A MOUNTING ARRANGEMENT FOR A GAS TURBINE ENGINE

Abstract: A linkage arrangement (20) joins a nacelle (12) enclosing a gas turbine engine (10) and a pylon (18) suspended from an aircraft wing. The linkage arrangement (20) counteracts the deflections of the nacelle (12) with respect to the free air stream due to the aerodynamic load. The linkage arrangement (20) inlcudes a plurality of links (22, 24, 32, 34) that substantially duplicate the motion of a fourbar linkage mechanism.

Description: DESCRIPTION A MOUNTING ARRANGEMENT FOR A GAS TURBINE ENGINE Technical Field This invention relates to gas turbine engines and, more particularly, to mounting arrangements therefor. Background of the Invention A typical gas turbine engine used to propel an airplane is encased in a nacelle. A pylon secures the nacelle onto the airplane. The newer generations of gas turbine engines tend to have larger diameter nacelles that accommodate larger diameter fans. One of the drawbacks of the newer engines is that larger diameter nacelles experience greater aerodynamic load. Increased aerodynamic loads result in greater angular deviation of the nacelle in pitch and yaw. The deflected position of the nacelle results in redistribution of the aerodynamic loads so that deflection increases even further, which in turn amplifies the aerodynamic loads. One problem caused by the angular deviation of the nacelle is that the center line of the nacelle becomes misaligned with the free air stream entering the nacelle. Such misalignment results in a momentum reaction force that acts on the nacelle and contributes to even greater deflection of the nacelle. Thus, both the aerodynamic load and the momentum force, caused by the aerodynamic load, contribute to the total angular deviation of the nacelle. Eventually, the elasticity of the pylon swings the nacelle to the other side like a pendulum and the cycle begins again. This pendulum effect can produce oscillations of the airplane wing, known as flutter. Severe oscillations or flutter may cause failure of the airplane wing. One solution for reducing the deflection of the nacelle and wing flutter is to add significant weight for stiffening of the aircraft wing. However, as is well known in the art, additional weight is highly undesirable in gas turbine engines and airplanes. Thus, the wing flutter problem presents a limitation to newer engines having larger diameter nacelles and fans. Disclosure of the Invention According to the present invention, a linkage arrangement between a nacelle, enclosing a gas turbine engine, and a pylon, attaching the nacelle and the gas turbine engine onto an aircraft wing, steers the nacelle to counteract deflections of the nacelle due to aerodynamic load. The linkage arrangement induces the nacelle to pivot about an instant center of rotation which is disposed forward of the point of application of the net aerodynamic load. The steering motion is achieved by having the linkage arrangement substantially duplicate the motion of a four bar linkage mechanism. A plurality of springs return the nacelle to its original central position. Depending on the specific application, the linkage arrangement of the present invention can be tailored to either mitigate the deflection of the nacelle, eliminate the deflection, or overcompensate for the deflection. One advantage of the present invention is that the linkage arrangement does not add significant weight to the aircraft. Another advantage of the present invention is that steering achieved by a passive device that does not require complicated active control mechanisms that would result in expensive hardware and software, require additional weight, and add a higher risk of failure. The foregoing and other objects and advantages of the present invention become more apparent in light of the following detailed description of the exemplary embodiments thereof, as illustrated in the accompanying drawings. Brief Description of the Drawings FIG. 1 is a simplified, schematic representation of an assembly including a gas turbine engine enclosed in a nacelle with the nacelle being attached onto a pylon by means of a linkage arrangement, according to the present invention; FIG. 2 is an enlarged, simplified, schematic representation of the linkage arrangement of FIG. 1 ; FIG. 3 is a simplified, schematic representation of the nacelle mounted on the pylon by means of the linkage arrangement of FIG. 2; FIG. 4 is a simplified, schematic representation of the nacelle mounted on the pylon by means of the linkage arrangement of FIG. 3 with the linkage arrangement eliminating the deflection of the nacelle; FIG. 5 is a simplified, schematic representation of the nacelle mounted on the pylon by means of the linkage arrangement of FIG. 3 with the linkage arrangement mitigating the deflection of the nacelle; FIG. 6 is a simplified, schematic representation of the nacelle mounted on the pylon by means of the linkage arrangement of FIG. 3 with the linkage arrangement overcompensating for the deflection of the nacelle; FIG. 7 is a simplified, schematic, representation of another embodiment of the linkage arrangement, according to the present invention; FIG. 8 is a simplified, schematic, representation of a further embodiment of the linkage arrangement, according to the present invention; and FIG. 9 is a simplified, schematic, representation of the linkage arrangement of FIG. 1 placed in a series, according to the present invention. Best Mode for Carrying Out the Invention Referring to FIG. 1 , an assembly 8 includes a gas turbine engine 10 enclosed in a nacelle 12. Both the gas turbine engine 10 and the nacelle 12 are centered about a longitudinal center axis 14. A nacelle structure 16 is fixedly attached to the nacelle 12. A pylon 18, suspended from an aircraft wing (not shown), secures the nacelle 12 with the gas turbine engine 10 onto the aircraft wing. An attachment between the pylon 18 and the nacelle structure 16 is facilitated by a linkage arrangement 20. The linkage arrangement 20, shown in greater detail in FIG. 2, includes two rigid upper links 22, 24 joining an upper nacelle structure surface 26 of the nacelle structure 16 and an upper pylon surface 28 of the pylon 18. Two rigid lower links 32, 34 join a lower nacelle structure surface 36 and a lower pylon surface 38. Each rigid link 22, 24, 32, 34 includes a link body 40 and a forward end 42 and an aft end 44. Each forward 42 end and each aft end 44 has a hole 46 formed therein. Each forward end 42 of each upper link 22, 24 attaches onto the upper nacelle structure surface 26 at a nacelle upper attachment point 50 by means of a pin 52 passing through the hole 46, so that each upper link 22, 24 is free to pivot about the nacelle upper attachment point 50. Similarly, each aft end 44 of each upper link 22, 24 attaches onto the upper pylon surface 28 at a pylon upper attachment point 54 by means of the pins 52 passing through the holes 46, so that each upper link 22, 24 is free to pivot about the pylon upper attachment point 54. Analogously, each forward and aft end of the lower links 32, 34 attaches to the lower nacelle structure surface 36 and to the lower pylon surface 38, respectively, at nacelle lower attachment points 56 and at pylon lower attachment points 58, respectively. Each lower link 32, 34 is free to pivot about the nacelle lower attachment point 56 and the pylon lower attachment point 58. The upper links 22, 24 and the lower links 32, 34 are in register with each other, respectively. Consequently, the nacelle upper attachment points 50 are in register with the nacelle lower attachment points 56. The pylon upper attachment points 54 are in register with the pylon lower attachment points 58. Each nacelle attachment line 60 passes through the nacelle upper attachment point 50 of the upper links 22, 24 and the nacelle lower attachment point 56 of the lower links 32, 34. Similarly, each pylon attachment line 62 passes through the upper and lower pylon attachment points 54, 58 of the upper and lower links 22, 24, 32, 34, respectively. The distance between the two nacelle attachment lines 60 is shorter than the distance between the two pylon attachment lines 62. A first spring 66, having two ends, attaches onto the lower and upper links 22, 32. A second spring 68, having two ends, attaches onto the lower and upper links 24, 34. The first spring 66 and the second spring 68 are oriented in opposite directions with respect to each other. Links 22, 32 have a local center line 70 and links 24, 34 have a local center line 72 that are depicted by dashed lines in FIG. 3. The local center lines 70, 72 of the upper rigid links 22, 24 are extended forward and intersect at an instant center of rotation 74. The rigid links 22, 24 are arranged so that the instant center of rotation 74 is disposed upstream from a point of application of the net aerodynamic load F. During operation of the gas turbine engine 10, air 78 enters the nacelle 12 in a substantially parallel relationship to the center axis 14 of the nacelle 12 and the gas turbine engine 10. During flight, a lateral aerodynamic load F, shown in FIG. 3, acts upon the nacelle 12. The aerodynamic load F tends to deflect the nacelle 12. As the nacelle deviates from its original position, the linkage arrangement 20 steers the nacelle 12 to counteract the angular deviation. Depending on the specific needs of the airplane, the linkage arrangement 20 of the present invention has the flexibility to either eliminate the deflection of the center axis 14 of the nacelle from the direction of the free air stream 78, mitigate such deflection, or overcompensate for such deflection. The flexibility can be controlled by changing the lengths of the links 22, 24, 32, 34. The elimination of the deviation, shown in FIG. 4, allows the center axis 14 of the deviated nacelle 12 to remain in a substantially parallel position to the direction of the free air stream 78. The mitigation of the angular deviation, shown in FIG. 5, allows for some correction of the deflection and can be accomplished by varying the length of the links. The overcompensation of the deviation, shown in FIG. 6, results in the gas turbine engine "nosing" into the opposite direction of the deflection. The linkage arrangement 20, reacting to applied aerodynamic load, exhibits the properties of a four bar linkage, with the pylon 18 acting as a frame, links 22, 24, 32, 34 acting as side links, and the nacelle structure 16 acting as a coupler. The motion of the four bar linkage is well known in the art. As the links 22, 24, 32, 34 pivot about the nacelle and pylon attachment lines 60, 62, in response to continuously changing aerodynamic load F, the local center lines 70, 72 of the links also continuously change their respective positions. As the local center lines 70, 72 change their positions, the instant center of rotation 74 also changes its location, as shown in FIGS. 3-6. The nacelle 12 with the gas turbine engine 10 effectively pivots about the instant center of rotation 74. For the mounting arrangement of the present invention to operate properly, the instant center of rotation 74 must be disposed forward of the application point of the net aerodynamic load F. The first and second springs 66, 68 provide a certain stiffness to the four bar linkage, as shown in FIG. 2. The springs enable the linkage arrangement 20 to return the nacelle 12 to its original position. Although springs 66, 68 are shown as coil springs, other types of springs or stiffening links can be used. For example, a plurality of belleville washers in compression placed in a tube can be used. The linkage arrangement of the present invention is a passive, self- correcting, structural control system. The linkage arrangement continuously counteracts the deflection of the nacelle in response to different magnitudes of the aerodynamic load. The springs return the nacelle to the original position. One advantage of the present invention is that the linkage does not add significant weight to the aircraft. Another advantage is that the linkage arrangement of the present invention does not require expensive hardware and software to control the deflections of the nacelle. Another embodiment of the present invention is shown in FIG. 7. The upper link 22 and the lower link 32 are replaced by a first plate 122 and the upper link 24 and the lower link 34 are replaced by a second plate 124. The first plate and the second plate of this embodiment act as side links of a four bar linkage mechanism. Each plate 122, 124 includes a forward end 142 and an aft end 144. The forward ends 142 of each plate 122, 124 are hingeably attached to the nacelle structure 116 so that nacelle attachment lines 160 pass through the hinges 152 attaching the plates 122, 124 to the nacelle structure 116. The aft ends 144 of each plate 122, 124 are hingeably attached to the pylon 118 so that pylon attachment lines 162 pass through the hinges 152 attaching the plates 122, 124 to the pylon 118. The distance between the nacelle attachment lines 160 is shorter than the distance between the pylon attachment lines 162. Extension lines 170, 172 of each plate 122, 124, respectively, extended forward, intersect at an instant center of rotation 174. The instant center of rotation is disposed forward of the application point of the net aerodynamic load. The length of both plates 122, 124 is substantially the same. The length of both plates 122, 124 is tailored to the particular application and can be chosen such that the linkage arrangement 120 can either mitigate deflection of the nacelle, eliminate the deflection, or overcompensate for the deflection. Another embodiment of the present invention is shown in FIG. 8. The linkage arrangement 220 includes two plates 222, 224 that attach to the nacelle structure 216 and to the pylon 218 by means of a plurality of "living" hinges 152. The distance between the nacelle attachment lines 260 is shorter than the distance between the pylon attachment lines 262. Extension lines 270, 271 of each plate 222, 224, extended forward, intersect at an instant center of rotation 274. The instant center of rotation 274 is disposed forward of the net application of the aerodynamic load F. The plates can be manufactured from a material such as spring steel to allow for flexibility thereof. The linkage arrangement 220 includes a motion restricting mechanism 280 that comprises a first bumper 282, a second bumper 284, and a snout 286. The first and second bumpers 282, 284 protrude from the pylon 218. The snout 286 protrudes from the nacelle structure 216 and fits between the first and second bumpers 282, 284. A predetermined spacing is provided between the snout 286 and the bumpers 282, 284. As the nacelle 212 is deflected, the plates 222, 224 steer the nacelle in the direction opposite to the deflection. Once the maximum amount of desired travel is achieved, the snout bumps against one of the bumpers and thereby restricts any additional travel of the nacelle structure 216. All embodiments of the present invention, as shown in FIGS. 2, 7, can include bumpers to restrict travel of the linkage arrangements. For example, a rubber bumper can be placed in either embodiment so that the links 22, 24, 32, 34 or plates 122, 124 bump into the bumpers preventing further displacement. Other motion restricting devices can be substituted to limit the travel of the four bar linkage. The linkage arrangements 20, 120, 220 shown in the FIGS. 2, 7, 8 counteract the angular deviations of the nacelle 12 in the yaw direction. To counteract deviation of the nacelle in the yaw and pitch directions, the linkage arrangements can be placed in series, as shown in FIG. 9. The linkage arrangements are positioned 90° out of phase with respect to each. Two linkage arrangements placed in the series will counteract the deviations of the nacelle in every direction.

Claims: Claims 1. An assembly for an aircraft characterized by: a gas turbine engine for powering said aircraft; a nacelle enclosing said gas turbine engine; a pylon suspended from said aircraft; and a linkage arrangement for mounting said nacelle with said gas turbine engine onto said pylon, said linkage arrangement having associated therewith an instant center of rotation disposed forward of a point of application of a net aerodynamic load, thereby steering said nacelle to counteract angular deflection of said pylon and said nacelle due to said aerodynamic load acting thereon and allowing said nacelle to pivot about said instant center of rotation. 2. The assembly according to claim 1 further characterized by said instant center of rotation being continuously relocated about said nacelle so that said nacelle pivots about a different point thereon. 3. The assembly according to claim 1 further characterized by said linkage arrangement substantially duplicating motion of a four bar linkage mechanism. 4. The assembly according to claim 3 further characterized by said linkage arrangement including a first side link and a second side link joining said pylon and said nacelle, each said side link having a body with a forward and an aft end, said forward end of said first side link attaching pivotably onto said nacelle at a first nacelle attachment point, said aft end of said first side link attaching pivotably onto said pylon at a first pylon attachment point, said body of said first side link having a first local center line passing therethrough, said forward end of said second side link attaching pivotably onto said nacelle at a second nacelle attachment point, said aft end of said second side link attaching pivotably onto said pylon at a second pylon attachment point, said body of said second side link having a second local center line passing therethrough, said first local center line and said second local center line being extended forward and intersecting at said instant center of rotation. 5. The assembly according to claim 4 further characterized by distance between said first nacelle attachment point and said second nacelle attachment point being shorter than the distance between said first pylon attachment point and said second pylon attachment point. 6. The assembly according to claim 4 further characterized by said linkage arrangement including a first spring and a second spring, said first spring and said second spring engaging said first side link and said second side link to return said nacelle to its original position. 7. The assembly according to claim 6 further characterized by said first spring attaching onto said aft end on an upper surface of said first side link and onto said forward end on an upper surface of said second side link, said second spring attaching onto said aft end on a lower surface of said second side link and onto said forward end on a lower surface of said first side link. 8. The assembly according to claim 4 further characterized by a plurality of bumpers limiting travel of said linkage arrangement. 9. The assembly according to claim 4 further characterized by said first side link being a plurality of first sublinks, each said first sublink of said plurality of first sublinks being in register with each other, said second side link being a plurality of second sublinks, each said second sublink of said plurality of second sublinks being in register with each other. 10. The assembly according to claim 9 further characterized by each said first sublink of said plurality of first sublinks pivotably attaching onto said nacelle and said pylon by means of a first pin, each said second sublink of said plurality of second sublinks pivotably attaching onto said nacelle and said pylon by means of a second pin. 11. The assembly according to claim 4 further characterized by said first side link being a first plate, said second side link being a second plate. 12. The assembly according to claim 11 further characterized by said first plate pivotably attaching onto said nacelle and said pylon by means of a first hinge, said second plate pivotably attaching onto said nacelle and said pylon by means of a second hinge.

Inventors: DUESLER PAUL W, DUESLER, PAUL, W.
Applicants: UNITED TECHNOLOGIES CORP, UNITED TECHNOLOGIES CORPORATION
Application year: 1995
Main classification: B64D27
IPC codes: B64D27, B64D29, F02C7, F02K3