FIELD

The present disclosure relates to a thrust reverser cascade for a nacelle of an aircraft turbojet engine.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

A turbojet engine nacelle generally has a substantially tubular structure comprising an air inlet upstream of the turbojet engine, a middle section intended to surround a fan of the turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and possibly embedding thrust reversal means. In general, the nacelle possibly terminates in an ejection nozzle whose outlet is located downstream of the turbojet engine.

Modern nacelles are intended to accommodate a bypass turbojet engine adapted to generate via the blades of the rotating fan a hot air flow (primary flow) and a cold air flow (secondary flow) which circulates outside the turbojet engine through an annular passage, also called flow path, formed between a fairing of the turbojet engine and an inner wall of the nacelle.

Both air flows are ejected from the turbojet engine at the rear of the nacelle. The role of a thrust reverser, during the landing of an aircraft, is to improve the braking capability of the latter by redirecting forwards at least one portion of the air ejected from the turbojet engine.

During this phase, the thrust reverser obstructs at least one portion of the flow path of the cold flow and directs this flow towards the front of the nacelle, thereby generating a counter-thrust which adds to the braking of the wheels and airbrakes of the airplane.

In general, the structure of a thrust reverser comprises a thrust reverser cowl displaceable between, on the one hand, a reverse jet position in which it opens in the nacelle a passage intended for the diverted air flow and, on the other hand, a direct jet position in which it closes this passage.

In the case of a thrust reverser with cascade vanes, also called thrust reverser vanes or cascades, the reorientation of the air flow is performed by cascade vanes, associated to thrust reverser flaps brought to block at least partially the air circulation flow path, the cowl having only but a sliding function aiming at uncovering or covering these thrust reverser cascades.

In a known manner, the thrust reverser cascades are mounted on at least one end frame transmitting the counter-thrust provided by the bladings to the entire thrust reverser structure which, in turn, is attached to the propulsion unit comprising the turbojet engine.

However, the thrust reverser cascades made according to the known manufacturing methods of drape-molding pre-impregnated fabrics around tooling are quite fragile because of the constitution of laminates prone to delamination. They are also expensive.

There are also manufacturing methods using materials with short or discontinuous randomly distributed fibers and thermo-compressed or injected, as described in U.S. Patent Publication No. 2016/0186689.

This document describes a thrust reverser cascade manufactured by co-consolidating stiffeners including the pre-consolidated fastening flanges and pre-consolidated blades. The stiffeners are constituted by a polymer reinforced with continuous fibers and the blades by a thermoplastic resin reinforced with discontinuous fibers.

However, these methods of the prior art allow for very limited mechanical characteristics, affecting the aerodynamic performance of the cascades and the lightweight thereof.

SUMMARY

This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

The present disclosure provides a thrust reverser cascade for a nacelle of an aircraft turbojet engine providing high mechanical characteristics and good aerodynamic performances while allowing the making of complex geometries.

The present disclosure concerns a thrust reverser cascade for an aircraft nacelle comprising a plurality of blades having a first and a second surface. The blades being linked to spars which are connected to fastening flanges intended for fastening the thrust reverser cascade on the nacelle.

According to the present disclosure, at least one of the aerodynamic surfaces of the blades is lined with at least one fibrous web comprising a plurality of fiber pieces pre-impregnated with resins. The fiber pieces are superimposed on each other, positioned parallel to the aerodynamic surface of the blade, parallel to each other and oriented according to different directions.

The aerodynamic surfaces of the blades correspond to the surfaces licked by the air flow during the use of the thrust reverser, that is to say the intrados and extrados surfaces of these blades.

Advantageously, the blades are entirely constituted by at least one fibrous web across the entire thickness thereof. In other words, the blades are entirely constituted by fiber pieces, that is to say they comprise fiber pieces across the entire thickness thereof. Thus, in such a configuration, at least one fibrous web delimits at least locally the thickness of the blade. Indeed, the blades may be formed across the entire thickness thereof by an aggregate of superimposed fiber pieces or according to another configuration, by an elementary preform or core of fiber pieces forming a first fibrous web used as a support to be covered afterwards at a second step with fibrous webs over its aerodynamic surfaces.

Advantageously, the blades are linked to the spars, by connection areas formed by fibrous webs disposed in a continuous manner over at least the junction of said blades with the associated adjacent spars, and in one form, at least from the blades to the areas of junction of said blades with the associated adjacent spars.

The areas of connection of a blade and of an adjacent spar are formed by the extension of at least one fibrous web of said blade over an adjacent spar portion. The fiber pieces are superimposed on each other, positioned parallel to the aerodynamic surface of the connection areas and oriented according to different directions.

According to a particular technical feature, the spars and/or the fastening flanges comprise fibrous webs7at least at the surface thereof and at least locally.

In a particular configuration, the spars and/or the fastening flanges are entirely formed by fibrous web(s), that is to say they are constituted by at least one fibrous web across the entire thickness thereof.

In an alternative configuration, the spars and/or the fastening flanges are formed by a combination between a composite material with continuous fibers and at least one fibrous web disposed at least locally at the surface, this fibrous web comprising fiber pieces superimposed on each other, positioned parallel to each other and oriented according to different directions.

According to a particular technical feature, the fastening flanges are mostly (that is to say more than 50%) constituted by fiber pieces superimposed on each other forming web(s), positioned parallel to the surfaces of the flanges and to the neighboring surfaces as well as the surfaces of connection with the flanges and oriented according to different directions. In one form, the fastening flanges are entirely constituted by fiber pieces superimposed on each other forming web(s).

According to an advantageous technical feature, the blades have a variable thickness.

In one form, the thickness of one blade varies by a factor between 1 and 15 times its smallest thickness, this allows creating performing aerodynamic profiles. The thickness varies along the direction of the air flow, that is to say from a leading edge up to a trailing edge of the blade.

According to one variant, the ratio of fibers is higher than 50% of the total volume of the composite material formed by the fibrous webs.

According to another variant, the ratio of fibers is in the range of 60% of the total volume of the composite material formed by the fibrous webs.

According to another variant, the fiber pieces have a thickness comprised between 0.1 mm and 0.4 mm, a length comprised between 15 mm and 60 mm and a width comprised between 10 mm and 40 mm.

According to another variant, the fiber pieces comprise fibers woven so as to form woven mats of fiber pieces pre-impregnated with resin.

According to one variant, the resin serving as a matrix embedding the fibers and consolidating the cascade is a thermosetting matrix. In one example, the fibers are trapped within a thermosetting matrix such as from the epoxides, benzoxazines, polyesters, bismaleimides family.

According to another variant, the resin may be a thermoplastic resin. In one example, the fibers are trapped within one or several thermoplastic matrix/matrices selected from the group consisting of polyamides, polypropylenes, polyetherimides (PEI), polyethersulfones (PES), polyphenylene sulfides (PPS), polyaryletherketones (PAEK), polyether-ether-ketones (PEEK), and Polyether-ketone-ketones (PEKK).

Thus, the present disclosure provides a thrust reverser cascade for a nacelle of an aircraft turbojet engine featuring high mechanical characteristics and good aerodynamic performances.

It also allows making complex geometries and is less expensive than those of the prior art.

Indeed, it is possible to make the shape of the blade (“C” like or “U” like shaped, for example), that of its leading edges (rounded or with sharp ridges) and the thickness of the blade from one edge to the other, vary more easily.

This allows creating performing aerodynamic profiles.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

