THRUST VECTORING EXHAUST NOZZLE ARRANGEMENT

Abstract: A two-dimensional thrust vectoring nozzle (10) includes aftward divergent flaps (26,28) positioned by a linkage assembly (38). The assembly (38) includes a linear track (42) pivotable about a transverse axis (44) for positioning a scissors linkage pivot (52) to selectively vary the divergence angle and vertical thrust vector of the nozzle (10).

Description: The present invention relates to a thrust vectoring exhaust nozzle having movable members for directing the flow of the exhaust gases. Thrust vectoring exhaust nozzles are well known for use in aircraft propulsion systems or the like. Such nozzles typically redirect a portion of the exhaust gases exiting the aircraft gas turbine engine for the purpose of enhancing aircraft manoeuvrability or takeoff thrust. One particular type of thrust vectoring nozzle is termed "two-dimensional" by virtue of its having a roughly rectangular exhaust flow path defined by two laterally spaced apart static sidewalls and two vertically spaced apart movable surfaces. The movable surfaces operate to direct the exhaust gas flow as desired to produce varying degrees of thrust vectoring in the vertical plane. As with any aircraft-related component or structure, the weight and complexity of such nozzles is of particular concern to the designers. Prior art nozzles, relying on a multiplicity of individual actuators and related movable structure have proved effective in achieving thrust vectoring, but have generally achieved such functional success at the expense of increased weight and complexity. Such designs are further complicated by the high gas temperature, up to 4,000°F (2,200°C) and pressure loading encountered by the flow directing surfaces. A two-dimensional thrust vectoring exhaust nozzle according to the precharacterizing portion of independent claim 1 is disclosed in GB-A-2 077 360 which uses separate electromechanical actuators to position the flap assemblies. The electromechanical actuators are disposed within the primary and secondary flaps of the nozzle and the same actuators that serve to symmetrically position the flaps in the forward thrust position also serve to asymmetrically position the flaps for thrust vectoring. Reference is also made to US-A-4 310 121 which discloses a convergent-divergent two-dimensional exhaust nozzle having upper and lower flap assemblies. To position the convergent and divergent flaps there are provided two linear actuators, each being connected to a sliding carriage member having a first and a second pair of links pivotably connected thereto. The first pair of links positions the convergent flaps and the second pair of links positions the divergent flaps. According to the invention, there is provided a two-dimensional thrust vectoring exhaust nozzle for a gas turbine engine, comprising first and second laterally spaced apart sidewalls for defining corresponding first and second lateral exhaust gas boundaries in the nozzle, upper and lower movable flap assemblies, each assembly extending between the first and second sidewalls and defining respective upper and lower gas flow boundaries, each flap assembly further including a forward flap, selectively pivotable about an axis extending between the first and second sidewalls and having a leading edge and a trailing edge, and an aftward flap, having a trailing edge and a leading edge pivotably secured to the trailing edge of the forward flap, characterized by linkage assemblies for selectively positioning the trailing edges of the aftward flaps of the upper and lower flap assemblies, including first and second scissors linkages, each scissors linkage including elongated, equal length upper and lower drag links, one end of each drag link being pivotally secured proximate the span end of the trailing edge of the corresponding upper or lower aftward flap, and the other end of each upper drag link being pivotally secured to the other end of the respective lower drag link, a first and a second linear drive track, each track secured to the respective first and second sidewalls and selectively pivotable in a plane substantially parallel thereto, and first and second trucks, each truck cooperatively engaged with the respective first and second drive track and selectively positionable therealong, each truck being pivotally secured to the respective first and second scissors linkage at the pivotable joint between the other ends of the upper and lower drag links. The divergence angle defined by the aftward flap of the upper and lower movable flap assemblies can be selected by moving the trucks in the drive tracks and thrust vectoring is achieved by pivoting the drive tracks relative to the sidewalls. Thus, the linkage assemblies according to the invention permit the use of independent actuators to vary the divergence angle and for thrust vectoring, namely first actuators to move the trucks along the tracks and independent second actuators to pivot the tracks relative to the sidewalls. With the linkage assemblies of the invention the use of such independent actuators is made possible with a minimum of individual actuators and total weight resulting in a strong and simple two-dimensional thrust vectoring nozzle. The linkage assemblies for orienting the divergent surfaces of the nozzle provide for independently achieving both a varying divergent exhaust gas flow path and selectively varying degrees of vectored thrust. Further the linkage assemblies are operable to position the divergent nozzle flaps in a variable outlet area exhaust nozzle arrangement, wherein the nozzle throat defined by the displacement between the leading edges of the divergent flaps varies as a function of engine power output. The pair of scissors linkages, disposed adjacent the sidewalls, positions the divergent flap trailing edges independent of the location of the aftward or divergent flap leading edge which may change in response to the current engine power level. Each truck is joined to the corresponding scissors linkage, thus forming first and second variable four bar linkages for accurately positioning the upper and lower divergent flap trailing edges. The linkage assemblies provide advantages over prior art actuators which may rely on a plurality of individual drivers and complex linkages to achieve thrust vectoring and variable divergence angle. Both these and other features and advantages of the present invention will be apparent to those skilled in the art upon review of the following specification and the appended claims and drawing figures, wherein: Figure 1 shows a schematic of the linkage and nozzle according to the present invention in an unvectored, augmented thrust configuration. Figure 2 shows a schematic of the nozzle flaps and scissor linkage according to the present invention in an unvectored, unaugmented configuration. Figure 3 shows the nozzle flaps and scissor linkage according to the present invention in a configuration for delivering unaugmented, 30° vectored thrust. Figure 4 shows the nozzle flaps and scissor linkage according to the present invention in a configuration for delivering augmented, 15° vectored thrust. Figure 5 shows a more detailed representation of the pivotable linear track according to the present invention. Figure 6 shows an external, isometric view of a nozzle according to the present invention as a complete package. Figure 1 shows a cutaway cross sectional schematic arrangement of an exhaust nozzle 10 according to the present invention. Exhaust gases 12 from a gas turbine engine (not shown) flow axially aftward in a flow channel having lateral boundaries defined by spaced apart sidewalls 14, one of which is shown in Figure 1, and upper and lower flow boundaries defined by upper and lower flap assemblies 16, 18. The flow passage is rectangular in cross-section and generally symmetrical about horizontal and vertical planes passing through the nozzle central axis 20. The upper and lower nozzle assemblies 16, 18 are each comprised of forward convergent flaps 22, 24 and aftward divergent flaps 26, 28. The convergent flaps 22 extend spanwisely between the sidewalls 14 and are each pivotable about a corresponding offset pivot axis 30, 32 which extends transversely across the nozzle 10. The divergent flaps 26, 28 in each assembly 16, 18 are pivotably secured to the trailing edge of the respective upper or lower convergent flap 22, 24 thereby achieving an articulated assembly which may be positioned to achieve both a variable nozzle throat area 50 and thrust vectoring as discussed hereinbelow. The divergent flaps 26, 28 are oriented within the nozzle 10 by a linkage assembly 38 which includes a scissors linkage 40 cooperatively linked to a linear track 42 which is in turn secured to one of the sidewalls 14 and pivotable about a transverse pivot point 44. The scissors linkage 40 is pivotally secured to the trailing edges 46, 48 of the divergent flaps 26, 28. A second linkage assembly similar to the linkage assembly 38 shown in Figure 1 is disposed in the opposite sidewall (not shown in this Figure) for cooperatively positioning the opposite span end. During operation of the nozzle 10 according to the present invention, the forward convergent flaps 22, 24 are pivoted about their respective pivot axes 30, 32 for achieving a variable nozzle throat area 50 defined by the displacement between the trailing edges of the convergent flaps 22, 24. The convergent flaps 22, 24 are pivoted symmetrically, ranging from the fully open position for receiving exhaust gases 12 during periods of full power, augmented engine operation, to a partially closed configuration for normal power, unaugmented engine operation as shown in Figures 2 and 3, to a fully closed configuration (not shown) wherein substantially all aftward exhaust gas flow is stopped for engine thrust reversing or other specialized operating conditions well known in the art. Due to the hinge connection 34, 36 between the convergent flaps 22, 24 and the divergent flaps 26, 28, the trailing edges of the convergent flaps 22, 24 both support and position the leading edges of the corresponding divergent flaps. The linkage 38 must therefore have the ability to orient the divergent flaps 26, 28 as desired independent of the operation of the symmetrical convergent flaps 22, 24. The divergent flaps 26, 28 serve a dual aerodynamic function in the nozzle 10 according to the present invention by defining both the angle of divergence of the exhaust gas stream passing therebetween, and the degree of thrust vectoring achieved by directing the axially flowing exhaust gases 12. The rate of divergence of the exhaust stream 12 is optimized responsive to the current mass flow, density, and engine power output to achieve the optimum thrust, efficiency, stall margin, etc. for the overall propulsion system. The configuration of Figure 1 shows a fully open nozzle throat 50 and divergent flaps 26, 28 opened to give slightly increasing nozzle area therebetween. Such configuration would be typical of a nozzle during a period of engine operation at full power and full thrust augmentation from an upstream afterburner section (not shown) or the like. As can be seen in Figure 1, the linear track 42 of the linkage assembly 38 is oriented parallel with the nozzle axis 20 and the scissors linkage 40 has been positioned to equally displace the divergent flap trailing edges 46, 48 by positioning the scissors pivot 52 axially rearwardly along the track 42. Figures 2, 3 and 4 show three additional operating configurations of the nozzle 10 according to the present invention. For simplicity, Figures 2, 3, and 4 show only the upper and lower flap assemblies 16, 18 and the scissors linkage 40. Figure 2 shows the flap assemblies 16, 18 positioned during a period of engine operation in an unaugmented, unvectored configuration. The convergent flaps 22, 24 have been pivoted to define a reduced nozzle throat 50 with the scissors pivot 52 being moved axially forward so as to orient the divergent flaps 26, 28 to provide a constant or slightly convergent flow passage downstream of the nozzle throat 50. By maintaining the scissors pivot 52 in the horizontal plane of the nozzle axis 20, the divergent flaps 26, 28 remain substantially vertically symmetrical with respect to the axis 20. Figure 3 shows the upper and lower assemblies 16, 18 again configured for unaugmented engine power, but with the divergent flaps 26, 28 positioned to deliver vectored thrust from the nozzle centerline 20 by an angle of 30°. The convergent flaps 22, 24 are positioned as in the Figure 2 configuration, however the divergent flaps 26, 28 are asymmetrically oriented by the scissors linkage 40. As can be seen from the broken outline of the linear track 42, the track 42 has been pivoted about the common pivot axis 44, thus displacing the scissors pivot 52 from the horizontal plane defined by the nozzle axis 20 by a distance 54. Such displacement positions the trailing edges 46, 48 of the divergent flaps 26, 28 asymmetrically with respect to the horizontal plane, thus directing the exhaust gases 12 at an angle from the nozzle axis 20. Figure 4 shows the flap assemblies 16, 18 configured so as to deliver 15° of vectored thrust during a period of augmented engine operation. It should be apparent without extensive discussion that the convergent flaps 22, 24 are fully open to define a maximum nozzle throat 50, and that the divergent flaps 26, 28 have been asymmetrically oriented with respect to the nozzle axis 20 by displacing the scissors pivot 52 a distance 54′ from the horizontal plane defined by such axis 20. The gases 12 are thus directed at an angle to the axis 20 thereby providing the desired degree of vectored thrust. Figure 5 shows a more detailed isometric view of the linkage assembly 38 according to the present invention. The linear track 42 is pivotable about the pivot axis 44 in a plane generally parallel to the sidewall 14. The pivoting motion 56 of the track 42 may be induced by a variety of angular actuators known in the art, one of which is shown in Figure 5 as including a combination ring gear 58 and driven worm gear 60 whereby a rotary motor (not shown) spins the worm gear 60, hence causing the ring gear 58 and linear track 46 to rotate 59 as desired. The drag links 62, 64 of the scissors linkage 40 are pivotally secured at the scissors pivot 52 to a movable truck 66 received within the linear track 42 and translatable therealong. Translation of the truck 66 is induced in the Figure 5 embodiment by a sprocket and chain arrangement including a pair of idler sprockets 68, 70, a chain 72 passing around the sprockets 68, 70 and linked to the truck 66, and a drive sprocket 74 rotating by a ring gear 76 and worm gear 78 combination for positioning the truck 66 along the linear truck 42 as desired. While many actuators may be used to position the truck 66 and track 42, the ring gear and worm gear combinations 58, 60, 72, 78 as shown in Figure 5 provide a simple, extremely powerful mechanism for positioning the various components. It will be appreciated by those skilled in the art of nozzle design that such variable surface nozzles require accurate scheduling of the surface position with the current or transitional engine power output. Such scheduling may utilize feedback position sensors to assist the various actuators in accurately positioning the various flaps 22, 24, 26, 28 and linkages 38 to achieve the desired optimum orientations. Figure 6 shows a nozzle 10 according to the present invention in an exterior view so as to better give an appreciation for the arrangement of the various components. The convergent and divergent flaps 22, 26 of the upper flap assembly 16 are visible as are both sidewalls 14, 14′. The drag links 62, 64, 62, 64′ of the scissors linkages are shown protruding from within the sidewalls 14, 14′ and connecting to the span ends of the trailing edges 46, 48 of the upper and lower divergent flaps 26, 28. Also shown in Figure 6 is an exit ramp 80 secured to the trailing edge 46 of the upper divergent flap 26 for providing an additional expansion surface for the exhaust gases exiting the nozzle 10. Such exit ramps may be used in conjunction with the nozzle 10 according to the present invention depending on the particular circumstances, requirements and expected operating environment. The nozzle and linkage according to the present invention is thus seen to provide a simple, accurate means for positioning nozzle surfaces for redirecting or otherwise modifying the flow of exhaust gases from a gas turbine engine. The combination of the scissors linkage and pivotable linear track allow a balancing of the forces on the various linkage components, thus reducing the working stress and extending the service life thereof. It should further be noted that the embodiment of the invention disclosed hereinabove is only one of a variety of equivalent embodiments which may occur to those skilled in the art, and as such should not be construed as limiting the scope of the present invention beyond the recitation of the claims presented hereinbelow.

Claims: 1. Two-dimensional thrust vectoring exhaust nozzle for a gas turbine engine, comprising: first and second laterally spaced apart sidewalls (14) for defining corresponding first and second lateral exhaust gas boundaries in the nozzle; upper and lower movable flap assemblies (16, 18), each assembly extending between the first and second sidewalls (14) and defining respective upper and lower gas flow boundaries, each flap assembly (16, 18) further including a forward flap (22, 24), selectively pivotable about an axis (30, 32) extending between the first and second sidewalls (14) and having a leading edge and a trailing edge, and an aftward flap (26, 28), having a trailing edge and a leading edge pivotably secured to the trailing edge of the forward flap (22, 24), characterized by linkage assemblies (38) for selectively positioning the trailing edges of the aftward flaps (26, 28) of the upper and lower flap assemblies (16, 18), including first and second scissors linkages (40), each scissors linkage (40) including elongated, equal length upper and lower drag links (62, 64, 62′, 64′), one end of each drag link being pivotally secured proximate the span end of the trailing edge of the corresponding upper or lower aftward flap (26, 28), and the other end of each upper drag link (62, 62′) being pivotally secured to the other end of the respective lower drag link (64, 64′), a first and a second linear drive track (42), each track (42) secured to the respective first and second sidewalls (14) and selectively pivotable in a plane substantially parallel thereto, and first and second trucks (66), each truck (66) cooperatively engaged with the respective first and second drive track (42) and selectively positionable therealong, each truck (66) being pivotally secured to the respective first and second scissors linkage (40) at the pivotable joint between the other ends of the upper and lower drag links (62, 64, 62′, 64′). 2. Exhaust nozzle according to claim 1, characterized by further comprising: means for selectively pivoting the first and second tracks (42), and means for selectively translating the first and second trucks (66) along the respective first and second tracks (42). 3. Exhaust nozzle according to claim 2, characterized in that the pivoting means for the first and second tracks (42) each include a ring gear and a worm gear (58, 60), and the means for selectively translating the first and second trucks (66) each include a sprocket and chain combination (68, 70, 72, 74). 4. Exhaust nozzle according to claim 1, characterized in that the forward flaps (22, 24) are each offset radially with respect to each of the corresponding pivot axes (30, 32).

Inventors: MADDEN, WILLIAM MARVIN
Applicants: UNITED TECHNOLOGIES CORPORATION
Application year: 1988
Main classification: F02K1
IPC codes: F02K1