Divergent slave petal for variable geometry exhaust nozzles

Abstract: Divergent slave petal for sealing in variable geometry exhaust nozzles for gas turbine propulsion units, consisting of a base plate (32) bearing the axial forces but with minimum capacity for transmitting torsional forces, and a plurality of discrete transverse elements (37), transmitters of transverse and shear forces but not those of torsion around the longitudinal axis (39) of the petal (31). The said plate and elements are linked by means of guide elements (33) running along the longitudinal edges of the base plate (32), and by means of intermediate transverse fasteners (41).

Description: This invention concerns a slave petal for the divergent section of a variable geometry convergent-divergent exhaust nozzle for gas turbine propulsion units, used as the means of propulsion in aviation. More specifically, the exhaust nozzle to which this invention refers is of the axisymmetric type, consisting of a convergent section followed, in the direction of the flow, by a divergent section, both formed on the basis of master petals connected to each other by means of linkages, and slave petals also connected together by means of linkages, whose convergent section defines a throat of variable area and whose divergent section, also with variable geometry, can be actuated in order to vector the gas flow, and therefore the thrust, in any direction on a cone located around the longitudinal axis of the propulsion unit. The manoeuvrability of aircraft is an essential factor. This manoeuvrability, which to date has been achieved by aerodynamic forces, can be substantially improved by modifying the vectoring of the flow starting from its normal axial direction of action. Vectoring of the gas flow has been used for many years in rocket engines. There, the systems are much simpler since the exhaust nozzles have constant geometry. Variable geometry convergent-divergent exhaust nozzles are a relatively recent introduction in supersonic aircraft powered by turboreactor or turbofan engines. In this class of exhaust nozzle, the vectoring of the flow is still not in an operational state, being at the research or development phase. Those that are at a more advanced state are the bidimensional type, in which the flow is vectored solely in one plane. Carrying out vectoring of the flow in exhaust nozzles with axial symmetry has a special advantage since the direction of the flow can then be varied in any axial plane, the pitch and yaw planes being particularly important. Several patents exist on mechanisms for vectoring of the flow in this class of exhaust nozzle, since it is theoretically possible to carry this out in various ways, though it is very difficult to ensure that there are no major complications. Vectoring solely the divergent section of the exhaust nozzle, downstream of the throat area, has the advantage that the perturbations induced by the vectoring are not transmitted upstream of the propulsion unit and the sealing of the interstices on the different moving parts is simplified. Even so, the problem of the sealing between divergent master petals during vectoring of the flow remains. In this regard, USA patent N o 4 994 665 or EP-557 229 can be pointed out, in which different designs of exhaust nozzle are included in which solely the divergent section, or part of it, respectively, is vectored. With the aim of solving the sealing of the interstices between divergent master petals, there exist various solutions such as those included in the USA patent N o 4 690 330, N o 4 662 566, N o 5 039 014 and N o 5 076 496, and EP-557 229. The present invention describes and claims a concept of divergent slave petal for the sealing of the longitudinal interstices between contiguous divergent master petals, furthermore pointing out the special advantages offered in comparison with other systems that have been subject of patent. The geometry of the longitudinal interstices between divergent master petals alters during vectoring of the flow, going from an approximately rectangular shape to that of a ruled surface whose sides cease to be parallel. In the USA patent N o 4 690 330 and 4 662 566 a divergent slave petal is proposed formed from a plurality of overlapping segments welded together and to a longitudinal dorsal metal sheet in specific areas, in such a way that the effect of the temperature gradient between the surface in contact with the gases and the external surface of the slave petal is absorbed by allowing a certain relative movement between the segments. In order to seal the longitudinal interstice between divergent master petals during vectoring of the flow, USA patent N o 5 039 014 describes another solution that consists of a dorsal bar on which is mounted a plurality of segments that can rotate around that bar. Although this solution solves the problem of sealing the interstice, the assembly of segments creates a wall of considerable roughness and with a multitude of ridges transverse to the direction of the flow. USA patent 5 076 496 of 1991 describes a divergent slave petal formed from a metal sealing sheet linked to a continuous support element in such a way that allows a certain relative movement between both in order to allow thermal differential movements. EP-557 229 claims an asymmetrical variable geometry vectoring exhaust nozzle for gas turbine propulsion units. That exhaust nozzle consists of a divergent section and a convergent section, both formed from master petals and slave petals, and which includes governing and 'external radial support means for regulating the throat area and governing means for regulating the vectoring of the flow, characterized by the fact that the variation in the throat area and the vectoring of the flow is carried out by means of a single governing system. This single governing system is made up of three annular pieces, concentric among themselves and with the axis of the propulsion unit, and of a plurality of linear actuators linked by the upstream end to the structure of the propulsion unit. These annular pieces are connected together and to the structure of the propulsion unit by means of linkage elements and guide devices, which allow the joint axial displacement of the three annular pieces by an equal amount with respect to the structure of the propulsion unit, as well as a relative rotatory movement of the intermediate and external annular pieces between themselves and with respect to the internal annular piece in any direction, thereby allowing the external annular piece to be inclined in any direction, with the centre of rotation in the axis of the propulsion unit. The convergent master petals are connected at their upstream end to the internal annular piece by means of tangential cylindrical linkages with axis perpendicular to the axis of the propulsion unit. The external annular piece is in turn connected by means of spherical linkages to the downstream end of the linear actuators mentioned above. The mechanism for varying the throat area A8 consists of a rod connected at one end, via a linkage, to the convergent master petal, while the other end is connected via another linkage to the fixed structure of the exhaust nozzle housing. The master petals in the divergent section are transversely subdivided into two segments joined together by means of a cylindrical linkage with axis perpendicular to that of the linkage between master petals in the convergent and divergent sections, the downstream segment being joined to the external annular piece by means of a strut, which is connected to this segment via a spherical linkage and to the external annular piece via a tangential cylindrical linkage with axis perpendicular to that of the propulsion unit. The upstream segment of the divergent master petal is connected at its upstream end to the corresponding convergent master petal via a tangential cylindrical linkage with axis perpendicular to the axis of the propulsion unit. The external annular piece is designed to consist of two half-ring segments interconnected with linkages and supported by four linear actuators. This design, consisting of two half-rings moved by four linear actuators, allows the outlet area A9 to be varied for a fixed value of the throat area A8. In the quoted European patent EP-557 229, the problem of sealing the interstice existing between contiguous divergent master petals is solved by means of slave petals consisting of a foldable plate provided with hinged linkages in each of its folds, the freedom of rotation of that linkage being limited but sufficient so that the different components of that plate can adapt themselves to the configuration of maximum distortion of the geometry of that interstice. The present patent application is an improvement on the European patent EP-557 229 from the same applicants, with regard to the slave petals in the divergent section during vectoring of the gas flow. In the present invention, it is proposed to convert all the divergent slave petals into a deformable structural unit with minimum rigidity under torsion, and consisting of a base plate and a plurality of discrete transverse elements inserted in that base plate. This base plate gives the assembly axial rigidity and is the element that bears the axial forces due to the gas flow, the cooling air, and inertial forces, but -nevertheless having minimum capacity for transmitting transverse forces. For their part, the discrete transverse elements lack the capacity to transmit torsions and they transmit the transverse and shear forces imposed both by the gas flow and by the divergent master petals, to which is transmitted the gas pressure exerted on the base plate bearing the axial forces. By its upstream end, the base plate bearing the axial forces transmits these axial forces to the downstream end of its corresponding convergent slave petal via a floating degenerate cylindrical linkage. The base plate and the discrete transverse elements are connected by means of guide devices running along the longitudinal edges of that plate and by means of intermediate transverse fasteners, which are secured to the base plate between consecutive transverse elements. The guide elements mentioned consist of channels which link the longitudinal edges of the base plate with the transverse edges of the discrete transverse elements, each of these channels including a wing parallel to the internal surface of the adjacent divergent master petal, this wing constituting the longitudinal seating of the deformable structural unit on the internal surface of the corresponding divergent master petal. This wing can be reinforced by an external rim for seating on the internal surface of the contiguous divergent master petal. The channels can be obtained starting from the base plate by means of longitudinal folds formed in their longitudinal edges, or they can be created by profiles that clasp the longitudinal edges of the base plate and the transverse edges of the discrete transverse elements, giving rise to two designs of the divergent slave petals: I) With longitudinal wings reinforced with a longitudinal rim and runners, forming an integral part of the base plate bearing the axial forces. II) With longitudinal profiles reinforced with a longitudinal rim and divided into sections that do not form part of the base plate bearing the axial forces, each section instead being integral with just one of the discrete transverse elements. The second of these designs has somewhat greater flexibility with regard to torsion compared with the first design. When the gas pressure on the internal surface of the divergent slave petal is greater than the air pressure on its external surface, the base plate bearing the axial forces is seated on the discrete transverse elements, forcing them to work under flexion at the same time as the base plate locally flexes as it covers the small longitudinal spans existing between those elements. The greater rigidity under transverse flexion shown by each of the discrete transverse elements with respect to that of the base plate bearing the axial forces is due mainly to the omega-shaped transverse cross-section that they have. The thickness of the base plate bearing the axial forces is the minimum necessary for transmitting axial force to its partner, the convergent slave petal, and at the same time bridging the spans existing between every two discrete transverse elements; in such a way that the set of base plates bearing the axial forces and the discrete transverse elements have the least rigidity possible under torsion, i.e., the maximum flexibility for being distorted without this causing destruction of the material due to fatigue. For centering the divergent slave petal between contiguous divergent master petals, the corresponding centralizing mechanism is provided, and each divergent slave petal has hangers for supporting it on those contiguous divergent master petals. Given that, in certain situations, the pressure of the gas on the internal surface of the divergent slave petal (exposed to the gases) can be less than the pressure of the air on the external surface, in order to increase the stability with regard to buckling due to depression of that portion of the base plate bearing the axial forces between its longitudinal edges and the transverse hanger sections, longitudinal fasteners are fitted in the areas between every two consecutive discrete transverse elements, which hang from those discrete transverse elements, while these hang from the longitudinal edges of the said base plate bearing the axial forces; and these longitudinal edges are in turn supported by the transverse hanger sections. All the characteristics stated, as well as others proper to the invention, as gathered together in the patent claims, will be able to be better understood with the following description, made with reference to the attached diagrams, in which is shown one possible way of carrying out the invention, given by way of an example only rather than being restrictive. In the diagrams: Figure 1 is a perspective, partially cross-sectioned, view of a vectoring exhaust nozzle designed in accordance with the description made. Figure 2 is a transverse cross-section of the exhaust nozzle, along line AA-AA of figure 5, in order to show the linkages between the elements making up the simultaneous governing system of the throat area and of vectoring of the flow. Figure 3 is a longitudinal cross-section of the exhaust nozzle, along the line BB-BB of figure 2, showing the exhaust nozzle in the open position and without vectoring of the flow. Figure 4 is a longitudinal cross-section of the exhaust nozzle, along the line BB-BB of figure 2, with the exhaust nozzle in the open position and with vectoring of the flow. Figure 5 is a longitudinal cross-section of the exhaust nozzle, along the line CC-CC of figure 2, with the exhaust nozzle in the closed position and without vectoring of the flow. Figure 6 is a side elevation view of a divergent master petal. Figure 7 is an external plan view of the divergent master petal of figure 6. Figures 8 and 9 are rear views of the exhaust nozzle, without and with vectoring of the flow, respectively. Figure 10 is a rear perspective view of a divergent slave petal, designed in accordance with this invention. Figure 11 is a plan view of the divergent slave petal of figure 10. Figure 12 is a side elevation view of the divergent slave petal of figure 10. Figures 13, 14 and 15 are cross-sections, to a greater scale, along the lines PP-PP, QQ-QQ and RR-RR of figure 11, respectively. Figures 16 and 17 are similar views to those of figures 11 and 12, respectively, showing an alternative design of the divergent slave petal. Figures 18 and 19 are cross-sections, to a greater scale, along the lines SS-SS and TT-TT of figure 16, respectively. In perspective and partially cross-sectioned diagrammatic form, figure 1 shows an exhaust nozzle created in accordance with the designs included in EP-557 229, arrow A indicating the direction of the flow or circulation of the gases. As with traditional exhaust nozzles, the one shown in figure 1 includes a rear casing referenced with number 1, a convergent section referenced with number 2 and a divergent section referenced with number 3. The convergent section 2 consists of a plurality of master petals referenced with number 4 and slave petals, which are not represented. In the same way, the divergent section 3 is created on the basis of master petals 5 and slave petals, which are not shown. The exhaust nozzle also includes a governing system for the throat area A8, defined by the intersection between the convergent petals 4 and divergent petals 5, and for vectoring of the flow. The variation of the throat area and the vectoring of the flow are done by means of a single governing system, which consists of three annular pieces 6, 7 and 8, concentric among themselves and with the axis of the propulsion unit, and of a plurality of linear actuators 9 that are linked by their upstream end to the structure of the casing 1. The convergent master petals 4 are connected by their upstream end to the internal annular piece 8. This connection is made by means of tangential cylindrical linkages 10, with axis perpendicular to that of the propulsion unit. Connected to the external annular piece 6, via spherical linkages 11, figures 1 and 2, are the downstream ends of the linear actuators 9. Moreover, the external annular piece 6 is connected to the divergent master petals 5 by means of struts 12 mounted concentrically around the axis of the propulsion unit. The connection of each strut 12 to the external annular piece 6 is made by means of the cylindrical linkage 13, while the connection to the divergent master petal 5 is made by means of a spherical linkage 14 (figures 1 and 3). The governing system for the exhaust nozzle also includes a modification mechanism of the throat area A8, which is referenced with number 15 and which, as shown in figure 3, consists of a rod 16 connected at one end by means of a linkage 17 to the convergent master petal 4, while its opposite end is connected via the linkage 18 to the fixed structure of the exhaust nozzle housing. The annular pieces 6, 7 and 8 are also linked together by means of devices that allow the axial displacement of the assembly of the three pieces, by an equal amount, with respect to the structure of the propulsion unit, as well as a relative rotatory movement of the intermediate 7 and external 6 annular pieces between them and with respect to the internal annular piece 8, in such a way that it allows the external annular piece 6 to incline in any direction, with its centre of rotation in the axis of the propulsion unit. In this way, the external and internal annular pieces 6 and 8 are, via the intermediate annular piece 7, allowed a relative rotational movement in space, determining a spherical joint. For this, the annular pieces 6 and 7 are joined together by a cylindrical linkage defined by the shafts 19, figure 2, aligned in a diametrically opposite position, while the annular pieces 7 and 8 are joined together by another cylindrical linkage defined by the shafts 20, figure 2, also aligned together and in a diametrical position perpendicular to the shafts 19. With the aim of reducing the clearances between the annular pieces 6, 7 and 8 and minimizing the friction between them during their relative rotation, certain axial thrust bearings, referenced with number 21 in figure 2, are provided concentrically with the shafts 19 and 20. As can be seen in figures 3 to 5, the annular piece 8 contains a cylindrical projection 8a, by means of which sealing of the post-combustor is achieved during regulation of the throat area 15 of the exhaust nozzle. The axis of this cylindrical projection must always be located on the longitudinal axis of the propulsion unit, for which it will have, outside the plane of the spherical joint, the rollers 22, figure 5, which will move solely in the axial direction along the interior of certain guides fixed to the structure of the propulsion unit, in order to define the guide device of the annular piece 8. For its part, the external annular piece 6 is guided by a device consisting of rollers 23, figures 2 and 5, which can move solely in the axial direction along the interior of guides fixed to the structure and with a small clearance to allow the rotation of this annular piece 6 around any diameter. The guides for the annular pieces 6 and 8 will have to absorb the net shear forces that might appear during vectoring of the flow and those due to asymmetries in the loads. Via the activation in one or other direction of the linear actuators 9, the arrangement described and represented in figures 1 to 5 allows the following movements: Axial movement of the assembly of annular pieces 6, 7 and 8, along with the struts 12 and the petals 4, allowing the throat area A8, referenced with number 15 in figure 3, to be varied. The displacement of the annular pieces 6, 7 and 8 by the action of the linear actuators 9 causes radial displacement of the convergent master petals 4 via the linkage 10. Due to the fixed structure and via the rod 16, these convergent master petals 4 are opened or closed in a radial direction, defining along with the struts 12 the position of the divergent master petals 5. In this case the linear actuators 9 will always have the same length. Each of the actuators 9 can be lengthened or shortened in such a way that the external annular piece 6 moves on a theoretical spherical surface, with centre in the axis of the propulsion unit, the annular piece 8 remaining fixed in the axial position, and then achieving vectoring of the flow in any direction around the axis of the propulsion unit via the same mechanisms. In the activation indicated, the struts 12, which are connected via a cylindrical linkage 13 to the annular piece 6, rotate with this and force the divergent master petals 5 to move in the radial direction, a movement indicated with arrow R in figure 9, and in the tangential direction, a movement referenced with arrow T in the same figure 9, thereby allowing vectoring of the flow to be achieved in the direction indicated by arrow B. For this, each divergent master petal is subdivided into two segments, referenced with the numbers 5a and 5b, joined together by means of a cylindrical linkage 24 arranged in a direction perpendicular to the base of the petal, as can be better seen in figures 3, 6 and 7. The element or segment 5a is joined by means of a cylindrical linkage 25 to the master petal 4, figures 3, 6 and 7. With this solution the problem of sealing the throat area 15 is solved in the simplest way since, during vectoring of the flow, both segments 5a and 5b move in the radial direction, but the segment 5a is prevented from moving in the tangential direction, only element 5b moving in that tangential direction. Vectoring of the gas flow, and therefore of the thrust, has indeed been achieved. The annular piece 6 is divided diametrically into two half-rings, referenced with numbers 6a and 6b, connected together by means of the same elements that shape the cylindrical linkages 19, as can be seen in figure 2. The linear actuators 9 that are connected to these cylindrical linkages 19 will remain fixed in length, those that are secured to the midpoint of the half-rings 6a and 6b being shortened or lengthened by the same amount with the aim of varying the outlet area A9 of the exhaust nozzle for a given throat area A8, since the struts 12 open or close the divergent master petals 5. The three possibilities of movement mentioned above can be carried out simultaneously, with the travel of the linear actuators 9 being suitably regulated. Figure 3 shows the exhaust nozzle is the open position and without vectoring of the flow, while figure 4 shows the same longitudinal cross-section of the exhaust nozzle but in the open position and with vectoring of the flow. Figure 5, which has the exhaust nozzle in the closed position and without vectoring of the flow, shows the bearings or rollers 22 and 23 that can be displaced along longitudinal guides for guiding the axial displacement of the annular pieces 6, 7 and 8. As already stated above, figures 6 and 7 show one of the divergent master petals 5 in plan and side elevation view. As stated above, the sealing between convergent master petals and between divergent master petals is done by means of the corresponding convergent and divergent slave petals 30 and 31, as shown and referenced in figures 5 and 8 to 19. Figure 8 is a rear view of the exhaust nozzle without vectoring, in which the sealing between divergent master petals 5 is done by means of the divergent slave petals 31 shown in figures 10 to 19. Figure 9 is a similar view to that of figure 8, with vectoring of the flow in the direction of arrow B. Returning to figure 1, around the convergent section 2 the exhaust nozzle includes a cover 26, and around the divergent section a cover made up of elements 27 and 28. As shown in figures 3 to 5, the elements 27 are connected by means of spherical linkages 29 to the fixed structure and guided by the struts 12, while the elements 28 are connected to these struts 12. In order to be adapted to the divergent master slave petals 5, consisting of segments 5a and 5b, and to solve the problem of sealing the interstice existing between contiguous divergent master petals, this patent application proposes a divergent slave petal 31 that constitutes a deformable structural assembly with minimum rigidity under torsion. Figures 10 to 15 represent a design of this divergent slave petal 31, consisting of: A base plate bearing the axial forces 32 deriving both from the flow of gas and from the cooling air and inertial forces. In this design, each base plate bearing the axial forces 32 has at each of its longitudinal edges longitudinal folds running in the opposite sense of folding, one on each side determining a channel 33 finished in a longitudinal wing 35 parallel to the internal surface of the contiguous divergent master petal 5 and forming a single element with the base plate bearing the axial forces 32. The longitudinal wing (35) can be reinforced with a rim, also longitudinal, 36 for seating on the internal surface of the contiguous divergent master petal 5. The base plate bearing the axial forces 32 also has a transverse closure lip 38 in its free transverse edge. An assembly of discrete transverse elements 37 which, being transmitters of the transverse and shear forces imposed both by the gas flow and by the movements of the contiguous divergent master petals 5, have no capacity at all for transmitting torsional movements around the longitudinal axis 39 of that divergent slave petal, since they allow a certain relative movement between them and with the base plate bearing the axial forces 32. An extreme discrete transverse element 40 for connection with the convergent slave petal, welded to the upstream end of the plate bearing the axial forces 32. A set of fasteners 41 that link to the base plate bearing the axial forces 32 with the discrete transverse elements 37, allowing a certain relative movement between them. The usual support and guiding systems, consisting of hangers 42 that will rest on the divergent master petals 5, a centralizing mechanism 43 and a sliding degenerate cylindrical linkage 44 for connecting the divergent slave petal 31 to the corresponding convergent slave petal 30. All these usual support and guiding systems 42, 43 and 44 are connected to the base plate bearing the axial forces 32. These usual support and guiding systems 42, 43 and 44 are shown by way of an example, and it is possible to use other normally applied systems (e.g., a duplicated centralizing mechanism 43 instead of the sliding degenerate cylindrical linkage 44). The sliding degenerate cylindrical linkage 44 allows the divergent slave petal 31 to be seated on the internal surface of contiguous divergent master petals 5 and also allows the whole divergent slave petal 31 to rotate through a certain angle in any direction with its centre in the said sliding degenerate cylindrical linkage 44, with the aim of the divergent slave petal 31 adopting the positions that are imposed on it by the contiguous divergent master petals 5 via the centralizing mechanism 43. This sliding degenerate cylindrical linkage is habitually used in axisymmetric convergent-divergent exhaust nozzles with conventional (non-vectoring) variable geometry currently under development or in operation. Given that no material continuity exists between the discrete transverse elements 37 and the base plate bearing the axial forces 32, nor between contiguous discrete transverse elements 37, the presence of thermal gradients, both longitudinal and transverse does not generate any thermal force in the divergent slave petal 31, since nothing hinders the thermal expansion movements of the base plate bearing the axial forces 32 nor those of each of the discrete transverse elements. Moreover, and given that the thickness of the base plate bearing the axial forces 32 is the minimum necessary for transmitting the axial forces (of small magnitude) to the corresponding convergent slave petal 30 and, in turn, bridging the spans existing between every two discrete transverse elements 37 or 37 and 40 (when the pressure on the internal surface of the divergent slave petal 31 is greater than the pressure on its external surface) the divergent slave petal 31 constitutes an assembly with low rigidity to torsion since the discrete transverse elements 37 cannot transmit it. In this way, the divergent slave petal 31 has great flexibility for being distorted with the aim of covering the interstice between contiguous divergent master petals 5 during vectoring of the flow without this leading to destruction of the material due to fatigue, the service life of the petal thereby being extended. When the pressure on the internal surface of the divergent slave petal 31 is greater than the pressure on its external surface, the base plate bearing the axial forces 32 is seated in its longitudinal central section on the discrete transverse elements 37, forcing them to work under flexion and transmitting the forces to the contiguous divergent master petals 5 via the longitudinal wings 35 and longitudinal rims 36. When the pressure on the internal surface of the divergent slave petal 31 is less than the pressure on its external surface (the order of magnitude of this pressure difference is small with respect to the pressure difference, with opposite sign, in normal operation) the divergent slave petal 31 is supported as a whole by the contiguous divergent master petals 5 via the hangers 42; while the stability of the base plate bearing the axial forces 32 with regard to the buckling is assured by the rigidity given to it by its longitudinal edges, on the one hand, the transverse sections reinforced by the hangers 42 and, on the other, the longitudinal folds that shape the channels 33, which are also hung from these reinforced transverse sections; and also by the fasteners 41 from which hangs the base plate 32 of the discrete transverse elements 37 which, in turn, will also be hanging from the channels 33. The channels 33, the longitudinal wings 35, the transverse closure lip 38, the extreme discrete transverse element 40 and the fasteners 41 prevent dismembering of the deformable structural assembly with minimum rigidity under torsion which constitutes the divergent slave petal 31. In the design shown in figures 16 to 19, the longitudinal edges of the base plate 32 are finished in a rib 34 directed towards the side opposite to that occupied by the discrete transverse elements 37. The channels 33 are created by profiles 45 which clasp the longitudinal edges of the base plate 32, with its ribs 34, and the transverse edges of the discrete transverse elements 37. The external wing 46 of the profiles 45 is reinforced, as in the above case, by an external rim 36a. Both the profiles 45 and rim 36a are divided into sections, each of which is integral with just one of the discrete transverse elements 37 and overlaps one or several contiguous discrete transverse elements 37. Figures 16 to 19 show a preferred design, consisting of arranging the whole of the interstice 47 between contiguous sections of longitudinal profile 45 and longitudinal rim 36a in such a way that it does not coincide with the separation interstice 48 between discrete transverse elements 37. Figures 10 to 15 show a design in which the relative axial movement between the different discrete transverse elements 37, on the one hand, and between these and the base plate bearing the axial forces 32, on the other hand, is restricted by some appendages 37a which are integral with those discrete transverse elements 37 and to 40, and are located at their two ends, in such a way that the interstice 48 between the said appendages 37a is less than the interstice 49 between discrete transverse elements 37 and fasteners 41. This configuration is applicable both to the design of the longitudinal wings and rims shown in figures 10 to 15 and to that shown in figures 16 to 19; the same as the design shown in figures 16 to 19, in which the discrete transverse elements 37 and 40 do not have the appendages 37a, the axial movement between them and with respect to the base plate bearing the axial forces being restricted by means of the fasteners 41. In figures 10 to 19 the support element for the hanger 42 and the fasteners 41 located in the same transverse section of the divergent slave petal 31 has been designed as a single piece. In the design shown in figures 10 to 19, the extreme discrete transverse element 40 is welded at its upstream end to the upstream end of the base plate bearing the axial forces 32, it being also feasible to provide a lip similar to the transverse closure lip 38 at that upstream end, with which the discrete transverse element 40 would not be directly linked to the base plate bearing the axial forces 32 (allowing a certain relative movement between them). It is clear that for any of the designs described, the longitudinal rims 36 and 36a can be eliminated, resting the divergent slave petal 31 directly on the contiguous divergent master petals 5 via the longitudinal wings 35 or 46. The characteristics described allow the following advantages to be obtained: A divergent slave petal in which the presence of thermal gradients does not generate any thermal force. The thermal expansion of the longitudinal element is not hindered by any other element. A divergent slave petal with the capacity for being torsioned and accommodating itself to the contiguous divergent master petals during vectoring of the gas flow in an axisymmetric convergent-divergent exhaust nozzle that only vectors the divergent section. A petal consisting of repetitive elements that are easy to manufacture.

Claims: Divergent slave petal (31) for sealing in variable geometry exhaust nozzles for gas turbine propulsion units, supported by means of hangers (42) from the adjacent divergent master petals (5) and centered between these by means of the corresponding centralizing mechanism (43), furthermore being linked to the corresponding convergent slave petal (30) via a sliding linkage (44), consisting of a deformable structural assembly with minimum rigidity, made up of a base plate (32) bearing the axial forces but with minimum capacity for transmitting torsional forces, and a plurality of discrete transverse elements (37), transmitters of transverse and shear forces but not of torsion forces around the longitudinal axis (39) of the petal (31); the base plate (32) and discrete transverse elements (37) being linked by means of guide elements (33) running along the longitudinal edges of the said base plate (32) and means of intermediate transverse fasteners (41) that are secured to the base plate (32) between consecutive transverse elements (37); those guide elements (33) and transverse fasteners (41) allowing a certain relative freedom of movement between the base plate (32) and the discrete transverse elements (37); the base plate (32) also having on its longer edges longitudinal seatings (35) for its support on the internal surface of adjacent divergent master petals (5). Petal according to patent claim 1, whereby that the said guide elements (33) consist of channels (33) linking the longitudinal edges of the base plate (32) and the transverse edges of the discrete transverse elements (37), each of these channels (33) including a wing (35 or 46) parallel to the internal surface of the adjacent divergent master petal (5), the wing constituting the longitudinal seating of the deformable structural assembly on the internal surface of the corresponding divergent master petal (5). Petal according to patent claim 2, whereby the said channels (33) are continuous and obtained from the longitudinal edges of the base plate (32). Petal according to patent claim 2, whereby by the fact that the said channels (33) are constituted by profiles (45) that clasp the longitudinal edges of the base plate (32) and the transverse edges of the discrete transverse elements (37), whose profiles (45) are subdivided into sections, each of which is linked to just one of the discrete transverse elements (37); these longitudinal edges of the said base plate (32) being finished in a rib (34) directed towards the side opposite to that occupied by the discrete transverse elements (37). Petal according to patent claims 2 and 3, whereby the wing (35) constituting the longitudinal seating of the deformable structural assembly is reinforced by an external longitudinal rim (36). Petal according to patent claims 2 and 4, whereby the wing (46) constituting the longitudinal seating of the deformable structural assembly in the sections in which the profiles (45) are subdivided is reinforced by external longitudinal rims (36a), also subdivided into sections coincident with those of the said profiles (45). Petal according to patent claim 5, whereby the said rim (36) is transversely subdivided into consecutive sections. Petal according to patent claims 4 or 6, whereby the interstices (47) existing between consecutive sections of the profiles (45) are longitudinally out of phase with respect to the interstices (48) existing between consecutive discrete transverse elements (37). Petal according to patent claim 1, whereby the relative freedom of movement between the base plate (32) and the discrete transverse elements (37) is restricted by appendages (37a) with mutual contact between the said discrete transverse elements (37). Petal according to patent claim 1, whereby the relative freedom of movement between the base plate (32) and the discrete transverse elements (37) is restricted by the geometry of the fasteners (41) and of the hangers (42) for supporting the divergent slave petal (5).

Inventors: IBARRECHE MENDIA JOSE IGNACIO, RIVACOBA URRUELA JOSE, IBARRECHE MENDIA, JOSE IGNACIO, RIVACOBA URRUELA, JOSE
Applicants: SENER ING & SIST, SENER, INGENIERIA Y SISTEMAS, S.A.
Application year: 1993
Main classification: F02K1
IPC codes: F02K1