Patent ID: 12221941

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS.1and2show an aircraft propulsion unit1having a longitudinal central axis A1.

Next, the terms “front” and “rear” are defined with respect to a general direction S1of the flow of the gases through the propulsion unit1, along the axis A1when the latter generates a thrust. These terms “front” and “rear” could be substituted, respectively, with the terms “upstream” and “downstream”, with the same meaning.

The propulsion unit1comprises a turbomachine2, a nacelle3as well as a mast (not shown), intended to connect the propulsion unit1to a wing (not shown) of the aircraft.

In this example, the turbomachine2is a twin-spool turbofan engine comprising, from the front to the rear, a fan5, a low-pressure compressor6, a high-pressure compressor7, a combustion chamber8, a high-pressure turbine9and a low-pressure turbine10. The compressors6and7, the combustion chamber8and the turbines9and10form a gas generator. The turbojet engine2is provided with a fan casing11connected to the gas generator by structural arms12.

The nacelle3comprises a front section forming an air inlet13, a middle section which includes two fan cowls14surrounding the fan casing11, and a rear section15.

In operation, an air flow20enters the propulsion unit1via the air inlet13, passes through the fan5and then splits into a primary flow20A and a secondary flow20B. The primary flow20A flows in a gas circulation primary flow path21A passing through the gas generator. The secondary flow20B flows in a secondary flow path21B surrounding the gas generator. The secondary flow path21B is delimited radially inwards by an inner fixed fairing which surrounds the gas generator. In this example, the inner fixed fairing comprises a first section17belonging to the middle section14, and a second section18extending rearwards starting from the first section17, so as to form a portion of the rear section15.

Radially outwards, the secondary flow path21B is delimited by the fan casing11, and, in the configuration ofFIG.1, by reverser movable cowls forming the rear section15of the nacelle3, which will be described later on.

The nacelle3includes a thrust reverser30comprising, on the one hand, a fixed structure31secured to the fan casing11and, on the other hand, a system29movable relative to the fixed structure31. The movable system29of the reverser30comprises at least one set32′ of cascade vanes32, the aforementioned reverser movable cowls33, the sealing flaps34and the connecting rods35. The thrust reverser30is also centred on the axis A1, like the turbomachine2.

FIG.1shows the reverser30in a direct thrust configuration. In this configuration, the movable cowls33and the set32′ of the movable system29are in a closure position, or advanced position, in which the reverser cowls33bear on the fixed structure31. In this same position of the movable system29, the cascade vanes32are accommodated in a space delimited radially by the fan casing11on the one hand, and by the fan cowls14on the other hand. In the direct thrust configuration, the sealing flaps34are retracted within a cavity36(cf.FIG.2) formed by the movable cowls33. Thus, the reverser30allows channelling the secondary flow20B towards the rear of the propulsion unit1, so as to generate a thrust. Thus, inFIG.1, the cascade vanes32and the movable cowls33, which are axially secured to one another, are in an advanced position called direct thrust position.

FIG.2shows the same reverse30in a thrust reversal configuration. In this configuration, the movable reverser cowls33and the set of the movable system29are in an opening position, or retracted position, in which the cowls33are longitudinally remote from the fixed structure31so as to define a radial opening of the secondary flow path21B. The cascades32extend through this radial opening. In this thrust reversal configuration, the sealing flaps34are deployed radially in the secondary flow path21B so as to direct the secondary flow20B towards the cascade vanes32, which allow directing the flow thus redirected towards the front of the propulsion unit1, in order to generate a reverse thrust. Thus, inFIG.2, the cascade vanes32and the movable cowls33of the movable system29are shown in a so-called backward thrust reversal position.

FIG.3shows a perspective exploded view of some elements of the nacelle3, among which a portion of the fixed structure31of the reverser30, which has an annular general shape centred on the axis A1. More specifically, in this preferred embodiment of the invention, the fixed structure31is provided with a closed curve shape defining a ring-like general shape, locally following the external contour of the secondary flow path21baccording to the circumferential direction of the nacelle43, with respect to the axis A1. The fixed structure31is also called “fixed frame” of the reverser.

The fixed structure31is equipped with elements for guiding the cascade vanes32during movement thereof between the advanced and backward positions, these elements comprising axial rails40. For example, these consist of two rails40secured to an upper portion of the ring, and two other rails40secured to a lower portion of this same ring. In this case, the rails40are fastened to the fixed structure31by their rear end, whereas their front end is fastened to another casing (not shown inFIG.3). Thus, the rails40ensure a function of guiding the cascade vanes32during the axial movement of these, but also, in the thrust reversal configuration, a function of taking up aerodynamic forces, primarily radial and tangential.

FIG.3schematically shows the cascade vanes32, which follow one another according to the circumferential direction43. In this case, they are grouped together into two lateral sets each comprising several cascade vanes32, these sets being so-called sets of cascade vanes32′.

Thus, each set of cascade vanes32′ includes several cascade vanes32, and extends over an angular sector close to 180°. Preferably, the two assemblies32′ are preferably spaced apart laterally from one another at their opposite ends in pairs, to form upper and lower spaces respectively dedicated to the passage of the mast42and a lower longitudinal beam44. Each set of cascade vanes32′ also includes a cascade vane support rear structure45, on which a rear end of each of the cascade vanes32of the set32′ is fastened. These rear structures45are also called “rear frames of cascade vanes”, and each extends circumferentially all along their associated lateral set32′, according to an identical or similar angular sector as shown inFIG.4. Hence, the rear end of each cascade vane32is intended to be fastened on its associated rear structure45, by conventional fastening means. Similarly, each set of cascade vanes32′ also includes a cascade vane support front structure45′, on which a front end of each of the cascade vanes32of the set32′ is fastened. These front structures45′ are also called “front frames of cascade vanes”, and each extends circumferentially all along their associated lateral set32′, according to an identical or similar angular sector. Hence, the front end of each cascade vane32is intended to be fastened on its associated front structure45′, by conventional fastening means.

The above-described configuration is particularly well suitable in the case of a nacelle design wherein the cowls18of the second section are hingedly mounted, the reverser30then having a so-called “D”-like architecture, known by the Anglo-Saxon name “D-Duct”. Nevertheless, the circumferential extent of the sets of cascade vanes32′ could be easily adapted according to the design of the reverser and of the nacelle, which could, for example, adopt a so-called “C”-like architecture, known by the Anglo-Saxon name “C-Duct”, or else a so-called “O”-like architecture, known by the Anglo-Saxon name “O-Duct”.

In a known manner, the fixed structure31includes members (not shown) forming radial and/or tangential and/or axial stops for the cascade vanes32of the sets32′.

InFIG.3, the elements of the nacelle3are completed by the hinged cowls18,33, allowing conferring the “D”-like architecture on the nacelle. In particular, the pivot axis48associated with each reverser cowl33has been illustrated, this pivot axis48being parallel or substantially parallel to the axis A1, and enabling the cowl33to be movable in rotation between a maintenance open position and a flight closed position, shown inFIG.3.

FIG.5shows in more details a portion of one of the two sets of cascade vanes32′. Preferably, the two sets32′ have an identical or similar design, while being symmetrical with respect to a vertical and longitudinal plane passing through the axis A1. Consequently, the description that will be made hereafter will apply equally to each of these two sets32′.

The set of cascade vanes32′ comprises inter-cascade axial structures47,47′ arranged between the cascade vanes32, according to the circumferential direction43of the nacelle and of its reverser30. These inter-cascade axial structures47,47′ extend over the entire length or substantially the entire axial length of the set32′, and are therefore arranged between the cascade vanes32, in the direction43. With their radially external surface49, these axial structures47,47′ form axial slide tracks for the movable system29. In addition, these may consist of several kinds of structures, including elements47ensuring the function of mechanical junction between the cascade vanes32, and inter-vane structures for limiting buckling47′, specific to the present invention. Only one single inter-cascade structure for limiting buckling47′ is visible inFIG.5, but it several ones could be provided for within each set cascade vanes32′, preferably as many actuators52associated with each set32′. Indeed, each structure47′ has a hollow shape internally defining a channel crossed by an actuator52, herein a hydraulic cylinder, but which could alternatively be formed by an electric actuator. Next, only the cooperation between one of the inter-cascade structures47′ and its associated cylinder52will be described hereinbelow, but it should be understood that such a cooperation applies for all of the other cylinders and inter-cascade structures47′ of each set of cascade vanes32′.

The cylinder52is formed by a fixed portion54comprising the cylinder sleeve, and a front end of which is for example fastened on the fan casing11. The cylinder52is also formed by a movable portion56formed by the cylinder rod, and a rear end of which is hingedly fastened on the support rear structure45.

The inter-cascade structure for limiting buckling47′ includes a front end conventionally fastened on the support front structure45′, this front end possibly including circumferential reinforcements58to reinforce mechanical fastening on this structure45′. Furthermore, the inter-cascade structure for limiting buckling47′ includes a rear end fastened on the support rear structure45, still using conventional means. Also, although this has not been shown, the inter-cascade structure for limiting buckling47′ may have along the latter means enabling fastening thereof on the two cascade vanes32arranged on either side according to the circumferential direction43.

The fixed portion54of the cylinder52opens forwards of the front end of the inter-cascade structure for limiting buckling47′, whereas the movable portion56of the cylinder52opens rearwards of the rear end of the inter-cascade structure47′, as also visible inFIGS.6and7which will be described hereinbelow.

FIG.6shows the movable system29of the reverser30in the advanced direct thrust position, in which the cylinder rod56is fully retracted into the cylinder sleeve54, and the cascade vanes32, inoperative, covered by the fan cowls14.FIG.7shows the movable system29in the backward thrust reversal position, in which the cylinder rod56is fully extended rearwards, and the cascade vanes32retracted rearwards so as to be able to generate the thrust reversal function.

InFIGS.6to8, the inter-cascade structure for limiting buckling47′ is shown with its internal channel60directed parallel to the axis A1, and crossed by the cylinder52also directed parallel to the axis A1The channel60is delimited by a cylindrical internal surface62extending circumferentially all along a first closed directrix curve64, in this case circular shaped and centred on an axis A2corresponding to the axis of the cylinder52in a mechanically unstressed configuration. The axis A2is parallel to the axis A1, or substantially parallel thereto. In other words, in this preferred embodiment, the cylindrical internal surface62of the inter-cascade structure47′ remains uninterrupted all along a circumferential direction43′ of this structure47′, with respect to the axis A2. Hence, the cylindrical internal surface62continuously follows the first closed directrix curve64in the form of a circle, defined by a generatrix parallel to the axis A2which follows this same curve64.

In this case, the channel60defined by the surface62extends cylindrically, preferably all along the inter-cascade structure47′. The fixed portion54of the cylinder that crosses the channel60comprises an outlet end66of the movable portion56, corresponding to its rear end. In the advanced direct thrust position ofFIG.6, this outlet end66is accommodated in the channel60, proximate to a rear end of the movable inter-cascade structure47′.

According to a particular feature of the invention, the outlet end66of the fixed portion of the cylinder52is equipped with an external ring70for limiting buckling of the cylinder. The ring70, arranged around the cylinder sleeve, has a cylindrical external surface62′ extending circumferentially all along a second closed directrix curve64′, herein circular shaped and also centred on the axis A2. In other words, in this preferred embodiment, the cylindrical external surface62′ of the inter-cascade structure47′ remains uninterrupted according to the circumferential direction43′ of this structure47′, with respect to the axis A2. Hence, the cylindrical external surface62′ continuously follows the second closed directrix curve64′ in the form of a circle, defined by a generatrix parallel to the axis A2that follows this same curve64′.

In a buckling unconstrained configuration of the cylinder52, as shown inFIGS.6to8in axial view according to the axes A1and A2, the first and second closed directrix curves64,64′ are preferably concentric and have the same shapes, the first one having a dimension greater than the second one so as to define a constant spacing72all along these according to the direction43′.

With such a design, in the event of a loading of the cylinder52resulting in buckling thereof, this phenomenon remains controlled thanks to the possible cooperation between the ring70and the internal surface62of the channel60. Indeed, the ring70equipping the outlet end66of the fixed portion of the cylinder52serves as a potential radial stop on the inter-cascade structure47′. Thus, during the movement of the movable system29of the reverser towards its advanced direct thrust position, the amplitude of a possible buckling of the cylinder52remains controlled by not being able to exceed the value of the initial spacing72between the two curves64,64′. When this gap72is consumed, the cylindrical external surface62′ of the ring70comes into contact with the cylindrical internal surface62of the channel60, thereby limiting buckling of the cylinder to a controlled and non-detrimental amplitude. Such a situation is schematised in dotted lines inFIG.8.

The external ring for limiting buckling70may be made in one-piece, i.e. a monolithic part, or preferably be split or sectorised to facilitate implantation and replacement thereof around the cylinder fixed sleeve. In the case where this ring70is sectorised, it may for example consist of two half-shells attached around the cylinder sleeve.

In order to limit the friction forces between the inter-cascade structure47′ and the ring70, during a movement of the movable system29and in case of a buckling of the cylinder contained by the inlet in contact with these elements47′,70, The ring is preferably made of a conventional antifriction material, known to a person skilled in the art. Alternatively, only one antifriction coating may be provided on the ring70to form the external surface64′, without departing from the scope of the invention. In case of wear, the ring70may advantageously be replaced around the cylinder sleeve.

During the movement of the movable system29of the reverser towards its backward thrust reversal position, the ring70moves axially relative to the moving channel60. In the backward thrust reversal position ofFIG.7, the outlet end66and the ring70which surrounds it are accommodated in the channel60, proximate to a front end of the movable inter-cascade structure47′.

All along an axial section of the fixed portion54of the cylinder, which, at least at one time point, is radially covered by the inter-cascade structure47′ during its movement accompanying the change in position of the movable system29, it is the ring70which forms the radially largest portion of this section, i.e. the portion with the largest diameter. This enables the ring70to create the privileged contact point of the cylinder52with the inter-cascade structure47′, in case of buckling of the cylinder.

FIG.6shows another functionality of the rear structure45of the set of cascade vanes32′, which consists in making the axial connection with the reverser cowl33, in its flight closed position. The rear end of the structure45comprises an axial connecting member76in the form of an annular groove open radially outwards, cooperating with a complementary axial connecting member78provided on a front end of the reverser cowl33. Preferably, this member78is in the form of a radial projection inwards, accommodated in the groove76so as to obtain the axial coupling in the closed position of the cowl33. When opening the latter towards its maintenance open position, the projection78is extracted from the groove76.

According to another embodiment shown inFIG.9, the two curves64,64′ remain circular in shape, but the cylindrical internal surface62of the channel is no longer continuous. It is circumferentially interrupted by extending along only one portion of the first closed directrix curve64, so as to define several cylindrical internal surface angular sectors62a. In this case, these are two angular sectors62a,62athat are spaced apart from one another by two surface interruptions80. In this configuration, the inter-cascade structure for limiting buckling47′ is preferably made using two axial beams47′a,47′arespectively defining the two angular sectors62a,62a. Each beam extends over the entire length of the set of cascade vanes32′, by being fastened at its ends on the front and rear support structures on which the front and rear ends of the cascade vanes32are also fastened.

The surface interruptions80, corresponding to empty portions between the two beams47′aof the inter-cascade structure47′, preferably extend over a small angular amplitude. Each cylindrical internal surface angular sector62a, as well as its entire associated beam47′a, may extend over an amplitude greater than 100°, and for example close to 180° as shown inFIG.9.

It should be noted that a similar principle could be adopted for the cylindrical external surface62′ of the ring70, by providing for surface interruptions spacing apart cylindrical external surface angular sectors.

According to another embodiment shown inFIG.10, the two closed directrix curves64,64′ are no longer in the form of a circle, but for example slightly ovalised on one side so as to take into account the general shape of the fixed portion54of the cylinder, provided with its external equipment like an oil return pipe82and its fitting84for holding the cylinder sleeve. Thus, the shape of the channel60and of the ring70may be adapted according to the external general shape of the fixed portion54of the cylinder52, still while preserving a constant radial spacing72in the buckling unconstrained state.

Of course, various modifications could be made by a person skilled in the art to the invention that has just been described, only as non-limiting examples, and the scope of which is defined by the appended claims. In particular, the different preferred embodiments that have been described can be combined. In addition, the thrust reverser30may alternatively have a “C”-like or “O”-like architecture.