Abstract:
A thrust reverser door is provided, in one configuration, with a plurality of peripherally-disposed frames circumferentially spaced apart from one another and projecting radially inwardly on an interior side of the door to thereby provide a channel for redirecting thrust.

Description:
TECHNICAL FIELD 
     The invention relates to a thrust reverser for a turbofan gas turbine engine, and in particular a thrust reverser door. 
     BACKGROUND 
     The width of the thrust reverser doors is one of the design parameters which is important, as it plays a direct role in the effectiveness and efficiency of a thrust reverser. While the geometrical width of the doors is often dependent on the cross section of the nacelle on which the thrust reverser is installed, the effective width of the doors tends to be smaller than the geometrical width because the relatively large longitudinal side frame members, provided for structural and aerodynamic reasons, decrease the reverser efficiency and increases the risk of reverse efflux side spillage. There is thus a need that the reverse efflux be better contained by the reverser doors and the reverser efficiency be higher than with known arrangements. 
     SUMMARY 
     In one aspect, the present concept provides a thrust reverser comprising a door having two longitudinal sides and a plurality of longitudinally-extending frames adjacent each of said longitudinal sides, the frames disposed on an interior side of the door, the frames having circumferentially spaced apart walls projecting radially from the interior side of the door, the walls extending generally along at least a portion of a length of the longitudinal sides, the walls defining at least one channel therebetween which is open on its radially inward side. 
     In another aspect, the present concept provides a thrust reverser comprising at least first and second doors movable between a stowed position and a deployed position, the doors defining a leading edge and two longitudinal sides extending therefrom and having an inner side with a thrust-deflecting surface redirecting engine thrust when the door is in the deployed position, the inner side defining a plurality of channels open to the inner side of the door, one channel extending along at least a portion of each longitudinal side of the door. 
     In another aspect, the present concept provides a method of redirecting engine thrust, the method comprising the steps of: (a) deploying a door in a thrust flow to provide thrust redirection, the door having a leading edge and longitudinal sides extending from the leading edge, said redirection having a primary flow in a forward direction toward the leading edge and at least&#39; one secondary flow in a lateral direction towards said longitudinal sides; and then (b) further redirecting said at least one secondary flow towards the leading edge. 
     In another aspect, the present concept provides a method of providing a thrust reverser door, the method comprising the steps of: providing a door skin having at least a leading edge and two longitudinal edges extending therefrom; providing a radially-inwardly-extending structural frame extending along at least a portion of each longitudinal edge; and providing an aerodynamic wall extending along the structural frame. 
     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 
         FIG. 1  is a side view of an example of a nacelle provided with a thrust reverser according to the present approach, its doors being shown in a stowed position; 
         FIG. 2  is a schematic side view of an example of a jet pipe to which are connected thrust reverser doors according to the present approach, which doors are shown in a deployed position; 
         FIG. 3  is a rear view of what is shown in  FIG. 2 ; 
         FIG. 4  is a schematic cross-sectional view showing an example of the thrust reverser door of  FIGS. 1 to 3 ; 
         FIG. 5  is a schematic cross-sectional view showing a portion of one embodiment of the door of  FIG. 4 ; 
         FIG. 6  is a view similar to  FIG. 5 , showing a portion of another embodiment of the door of  FIG. 4 ; 
         FIG. 7  is a somewhat schematic face-on view of the interior side of an example of a deployed upper door; 
         FIG. 8  is a view similar to  FIG. 5 , showing a portion of another embodiment of the door; 
         FIG. 9  is a view similar to  FIG. 5 , showing a portion of another embodiment of the door; and 
         FIG. 10  is a somewhat schematic view showing another embodiment, in which the frame pivots around a transverse axis. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , there is shown an example of a nacelle  20  including a thrust reverser  22  in the aft section  20   a  of the nacelle  20 . The turbofan gas turbine engine is located within the nacelle  20  and the nacelle  20  is attached under the wings or on the fuselage of the aircraft using an appropriate arrangement (not shown). The thrust reverser  22  comprises two opposite pivoting doors  24 ,  26  of the target/bucket door type, forming most of the exhaust nozzle of the nacelle  20  when they are in their stowed position. In the example illustrated in  FIG. 2 , one door  24  is at the upper side and the other door  26  is at the bottom side. 
     Each door  24 ,  26  has a trailing edge  24   a ,  26   a  adjacent to the propulsive jet outlet  28 . The arrows in  FIG. 1  show the direct thrust operation of the engine. The trailing edges  24   a ,  26   a  cooperate with the trailing edge of side arms  32  of a jet pipe  30  located inside the aft section  20   a  of the nacelle  20  and to which the doors  24 ,  26  are pivotally connected, as shown in  FIG. 2 .  FIG. 2  is an enlarged view showing an example of the jet pipe  30  and the doors  24 ,  26  in their deployed position.  FIG. 3  is a rear view of what is shown in  FIG. 2 . 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 . 
     The arrows in  FIG. 2  indicate the main flow path when the engine is operated during a thrust reversal. As can be seen, gases coming out of the engine are deviated substantially toward the front 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 . These edges  24   b ,  26   b  are located at the front of the doors  24 ,  26  and are referred to as “leading” edges with reference to the travel path of the aircraft. The reverser doors  24 ,  26  redirect the gases coming out of the engine for generating a resulting 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 center plane of the jet pipe  30  as disclosed in applicant&#39;s co-pending application Ser. No. 11/534,202, filed Sep. 21, 2006. The operation of the presently-described concept, however, is not dependent on such a door and pivot configuration, and any suitable arrangement may be employed. 
     It should be noted that although the doors  24 ,  26  are described herein and shown in the drawings as being an upper reverser door  24  and a lower reverser door  26  movable in a vertical plane, doors can also be configured with another orientation, such as a left door and right door movable in a horizontal plane. Also, the skilled reader will appreciate that it is possible to provide an arrangement using the present techniques in which the trailing edge  26   a  of the lower door  26  is pivoted behind the trailing edge  24   a  of the front door  24  as mentioned above. Other arrangements are possible as well. 
       FIG. 4  schematically shows a cross section taken along the lines  4 - 4  in  FIG. 3 , with a view of the interior side of the thrust reverser door  24 . A similar view could be made of the inside of the lower door  26 . The reverser door  24  includes, extending longitudinally or axially along, and parallel to and in the vicinity of each of the door&#39;s longitudinal sides  40   a ,  40   b , preferably two longitudinal frame walls  40 ,  42  that are substantially parallel to one another and extend generally radially inwardly relative to the door  26 . The frames  40 ,  42  are preferably provided relatively close to the longitudinal sides to provide structural support thereto. The frames  40 ,  42  may be machined integrally with the single skin  44  of the door, as shown in  FIG. 5 , or provided as a separate element(s)  46  mounted to the skin  44  of the door, as shown in  FIG. 6 . The connection of the element  46  to skin  44  can be made using an appropriate arrangement, such as bolts, rivets, welding, etc. Other arrangements are possible as well. The frame members  40 ,  42  are, in this example, in the form of a channel with two spaced-apart frame walls  40 ,  42 , namely an outer frame wall  40  and an inner frame wall  42 , extending radially inwardly from the skin  44  of the reverser door  24 . The height of inner frame wall  42  is preferably smaller than the height of the outer frame wall  40 , as discussed further below. For structural purposes, the longitudinal frame walls  40 ,  42  preferably connect to a laterally-extending radial frame wall  50 , as shown in  FIG. 7 , located in the vicinity of the reverser door&#39;s leading edge  24   b , and to the rear frame of the door  24  in a suitable manner (not shown). The length of the longitudinal frame members  40 ,  42  may be less than the length of the door  24 ,  26 . As seen in  FIG. 7 , the lateral frames  40 ,  42  need not extend along the entire longitudinal length of the door, but preferably extend at least to the door leading edge. In the example of  FIG. 7 , the frames  40 ,  42  extend from the vicinity of the leading edge of the doors  24  to the vicinity of the door pivot arms (not shown). 
     As can be seen in  FIG. 4 , the frame walls  40 ,  42  are circumferentially spaced from each other by a distance “s”. The inner frame wall  42  has a height “h 1 ” that is preferably smaller than a height “h 2 ” of outer frame wall  40 , as shown in  FIG. 5 . The values of “h 1 ” and “h 2 ” are chosen to provide the desired structural rigidity and aerodynamic performance of the thrust reverser door (as discussed further below), as well as to fit within the space available between the nacelle  20  and the jet pipe  30  when the doors  24 ,  26  are in their stowed position. Whether or not h 2 &gt;h 1  is possible will depend on the envelope available, the structural requirements, etc, as the skilled reader will appreciate. It will also be understood that, because the inner and outer profiles of the reverser door are typically converging from the reverser door leading edge to trailing edge, the heights h 1 , h 2  may not be constant along the length of frames  40 ,  42 , and will typically decrease from the leading edge toward the trailing edge. 
     Referring to  FIG. 7 , in use the doors of the thrust reverser are deployed when the aircraft is on the ground to generate reverse thrust. As thrust flows (indicated by the large arrows) into the door, it is redirected generally forwardly (See also  FIG. 2 ). Laterally flowing air (i.e. what would otherwise be side spillage) enters channels  60 ,  62 , and is generally captured therein, and redirected along the channels  60 ,  62  towards the door leading edge  24   b , and ultimately redirected forwardly, along with the main efflux of the reverser. Hence, what would otherwise be side spillage is captured and redirected in the forward direction to generate useful work. As mentioned, the role of the two frames  40 ,  42  is therefore both structural and aerodynamic. The frames  40 ,  42  maintain the structural integrity of the door, but they also help to reduce the sideways spillage or leakage of the exhaust gases from the door when deployed, the skilled reader appreciating that thrust diverted laterally (sideways) does not participate in the retarding force of the thrust reverser and consequently decreases the overall thrust reversing efficiency of the efflux that is directed forwardly. As can be seen in  FIG. 4 , the door width is characterized by two distinct dimensions; the first one is the geometrical width “W 1 ”, the second one is the effective width “W 2 ”. The geometrical width W 1  is the actual geometrical width dimension of the door between the edges of its opposite longitudinal sides. The effective width W 2  is the actual width dimension between the two opposite innermost longitudinal frame members  42 . In the reverser door  24 , the pair of longitudinal frames  40 ,  42  on each side provides respective channels  60 ,  62  formed between the frame walls  40 ,  42 , having a circumferential width “s”, through which the reverser thrust air flow circulates when the reverser door  24  is deployed. The channels  60 ,  62  are preferably uninterrupted along their lengths and open to the interior of the door  24 , so that an air flow, such as engine thrust, may enter the channels  60 ,  62 , travel along its length, and then exit the channel. The channels  60 ,  62  increase the effectiveness of the reverser door  24  since air is directed to now flow, in a contained manner, longitudinally near to reverser door sides to reduce, and preferably even effectively eliminate, the reverse thrust flow spillage laterally over each side of the reverser door  24  when deployed. Since two channels  60 , 62  are provided with circumferential width “s” having corresponding lateral width “d”, the width of the effective thrust reversing surface may therefore be increased by a value equal to “2d,” or W 2 +2d. As mentioned above, when the thrust reverser doors  24 ,  26  are deployed they need to contain the engine gas efflux and re-direct it in the forward direction efficiently. The containment of the lateral efflux contributes to a high reversing efficiency and prevents impingement of lateral efflux on critical control surface of the aircraft. The longitudinal frames  40 ,  42  of the reverser door  24 ,  26  significantly improve the aerodynamic efficiency of the reverser doors  24 ,  26  by improving containment of the efflux by capturing the efflux in the channels and permitting thrust to be contained on a larger area of the reverser door. The side spillage, if any, is decreased, the thrust reversing efficiency is improved as well as the controllability of the aircraft on the ground. 
     Additional longitudinal frames may be provided. For example, as shown in  FIG. 8 , a third longitudinal frame  51  is provided between longitudinal frames  40 ,  42 . The third longitudinal frame  51  in this example extends along the skin  44  between the other two frames  40 ,  42 . The third frame  51  can be made adjustable using screws  52  (only one being shown) so that its position can be changed along the sides of the door, moving closer to one or the frames  40 ,  42  or the other. This feature allows the width of the door to be adjusted, which feature can be useful during tests or to adapt a same door model on different aircraft. 
     Referring to  FIG. 9 , showing another embodiment, a third frame  51  is provided with a pivot connect  90 , such that the third frame  51  may pivot between the frames  40 ,  42  around a longitudinal axis located in the vicinity of the free edge of the frame  40  to effectively extend the height of the frame  40  during door deployment. This allows an increase of the deployed height h 3  that is greater than the height h 2  of the frame  40 . The pivoting frame  51  may be biased (e.g. spring-loaded, not shown) towards its extended position, and when the reverser doors  24 ,  26  are stowed, the pivoting third frame  51  is forced by the fixed structure to pivot back into its stowed position. When the reverser doors  24 ,  26  are subsequently deployed again, the third frame  51  pivots back to its open position, and so on. This approach may be employed, for example, in the case where the space available when the doors  24 ,  26  are stowed is not sufficient to give the frame  40  the desired aerodynamic height. 
     While additional frame  51  is shown having a longitudinal pivoting axis following the free edge of frame  40 , in another embodiment shown in  FIG. 10 , frame  51  may have its pivoting axis substantially transverse to frames  40  and  42 . In such case, the pivoting axis is located in the vicinity of the reverser door leading edge, and when the reverser doors are deployed, frame  51  that is biased towards its opened position, opens and gradually increases the height of frame  40  from a minimum value located in the vicinity of the frame pivoting axis to a maximum value located at the opposite end of the frame  51 . In this embodiment, frame  51  induces a maximum increase of the height of frame  40  in the vicinity of the reverser doors hinges, area that is most likely to generate side spillage. 
     The above description is meant to be exemplary only, and one skilled in the art will recognize that other changes may also be made to the embodiments described without departing from the scope of the invention disclosed. For instance, the shape and configuration of the doors may be different to what is described, and any suitable door arrangement may be employed. The longitudinal frames may be identical to one another, or may have different sizes, configurations, etc. The longitudinal frames may also may not be symmetrically shaped or placed on the door. The width W 2  may be constant or vary along the door length. The heights h 1  and/or h 2  may be constant or vary along the door length. The spacing may be constant or vary along the door length. Frames  40 ,  42  need not be provided to define channels  60 ,  62 , but rather any suitable manner of defining the channels may be used, such as defining with other mechanical structures mounted to the door, or the channels may be defined in a surface of the door itself, and so on. 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.