Aircraft jet engine nacelle, propulsion assembly and aircraft comprising such a nacelle

A nacelle for an aircraft turbofan includes a rear section including a thrust reversal device having an upper door and a lower door, the upper and lower doors being mobile in rotation between a stowed position in which they are aerodynamically continuous with the rest of the nacelle and a deployed position in which the upper and lower doors are able to redirect forward the core and bypass flows produced by the jet engine, each door being moved from one position to the other by at least one dedicated actuator. The opening angle (X) of the upper door in the deployed position is smaller than the opening angle (Y) of the lower door.

FIELD

The present disclosure relates to a turbojet engine nacelle equipped with a rear door thrust reverser, an aircraft propulsion unit and an aircraft including a nacelle.

BACKGROUND

A nacelle for a bypass-type turbojet engine is typically equipped with a fan located upstream of the engine and ensuring the circulation of a cold air flow in an annular channel called secondary flow path and surrounding the gas generator. A nacelle for a turbojet engine of the aforementioned type includes the cold air flow (or secondary flow) and the hot gas flow (or primary flow) meeting in a downstream passage of substantially circular section before being ejected together.

In a more specific manner, such a nacelle for a bypass turbojet engine incorporates a thrust reverser system including two doors each having an upstream edge and a downstream edge, with reference to the flowing direction of gases, said doors being disposed downstream of the nacelle and each being pivotally mounted about hinge axes between a stowed position (not interfering with the direct jet gas ejection), and a deployed position (causing the thrust reversal) in which said doors ensure forward redirection of the primary and secondary flows.

A thrust reverser assembly of this type is already known in particular by the application WO 98/55754. This type of thrust reverser generally equips nacelles for small-sized turbojet engines, such as for example those mounted on the fuselage of business aircrafts. In such a configuration, during the phases of deployment of the thrust reversers, the forward thrust generated by the turbojet engines, due to the position thereof, induces a nose-up pitching moment. Thus, the action of the thrust reversers tends to lift the nose of the aircraft, which is of course harmful to the proper control thereof. It is therefore necessary to provide a configuration such that the thrust of the turbojet engines in the thrust reversal phase generates a nose-down moment and not a nose-up moment.

A solution to this issue is known from U.S. Pat. No. 8,051,639. The solution proposed in this document consists in providing thrust reverser doors offset along the longitudinal axis of the engine in the deployed position, enabling a part of the gas flow from the engine to escape backward and downward. This part thus generates a thrust directed towards the rear of the aircraft and towards the ground, thus inducing a nose-down moment, since this thrust is generated at a point located behind the center of gravity of the aircraft.

This solution, however, has the disadvantage that the thrust generating this nose-down moment is also directed rearward, thus reducing the overall efficiency of the thrust reverser. Furthermore, the offset position (along the longitudinal axis of the engine) of the thrust reverser doors constitutes a complex architecture, which makes the design of such an assembly difficult. Finally, such a configuration can degrade the aerodynamic qualities of the assembly when the thrust reverser doors are in the deployed position.

SUMMARY

The present disclosure provides a nacelle for an aircraft bypass turbojet engine, including a rear section, a thrust reverser device, the thrust reverser system including an upper door and a lower door, the doors being movable in rotation between a stowed position, in which they provide an aerodynamic continuity with the rest of the rear section, and a deployed position, in which the doors are capable of redirecting forward the primary and secondary flows generated by the turbojet engine, each door being displaced from one position to the other by at least one dedicated actuator, the opening angle of the upper door in the deployed position being less than the opening angle of the lower door.

Thus, by providing an opening angle for the lower door larger than for the upper door, the sum of the counter-thrusts generated by both doors includes a vertical component directed downward. During the thrust reversal phases, this vertical component induces on the propulsion unit an upward directed force which, when the propulsion unit is located at the rear of the fuselage of an aircraft, generates a nose-down pitching moment. In addition, the differentiated opening of both doors can be obtained simply by a differentiated stroke of the actuators respectively dedicated to each door. This differentiated opening is thus obtained in a simple and reliable manner, and in any case without causing loss of efficiency of the thrust reverser device. Moreover, the symmetrical positioning of the doors (relative to a plane containing the longitudinal axis of the engine), constitutes a simpler architecture and having better aerodynamic qualities when the doors are in the deployed position (even if their opening is asymmetrical).

In one form, the stroke of the upper actuator, actuating the upper door, is smaller than the stroke of the lower actuator, actuating the lower door.

In another form, the difference in opening angle between the lower and upper doors is between 3° and 10°.

In another form, the difference in opening angle between the lower and upper doors is between 4° and 6°.

In yet another form, the lower and upper doors are movable in rotation about respective axes, these axes of rotation being symmetrical relative to the longitudinal axis of the nacelle.

The present disclosure also concerns an aircraft propulsion unit, including a bypass turbojet engine, the propulsion unit including a nacelle as defined above.

Further, the present disclosure relates to an aircraft including at least one propulsion unit as defined above, the propulsion unit being attached to the fuselage of the aircraft, in the rear position relative to the center of gravity of the aircraft.

DETAILED DESCRIPTION

FIG. 1shows a propulsion unit1in accordance with the present disclosure, provided to be disposed on the fuselage of an aircraft, at the rear thereof.

The propulsion unit1includes a bypass turbojet engine2equipped with a nacelle3. The nacelle3includes, in a conventional manner, an air inlet30, a median section32(surrounding in particular a fan20of the turbojet engine2), as well as a rear section34. As shown inFIG. 1the turbojet engine2is capable of generating, via the gas generator22, a hot gas flow F1, called primary flow, and, via the fan20a cold air flow F2, called secondary flow, which circulates outside the turbojet engine2, through an annular channel called secondary flow path36. The secondary flow path36is delimited between an inner fixed structure38and an outer fixed structure40of the nacelle3. Both air flows F1and F2are ejected from the propulsion unit1from the rear of the nacelle.

The rear section34integrates a thrust reverser device42and is terminated by an ejection nozzle whose outlet is located downstream of the turbojet engine. The thrust reverser device42comprises two doors, an upper door44and a lower door46, which are pivotally mounted so as to be able, under the action of driving means, to switch between a stowed position corresponding to a direct jet configuration, and a deployed position, corresponding to a reverse jet configuration. In the stowed position (position in which the upper door44is shown), the doors44,46provide, with a fixed structure of the rear section34, an aerodynamic continuity with the rest of the nacelle. In the deployed position (position in which the lower door46is shown), the doors44,46are deployed so that each door at least partially obstructs the ejection nozzle of the propulsion unit, thus redirecting forward the primary F1and secondary F2flows. The movement of the doors44,46from one position to another is performed by rotation about a respective axis of rotation48,49, the axes of rotation48,49being symmetrical relative to the longitudinal axis of the engine.

FIGS. 2aand 2bare perspective views of the rear section34of the nacelle3, the thrust reverser device42being respectively in the stowed position and in the deployed position.FIGS. 3aand 3bare side views corresponding toFIGS. 2aand2b.

FIGS. 2aand 3athus show the upper44and lower46doors in their stowed position, a position in which they provide an aerodynamic continuity with the rest of the rear section34, vis-à-vis the outer surface340and vis-à-vis the inner surface342thereof. As visible more particularly inFIG. 3a, the doors are symmetrical relative to a plane containing the longitudinal axis of the nacelle.

FIGS. 2band 3bshow in turn the thrust reverser device42in its deployed position. It is therefore seen that the doors44,46have pivoted, each actuated by a dedicated cylinder50,52, and are in a position in which they redirect forward the gas flows from the turbojet engine (hot or primary flow, and cold or secondary flow). As visible more particularly inFIG. 3b, due to the symmetrical positioning of the axes of rotation48,49of the doors44,46, the rear (or downstream) edges of the doors44,46are not offset along the longitudinal axis of the nacelle when the doors are in the deployed position.

In accordance with the present disclosure, the opening angle X of the upper door44(that is to say the angle between the stowed and deployed positions) is less than the opening angle Y of the lower door46. Thus, the part of gas flow redirected downward (and therefore the thrust induced downward) by the lower door46is greater than the part of gas flow redirected upward (and therefore the thrust induced upward) by the upper door44. As shown inFIG. 2b, the sum of thrusts generated by the doors44,46in their deployed position (materialized by the arrow F3, the thrusts generated at each door being respectively materialized by the arrows F5and F6) integrates a vertical component directed downward (materialized by the arrow F4). Thanks to this vertical component, an upward directed force is applied on the propulsion unit in the thrust reversal phases. Thus, when the propulsion unit1is located at the rear of the fuselage of an aircraft, behind the center of gravity of the aircraft, this upward directed force generates a nose-down pitching moment on the aircraft.

As specified above, the upper door44is actuated by an upper actuator50, the lower door46being actuated by a lower actuator52. As visible more particularly inFIG. 3b, the differentiated opening of the doors44,46is obtained in the example by a differentiated stroke of both actuators50,52. Thus, the lower actuator52has a longer stroke than the upper actuator50. The stroke difference will of course be provided in order to obtain the desired difference between the angles Y and X. In one example, the difference in opening angle between the doors44,46is between 3° and 10°, and in another example is between 4° and 6°. The stroke of the lower actuator52being greater than that of the upper actuator50, it can be considered that the first one is controlled in order to generate a deployment (and/or retraction) speed greater than that of the second one. Moreover, the arrangement of the actuators50,52is symmetrical (relative to a plane containing the longitudinal axis of the engine), when the doors are in the stowed position. However, it will be possible to consider an asymmetrical positioning of the actuators, in which case the stroke of both actuators will not necessarily be differentiated.

Although the present disclosure has been described in connection with a particular example of one form, it is quite obvious that it is in no way limited thereto and that it comprises all the technical equivalents of the described means as well as the combinations thereof.

Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, manufacturing technology, and testing capability.