Aircraft engine nacelle

A nacelle of an aircraft turbofan engine including an air inlet upstream from the engine, a median section configured to surround a fan of the engine and delimited on the outside by a fan cowl supported by a fan housing to which it is attached at the upstream portion, a downstream section delimiting an annular flow path in which the air is configured to flow and housing thrust reversal devices, the thrust reversal approach including a movable cowl associated with at least one actuator for moving the movable cowl between a direct jet position, in which it provides the aerodynamic continuity of the nacelle and an indirect jet position in which it opens up a passage in the nacelle by uncovering cascade vanes arranged around this flow path that receive the cold air flow to return it towards the outside and forwards, the cascade vanes being attached to the movable cowl.

FIELD

The present disclosure relates to an aircraft engine nacelle including a sliding cascade thrust reverser.

BACKGROUND

An airplane is propelled by one or more propulsion unit(s) comprising a turbojet engine housed in a tubular nacelle. Each propulsion unit is attached to the airplane by a strut generally located under a wing or at the fuselage.

A nacelle generally has a structure comprising an air inlet upstream of the engine, a middle section configured to surround a fan of the turbojet engine, a downstream section accommodating thrust reversal means and configured to surround the combustion chamber of the turbojet engine, and is generally terminated by an ejection nozzle whose outlet is located downstream of the turbojet engine.

The thrust reverser is a device which allows directing the air flow generated by the turbojet engine forwards, allowing both shortening the landing distance and also limiting the stress on the brakes at the undercarriages.

The most modern technologies use bypass turbojet engines; in these turbojet engines, both a hot air flow called primary flow, and a cold air flow called secondary flow are generated via the blades of the fan.

This second flow called cold air flow circulates outside the turbojet engine through an annular passage also called flow path, this flow path being formed between a fairing of the turbojet engine and the inner wall of the nacelle.

In this type of engine, the thrust reverser completely or partially obstructs the cold air flow path, in order to redirect this flow forwardly of the nacelle.

There are several different technologies for making these thrust reversers.

A particularly interesting technology because it reduces the length of the nacelle and consequently limits both the mass of the latter and the drag thereof, consists in designing movable cascade thrust reversers in which the cascades are housed between the casings and the cowl of the fan, during a direct jet operation of the nacelle.

In this type of thrust reverser, the reversal is carried out by translating an outer movable cowl with the cascades which thus come out of their housing and allow the air flow to be redirected forwards.

On such sliding cascade thrust reversers, the outer cowl of the fan, that is to say of the middle section surrounding the fan, is located radially outside the casing of this middle section, the fan cowl being in interface with the fan casing via a front support in the front area.

A downstream end of the fan cowl is, in turn, in interface with an upstream end of the movable cowl of the sliding cascade thrust reverser.

During the deployment of the thrust reverser, the rear edge of the fan cowl is found free (cantilevered) above the cascade vanes. During the closing phase of the thrust reverser, the downstream edge of the fan cowl can then be displaced under the effects of aerodynamic inertia or loading (cascade vanes, external forces, lateral wind) and risks coming into contact either with the cascade vanes, or with the support of the movable cowl.

On the current sliding cascade thrust reversers, the fan cowl is fixed. Fasteners hold the fan cowl on the front support. They remain free at the downstream edge.

However, such apparatuses are used today on nacelles of a substantially reduced size, and the parts are dimensioned so as to use the internal stiffness of the fan cowl to limit the displacements and the unwanted contacts (cascade vanes and support of the movable cowls). These apparatuses cannot be used with large size nacelles.

SUMMARY

The present disclosure falls within the category of movable (sliding) cascade thrust reversers.

The present disclosure provides large size nacelles equipped with a movable cascade thrust reverser device configured so that the movable cowl easily fits into the fan cowl during a passage from the deployed position to the retracted position of the thrust reverser device.

According to the present disclosure, a bypass aircraft engine nacelle is provided. The bypass aircraft engine nacelle comprises an air inlet upstream of the engine, a middle section configured to surround a fan of the engine and delimited externally by a fan cowl supported by a fan casing to which it is fastened in the upstream portion, a downstream section delimiting an annular flow path adapted to circulate the air flow and accommodating thrust reversal devices, the thrust reversal devices comprising a movable cowl associated with at least one actuator to displace the movable cowl between a direct jet position, in which it provides the aerodynamic continuity of the nacelle and an indirect jet position in which it opens a passage in the nacelle by uncovering cascade vanes disposed around this flow path which receive the cold air flow to return it outwards and forwards, the cascade vanes being fastened to the movable cowl and sliding with it, the nacelle being including a series of guide devices distributed about a longitudinal axis of the nacelle, and each including a first guide element secured to the middle section and a second guide element secured to the downstream section.

The term “secured to the middle section or the downstream section” means fastened to the middle section or the downstream section.

Thus, the different guide devices are rigidly connected to each other by the element of the middle section to which they are coupled so that the cohesion of the entire nacelle is reinforced.

More particularly, the first and second guide elements are fastened directly to the middle section and the downstream section respectively.

According to an advantageous version of the present disclosure, at least one of the guide devices at least partially surrounds at least one actuator. Thus, the guiding is carried out compactly.

According to at least one advantageous aspect of the present disclosure, at least one of the guide devices includes a guide element interposed between the fan casing and a portion of at least one actuator.

According to another advantageous aspect of the present disclosure, at least one of the guide devices includes a U-shaped guide shoe carried by the fan casing and an associated U-shaped track, carried by the downstream section.

According to yet other aspects of the present disclosure, taken separately or in combination:

at least one of the guide devices includes an O-shaped guide track associated with the U-shaped guide shoe, and a guide track associated with the O-shaped guide track on a face of the O-shaped guide track opposite to the U-shaped guide shoe;

at least one of the guide devices is dimensioned to provide a locking of the fan cowl and the movable cowl relative to each other for a retracted position of the movable cowl;

at least one of the guide devices is dimensioned to be unlocked after a displacement in a direction of deployment comprised between 1% and 30%, and in one form 20% displacement, of the stroke of the movable cowl;

at least one of the guide devices includes a T-shaped track having a tail engaged between two cascade elements, and a head extending opposite to a flat track carried by the fan cowl;

the nacelle includes at least one device of two distinct types selected from types with a U-shaped track, an O-shaped track, or a T-shaped track;

the nacelle includes two devices of each type;

the nacelle comprises two U-shaped tracks extending in a lower half of the nacelle, two T-shaped tracks extending in a horizontal median plane, and two O-shaped tracks extending in an upper half of the nacelle;

the nacelle includes at least one centering member secured to the movable cowl and extending opposite to a cavity of the fan cowl; and

the centering member is configured to carry out a locking of the fan cowl and the movable cowl relative to each other for a retracted position of the movable cowl.

DETAILED DESCRIPTION

With reference toFIGS. 1 to 4, the nacelle1has a substantially tubular shape along a longitudinal axis Δ. The nacelle1comprises an upstream section2with an air inlet lip3, a middle section4surrounding a fan5of an engine such as a bypass turbojet engine, and a downstream section.

In particular, the middle section comprises a fan casing8surrounding the fan5, the fan casing supporting a fan cowl6, the fan cowl being adapted to be impacted by the external air flow of the nacelle1during the flight.

The downstream section includes at least one movable cowl9including thrust reversal devices. The movable cowls9are linked to cascade vanes10of the thrust reverser and are driven, during the thrust reversal by actuators, here four electromechanical cylinders, regularly distributed about the axis Δ and including rods11having an end13secured to the downstream section, and an engine12fastened to the middle section. During the displacements of the downstream section, the forces are supported by a rail14in the upper portion, in the position commonly called the 12 o'clock position, and a rail15in the lower portion, also called the 6 o'clock position by comparison with a dial of a clock.

According to the present disclosure, the nacelle includes a series of guide devices distributed about the longitudinal axis Δ of the nacelle1. In other words, the guide devices are distributed circumferentially relative to the nacelle, and in one form are evenly distributed. Generally, these guide devices comprise at least one first guide element secured to the middle section and a second guide element secured to the downstream section, the first and second guide elements cooperating with each other to provide a guide link, such as for example a slide link.

Referring now toFIGS. 2 and 5, the nacelle1comprises guide devices16having a first guide element20forming a U-shaped shoe and secured to the fan casing8cooperating with a second guide element19, forming a U-shaped guide track and secured to the structure supporting the cascade vanes, and in particular front and rear frames supporting the cascade vanes.

These guide devices16have a substantially U-shaped guide track are two and are associated with the lower actuators, that is to say to the actuators extending below a horizontal diametrical plane of the nacelle.

Now referring toFIGS. 2 and 6, the nacelle1comprises guide devices17having a first guide element23forming a flat track and secured to the fan cowl cooperating with a second guide element22, forming a complementary inverted U-shaped track and secured to the movable cowl of the thrust reverser.

These two guide devices17have a substantially O-shaped guide track and are associated with the upper actuators, that is to say to the actuators extending above a horizontal diametrical plane of the nacelle1.

Referring now toFIGS. 2 and 7, the nacelle1also comprises guide devices18having a first guide element27forming a flat track and secured to the fan cowl cooperating with a second guide element24, forming a T-shaped track and secured to the front and rear frames supporting the cascade vanes.

These two T-shaped guide devices18are interposed between cascade vanes10in a horizontal diametrical plane of the nacelle and located on each side of the nacelle. Of course, this configuration can be changed depending on the configuration of each nacelle1.

Now referring toFIGS. 1 to 6, the guide devices16have a U-shaped guide track each comprise a U-shaped guide track19which partially surrounds the rod11of an actuator radially under the rod, and whose downstream end, with reference to a gas flow direction for a direct jet position of the thrust reverser device, is fastened to a yoke connected to the engine12of the actuator.

A U-shaped shoe20is fastened to the fan casing8and is in contact with the U-shaped guide track19. In the vicinity of the downstream end thereof, the bottom21of the U-shaped guide track19is curved so as to carry out a locking of the fan cowl6and the movable cowl9relative to each other, by embedding the U-shaped guide track19between the U-shaped shoe20and the fan cowl6, for a retracted position of the movable cowl.

The guide devices17comprise, as previously, a U-shaped guide track19, but this is completed by an inverted U-shaped track22embedded in the U-shaped guide track19to form an O-shaped track which extends opposite to a flat track23carried by the fan cowl6. This O-shaped track is, more generally, a track having a section which has a closed contour, and which completely surrounds the rod11of the actuator, while being substantially concentric relative thereto.

In one form, the guide devices17at least have at least one transition area during the stroke of the movable cowl between its direct jet and indirect jet positions so that, when the movable cowl is displaced to the deployed thrust reversal position, a release of the clearances takes place between the middle and downstream sections.

The transition area is located over a range of about 1 to 30% of the stroke of the movable cowl taken from its direct jet position, and in another form between 1% and 20%. In yet another form, this transition area is an intermediate area located between a proximal area and a distal area.

Now referring toFIGS. 2-4 and 8, the proximal area correctly engages the movable cowl in the fixed cowl: this area is located at the start of the stroke of the movable cowl when it is opened, that is to say at the end of the stroke when it is closed. In other words, it is located on an area close to the closed position of the thrust reverser, i.e. to the direct jet position. This proximal area corresponds to a range of about 0 to 2% of the stroke of the movable cowl taken from its direct jet position, and in other forms in the range of 1%. The stroke of a movable cowl between its direct jet and indirect jet positions being in the range of 500 mm, this area is reduced to substantially a few millimeters, this for allowing the proper engagement of the movable cowl, in particular of the centering members28in cavities29.

The distal area reduces the contacts on the one hand, between the cascade vanes and a diverting edge, and on the other hand, between the cascade vanes and the movable cowl, the clearance being able to be quite different depending on the dimensions and configurations of the nacelles, as for example depending on the line thickness of the nacelle or the relative positions between the parts. This area is located after the intermediate transition area up to 100% of the stroke of the movable cowl taken from its direct jet position. During this stroke, the clearance released during the transition phase is maintained substantially constant while reducing the aforementioned contacts.

During the stroke of the movable cowl in the proximal area, the radial clearances between the parts are substantially on the order of millimeter, it is an area of the stroke of the movable cowl where the guiding should be relatively fine to allow the accurate closure of the movable cowl without difficulties while allowing the centering of the movable cowl. When the stroke of the movable cowl then enters the transition area, the clearances are thus released, to reach between 3 and 10 times the value of the clearance in the direct jet position, and in numerous forms between 5 and 10 times this value. In this example, the radial clearances thus increase up to about 10 mm to then maintain a similar clearance up to the indirect jet position of the transition area until the end of the stroke, after having traveled the distal area.

In at least one form, the guide devices17form a ramp along this transition area which extends over a length comprised between 1% and 30%, and in some forms 20%, of the stroke of the movable cowl taken from its position direct jet. This ramp has an inclination so that, when the movable cowl is displaced to the deployed thrust reversal position, a release of the clearances takes place between the middle and downstream sections. This inclination advantageously has a slope between 0.5 and 5%, and in at least one form about 1%.

Referring toFIGS. 2-4 and 7-8, the guide devices18comprise a T-shaped track24having a tail35engaged between two cascade vanes10, and a head26extending opposite to a flat track27carried by the fan cowl6.

Now referring toFIGS. 3-4 and 8, the guide devices are configured, in particular from the point of view of the clearances between the different components, to be active in the transit position or in the total thrust reversal position. In order to provide a centering of the fan cowl portions relative to each other when the thrust reverser is in a direct jet position, the nacelle includes centering members28fastened to the front end of the movable portion and extending axially in cavities29at the periphery of the downstream edge of the fan cowl. In order to allow a centering without blocking the fan cowl and the movable cowl relative to each other when the actuators are in abutment, the centering members are mounted with an axial clearance30and a radial clearance31of a few millimeters.

Of course, the present disclosure is not limited to the described forms and is capable of further variants without departing from the scope of the present disclosure as defined by the claims.

In particular, although the device according to the present disclosure has been described with reference to a variation according to which the guide devices surround the actuators, the present disclosure concerns a nacelle equipped with guide devices regardless of the location of these devices.

Although the present disclosure has been described with reference to a nacelle including guide devices of different types, the present disclosure can be carried out with guide devices of a single type.