Abstract:
An integrated exhaust nozzle and thrust reverser for a turbojet engine is provided. The exhaust nozzle comprises an exhaust duct situated within a fairing ( 9 ), a set of hot flaps ( 14 ) at a downstream end of the duct, a set of cold flaps ( 16 ) at a downsteam end of the fairing ( 9 ), and a thrust reverser ( 30 ). The thrust reverser comprises two eyelids ( 31, 32 ) which are movable between a thrust reversal position wherein they project into the duct and a forward-thrust position. In a takeoff mode, the eyelids ( 32, 33 ) are moved away from each other by one or more actuators ( 50 ) acting on arms ( 33, 34 ) pivotably connected to the eyelids ( 31, 32 ). Movement of the eyelids ( 31, 32 ) from the reverse-thrust position to the forward-thrust position, or vice-versa, is implemented by control actuators ( 35, 36 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a turbojet engine exhaust nozzle mounted on a civilian supersonic aircraft and comprising a thrust reverser. 
     More specifically, the invention relates to a turbojet engine exhaust nozzle mounted on a supersonic aircraft and comprising an exhaust duct defined within an external cowling, a set of hot flaps mounted in a pivotable manner on the end of said duct, a set of cold flaps mounted in a pivotable manner on a downstream end of the cowling, a thrust reverser comprising two identical eyelids mounted in a pivotable manner downstream of the exhaust duct on either side of an axial plane of symmetry, means for controlling the hot and the cold flaps depending on the flight mode, and means for driving the eyelids from an inactive to an active position or vice-versa. 
     2. Description of the Related Art 
     The eyelids of such an exhaust nozzle are each mounted on a stationary structure so as to be pivotable about a transverse axis near the axial plane of symmetry in order to regulate the exhaust cross-section of the engine&#39;s exhaust gases as a function of the flight modes. However, this cross-section varies only slightly. On the other hand, noise standards for aircraft in the vicinity of civilian airports require lowering the gas exhaust speeds, especially at takeoff. 
     These standards require special designs because the engine at takeoff is at full power and the gas flows are substantial. 
     SUMMARY OF THE INVENTION 
     The objective of the invention is to provide an exhaust nozzle of the above described kind which reduces noise at takeoff while increasing the gas exhaust cross section. 
     This goal of the invention is attained by an exhaust nozzle comprising a control mechanism which, in the takeoff mode, moves the two eyelids away from the axial plane of symmetry. 
     Moreover, the following design steps are taken: 
     the cold flaps are driven to ensure an obstruction-free, aerodynamic profile with the two eyelids in both the takeoff and the cruise modes; 
     the cold flaps are linked to the hot flaps by linkrods; 
     the two eyelids hinge on the ends of two lateral pairs of arms and on the ends of at least one pair of actuators, the arms of each pair of arms and the actuators of each pair of actuators being configured symmetrically relative to the axial plane of symmetry and hinging at their other ends on a stationary structure, and the actuators comprising the control mechanism for the eyelids; 
     the control mechanism moving the eyelids comprises an actuator connected between the arms of at least one of the pairs of arms; 
     the two arms of at least one of the pairs of arms are connected by sector gears to assure symmetrical displacement of the eyelids on the arms relative to the axial plane of symmetry; 
     the actuators comprising the control mechanism for the eyelids may be actuated in an opposing manner in the takeoff mode in order to slightly deflect the gas flow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages and features of the invention are elucidated in the following illustrative description, with reference to the attached drawings, in which: 
     FIG. 1 is a cross-section in a vertical plane of symmetry of an exhaust nozzle of a turbojet engine mounted on a supersonic aircraft according to a first embodiment of the invention in a cruise mode; 
     FIG. 2 shows, on an enlarged scale, a rear portion of the exhaust nozzle of FIG. 1 in the cruise mode; 
     FIG. 3 is a cross-section in the vertical plane of symmetry of the exhaust nozzle of FIG. 1 in a takeoff mode; 
     FIG. 4 shows, on an enlarged scale, the rear portion of the exhaust nozzle in the takeoff mode; 
     FIG. 5 is a cross-section in the vertical plane of symmetry of the exhaust nozzle of FIG. 1 in a thrust-reversal mode; 
     FIG. 6 shows, on an enlarged scale, the rear portion of the exhaust nozzle in the thrust reversal mode; and 
     FIG. 7 is similar to FIG.  4  and shows the positions of the flaps and the actuators in the takeoff mode with deflection of the gases. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The drawings show an exhaust nozzle  1  for the gases issuing from a bypass, double barrel turbojet engine mounted on a civilian supersonic aircraft. 
     A turbine  2  of this turbojet engine emits a hot flow F h  an annular space  3  enclosing a cone  4  of the turbine  2 . A cold flow F c  issues from an annular duct  5  enclosing an external casing  6  of the turbine  2 . The annular duct  5  is externally bounded by an inner annular wall  7  extending in a downstream direction, in the direction of flow of the gases, and beyond the end of the cone  4 . The inner wall  7  is part of a stationary, annular structure  8  which is externally bounded by an aerodynamic fairing  9  so as to comprise an external cowling. 
     The inner wall  7  of the stationary structure  8  bounds an inner cylindrical chamber  11  with an axis of revolution  12  coinciding with the axis of the turbojet engine. The hot flow F h  issuing from the turbine and the cold flow F c  issuing from the annular duct  5  are mixed in the chamber  11 , in particular by a mixer with lobes  13  such as are shown in FIG. 3 (shown retracted in FIG.  1 ). The resulting gaseous mixture may be enriched with fuel by injection manifolds and afterburned in the inner chamber  11  in order to boost the turbojet engine thrust. in particular during takeoff. 
     Hot flaps  14  hinge on a downstream end  15  of the inner wall  7  and cold flaps  16  hinge on a downstream end  17  of the fairing  9 . The downstream ends  15  and  17  are situated substantially in the same plane transverse to the axis  12 . 
     The cold flaps  16  are preferably connected to the hot flaps by linkrods  18 . The hot flaps  14  are connected by linkrods  20  to a control ring  19 . The control ring  19  is arranged in an annular space between the inner wall  7  and the fairing  9  and is displaced parallel to the axis  12  by a plurality of synchronized control actuators  21  anchored on the stationary structure  8 . 
     Because of the linkrods  18 , the displacements of the cold flaps  16  are made to follow the displacements of the hot flaps  14 . The hot flaps  14  are driven by the actuators  21  as a function of the flight modes between a maximally convergent position, namely in the cruise mode shown in FIGS. 1 and 2, and a substantially cylindrical position, namely in the takeoff and landing configurations shown in FIGS. 3 through 7. 
     When in the cruise mode shown in FIGS. 1 and 2, the cold flaps  16  slightly converge and are situated in a downstream extension of the fairing  9 . In this configuration the cold flaps  16  will at most subtend an angle of 6° with the axis of revolution  12 . In other configurations, the cold flaps  16  diverge outwardly. 
     A thrust reverser  30  is situated downstream of the hot and cold flaps  14  and  16 . This thrust reverser  30  comprises two identical eyelids  31  and  32  situated symmetrically relative to a horizontal plane passing through the axis of revolution  12  and perpendicular to the vertical planes of the cross sections of FIGS. 1 through 7. 
     These eyelids  31  and  32  are pivotably mounted on two pairs of arms  33 ,  34 , on two pairs of linear control actuators  35 ,  36  and on the stationary structure  8 . Each pair of arms and each pair of linear actuators are situated laterally outside the eyelids  31  and  32  and inside a lateral extension of the stationary structure  8 . 
     In particular, one of the eyelids  31  hinges on downstream end  37  of two upper arms  33  having upstream ends  38  which hinge on the stationary structure  8 . The eyelid  31  also hinges on free ends  39  of rods  40  of the upper control actuators  35  which, in turn, hinge at pivot points  41  on the stationary structure  8 . The other one of the eyelids  32  is mounted in the same manner on the two lower arms  34  and the two lower control actuators  36 . 
     The arms  33  and  34  of at least one pair of arms preferably include mutually meshing gear sectors  43 ,  44  mounted at ends  38 , which assure symmetrical displacement of the two eyelids  31  and  32  relative to the axial plane of symmetry via the downstream ends  37  of the arms  33 ,  34 . 
     An actuator  50  is inserted between the two arms  33  and  34  of at least one pair of arms. A cylinder  51  of this actuator  50  hinges at a pivot point  52  on the lower arm  34  and has a rod  53  which hinges at another point  54  on the upper arm  33 . The points  52  and  54  are symmetrical relative to the axial plane of symmetry of the eyelids  31  and  32 . 
     Each eyelid  31 ,  32  preferably assumes the shape of an arch which is of triangular cross-section and which is bounded by an inner wall  61 , an outer wall  62  and a front wall  63 . 
     When in the cruise mode shown in FIGS. 1 and 2, the outer wall  62  is situated in an extension of the cold flaps  16  and preferably subtends an angle of  60  with the axis of revolution  12 . The cold flaps  16  preferably run backwards over a distance substantially twice the length of the hot flaps  14 . An intake cross section of the eyelids  31  and  32  is defined by a junction of the inner walls  61  and the outer walls  63  and exceeds an exhaust cross section of the hot flaps  14 . The inner walls  61  constitute a diverging exhaust nozzle in the cruise mode. In this configuration, the actuator  50  and the control actuators  35  and  36  are retracted. 
     As regards the takeoff mode shown in FIGS. 3 and 4, the actuator  50  is extended and the control actuators  35  and  36  are retracted. Furthermore, the hot flaps  14  are aligned with the inner wall  7 . The hinging on the downstream ends  37  of the arms  33  and  34  and the hinging on the downstream ends  39  of the control actuators  35  and  36  by the eyelids  31  and  32  are arranged in such a way in this takeoff mode that the inner walls  61  of the eyelids  31  and  32  also are situated in the extension of the inner wall  7  of the stationary structure  8 . The cold flaps  16  are diverging and assure the aerodynamic continuity, without hindrance, of the fairing  9  and the outer wall  62  of the eyelids  31  and  32 . 
     Based on the takeoff mode shown in FIGS. 3 and 4, it is possible to further retract the lower control actuator  36  and to slightly extend the upper control actuator  35  in order to slant the inner walls  61  of the eyelids  31  and  32  by about 5° relative to the axis of revolution  12  in a manner shown in FIG.  7 . Thanks to this arrangement, the gasses are directed at 5° toward the ground during takeoff. This design mainly allows decreasing the surfaces of the aircraft&#39;s stabilizers and controls which are sized for the event of wing-engine failure during takeoff. 
     The function of the eyelids  31  and  32  is to implement thrust reversal during landing. For that purpose, the two eyelids  31  and  32  are pivoted by extending the control actuators  35  and  36  with the actuator  50  retracted. This thrust-reversal mode is shown in FIGS. 5 and 6, wherein the inner walls  61  of the two eyelids  31  and  32  abut at the axial plane of symmetry and deflect the gas flow issuing from the chamber  11  forward and outward, through side apertures  70 ,  71  between the cold flaps  16  and the eyelids  31 ,  32 . As a result, the aircraft is decelerated. In this configuration, the hot flaps  14  are situated in the extension of the inner wall  7  of the stationary structure  8  and the cold flaps  16  diverge outward. 
     While the present invention has been described herein with respect to a particular preferred embodiment, it is to be understood that various modifications may be made to the present invention without departing from the spirit and scope thereof. As such, the present invention should not be considered as restricted to the disclosed embodiment, but rather should be limited in scope only by the following claims.