Turbojet gas generator fairing

Abstract

The fairing of a turbojet gas generator comprises a shell consisting of an upstream part and a downstream part. The upstream part is provided with at least one pair of hinges in the upper part of the gas generator nacelle. The downstream part is fastened to a guide. Other guides are mounted on the lower part of the fairing. All guides are equidistantly distributed around the circumference of the engine casing; the front end of the guide is mounted on a front ring via a sliding connection, and the rear end of the guide is fastened to a rear ring, wherein the front ring is mounted on the engine casing and is centered relative to the casing by radially arranged tensile members, and is mounted on the engine via a floating bearing. The present invention can reduce the stress caused by inertial forces.

Description

Technical Field

[0001] The present invention relates to a gas turbine engine structure, in particular to a design and method of a gas generator cowl attachment structure of a turbojet engine. Background Art

[0002] In general, the nacelle of a turbojet bypass engine consists of the following components listed along the airflow direction of the engine: air inlet, fan case cowling, rear nacelle assembly.

[0003] In particular, the technical solution of the design of a gas generator cowl is known from patent RU2135397 (IPC B64D29 / 06, published on August 27, 1999). According to this design, the housing is attached to four guides evenly distributed on the circumference of the engine. The front end of the guide is fixed to the engine casing, and the rear end is fixed with clearance to a ring mounted on the engine by means of an inclined saddle.

[0004] The disadvantage of this design is the restriction on the shape of the fairing, which does not allow it to be used, for example, for the spindle-shaped fairing widely used in modern gas turbine engines. For the spindle-shaped fairing, the diameter of the central part is larger than the diameter of the front and rear ends, and when the spindle-shaped fairing slides, it is possible to get stuck in the gas generator structural elements.

[0005] To solve this problem, it is proposed to divide the fairing into two parts: a sliding downstream part and a swinging upstream part. When dividing the fairing into kinematically independent parts, the design characteristics of the engine need to be considered.

[0006] For example, it may be necessary to divide the fairing into three parts, if there are struts in the downstream bypass duct to prevent the swinging section from opening, then the upstream part of the fairing will be composed of several independent sector panels.

[0007] A technical solution CA2780299 (IPC B64D33 / 04, published on June 16, 2011) for designing a gas generator fairing as part of a rear assembly of the nacelle is known. It is considered to be the closest analogue (prototype). In this rear assembly of the nacelle, the space between the external structure and the gas generator fairing forms a bypass duct of annular cross-section, ending in a reaction nozzle. If necessary, and depending on the type of aircraft, the external structure can be a reverser, which ensures the reversal of the engine thrust during landing by reversing the airflow of the bypass duct in the direction of movement. Through this design of the rear assembly of the nacelle, the gas generator can be approached by axial displacement of the external structure and the gas generator fairing. The fairing structure consists of two parts.

[0008] A turbojet gas generator cowling comprises a housing consisting of at least one upper downstream part and one lower downstream part, each downstream part having a movable connection to a fastening element and allowing the parts to be moved between an operating position in which the parts are connected to each other, thereby closing the turbojet gas generator, and a position for servicing the engine, wherein the downstream part is movable in an axially movable manner and the upstream part is movable due to the outward opening of at least one flap, wherein the downstream part and the upstream part are provided with elements engaging with each other, wherein the upstream part is provided with at least one pair of hinged assemblies in the upper part of the gas generator chamber connected by a beam, and the downstream part is fixed to a guide.

[0009] In addition to introducing an additional swinging portion in the fairing structure, a plurality of guides attached to the engine are replaced by guides fixed to the pylon, so that the contact elements for attaching to the guides are located only in the upper part of the downstream part of the fairing.

[0010] This one-sided arrangement of the guide has a number of disadvantages. Inertial forces affect the fairing during the evolution of the vehicle due to overloads, and the point of action of this force is located at the center of mass of the fairing near the axis of rotation. Since such a fairing structure has an attachment point in the upper part, which is far away from the center of mass of the fairing, the lateral component of the inertial force will generate additional stresses in the guide from the bending moment proportional to the distance between the center of mass and the attachment point.

[0011] In addition to the above, the difference between the movement of the cowling mounted on the pylon and the engine may cause the cowling to contact engine structural components located on the gas generator, thereby damaging said components or the cowling itself.

[0012] It is common practice to use a spring stop between the rear of the cowling and the gas generator for additional support of the cowling of this design. However, this solution leads to an additional problem of fretting corrosion of metal parts at the contact points of the cowling and the gas generator due to vibrations during engine operation. Summary of the invention

[0013] The technical problem that is solved only by using the proposed invention and that could not be solved when using the prototype is that the fairing is subjected to the impact of inertial forces due to overloads during the evolution of the aircraft, the fairing has an attachment point in the upper part, which is far away from the center of mass of the fairing, and the lateral component of the inertial force will generate additional stresses on the guide device, and the generated bending moment is proportional to the distance between the center of mass and the attachment point.

[0014] The technical objective of the proposed invention is to create a gas generator fairing design in which the above-mentioned drawbacks will be eliminated, in particular to create a spindle-shaped fairing that moves with the engine and has a distributed attachment scheme with minimal stresses caused by inertial forces.

[0015] The technical problem can be solved as follows: a turbojet gas generator fairing comprises a casing consisting of at least one upstream part and one downstream part, each of the upstream and downstream parts being movably connected to an attachment element and allowing the parts to be moved between an operating position, in which the parts are connected to each other, thereby shutting down the turbojet gas generator, and a position for servicing the engine, wherein the downstream part is movable in an axially movable manner and the upstream part is movable due to the outward opening of at least one flap, wherein the downstream part and the upstream part are provided with elements engaging with each other.

[0016] The upstream part is provided with at least one pair of hinge units connected to each other by beams at the upper part of the gas generator chamber, and the downstream part is fixed to the guide. According to the present invention, an additional guide is included in the lower part of the fairing, wherein the guide and the additional guide are evenly distributed around the circumference of the engine casing, and the front end is mounted on the front ring by a sliding connection, thereby providing mutual movement of the connected parts in the axial direction, and the rear end is attached to the rear ring, wherein the front ring is mounted on the engine casing and centered relative to the casing by radial rods, and the rear ring is mounted on the engine by an intermediate inclined saddle, the design of which ensures that the rear ring is centered relative to the engine casing by the relative movement of the parts in the radial direction.

[0017] Compared to the prototype, the proposed invention comprises additional guides in the lower part of the fairing, wherein the guides and the additional guides are evenly distributed along the circumference of the engine casing, and their front ends are mounted on a front ring by a sliding connection, thereby providing mutual movement of the connected parts in the axial direction, and the rear ends are attached to a rear ring, wherein the front ring is mounted on the engine casing and centered relative to the casing by radial rods, and the rear ring is mounted on the engine by an intermediate inclined saddle, the design of which centers the rear ring relative to the engine casing due to the relative movement of the parts in the radial direction, which reduces the inertial force load on the attachment element by the even distribution of the guides on the surface of the fairing shell.

[0018] The technical solution proposed to this problem is to improve the known fairing structure consisting of at least one upstream part and one downstream part, each part being installed in a manner movable between an operating position and a position for servicing the engine, and wherein the parts are attached to each other in the working position, the downstream part having a guide device for axial movement, and the upstream part having a hinge unit for opening the flaps.

[0019] The improvement lies in using the downstream parts of multiple guide members as guide devices. The guide members are distributed along the circumference of the engine casing and are fixed to the front ring through their front ends. The front ring is hinged to the pull rod, which is hinged to the engine casing and has its rear end fixed to the rear ring installed on the engine casing with the help of an inclined saddle.

[0020] Attaching the guides to the respective rings centered relative to the engine casing by means of tie rods with hinges and tilting saddles makes it possible to compensate for thermal expansion of the engine casing. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A turbojet gas generator cowling is shown;

[0022] Figure 2 The AA section of the attachment of the swinging part of the fairing is shown;

[0023] Figure 3 The BB section of the front ring of the guide attachment is shown;

[0024] Figure 4 The VV section of the rear ring of the guide attachment is shown;

[0025] Figure 5 View G showing the rear ring tilt saddle;

[0026] Figure 6 The DD section of the rear ring tilted saddle is shown;

[0027] Figure 7 A structure for a gas generator fairing attachment is shown;

[0028] Figure 8 Brackets for attaching the fairing to the guide are shown. DETAILED DESCRIPTION

[0029] The fairing of the gas generator 1 is fixed to the fan casing 2 through the upstream part of the fairing 3 by means of a connection consisting of a semicircular protrusion with a V-shaped cross-section on the fairing and a corresponding groove on the fan casing 2.

[0030] The oscillating upstream part of the fairing 3 consists of two flaps 4, 5, each of which has a plurality of hinge units 6 for articulation, which form a common axis of rotation. In this particular version, the hinge units are embedded in a beam 7, which together with five longitudinal beams 8 forms a structure attached to the fan casing at the front and to the front ring 9 at the rear.

[0031] The beam 7 can be attached to the pylon 10. The attachment should ensure independence of the movement of the beam 7 and the pylon 10 in the operating position of the fairing, in order to prevent additional stresses in the parts due to the different movements of the engine and the pylon during flight of the aircraft.

[0032] At the bottom, the flaps are connected by means of latches, which prestress the flaps and thereby reduce the play in the projection-groove connection.

[0033] The downstream part of the fairing 11 is mounted on the guide 12 and the further guide 13 by means of a bracket 14 which clamps the guide 12 and the further guide 13 by means of rollers 15 mounted therein, thereby fixing the fairing in all directions except the axial direction, forming a sliding connection 16.

[0034] In this design, the bracket can be replaced by a sleeve with an anti-friction coating.

[0035] In the operating position, the downstream portion of the fairing 11 is axially fixed by a lug-slot connection similar to the connection of the upstream portion of the fairing 3 to the fan casing 2 .

[0036] To facilitate installation, the downstream portion of the fairing 11 can be divided into two left and right panels, with the lower portion having a flange connection.

[0037] In this particular version, two guides 12 and two further guides 13 are used to fix the downstream portion of the fairing 11. The guides 12 and further guides 13 are arranged uniformly along the circumference of the engine casing 17, parallel to its longitudinal axis. The front ends of the guides are inserted into brackets 18 fixed to the front ring 9. The guides 12, further guides 13 and brackets 18 form a sliding connection 16 similar to the sliding connection 16 of the guides 12, further guides 13 and brackets 14.

[0038] Ten tie rods 19 are used to mount the ring relative to the engine and to center it, one end of which is attached to the engine casing by an articulated joint. The tie rods 19 are arranged in pairs at regular intervals around the engine casing 17 so that the hinge axes of each pair are collinear. The free ends of the tie rods 19 are also fixed in pairs in brackets 20 by bolts, which are the rotation axes of the tie rods 19. The structure consisting of two tie rods 19 and brackets 20 forms a triangle, the rotation axis of which lies in a plane perpendicular to the engine axis. The triangle is combined by the front ring 9 into a single kinematic system without degrees of freedom by means of a rigid connection with brackets 20.

[0039] The way this arrangement works is that when the housing expands due to heat during engine operation, thereby moving the attachment point of the tie rod 19, the tie rod 19 reduces its inclination angle relative to the engine axis in order to maintain its length, thereby allowing the front ring 9 to move along the guides 12, 13 while maintaining alignment with the engine housing 17.

[0040] The rear end of the guide is fixed by means of a rear bracket 21 placed on a rear ring 22. The rear ring 22 is mounted on the engine housing 17 by means of inclined saddles 23 arranged evenly along the circumference. The inclined saddles consist of two plates 24, 25 between which the rod 26 is sandwiched, and the plate 24 is directly connected to the engine housing. The rear ring 22 is placed between the plates 24, 25 with a small gap Δ so that the rod 26 is located in the radial groove of the rear ring 22.

[0041] Thus, the implementation of the proposed invention with the above-described characteristics, combined with the known features, makes it possible to compensate for the thermal expansion of the engine casing by attaching the guides to the respective rings centered relative to the engine casing by means of hinged tie rods and inclined saddles, and to reduce the loads of inertial forces on the attachment elements due to their uniform distribution over the shell surface of the spindle-shaped fairing that moves with the engine.

Claims

1. A turbojet gas generator cowling, comprising a casing consisting of at least one upstream portion and one downstream portion, each of the upstream and downstream portions being movably connected to an attachment element and allowing each portion to be moved between an operating position, in which the upstream and downstream portions are connected to each other, thereby closing the turbojet gas generator, and a position for servicing the engine, wherein: The downstream part can be moved in an axially movable manner, and the upstream part can be moved due to the outward opening of at least one flap, wherein the downstream part and the upstream part are provided with elements that engage with each other, wherein the upstream part is provided with at least one pair of hinge units connected to each other by a beam at the upper part of the gas generator chamber, and the downstream part is fixed to the guide member, characterized in that the guide member includes a first guide member at the upper part of the fairing and a second guide member at the lower part of the fairing, wherein the first guide member and the second guide member are evenly distributed around the circumference of the engine casing, and the front ends of the first guide member and the second guide member are mounted on the front ring through a sliding connection to provide mutual movement of the connected parts in the axial direction, and the rear ends are attached to the rear ring, wherein the front ring is mounted on the engine casing and is centered relative to the engine casing by radial tie rods, and the rear ring is mounted on the engine through an intermediate inclined saddle, and the design of the inclined saddle ensures that the rear ring is centered relative to the engine casing through the relative movement of the parts in the radial direction.

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