Abstract:
A variable-section nozzle for an aircraft nacelle includes a deformable portion of which is movable between a narrow section position and a wide section position. In particular, the variable-section nozzle includes piezoelectric actuators and a controller to control the piezoelectric actuators in order to displace the deformable portion between the narrow and wide section positions. The piezoelectric actuators can be disposed on at least one faces of the deformable portion or be disposed end-to-end to form actuating rods.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/FR2013/050585, filed on Mar. 19, 2013, which claims the benefit of FR 12/52472, filed on Mar. 20, 2012. The disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a nacelle for an aircraft engine, with a variable-section nozzle. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     An aircraft engine nacelle allows channeling external air toward this engine, and providing high-velocity ejection of this air to provide the necessary thrust. 
     In the bypass turbojet engines, the airflow blown by the fan is divided, downstream thereof, into a primary flow (also called “hot” flow) which penetrates into the heart of the turbojet engine to undergo therein several compressions and an expansion, and into a secondary flow (also called “cold” flow), which circulates within a substantially annular flow path, defined on the one hand by an engine fairing (internal fixed structure, also called “IFS”) and on the other hand by the outer fairing of the nacelle. 
     The cold airflow, coming out downstream of the nacelle via an outlet nozzle defined by the downstream edge of this nacelle, provides the essential part of the thrust. 
     In the case of engines with a very high dilution rate, for aerodynamic optimization reasons to provide a proper operation of the fan and also to optimize fuel consumption, it is quite advantageous to adjust the cold airflow outlet section downstream of the nacelle: it is indeed useful to increase this section during takeoff and landing phases, and reduce it during the cruise phases: this is often referred to as adaptive nozzle, or even “VFN” (Variable Fan Nozzle). 
     Examples of such adaptive nozzles are known for example from patent applications FR10/52971, FR10/53282, FR10/57240 filed by the applicant. 
     Conventionally, the variation of the cold flow outlet section is carried out by means of hydraulic or electromechanical actuators, allowing displacing all or part of the outer fairing of the nacelle. 
     The use of such actuators results in additional weight, space and cost. Their integration into the nacelle, already overcrowded with a large number of members, presents a number of technical difficulties. 
     SUMMARY 
     The present disclosure provides a variable-section nozzle for an aircraft nacelle, at least a portion of which is movable between at least a position of smaller section and at least a position of larger section, and comprising means for displacing said portion between said positions, these displacing means comprising on the one hand piezoelectric actuators, and on the other hand means for controlling these actuators, said actuators being disposed in one selected of the two following manners: 
     said actuators are disposed on both sides of said portion, 
     said actuators are disposed end-to-end to form actuating rods. 
     With these features, small-size, lightweight and space-saving displacing means are obtained, which can be controlled by a suitable supply in electrical voltage. 
     According to other features of the present disclosure: 
     said actuators are bonded onto said deformable movable portion; 
     said movable portion comprises at least one hinged flap; 
     movement amplification means are interposed between said rods and said movable portion: these amplifying means, which can consist for example of a lever arm, allow converting the small displacements of the piezoelectric actuators, into displacements with greater amplitude; 
     piezoelectric sensors are positioned to detect the position of said movable portion: as a property of the piezoelectric elements indeed is that they can be used in the reverse direction, that is to say they can generate an electrical voltage depending on the displacements to which they are subjected; 
     said control means comprise on the one hand an electronic supervision module able to send a control voltage into said piezoelectric actuators, and on the other hand an electronic acquisition module, able to receive a position voltage from said piezoelectric sensors, these two modules defining a servo loop. 
     The present disclosure also relates to a nacelle, characterized in that it comprises a variable-section nozzle in accordance with the foregoing. 
     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. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a nacelle for an aircraft turbojet engine, equipped with a variable-section nozzle in accordance with the present disclosure; 
         FIG. 2  is an exploded perspective view of a piezoelectric actuator equipping the nacelle of  FIG. 1 ; 
         FIG. 3  is a axial sectional schematic view of the actuating mechanism of the nozzle flaps of  FIG. 1 ; 
         FIGS. 4, 5 and 6  are views similar to those of  FIG. 3  of other forms of a variable-section nozzle according to the present disclosure; and 
         FIG. 7  is a schematic view of a control circuit of a variable-section nozzle according to the present disclosure. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     Referring now to  FIG. 1 , which shows a nacelle  1  for an aircraft turbojet engine of a longitudinal axis A, equipped with a variable-section nozzle  3  in accordance with the present disclosure. 
     In this  FIG. 1 , the upstream of the nacelle is shown on the left-hand side, and the downstream of this nacelle on the right-hand side. 
     Thus, in operation, air enters through the air inlet  5  of the nacelle, and exits through the variable-section nozzle  3 . 
     In the relevant field of art, it is desirable to vary the section of the nozzle  3 , during the various phases of the aircraft flight. 
     In the form shown in  FIG. 1 , this variation in the nozzle outlet section is obtained by rotating the movable flaps V 1 , V 2 , V 3 , . . . around respective axes A 1 , A 2 , A 3 , . . . , these axes being substantially perpendicular to the longitudinal A axis of the nacelle. 
     Conventionally, this rotation is obtained by means of hydraulic or electromechanical actuators. 
     In the present disclosure, these conventional actuators are replaced by piezoelectric actuators. 
       FIG. 2  shows an example of piezoelectric element which may be involved in making these actuators. 
     Such a piezoelectric element can typically comprise a multilayer complex, formed with piezo-ceramic crystals  7  sandwiched between two layers  9   a ,  9   b  of epoxy, these being likewise sandwiched between two layers of polyimides  11   a ,  11   b , in which electrodes  13   a ,  13   b  are embedded. 
     Such piezoelectric elements are marketed for example by the company SMART MATERIAL. 
     When an electrical voltage is passed into the electrodes  13   a ,  13   b , the piezo-ceramic fibers  7  are deformed, leading to a variation in the thickness of the element shown in  FIG. 2 . 
     Conversely, when this element is subjected to stresses coming from the surrounding members, it causes a variation in the electrical voltage measured to the terminals of these electrodes  13   a ,  13   b.    
     The principle of the present disclosure consists in taking advantage of these properties of the piezoelectric element shown in  FIG. 2 , to allow displacement of the movable portions of the variable-section nozzle  3 . 
     Thus, in the form of  FIG. 1 , several piezoelectric elements P can be stacked so that when they are subjected to an electrical voltage, they cause a displacement of the flaps V 1 , V 2 , V 3 , . . . . 
     More specifically, as is shown in  FIG. 3 , a system for amplifying the movements of the piezoelectric elements P can be considered, comprising, for example, an arm  15  hinged around an axis  17  placed downstream of the nacelle  1 , interposed between on the one hand the piezoelectric stack P, and on the other hand each flap V 1 , V 2 , V 3 , . . . , hinged around its respective axis A 1 , A 2 , A 3 , . . . . 
     The system shown in  FIG. 3  allows thus, through a lever arm effect, imparting to the flaps V 1 , V 2 , V 3 , . . . the desired movement amplitude, both outwardly and inwardly of the nacelle, as indicated by the arrow F. 
     In the alternative shown in  FIG. 4 , there is no longer any flap V as shown in  FIG. 1 , but the downstream edge B of the nacelle  1  is deformable. 
     This may be obtained for example by making this edge in a fine thickness sheet. 
     In this case, in order to allow the displacements of the downstream edge of the nozzle B so as to vary the nozzle outlet section, piezoelectric elements P 1 , P 2 , are fixed on the extrados and the intrados of the edge B. 
     Note that we could consider fixing such piezoelectric elements only on one of the faces of this edge B. 
     These piezoelectric elements can be fixed for example by bonding onto the edge B. 
     In the event where the edge B is made of a composite material, we can consider embedding the piezoelectric elements P 1 , P 2  in the mass of the composite. 
     With appropriate electrical controls of these piezoelectric elements P 1 , P 2 , the edge B can be opened outwardly of the nacelle, or pushed inwardly thereof, thus providing the means for varying the outlet nozzle section of this nacelle. 
     In the form of  FIG. 5 , the piezoelectric elements P 1 , P 2  again allow deforming the edge B inwardly or outwardly of the nacelle, as indicated by the arrow F, while noting that in this case this edge B is guided in these displacements by a system of slides  19  slidably mounted inside the rails  21  integral with the nacelle  1 . 
     In the example shown in  FIG. 6 , the piezoelectric elements P are stacked inside the downstream edge B of the nacelle  1 , so as to form the equivalent of actuating rods. 
     Thus, by subjecting these piezoelectric elements to appropriate electrical voltages, the rods they form can extend or retract. 
     By correctly arranging such rods inside the edge B of the nacelle  1 , the desired deformations outwardly or inwardly of the nacelle can be obtained, as indicated by the arrows F and the dotted lines shown in  FIG. 6 . 
     A set of controls of the variable-section nozzle in accordance with the present disclosure is shown in  FIG. 7 . 
     As shown in this figure, this set of controls comprises an electronic supervision module electrically connected to the piezoelectric actuators P 1 , P 2  by a circuit  25  and supplied with a power current by a circuit  27 . 
     This set of controls further comprises an electronic acquisition module  29 , connected by an electrical circuit  31  to a plurality of piezoelectric sensors C 1 , C 2 . 
     The electronic supervision module  23  and the electronic acquisition module  29  are interfaced with each other, so that the set shown in  FIG. 7  forms a servo loop. 
     More specifically, when it is desired to increase or reduce the variable-section nozzle, a command is sent to the electronic supervision circuit  23 , which will send via the circuit  25  electrical information to the piezoelectric actuators P 1 , P 2 , allowing making the articulation or deformation of the rear edge of the nacelle  1 , as indicated above. 
     The piezoelectric sensors C 1 , C 2 , placed so as to be able to detect the movements of the displaced or deformed portion of the downstream edge of the nacelle, in turn send to the electronic acquisition modules  29  electric information representative of this displacement or of this deformation. 
     Communication between the module  29  and the module  23  allows acting on the piezoelectric actuators P 1 , P 2  until the desired position or deformation is obtained. 
     As can therefore be understood, this set of controls uses the dual property of the piezoelectric elements, consisting not only in the ability to be deformed and thus to cause a movement when they are subjected to an electric field variation, but also the ability to generate such an electric field variation when they are subjected to displacing forces. 
     As an indication, the voltages used with the piezoelectric elements range between 100 volts and 1500 volts. 
     As can now be understood in the light of the foregoing description, the present disclosure provides extremely simple, lightweight and space-saving means, allowing varying the section of a nacelle nozzle. 
     Such variation is obtained by simply sending an appropriate electrical voltage into correctly placed piezoelectric elements. 
     The present disclosure is particularly suitable for next-generation nacelles, intended for engines with a very high dilution rate, which are thinner and shorter. 
     So far, it has never been thought to use piezoelectric elements to make variable-section nozzles, because it was thought that the forces involved were incompatible with those that such elements allow to provide. 
     It was during repeated experiments that the applicant realized that by stacking such elements, actuating forces entirely compatible with those required in the nacelle could be obtained, and this, with an overall weight of these elements significantly lower than that of the conventional hydraulic or electromechanical actuators. 
     Of course, the present disclosure is not limited to the forms described and shown, provided as simple examples.