RU2730565C1 - Double-flow turbine jet engine - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to gas turbine engines and can be used in supports of rotors of axial fans of aircraft double-flow turbojet engines. Double-flow turbojet engine, in which housings of bearings 6 and 8 are fixed on intermediate housing 2. Housing 6 of first bearing 5 is equipped with flange 10 fixed in bore 11 of the intermediate housing in axial direction by means of pressure flange 12 fixed by screws 13 in intermediate housing 2. In radial direction flange 10 is fixed in bore 11 with shear pins 14 ("Weak Link") with provision of radial gap 15 between outer cylindrical surface of flange 10 of housing of first bearing and inner cylindrical surface of bore 11, wherein pins 14 and screws 13 axes are parallel to the fan rotor rotation axis 3 Sealing of oil cavity 9 of the support along the mating surfaces of flange 10 of housing 6 of first bearing 5 with intermediate housing 2 is provided by elastic ring 17.

EFFECT: thus, proposed design of support of rotor of fan of double-flow turbojet engine excludes rotor displacement in axial direction and provides possibility of shift of first radially-thrust ball bearing of its support in radial direction without breaching tightness of oil cavity, that minimizes considerable destruction of engine structure at break of rotor blade of its fan.

1 cl, 3 dwg

Description

The invention relates to gas turbine engines and can be used in the bearings of the rotors of axial fans of aircraft bypass turbojet engines in order to minimize secondary damage to the engine structure when the rotor blade of its fan breaks.

Breakage of blades of bladed machines can be associated with the impact of random operating factors. The level and nature of damage to the blade machine is determined by the size and number of fragments, the level of their kinetic energy. Secondary damage to the engine structure can lead to more serious consequences than the direct destruction of the flow path of the blade machine itself. Large unbalanced forces of the fan rotor arising after the breakage of its blade and acting from the fan rotor on the engine casing create increased dynamic loads in the nodes of its suspension in the engine nacelle of the aircraft. Three phases of the process can be distinguished:

- the actual moment of blade breakage with the destruction of a part of the housing elements of the structure and contact of the fan rotor blades with the casing of its stator,

- the run-out of the rotor after turning off the fuel supply to the combustion chamber with a decrease in its speed to autorotation,

- autorotation mode.

One of the design elements of the engine that prevents significant damage in the event of a fan blade breakage is a special device introduced into the design of its rotor supports. In foreign literature, the term “Load Reduction Device (LRD)” is used, and in the domestic literature, the term “Weak Link” is used. Modern engines with a high bypass ratio, having large dimension fan blades with a significant mass, are equipped with such devices. In connection with the use of high-pressure fans with so-called "wide chord blades" with a significant mass, the need for these special devices may also arise for engines with a relatively small degree of bypass.

Known turbojet engine, the rotor shaft of the fan which is supported by a support with two bearings. The first bearing is supported by a support piece, which forms a shell around the shaft, oriented backward from the first bearing and attached to the stationary structure of the motor. The second bearing is supported by a support piece that is also attached to the fixed engine structure. A part of the first bearing support is attached to the fixed structure of the engine by so-called "shear screws" with a weakened groove section of the cylindrical rod, along which their destruction occurs under the action of increased applied loads (Patent FR No. 2752024, IPC F16C 13/02, F16B 31/00, F01D 25/16, published 02/06/1998).

Unbalanced forces of the fan rotor, arising after the breakage of its blade and acting from the fan rotor on the fixed engine structure, create increased dynamic loads on the shear screws, which break, disconnecting the first bearing support part from the fixed engine structure. After detaching the first bearing support part from the fixed structure of the motor, the fan rotor is randomly displaced and continues to rotate. In this case, the tightness of the oil cavity of the first and second bearings is broken, which can lead to increased fire hazard and is a disadvantage.

The closest proposed technical solution is a turbojet engine with a fan rotor integral with a drive shaft supported by the first and second bearings, containing a stator and a fan rotor with a shaft supported by the first and second bearings, as well as a retaining disk on the fan shaft, interacting with a stator disk to form an emergency bearing that holds the fan rotor in the axial direction. (RF patent No. 2386050, IPC F02K 3/04, published on 10.04.2010).

In the event of the destruction of the shear screws of the support ("weak link") of the housing of the first bearing from the effect of large unbalanced forces of the fan rotor caused by the breakage of its blade, under the action of the axial force, the rotor is displaced towards the air flow entering the fan until the dynamic contact of the retaining disk on the fan shaft with its stator limiting disc in the area of the second bearing with the formation of an emergency bearing. In this case, the tightness of the oil cavity of the first and second bearings is disrupted, and the radial force from the fan rotor can be transmitted to its stator by arbitrary dynamic contact with the ends of the rotor blades. This can lead to increased fire hazard and is a disadvantage of the known engine.

The proposed invention is aimed at minimizing secondary damage to the engine structure when the rotor blade of its fan breaks by creating a fan support structure with a "Weak Link", which excludes the displacement of the rotor in the axial direction and provides the possibility of displacing the housing of the first bearing of its support in the radial direction without breaking the tightness of the oil cavity.

The creation of this invention solves the problem of expanding the arsenal of technical means - supports of the fan rotor of a turbojet engine with a "Weak Link" device, which prevents significant damage in the event of a fan blade breakage.

The problem is solved by the fact that in a double-circuit turbojet engine containing a fan rotor with a shaft supported by the first angular contact ball and second radial roller bearings installed in the corresponding housings fixed on the intermediate engine casing, the housing of the first bearing is equipped with a flange, which is fixed in the bore of the intermediate casing in the axial direction by the clamping flange, and in the radial direction - by shear pins providing a radial clearance between the outer cylindrical surface of the flange of the first bearing housing and the inner cylindrical surface of the bore, while the axes of the shear pins are oriented parallel to the rotation axis of the fan rotor, and the flange of the first bearing housing and the bore of the intermediate housing are sealed to each other by an elastic ring.

FIG. 1 shows a two-circuit turbojet engine with a fan support; in fig. 2 - fan support with first and second bearings (view A in Fig. 1); in fig. 3 - connection of the housing of the first bearing with the intermediate housing of the by-pass turbojet engine (view B in Fig. 3).

A two-circuit turbojet engine contains a stator 1, fixed on the intermediate casing of the engine 2, and a fan rotor 3 with a shaft 4. The fan rotor 3 is supported by a first angular contact ball bearing 5 with a casing 6 and a second radial roller bearing 7 with a casing 8 providing regulated radial clearances between the ends of the blades of the rotor 3 and the stator 1 of the fan, and the bearing housings 6 and 8 are fixed on the intermediate casing 2. The fan support has an oil cavity 9. The casing 6 of the first bearing 5 is equipped with a flange 10, which is fixed in the bore 11 of the intermediate casing in the axial direction by clamping flange 12, fixed with screws 13 in the intermediate casing 2. In the radial direction, the flange 10 is fixed in the bore 11 with shear pins 14 ("Weak Link") providing a radial clearance 15 between the outer cylindrical surface of the flange 10 of the first bearing housing and the inner cylindrical surface of the bore 11 ... The flange 10 is centered by means of pins 14 to ensure the tightness of joints along the surfaces 16, while the axes of the pins 14 and screws 13 are parallel to the axis of rotation of the fan rotor 3. Sealing of the oil cavity 9 of the support along the mating surfaces of the flange 10 of the housing 6 of the first bearing 5 with the intermediate housing 2 is carried out elastic ring 17.

When manufacturing the rotor of the fan 3 with the shaft 4, it is dynamically balanced on bearings 5 and 7 in order to minimize the dynamic loads on the bearings during its normal operation as part of a by-pass turbojet engine. When assembling a two-circuit turbojet engine, the alignment of the seats for bearings 5 and 7 in their housings 6 and 8, fixed on the intermediate casing 2, is monitored. Thus, the center of mass of the rotor of the fan 3 and the shaft 4 is aligned with the axis of its rotation as part of the engine fan and calculated level of axial and radial forces on bearings 5 and 7 during normal operation of a bypass turbojet engine.

In the event of a break in the fan rotor blade 3 as a result of the impact of random operating factors, which are flight modes with the maximum air flow rate entering the fan and the maximum rotational speed of its rotor, the following occurs:

- a broken blade has a dynamic force effect on the stator of the fan 1, the force from the stator 1 through the intermediate casing 2 of the bypass turbojet engine is transmitted to its suspension units in the engine nacelle of the aircraft (not shown),

- the rotor of the fan 3 without a rotor blade becomes dynamically unbalanced, since its center of mass does not coincide with the axis of rotation of its shaft 4 in bearings 5 and 7; the blades of the rotating rotor of the fan 3 come into contact with the stator 1 and are partially destroyed;

- the forces acting on the bearings 5 and 7 sharply and significantly increase, which leads to dynamic loading of their housings 6 and 8, as well as their attachment points on the intermediate housing 2 - first of all, the housing 6 of the first angular contact ball bearing 5, flange 10 which is fixed in the intermediate housing 2 with screws 13 by means of a clamping flange 12 and pins 14 to a bore 11;

- under the action of a dynamic radial force, the pins 14 are sheared along the planes of the surfaces 16, which makes it possible to displace the housing 6 with the bearing 5 in the radial direction by the amount of the gap 15 and thereby significantly reduce the value of the radial force from the bearing 5 transmitted through the intermediate housing 2 of the engine by nodes of its suspension;

- the axial force in this case is constantly perceived by the clamping flange 12, fixed by the fastening screws 13 in the intermediate casing, and, accordingly, is transmitted through the intermediate casing 2 of the engine to its suspension units,

- in this case, the tightness of the oil cavity 9 of the support is provided by an elastic ring 17, by means of which the flange 10 of the housing of the first bearing and the bore 11 of the intermediate housing are sealed;

- after turning off the fuel supply to the engine combustion chamber, the fan rotor speed decreases to the autorotation mode.

Thus, the proposed design of the fan rotor support of a dual-circuit turbojet engine excludes the displacement of the rotor in the axial direction and provides the possibility of displacement of the first angular contact ball bearing of its support in the radial direction without breaking the tightness of the oil cavity, which minimizes significant destruction of the engine structure when the rotor blade of its fan breaks. ...

Claims (1)

A two-circuit turbojet engine containing a fan rotor with a shaft supported by the first angular contact ball and second radial roller bearings installed in the corresponding housings fixed on the intermediate housing of the engine, characterized in that the housing of the first bearing is equipped with a flange that is fixed in the bore of the intermediate housing in in the axial direction with the clamping flange, and in the radial direction - with shear pins providing a radial clearance between the outer cylindrical surface of the flange of the first bearing housing and the inner cylindrical surface of the bore, while the axes of the shear pins are oriented parallel to the rotation axis of the fan rotor, and the flange of the first bearing housing and the intermediate bore the housings are sealed together with an elastic ring.

Images