, which give a certain thrust.

The turbofan engines have around this turbojet fan blades generating a large secondary flow of cold air along an annular vein passing between the engine and the nacelle, which brings most of the thrust on the aircraft. civil transport.

Some nacelles comprise a thrust reversal system that closes at least part of the annular cold air duct with shutters, and redirects the secondary flow forward by passing through blade grids to generate thrust. braking of the aircraft.

A known type of thrust reverser, presented in particular by the document FR-A1-2987080, comprises rear mobile covers called "Trans-cowl", sliding axially backwards under the effect of cylinders by deploying grilles initially integrated in these hoods. During the opening of the movable covers, the grids are deployed by a simple rotation in the annular channel to partially close, and deflect the airflow radially outward through the openings released by these covers. This principle replaces the shutters and fixed grids commonly used in standard grid inverters, with rotating grids acting both as shutters and as fixed grilles.

With this type of inverter, an annular vein is obtained which does not contain a closure flap equipped with rods which traverse radially this vein, generally intended to control them, which improves the efficiency with the direct jet stream which is the flight position of the nacelle. In addition, mass gains are achieved, particularly for large diameter annular veins.

However, this type of inverter poses problems of integration of the structure comprising the grids which are relatively long, in the mobile hoods when these hoods are closed, particularly if one wants to maintain a high-performance aerodynamic profile of the hoods. Moreover the surface of these covers that can be treated acoustically, can be limited by long grids that interfere with him, which does not optimize the acoustic performance.

The present invention is intended to avoid these disadvantages of the prior art.

To this end, it proposes a thrust reverser of a turbojet turbojet engine nacelle, comprising movable cowls which recoil with respect to a fixed front structure to disengage radially outward openings, as well as rotary grilles connected to the engine. front structure by pivots, which when opening these covers pivot in the annular vein by partially closing and returning the flow through the openings to the front, the rotating grids are when the covers are closed, contained at least partly in the front structure, the inverter comprising guiding means, when opening the covers, a displacement of these grids rearward in addition to the pivoting, characterized in that cap control means are connected to the grids by links having joints.

An advantage of this thrust reverser is that thanks to the rearward movement of the grids which is added to their rotation, these grids can be housed at least partly in the structure in front of the hoods, which reduces the space taken in these hoods and facilitates their drawing. In addition, by providing control means hoods connected to the grids by connecting rods with joints, it is possible, from a sliding back of these control means, follow the pivoting of the grids. The thrust reverser according to the invention may further comprise one or more of the following features, which may be combined with one another.

Advantageously, the pivots of the grids are connected to the fixed front structure by sliders arranged substantially longitudinally. Thus, a linear guiding guide means that is simple and effective.

In particular, the guide means may comprise shapes ensuring first a sliding back of the grids before pivoting.

According to one embodiment, the guide means comprise a cam guiding the movement of the grids. One can thus easily choose by adapting the cam profile, the movement kinematics grids.

The cam may in particular comprise a substantially rectilinear portion disposed longitudinally, ending at the rear by a curve turned radially outwards, ensuring the pivoting of the grids.

The grids may include a support means on the cam, which is disposed radially outside the pivot, and in front of this pivot.

Advantageously, the covers being closed, the grids are integrated substantially entirely in the fixed front structure. This releases all the space in the sliding cover of the inverter, which reduces the drag of the nacelle by optimizing the aerodynamic lines of its rear part.

In particular the thrust reverser may comprise a low to moderate reversal efficiency, which is of the order of 10 to 35%. This level of efficiency is well suited for large diameter nacelles with a high dilution rate with a high secondary flow rate.

The invention also relates to a turbojet engine nacelle comprising a thrust reverser comprising any one of the preceding features.

The invention will be better understood and other features and advantages will emerge more clearly on reading the following description given by way of example, with reference to the appended drawings in which: - Figure 1 is a view of a thrust reverser according to the prior art, simply rotatable grid;

FIG. 2 is a diagram showing a deflection of the thrust reversal flux for an inverter according to the invention; and

FIGS. 3a, 3b and 3c are diagrams in axial section of a thrust reverser according to the invention, successively presented in the closed position, with the hoods being opened, the grids being moved backwards, and with the hoods fully open; the grids having finished their rotations.

FIG. 1 shows the rear part of a turbojet engine nacelle, the rear axial direction being indicated by the arrow "AR", comprising a fixed front structure 10 surrounding an internal structure 2, and movable covers 4 fitted behind this structure when they are closed.

In particular, one can have a single cover 4 forming a complete turn, or two half-covers each forming a half turn. A rear ferrule 16 is disposed behind the movable covers 4.

Each cover 4 is connected to the front structure 2 by longitudinal guiding means comprising rails 6, which allow sliding of these covers rearwardly controlled by jacks 8, to open the passage of the secondary flow radially outwards .

Thrust reversal grids 12 each forming an angular sector, comprising a series of profiled vanes, have a front end connected by a pivot arranged tangentially to the front structure 10, and a rear end connected by a connecting rod 14 to the hoods 4 .

The retreat of the covers 4 causes by a movement of the links 14, a rotation of the grids 12 which partially close the passage of the flow backwards, to send the flow forward through the openings released by these covers.

Thus, a simple movement of the thrust reversal grids 12 is carried out. However, these grids 12 are housed in the moving hoods 4 when they are closed, which prevents the design of hoods comprising an aerodynamic profile having a thin thickness. In addition the covers 4 are then relatively long, which increases the drag of the nacelle. FIG. 2 shows the principle of deflecting the cold air flow coming from upstream 20 by rotary grids 12, allowing a direct flow 22 corresponding to a leak rate which can be in particular less than 25 %, especially equal to 15%, and radially outwardly returning an inverted flow 24 at an angle α relative to the transverse direction.

It can be sought in particular to obtain an angle α close to 35 ° to give a sufficient braking thrust, which makes a deviation of the direct flow on average greater than 125 °. The boss formed on the internal structure 2 at the level of the thrust reversal grids 12, causes a certain deflection of the flow radially upstream of the grids which facilitates the holding of this objective of deflection of the flow.

FIG. 3a shows a closed movable hood 4 comprising inside a sound-absorbing coating 46 disposed on the external wall of the secondary vein, this hood being downstream of the grilles 12 completely folded over the fixed front structure 10 forming the housing blower.

Each grid 12 has a base 30 substantially parallel to the axis of the nacelle, supporting a series of profiled blades 32 inclined forward, ending in the rear by a blade thicker. The length of the grids 12 may be in particular of the order of 750 mm, the height of the blades being about 50 mm.

The base 30 of the grids 12 comprises at the front a pivot 48 arranged tangentially in the nacelle, connected to a slider 34 which is guided by a longitudinal axis 36 fixed to the front structure 10.

A connecting piece 38 forms an arcuate structure disposed rearwardly of the grids 12, connecting a plurality of jack rods 8 and several grids therebetween, which slides axially under the effect of these jacks. In particular, it is possible to have a single connecting piece 38 forming a complete revolution of the nacelle, or several parts depending on the number of jacks 8, in order to obtain sufficient rigidity of the assembly ensuring a safe sliding, without any risk of bracing in its guide rails.

At least one link 40 is connected by articulations on one side to the front end of a longitudinal arm returning towards the front of the workpiece. link 38, and the other side to the base 30 of each grid 12, a little above and behind their pivot 48.

The base 30 of the grids 12 is extended in front of the pivot 48, by an arm terminating in a wheel 42 which bears under a cam 44 comprising an axial rectilinear part, ending towards the rear by a turned flare outwards.

The operating principle of the thrust reverser according to the invention is as follows.

The recoil of the movable covers 4 controlled by the cylinders 8, shown in FIG. 3b, at the same time causes the grids 12 to retract, the slider 34 being guided by the spindle 36. The spool 42 remaining in abutment on the axial rectilinear part of the cam 44, the grid 12 can not rotate around its pivot 48, it then moves parallel to itself, along the axis of the nacelle.

A little before the end of its stroke, as shown in FIG 3b, the wheel 42 arrives on the rounded outwardly of the rear portion of the cam 44, which allows clearance of the wheel to the outside, and a tilting of the gate 12 which rotates about its pivot 48 down into the annular vein.

Note that the joints of the rod 40 allow its pivoting, to ensure the connection between the gate 12 which tilts and the connecting piece 38 which continues its axial sliding.

At the end of the opening of the flaps, shown in FIG. 3c, the connecting piece 38 being in its maximum rear position, holds firmly by the link 40 the angular position of the grid 12 which undergoes a large aerodynamic thrust by deflecting the air flow. cold.

This principle of kinematics thus provides a simple way of controlling the grids 12 which are firstly sliding and then pivoting, which allows them to be housed entirely in the fixed front structure 10, and to make movable covers 4 comprising a reduced thickness having a good aerodynamic profile. It will be noted that the space available in the mobile hoods 4 makes it possible to have inside a soundproofing cellular structure 46 which can completely cover their internal surface, which gives a high acoustic level.

Moreover, the number and the position of the links 40 and the axes of rotation can be adapted to optimize the integration in a given nacelle geometry, for example by arranging the links near the plane of symmetry of the grids 12 to increase the lever arm. during movement and in the deployed position. However this provision is at the expense of the stroke of the cylinder necessary for the rotation of the grids.

In addition, the inverter has no shutter flap, or connecting rod permanently through the annular vein to control these flaps, which slow down the flow in direct jet.

This type of inverter is particularly suitable for obtaining a low to moderate inversion efficiency, which can be of the order of 10 to 35%, and for large diameter nacelles comprising a high flow rate in the secondary flow and a large dilution rate. Indeed for these nacelles it is not necessary to use an inverter generating a strong counterpoise with great efficiency, the ground intrinsic drag of the nacelle already contributing a lot to braking. For this type of nacelle it is advisable to optimize the aerodynamic lines in flight by making them the finest and shortest possible, to the detriment of the counterpulse in phase of thrust reversal.

Claims

1 - thrust reverser of a turbofan engine nacelle, comprising movable covers (4) which recede relative to a fixed front structure (10) to disengage radially outward openings, and rotary grilles ( 12) connected to the front structure by pivots (48), which when opening these covers pivot in the annular vein by partially closing and returning the flow through the openings to the front, the rotating grids (12). ) are when the covers (4) are closed, contained at least partly in the front structure (10), the inverter comprising guiding means (44) giving when opening the covers a movement of these grids to the l in addition to the pivoting, characterized in that control means (8) of the covers (4) are connected to the grids (12) by links (40) having joints.

2 - thrust reverser according to claim 1, characterized in that the pivots (48) of the grids (12) are connected to the fixed front structure (10) by sliders (34) arranged substantially longitudinally.

3 - thrust reverser according to any one of the preceding claims, characterized in that the guide means (44) comprise shapes ensuring first sliding back of the grids (12) before pivoting.

4 - thrust reverser according to any one of the preceding claims, characterized in that the guide means comprise a cam (44) guiding the movement of the grids (12).

5 - thrust reverser according to claim 4, characterized in that the cam (44) comprises a substantially straight portion arranged longitudinally, ending at the rear by a curve turned radially outwardly, ensuring the pivoting of the grids (12). ).

6 - thrust reverser according to claim 5, characterized in that the grids (12) comprise a support means (42) on the cam (44), which is arranged radially outside the pivot (48), and in front of this pivot. 7 - thrust reverser according to any one of the preceding claims, characterized in that the covers (4) being closed, the grids (12) are integrated substantially entirely in the fixed front structure (10).

8 - turbojet engine nacelle comprising a thrust reverser, characterized in that the inverter is made according to any one of the preceding claims.