Engine assembly for an aircraft comprising a primary structure of a mounting pylon equipped with a box extension comprising two parts in the overall shape of an arch

An engine assembly for an aircraft rigid structure comprising a mounting pylon comprising a central box and a box extension connected to a reducing gear case of the turboreactor. The box extension includes two parts bearing the front engine attachments, these pieces each comprising a structure forming a reinforcing rib of the central box, as well as two parts of horseshoe shape surrounding the reducing gear case.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No. 1557719 filed on Aug. 13, 2015, the entire disclosures of which are incorporated herein by way of reference.

BACKGROUND OF THE INVENTION

The present invention relates to an engine assembly for an aircraft comprising a turbofan turbine engine of which the fan is driven by reduction gearing, a turbine engine mounting pylon and attachment means for attaching the turbine engine to the primary structure of the mounting pylon.

The invention also relates to an aircraft equipped with at least one such engine assembly. It preferably applies to commercial airplanes.

On existing aircraft, the engines such as the turbine engines are suspended beneath the wing structure by complex attachment devices also referred to as EMS (which stands for Engine Mounting Structure), or even referred to as “mounting pylons.” The mounting structures usually employed have a rigid structure referred to as a primary structure. This primary structure generally comprises a box, which means to say, a structure formed by the assembly of lower and upper longitudinal members connected to one another by a plurality of transverse stiffening ribs situated on the inside of the box. The longitudinal members are arranged on the upper and lower faces, while lateral panels close the lateral faces of the box.

In the known way, the primary structure of these pylons is designed to allow the static and dynamic loads generated by the engines, such as the weight and the thrust, or even the various dynamic loadings to be transmitted to the wing structure.

In the solutions known from the prior art, the transmission of load between the engine and the primary structure is performed traditionally by attachment means consisting of one or more front engine mounts, a rear engine mount, and a thrust load reacting device formed by two lateral link rods articulated to a balance beam. One embodiment of such an engine assembly is known, for example, from document FR 3 014 841.

In the case of a turbofan turbine engine in which the fan is driven by reduction gearing, there is a need to optimize the existing solutions with a view notably to reducing the bulk, the overall weight, and the aerodynamic disturbances generated by the presence of the pylon attachment means on the turbine engine.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to propose an engine assembly for an aircraft that at least partially meets the requirement mentioned hereinabove.

To do this, one subject of the invention is an engine assembly for an aircraft comprising:

a turbofan turbine engine of which a fan is driven by reduction gear, the turbine engine comprising a reducing-gear case surrounding the reduction gear;

a turbine engine mounting pylon, comprising a primary structure equipped with a central box; and

means for attaching the turbine engine to the primary structure of the mounting pylon.

According to the invention, the rigid structure of the mounting pylon also comprises a box extension connected to the front of the central box, the box extension comprising:

a first component produced as a single piece and arranged in a vertical and transverse plane of the engine assembly, the first component comprising a first part in the overall shape of an arch extending around the reducing-gear case, and a first connecting structure constituting a transverse stiffening rib of the central box, the first part in the overall shape of an arch having two first opposite ends; and

a second component produced as a single piece and comprising a second part in the overall shape of an arch extending at least partly around the reducing-gear case, and a second connecting structure constituting an interior transverse stiffening rib of the central box, the second part in the overall shape of an arch having two second opposite ends respectively mounted on the two first opposite ends, the second part in the overall shape of an arch extending rearward and toward the central box from its second opposite ends.

In addition, the attachment means comprise two lateral front attachments and a central front attachment, each of the two lateral front attachments connecting the reducing-gear case to one of the two first ends of the first part in the overall shape of an arch and each reacting load in a longitudinal direction and in a vertical direction of the engine assembly, and the central front attachment connecting the reducing-gear case to a first central portion of the first part in the overall shape of an arch and reacting load in a transverse direction of the engine assembly.

The invention proposes a simple solution that meets the requirement identified hereinabove, notably thanks to the use of the first and second one-piece components which allow improved transmission of load because they extend as far as the central box of the mounting pylon. That in particular makes it possible to reduce the bulk and mass of the engine assembly comprising the pylon, which assembly no longer requires lateral thrust-load reacting link rods. This reduction in mass is advantageously accompanied by a reduction in specific fuel consumption.

Also, the lateral and central front attachments are able to react most of the load at the level of the reducing-gear case. This particular feature is not only beneficial insofar as it allows the load to be reacted as close as possible to a center of gravity of the turbine engine for purer transmission of this load, but also because it makes it possible to provide a rear engine mount of simplified design and therefore small bulk. Simplifying this rear engine mount, which is positioned in the bypass stream of the turbine engine, makes it possible to limit the aerodynamic disturbances on the bypass flow. All of the aerodynamic performance aspects of the engine assembly are therefore improved as a result.

Finally, connecting the lateral and central front attachments to the reducing-gear case rather than to the fan case means that a larger sized turbine engine can be incorporated while at the same time maintaining sufficient ground clearance. That also makes it possible to limit the deformation of the various bodies of the engine case, under the application of load.

The invention preferably envisions at least one of the following optional features, considered in isolation or in combination.

The second component of the box extension extends in a plane that is inclined with respect to the vertical and longitudinal directions of the engine assembly, preferably inclined by an angle comprised between 30 and 60° with respect to the longitudinal direction.

The two lateral front attachments are arranged symmetrically with respect to a vertical and longitudinal midplane of the engine assembly, the vertical and longitudinal midplane passing through the central front attachment.

The two lateral front attachments are arranged in angular positions one of them between 2 o'clock and 3 o'clock and the other between 9 o'clock and 10 o'clock.

The attachment means form a statically determinate load-reacting system and are made up of the two lateral front attachments, the central front attachment, and a rear attachment reacting load in the vertical direction, and preferably only in this vertical direction.

The box extension comprises at least one skin externally covering the first and second parts in the overall shape of an arch.

The second opposite ends are mounted on the two first opposite ends by two shear pins respectively, these preferably being oriented in the transverse direction.

The turbine engine comprises, in succession, from the front toward the rear, a fan case, an intermediate case, the reducing-gear case, a central case and a turbine case.

Another subject of the invention is an aircraft comprising at least one such engine assembly and a wing on which the engine assembly is mounted.

For preference, the engine assembly is suspended beneath the wing, even though another solution could be adopted, in which the turbine engine would be arranged above the wing of the aircraft.

Further advantages and features of the invention will become apparent from the nonlimiting detailed description below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is made toFIG. 1which depicts an aircraft100comprising a fuselage3to which two wings2are fixed. Underneath each of these wings2is suspended one or more engine assemblies1according to the invention. Each engine assembly1comprises a bypass turbofan turbine engine10of the type comprising reduction gearing for driving the fan, a mounting pylon4for mounting the turbine engine10, and means (not visible inFIG. 1) for attaching the turbine engine10to a rigid structure of the pylon4.

Throughout the description which will follow, by convention, the X-direction corresponds to the longitudinal direction of the engine assembly1, which is also likenable to the longitudinal direction of the turbine engine10and of the pylon4. This X-direction is parallel to a longitudinal axis5of this turbine engine10. Furthermore, the Y-direction corresponds to the direction oriented transversely with respect to the engine assembly1, and also likenable to the transverse direction of the turbine engine10and of the pylon4, whereas the Z-direction corresponds to the vertical or height direction. These three directions, X, Y and Z are mutually orthogonal and form a direct trihedron.

Furthermore, the terms “front” and “rear” are to be considered with respect to a direction of forward travel of the aircraft encountered as a result of the thrust applied by the turbine engines10, this direction being schematically depicted by the arrow19.

Reference is now made toFIG. 2which schematically depicts an engine assembly1according to a preferred embodiment of the invention. This assembly therefore comprises the turbine engine10, the specific feature of which is that it incorporates a fan12driven by reduction gearing14. This type of turbine engine is known as a GTF turbine engine (which stands for Geared Turbofan Engine).

The turbine engine comprises, from the front toward the rear, a fan case16, and an intermediate case18, an outer shroud20of which axially extends the fan case16. The intermediate case18also comprises a hub22and radial structural arms24connecting the hub22to the outer shroud20. These arms24are arranged inside an annular row of outlet guide vanes, also abbreviated to OGV.

At the rear of the intermediate case18, the turbine engine10comprises a reducing-gear case26enclosing the reduction gearing14. This reducing-gear case26has a diameter very much smaller than that of the outer shroud20. Still toward the rear, there is then a central case28, also referred to as the “core case” which constitutes the narrowest part of the turbine engine and notably contains the combustion chamber (not depicted). The central case28is then extended toward the rear by a turbine case30of larger size, and from which the gases of the primary stream can escape, as depicted schematically by the arrow32.

In the known way, in this type of turbine engine10, combustion has the effect of driving the high-pressure and low-pressure spools and it is the low-pressure spool that transmits the mechanical energy to the reduction gearing14, which itself then drives the fan12.

The engine assembly1also comprises the mounting pylon4, only the rigid structure34of which has been depicted inFIG. 2. The primary structure34is designed to allow the static and dynamic loads generated by the engines, such as the weight and the thrust, or even the various dynamic loads, notably those associated with failures such as: loss of blades (FBD), retraction of the front landing gear, dynamic landing, etc. to be transmitted to the wing structure. The other constituent elements of this pylon4, which have not been depicted and which are of secondary structure type providing segregation and retention of systems while at the same time supporting the aerodynamic fairings, are conventional elements similar to those encountered in the prior art. For this reason, no detailed description thereof will be given.

The primary structure34, or rigid structure, comprises by way of main element a central box36extending over the engine length of the primary structure34in the X-direction. The central box36is of substantially conventional design, which means to say is delimited at the top by upper longitudinal members40, at the bottom by lower longitudinal members42, and laterally by an outer lateral panel44and an inner lateral panel46. By way of indication, it is noted that the upper longitudinal members40are also referred to as the “pylon box upper panel” and that the lower longitudinal members42are also referred to as the “pylon box lower panel”. Furthermore, the central box36is equipped with interior transverse stiffening ribs52, preferably hollowed at their center and preferably arranged mostly in YZ planes. This central box36has a YZ cross section of square or rectangular overall shape, of a size that evolves along the X-direction. This cross section may remain substantially constant for the rear part situated at the level of the wing, but then narrows as it extends forward, as far as its front end situated in the vicinity of the reducing-gear case26.

One of the particular features of the invention lies in the presence of a box extension54connected to the front of the central box36and extending the latter substantially downward toward the reducing-gear case26. This box extension54will be detailed hereinafter with reference toFIGS. 3 to 5.

Furthermore, the engine assembly1comprises attachment means7a-7dfor attaching the turbine engine10to the rigid structure34of the pylon. These attachment means7a-7dconsist of two lateral front attachments7a,7b,of a central front attachment7c,and of a rear attachment7d.The front attachments7a-7cconnect the box extension54to the reducing-gear case26, whereas the rear attachment7dconnects the lower longitudinal member42to the turbine case30, being situated in a bypass stream59of the turbine engine.

Reference is now made more specifically toFIGS. 3 to 5which depict in detail the design of the box extension54. This first of all comprises a first component60produced as a single piece, preferably from a metallic material. This first component60is substantially planar and arranged in a vertical and transverse YZ plane, namely in a plane orthogonal to the X-direction. It comprises two vertically adjacent parts, namely a first part62in the overall shape of an arch extending around an upper portion of the reducing-gear case26, and a first connecting structure63constituting one of the transverse stiffening ribs of the central box. More specifically, this first connecting structure63constitutes the rib that closes the front of the central box36, even if this rib is likewise also preferably hollowed at its center, so that it has the overall shape of a square or of a rectangle.

The first part62is also referred to as being horseshoe-shaped, open at the bottom. It has two first opposite ends64a,64b,to which the two lateral front attachments7a,7bare respectively connected. These, just like the other attachments7c,7d,are produced in the conventional way using yokes and/or collars and/or clevises. The two attachments7a,7bare preferably arranged in 2 o'clock and 10 o'clock angular positions in a clock frame of reference centered on the axis5. 3 o'clock and 9 o'clock positions may also be envisioned, without departing from the scope of the invention. In that case, the two lateral front attachments7a,7bare then diametrically opposed. In any case, the two attachments7a,7bare preferably arranged symmetrically with respect to a vertical and longitudinal midplane57of the assembly1.

This same plane57passes through the central front attachment7cwhich connects an upper end of the reducing-gear case26to a first central portion65of the first component60. The three front attachments7a-7care thus arranged in the same vertical and transverse YZ plane in which the first component60is inscribed. In addition, it is noted that it is from the central portion65that the first connecting structure63extends upward, forming the rib closing the front of the central box36.

The box extension54also comprises a second component70produced as a single piece, preferably from a metallic material. This second component70is substantially planar and arranged in a plane78parallel to the transverse direction Y, but inclined with respect to the vertical direction Z and longitudinal direction X. By way of nonlimiting example, the second component70is inclined by an angle79of approximately 45° with respect to each of the two directions X and Z.

The second component70comprises two vertically adjacent parts, namely a second part72in the overall shape of an arch extending at least partially around an upper portion of the reducing-gear case26, and a second connecting structure73constituting one of the transverse interior stiffening ribs of the central box. More specifically, this second connecting structure73constitutes the second interior rib of the central box36, counting from the front. It is also preferably hollowed out at its center, so as to have the overall shape of a square or rectangle.

The second part72is also referred to as being horseshoe-shaped, open at the bottom and toward the front. It has two second opposite ends74a,74b,respectively mounted on the two first opposite ends64a,64b.This mounting is via shear pins80and/or bolts, oriented in the Y-direction. These pins80are thus positioned near the two lateral front attachments7a,7b,also connected to the first ends64a,64b.

As is clear from the foregoing, the second component70of the box extension54differs from the vertical first component60in that it is inclined so that it extends rearward and toward the central box36from its second ends74a,74b.

The attachment means7a-7dform a statically determinate load-reacting system. Specifically, as indicated schematically inFIG. 3, each of the two lateral front attachments7a,7breacts load only in the X direction and Z direction, whereas the central front attachment7creacts load only in the Y direction. As for the rear engine attachment7d,this reacts load only in the Z direction. In this regard, the foregoing description applies to how load is reacted under normal circumstances. However, if one of the attachments7a-7dfails, the load-reaction distribution may differ.

Thus, under normal circumstances, the moment applied in the X direction is reacted vertically using the two lateral front attachments7a,7b,whereas the moment applied in the Z direction is reacted longitudinally using these same attachments7a,7b.

The invention therefore contrasts with the solutions of the prior art notably in that it no longer requires link rods for reacting thrust load. Here, loads in the X direction pass via the attachments7a,7band then essentially via the second inclined and arch-shaped component70. The fitting of a skin82externally covering the first and second parts62,72also contributes to causing longitudinal load to pass through the entirety of the box extension54, rather than through its second component70alone.

Of course, various modifications may be made by those skilled in the art to the invention that has just been described solely by way of nonlimiting examples.