Abstract:
The thrust reverser includes, in one aspect, an interior flow deflector which defines a portion of a substantially continuous and uninterrupted nozzle interior surface with the interior of a jet pipe when the door is in a stowed position, thereby reducing aerodynamic losses and improving efficiency. In another aspect, improved sealing arrangement between the jet pipe and the door provides increased performance when the doors are stowed.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to thrust reversers for turbofan gas turbine engines. 
       BACKGROUND 
       [0002]    Thrust reversers on gas turbine engines have to fulfill two functions: while stowed, to provide an exhaust nozzle for the direct thrust generated by the engine; and while deployed, to redirect the engine thrust to order to provide a decelerating force after landing. Since almost the entire flight sequence occurs with the thrust reverser in the stowed position, it is desirable that the presence of the thrust reverser does not degrade the direct thrust performance of the engine. 
         [0003]    While many thrust reversers models have been used successfully for a number of years, there is a need to provide an improved arrangement. 
       SUMMARY 
       [0004]    In one aspect, the present concept provides a thrust reverser for a turbofan engine, the thrust reverser comprising at least first and second doors pivotally connected to a jet pipe, the jet pipe having an exit defined by an exit profile, each door having an outer skin and an inner skin mounted to the outer skin, the inner skin extending along only a portion of an axial length of the outer skin, the inner skin of the doors having edges that matingly engage the edges of the jet pipe substantially along the length of the exit profile. 
         [0005]    In another aspect, the present concept provides a thrust reverser comprising: a jet pipe having an inner flow surface for receiving engine exhaust gases, the jet pipe having a circular portion and two arms extending rearward of the circular portion; and a pair of opposed doors pivotally connected to the jet pipe arms, each door having an inner flow surface in registry with the inner flow surface of the jet pipe and mating therewith to engage the jet pipe along its exit length when the doors are closed, wherein the inner surface of the jet pipe and the inner surfaces of the doors co-operate to provide a nozzle for engine exhaust gases. 
         [0006]    In another aspect, the present concept provides a thrust reverser for a turbofan engine, the thrust reverser comprising an interior wall defining a continuous nozzle interior surface from a nozzle inlet to a thrust reverser exit when the doors are in a stowed position, the nozzle interior surface co-operatively defined by an internal surface of a jet pipe of the thrust reverser, internal surfaces of a plurality of closed thrust reverser doors of the thrust reverser, and seals extending between the jet pipe and each door substantially along an interface between the jet pipe and said door. 
         [0007]    Further details of these and other aspects of the improvements presented herein will be apparent from the detailed description and appended figures. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0008]      FIG. 1  is a side view of an example of a nacelle provided with a thrust reverser according to the present arrangement, its doors being shown in a stowed position; 
           [0009]      FIG. 2  is a schematic side view of the thrust reverser of  FIG. 1 , with doors shown in a deployed position; 
           [0010]      FIG. 3  is a rear view of what is shown in  FIG. 2 ; 
           [0011]      FIG. 4  is a schematic longitudinal cross-sectional view showing an example of the improved arrangement with the thrust reverser doors in the stowed position; 
           [0012]      FIG. 5  is a view similar to  FIG. 4 , showing the doors in a deployed position; 
           [0013]      FIG. 6  is an isometric view showing an example of an improved upper door; 
           [0014]      FIG. 7  is an isometric view showing an example of an improved lower door; 
           [0015]      FIG. 8  is a cross-section through lines  8 - 8  of  FIG. 1 ; 
           [0016]      FIG. 9A  is an isometric view of the upper seal shown in  FIG. 4  and  FIG. 9B  is an enlarged cross section of an example of the seal mounted to the jet pipe; and 
           [0017]      FIG. 10  is a view similar to  FIG. 4 , showing another embodiment of the improved arrangement. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Referring now to  FIG. 1 , there is shown an example of a nacelle  20  including a thrust reverser  22  of the target/bucket type, located in the aft section  20   a  of the nacelle  20 . The turbofan gas turbine engine is located within the nacelle  20  and the engine and nacelle  20  are attached under the wings, or to the fuselage, of the aircraft using an appropriate arrangement (not shown). The thrust reverser  22  comprises two opposite pivoting doors  24 ,  26  forming an exhaust exit nozzle of the nacelle  20 , having a planar exit  28 , when the doors are in their stowed position. One door  24  is at the upper side and the other door  26  is at the lower side. 
         [0019]    Each door  24 ,  26  has a trailing edge  24   a ,  26   a  defining a portion of the exit  28 . The arrows in  FIG. 1  represent the direct thrust air flow generated by operation of the engine.  FIG. 2  is an enlarged view of only the thrust reverser of  FIG. 1 , showing a jet pipe  30  to which doors  24 ,  26  are pivotally connected.  FIG. 3  is a rear view of what is shown in  FIG. 2 . The doors  24 ,  26  are in their deployed position in  FIGS. 2 and 3 . The jet pipe  30  is concealed inside the aft section  20   a  of the nacelle  20  when the doors  24 ,  26  are in their stowed position, as in  FIG. 1 . 
         [0020]    As shown in  FIG. 4 , the jet pipe  30  has axially-downstream-extending arms  32  on either side of upper and lower cutouts  34 , with peripheral edges defining the cutouts  34 , each edge having substantially horizontal or longitudinal portion  38  and a generally vertical or circumferential portion  40  (which the reader will appreciate a semi-circular in shape, extending from the substantially horizontal portion  38  on one side or arm of the jet pipe  30 , to the substantially horizontal portion  38  on the other side or arm of the jet pipe  30 ). Peripheral edges preferably include a seal  52  along the lengths of portions  38  and  40 , as will be described further below. 
         [0021]    The arrows in  FIG. 2  indicate the main exhaust gas flow path during thrust reversal. Exhaust gases coming out of the engine are redirected substantially forwardly when the doors  24 ,  26  are in their deployed position. The gases exit the doors  24 ,  26  in the vicinity of their leading edges  24   b ,  26   b . The leading edges  24   b ,  26   b  are located at the front of the doors  24 ,  26 , and hence are “leading” edges with reference to the travel path of the aircraft. The redirection of the gases coming out of the engine creates a horizontal retarding force opposing the forward movement of the aircraft. Increasing the output thrust generated by the engine increases the aerodynamic decelerating force. In the illustrated example, the trailing edge  24   a  of the upper door  24  is pivoted behind the trailing edge  26   a  of the lower door  26 , this resulting from the asymmetrical positioning of the pivots with reference to the horizontal medial plane of the jet pipe  30 , as described in applicant&#39;s co-pending application Ser. No. 11/534,202, filed Sep. 21, 2006. 
         [0022]    It should be noted that, although the doors  24 ,  26  are described herein and shown in the figures as an upper reverser door  24  and a lower reverser door  26  movable in a vertical plane, doors may instead be configured with any other suitable orientation, such as a left door and right door movable in a horizontal plane. Other suitable arrangements are possible, as well, within the teachings of the present concepts. 
         [0023]      FIG. 4  schematically shows a longitudinal cross section of the thrust reverser of  FIG. 1 , and shows an example of the thrust reverser with doors  24 ,  26  in a stowed position, adjacent a jet pipe  30 , such as is the case during direct thrust generation through operation of the engine. Each door  24 ,  26  has an outer skin or wall  44  extending from the leading edge  24   b ,  26   b  to the trailing edge  24   a ,  26   a  thereof. An inwardly extending rib(s)  45  (only one is shown) is provided adjacent the leading edge  24   b ,  26   b , for strength and stiffness, and similar ribs extend along the sides of the door (not shown). On the interior side of outer skin  44 , each door  24 ,  26  has an inner skin, configured to provide a flow deflector  50  as will be described further below, mounted to the aft portion of the outer skin or wall  44 . Each flow deflector  50  has an axial or longitudinal length that is preferably less than the length of the outer skin of wall  44  of the corresponding door  24 ,  26 . Each flow deflector  50  is defined by a leading edge  56  and lateral edges  58  (see  FIGS. 6 and 7 ) that preferably matingly correspond to the shape of the cutouts  34  of the jet pipe  30 , as will be described further below, to provide a substantially continuous exit nozzle  60  when doors  24 ,  26  are stowed, as shown in  FIG. 4 . Each flow deflector  50  is preferably shaped and configured to create a substantially uniform interior flow surface, sometimes referred to as an inner mold line (IML), for exit nozzle  60  when the doors  24 ,  26  are in their stowed position. The nozzle  60  is preferably defined by surface  62  on the inside of jet pipe  30  and arm  32 , and surfaces  64  provided by deflectors  50 . In this case, where the jet pipe  30  and deflectors  50  has interior flow lines which provide a fully-convergent (e.g. such as frustoconical) nozzle  60 , the flow deflectors  50  are preferably have an inner surface  54  shaped and configured to continue the interior flow lines of jet pipe  30  in a fully-convergent fashion. That is, the flow deflectors  50  complete the interior flow lines otherwise interrupted by the cutout portions  34  of the jet pipe  30 , and thus the surfaces  64  of the flow deflectors  50  create a substantially continuous and uninterrupted surface with the interior surface  62  of the jet pipe  30 . 
         [0024]    As can be seen, in this example each flow deflector  50  extends from its trailing edge  24   a ,  26   a  to about the axial midpoint of its door  24 ,  26 . This leaves the front or leading portion of each door  24 ,  26  with a single layer skin or wall  44 , and results in a construction for the doors  24 ,  26  which is lighter than a double skin construction. The outer and inner skins may be sheet metal, cast, machined from solid, or made by other suitable technique. The inner skin/flow deflector  50  can be a single piece or multiple pieces joined together. The deflectors  50  can be attached to skin  44  by rivets  70  (see  FIGS. 6 and 7 ) or otherwise suitably fastened to the wall  44  of the doors  24 ,  26 . Reinforcing radial frames(s)  80  (only one is shown per door in  FIGS. 4 and 5 ) or other suitable structural reinforcement is preferably provided under flow deflectors  50 , if required or desired, for example to stiffen skin  44  or structurally support flow deflector  50 . 
         [0025]    Referring to  FIG. 8 , shown is a schematic lateral cross-section of the thrust reverser, taken generally along the lines  8 - 8  in  FIG. 1  (door hinges, actuators, etc. are omitted, for clarity). As can be seen, a substantially continuous nozzle surface  60  is provided, through the co-operation of flow deflectors  50  and jet pipe  30  and arms  32  of jet pipe  30 . 
         [0026]    In use, when the doors  24 ,  26  are stowed, the flow deflectors  50  preferably matingly engage the jet pipe  30  substantially all along the peripheral edges. The edges are provided with a preferably continuous peripheral seal  52  preferably substantially along the entire length of the peripheral edges, i.e. along portions  38  and  40 . The peripheral seals  52  are preferably of the resilient type and are compressed substantially along their entire lengths when the doors are stowed. In this example, the seal  52  is engaged and compressed by the leading edges  56  and lateral edges  58  of the flow deflectors  50  when the doors are stowed, to provide a complete sealing substantially around flow deflectors  50 , and thus impeding engine exhaust gases from leaking past the seals  52  during the direct thrust operation (i.e. doors stowed). This has beneficial implications for powerplant efficiency because there are reduced aerodynamic losses within the nozzle  60 . To facilitate sealing in this example, leading edges  56  and lateral edges  58  are preferably smooth and contiguous, so that seal  52  is continuously sealingly engaged by the edges  56 ,  58 , when the doors are stowed. 
         [0027]    As described above, the peripheral seals  52  extend substantially along the longitudinal portion  38 , i.e. along the edges of the extending jet pipe arms  32 , and along the substantially circumferential portion  40 , along the edges of the jet pipe cutouts  34 . The seals  52  are the same length on the upper and lower sides of the jet pipe  30  when the jet pipe cutouts are symmetrical, as shown in  FIGS. 4 and 5 . Referring to  FIG. 10 , showing another embodiment, lower cutout  34   b  is larger than upper cutout  34   a , and with this arrangement, the seal  52   b  is necessarily longer than seal  52   a , since the perimeter of cutout  34   b  is longer than that of cutout  34   a , as the reader will appreciate. The asymmetrical cutout of the jet pipe shown in  FIG. 10  is meant to provide substantially the same efflux exit effective area for the top and the lower reverser doors when said doors  24 ,  26  are in their deployed position. 
         [0028]      FIG. 5  shows the example thrust reverser of  FIG. 3  with the doors  24 ,  26  in a deployed position. As can be seen, gases flowing out through the jet pipe  30  are deflected by the doors  24 ,  26  toward the front of the aircraft. It also shows that the front or leading edge  56  of the deflectors  50  is inclined to more smoothly blend to the inner surface of the skin/wall  44 . Other shapes, configuration and arrangements are possible for cutouts  34  and flow deflectors  50 . The reverse efflux preferably does not impinge the seals. 
         [0029]      FIGS. 6 and 7  show isometric views of the example thrust reverser doors  24 ,  26  of  FIGS. 2 to 5 , each door being provided with a flow deflector  50 .  FIG. 6  shows an upper door  24  and  FIG. 7  shows a lower door  26 .  FIG. 9A  shows an isometric view of the shape of upper seal  52  when installed on peripheral edge. As can be seen in this figure, and in  FIGS. 6 and 7 , the shape of the seal  52  and peripheral edge, and the shape of deflector  50 , matingly engage along a three-dimensional interface defined between them. Longitudinal portion  38  has a slight curved portion  39  in the region of the door hinges, to facilitate sealing in this area.  FIG. 9B  shows an example seal  52 , having a mounting portion  52   a  suitably mounted (e.g. by bonding, riveting with the addition of a seal retainer (not shown) etc.) to jet pipe  30 , and a resilient sealing portion  52   b  which is engaged and compressed by door  24  (in this case) when the door is closed (depicted by in broken lines). 
         [0030]    As can be appreciated, the arrangement described herein provides a way to seal the interface between doors  24 ,  26  and jet pipe  30 , when the doors are in a stowed position, to eliminate cavities and provide a continuous aerodynamic nozzle surface for exhaust gases exiting the engine through the thrust reverser. These cavities may otherwise generate turbulence or other aerodynamic losses, thus decrease the overall efficiency of the thrust reverser nozzle during the direct thrust operation of the engine. Using substantially continuous peripheral seals, preferably along the entire length of edges  52 , between the jet pipe arms  32 , cutouts  34  and the doors  24 ,  26 , is therefore an improvement to reverser efficiency when stowed. As mentioned, the seal is preferably compressed all along its length, preferably at a substantial constant compression sufficient to provide effective sealing in view of the pressure drop across the sealed interface and temperature of the exhaust gases. The seal  52  may be provided in any material(s) and configuration(s) suitable to provide the sealing taught herein. 
         [0031]    The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the spirit of the invention disclosed. For instance, the shapes and the configuration of the doors may differ from what is shown and described. Although the reverser nozzle described is fully convergent when the reverser doors are stowed, the flow lines (IML) of the nozzle could be any suitable design, such as convergent-divergent, if desired. The shape and the configuration of the deflectors may also differ from what is shown and described without departing from the concepts taught. Any surface(s) of the deflector maybe used to engage the surface to be sealed. It should be noted that the flow deflectors  50  of the two doors  24 ,  26  do not need to be identical, as for example is shown in  FIG. 10 . As mentioned, the present approach is not limited to a particular seal composition or configuration. Still other modifications will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the scope of the appended claims.