RU2433281C2 - Device to retain broken blades in bypass jet - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: device to retain broken blades is installed on a body of a bypass jet fan. The device is arranged in the form of a jacket and comprises a protective shell from a fibrous material, which covers the body along the outer surface. The protective shell is made with circular corrugations from layers of high-strength cloth wound and fixed on the body with a braid. The braid is wound between corrugations, via an intermediate layer of easily deformable material or rings from it, for instance, rings from porous rubber. Rings in process of retention form a circular gap between the protective shell and the body and a local cavity in the form of a "trap" of a blade. Along the perimetre under the protective shell on the fan body there might be metal plates installed rolled along the circumference with an overlap towards the side of the rotor rotation. The plates are attached to each other by an easily breakable mechanical or adhesive joint, for instance, with the help of rivets or glue.

EFFECT: device makes it possible to increase ballistic efficiency, damping properties and mass characteristics of protective shell and fan body as a whole as a result of stage-by-stage optimisation of energy absorption extent in elements of body structure and protective shell.

2 cl, 4 dwg

Description

The invention relates to the field of aircraft engineering and can be used in the design, manufacture and operation of aircraft engines.

Known technical solutions aimed at holding off the blades and their fragments as a power rigid fan casing [Peychev GI, Nikolaevsky SV, Vigant Yu.V. Composites in aircraft engines of the D-36 family. - Technological systems: scientific and technical journal, 2000, No. 2 (4), pp. 15-21], as well as devices mounted on the case in the form of covers, toroidal cameras, etc., in which annular cavities are provided between the case and a case, body and camera, filled with lightweight hard materials or, for example, honeycombs [US patent No. 6814541].

The retention of the blades and their fragments by the rigid casing provides only partial energy absorption due to local resistance to the elastic properties of the casing materials and their partial destruction, and the main part of the energy is absorbed by rebounding the blades from the casing walls into the flow part of the fan circuit. In this case, the collapsed blade collides with the remaining blades on the rotor and other structural elements of the engine in an indefinite manner and is thrown out of the engine. In addition, such structures have large dimensions and weight, which do not allow them to fit (adapt) into the layout of existing aircraft engines without changing adjacent components and assemblies.

Holding the blades using devices such as non-rigid covers mounted on the fan case implies a higher degree of energy absorption efficiency in relation to a rigid case without a cover and introduces some certainty when the torn blade does not ricochet into the flow part, but is caught by the cover and gets stuck between the cover and case outside the flow part of the fan circuit. This reduces the likelihood of collision of a blade stuck in the cover with the remaining blades.

Closest to the claimed device for holding off the blades is the solution set forth in US patent No. 6814541 from 10/07/2002. A device is proposed for the protective shell of the fan casing of an aircraft turbofan engine, consisting of an internal honeycomb aluminum structure and an outer cover of a multilayer version based on polyurethane reinforced with Kevlar-type material.

The main disadvantage of this technical solution is the large dimensions of the device associated with the need to create a special volumetric annular chamber filled with honeycombs to accommodate - "catching" the torn-off blade in it and moving in the circumferential direction between the outer holding cover and the fan casing in order to maximize energy absorption.

The technical task of the invention is:

1. Improving the reliability of the device for holding off the blades or their fragments in a double-circuit turbojet engine in order to ensure flight safety.

2. Increase in ballistic efficiency and damping ability of the retaining device with minimum weight and dimensions of the structure in strict overall and mass restrictions associated with the fact that the fan casing with the holding device must fit (adapt) without changing adjacent components and assemblies into the existing aircraft engine with some modification .

The essence of the invention lies in the fact that in the device for holding off the blades mounted on the fan casing of a dual-circuit turbojet engine, made in the form of a cover containing a protective sheath of fibrous material, covering the body on the outer surface, the protective sheath is made with ring corrugations of layers of high-strength fabric wound and secured to the body with a bundle wound between the corrugations through an intermediate layer of easily deformable material or rings from it, for example q of cellular rubber, which form in the process of retaining the annular clearance between the protective casing and housing and a local cavity in the form of "traps" blade. Along the perimeter under the protective shell on the fan case, metal plates rolled around the circumference with an overlap in the direction of rotation of the rotor can be installed, which are fastened together by an easily destroyed mechanical or adhesive connection, for example, using rivets or glue.

The technical result is achieved by the fact that in order to ensure maximum ballistic efficiency and damping properties under severe dimensional and mass restrictions, the protective shell is made with ring corrugations made of layers of high-strength fabric, for example, Rusar type fabric, wound and secured to the body with a bundle wound between the corrugations through an intermediate layer of easily deformable material or rings of it, for example, rings of porous rubber. The rings form the initial annular gap of a given size between the body and the shell, which, in the process of hitting the blade and breaking through the power wall of the body, is selected around the perimeter by tensioning the shell, compressing the rubber rings. The stretched shell, spreading the corrugations, forms a local cavity in the form of a “trap” of sufficient size for radial and tangential penetration and movement with braking of the scapula under the shell. Thus, the main part of the kinetic energy of the impact of the blade is absorbed due to the resistance of the fibers of the fabric with elastic properties, the resulting friction and damping forces, with partial destruction of the elements of the device and the fan casing. The protective shell holds the blade and its fragments "trapped", reducing the likelihood of collision with other blades on the rotor. To reduce the effect of “cutting” the protective shell by the sharp edges of the blade and the distribution of the impact force of the blade on the largest surface of the shell around the perimeter, metal plates rolled around the circumference are installed with an overlap in the direction of rotation of the rotor, which are fastened together by an easily destroyed mechanical or adhesive joint, for example, with using rivets.

Thus, the proposed device allows you to do without special annular chambers of large dimensions for trapping the blades like US patent No. 6814541.

Figure 1 presents a sketch of the proposed device for holding torn blades mounted on the fan casing:

1 - fan housing made of metal or composite materials;

2 - corrugated protective shell made of numerous layers of high-strength fabric, for example, organ tissue type "Rusar;

3 - bundles of high-strength fibers, for example, such as "Rusar", fastening the protective shell on the body with the formation of a given number of corrugations;

4 - rings of porous rubber, forming the initial annular gap of a given size between the housing and the protective sheath;

5 - metal plates rolled around the circumference, mounted on the housing along the perimeter under the protective sheath;

6 - a detached blade (in figures 1 and 2, one blade is conventionally shown);

7 - rivets;

8 - local cavity in the form of a "trap".

The operation scheme of the proposed device for holding fan blades and their fragments with conventionally distributed motion on the radial and peripheral components is presented:

- figure 2 is the initial position (view aa of figure 1);

- figure 3 - the movement of the blades in the radial direction;

- figure 4 - the movement of the blades in the circumferential direction.

I stage (figure 3). Partial absorption of energy occurs due to deformation and local destruction during the penetration by the blade 6 of the hole in the housing 1 made of metal or composite material.

II stage (figure 3). Partial absorption of energy due to deformation of the metal plates 5 and rupture of the easily destructible connection of the plates at the places of overlaps fastened with rivets 7. The impact energy is also distributed on the largest surface of the containment shell 2 and the effect of cutting it by the sharp edges of the blade 6 decreases.

III stage (figure 3). Partial energy absorption due to the radial movement of the plates 5 together with the protective shell 2 by sampling a predetermined initial clearance with compression of easily deformable rubber rings 4 around the perimeter of the housing 1 and the formation of a calculated local cavity in the form of a “trap” 8.

IV stage (figures 3, 4). Partial absorption of energy by breaking the bundles 3 and straightening the corrugations under tension upon impact of the blade 6, which creates additional friction between the layers of fabric and fibers. At the same time, the volume of the "trap" 8 increases, which ensures the placement and fixation of the detached blade and its fragments in it.

V stage (figures 3, 4). The blade 6, which did not overcome the resistance in stages I ... IV, in order to break through the protective shell 2, continues to move in a "trap" 8 under the shell 2 in the circumferential direction on a much larger portion of the path than in the radial direction, until the fixation - "capture", absorbing most of the energy due to the resistance of the fibers of the fabric with elastic properties and the resulting friction and damping forces.

It should be noted that the initial clearance (or the thickness of the rubber rings) and the corresponding dimensions of the "trap" are determined as a first approximation by calculation and are refined according to the test results.

The results of ballistic tests of a corrugated protective shell made of Rusar-type organotissue on a model sample of a fan casing at a scale of 1: 3 according to the proposed scheme showed an increase in ballistic efficiency by more than 2 times with respect to a protective shell without corrugations, all other things being equal. During the high-speed shooting by the camera of the process of impact and the motion of the blade simulator in the “trap” in the circumferential direction, a positive damping effect with a reverse movement of the simulator after stopping was recorded.

Such tests on model samples allow us to predict the overall dimensions, thickness and weight of the protective shell according to the proposed design scheme.

Thus, the proposed device for holding off the blades of the fan allows you to increase ballistic efficiency, damping properties and mass characteristics of the protective shell and the fan casing as a whole due to the step-by-step optimization of the degree of energy absorption by structural elements of the casing and protective casing under severe dimensional and mass restrictions. In this case, the main role in the absorption of the largest share of the energy of the torn blade is assigned to the protective corrugated shell.

Claims (2)

1. A device for holding off the blades mounted on the fan casing of a dual-circuit turbojet engine, made in the form of a cover, containing a protective shell made of fibrous material, covering the housing on the outer surface, characterized in that the protective shell is made with annular corrugations of layers of high-strength fabric wound and fixed to the body with a bundle wound between the corrugations, through an intermediate layer of easily deformable material or rings of it, for example, rings of porous rubber, which matured form in the process of retaining the annular clearance between the protective casing and housing and a local cavity in the form of "traps" blade. 2. The device for holding off the blades mounted on the fan casing of a dual-circuit turbojet engine according to claim 1, characterized in that around the perimeter under the protective shell on the fan casing there are metal plates rolled around the circumference, with an overlap in the direction of rotation of the rotor, which are fastened together easily destructible mechanical or adhesive connection, for example with rivets or glue.

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