EP1605139A1 - Turbomachine with axial retention means for the rotor - Google Patents

Abstract

The turbomachine has an air blower (2) integral to a compressor shaft (5) supported by a bearing (6) mounted on turbomachine`s fixed structure by a bearing support part (11). A spring retaining ring (30) is mounted on the structure to cooperate with the part and ensure, when the blower`s rotor is displaced relative to the structure, axial retaining function of the rotor independent of an angle between axes of the turbomachine and shaft.

Description

The invention relates to the field of turbomachines and in particular turbofan engines with fan attached to a drive shaft which is supported by at least a first landing.

Such a turbojet engine comprises, from upstream to downstream in the direction of the flow gases, a blower, one or more stages of compressors, a chamber of compression, one or more stages of turbines and a gas exhaust nozzle. The fan comprises a rotor provided with vanes at its periphery which, when they are rotated, drive the air in the turbojet engine. The fan rotor is supported by the low pressure rotor shaft of the motor. It is centered on the axis of turbojet engine by a first bearing which is upstream of a second bearing connected to the fixed structure, in particular the intermediate casing.

In the remainder of the description, to the extent that the blower is mounted integral with the compressor shaft, which is the low pressure rotor shaft in a double-body engine, this shaft is designated by the single term compressor shaft.

The first bearing is supported by a support piece, forming a envelope around the compressor shaft, facing downstream of the first landing and fixed to a fixed structure of the turbojet engine. The second tier is supported by a support piece also fixed to a fixed structure of the turbojet engine.

It can happen, accidentally, the loss of a fan blade. he a major imbalance ensues on the compressor shaft, which causes loads and vibrations on the bearings, transmitted by their supporting parts to the structures turbojet engines, which can therefore be damaged.

To prevent a risk of excessive deterioration of the turbojet engine, can over-size the structure or, as in the patent FR 2, 752, 024, propose a decoupling system of the first stage. The support piece of the first landing is attached to the structure of the turbojet engine by said fusible screws, comprising a portion weakened causing their breakage in case of excessive effort. So, at the appearance of unbalance on the compressor shaft, the forces induced on the first bearing are transmitted to the fusible screws which break, uncoupling the support part of the first bearing of the turbojet engine structure. According to other embodiments, the support of second tier is associated with that of the first landing to accompany him in case of decoupling, or includes its own decoupling system, independent of that of the first landing. After decoupling, the forces caused by the unbalance are no longer transmitted to the fixed structure of the turbojet engine by the support parts of the bearing or bearings.

However, after the decoupling of one or both bearings, the blower continues turn and the compressor shaft may no longer rotate on its axis and suffer large deflections that can damage the fixed structure of the turbojet engine. The patent FR 2, 752, 024 proposes in this case to provide, on the fixed structure of turbojet, a rib surrounding the support part of the first bearing, of which here is solidary that of the second bearing, and fulfilling a function of limiter of movements or emergency landing.

Continued rotation of the blower may nevertheless lead to constraints on the compressor shaft and the turbine shaft, which are integral, and cause the rupture of one or both of them. We will talk about whatever the case rupture of the compressor shaft. In this case, the rotation of the fan causes the latter, as well as the compressor shaft which it is secured, forward. The The blower is then expelled from the turbojet, which must be avoided.

The rib proposed in the patent FR 2, 752, 024 can however ensure, in case of rupture of the compressor shaft, a function of axial retention of the rotor of the fan, the fixing flange of the support part of the first bearing to the fixed structure the turbojet then abutting on a radial wall of this rib. However, because of the bending to which the compressor shaft can be subjected in this situation, an angle can exist between the wall of the flange and the wall of the rib intended to come to a stop, implying either an inefficient stop of the tree with degradation of the elements by friction, or even, if the angle is too important, a passage of the flange, inclined radially towards the axis of the turbojet engine, beyond the rib and therefore the impossibility of stemming the advance of the compressor shaft and the rotor of the blower, which is then expelled or stuck across its crankcase retention, thereby deteriorating the entire structure of the turbojet engine.

The present invention aims to overcome these disadvantages.

For this purpose, the invention relates to a turbomachine, extending longitudinally along an axis, comprising a rotor, integral with a drive shaft, arranged to rotate about an axis, supported by at least a first bearing, mounted on the fixed structure of the turbomachine by a bearing support piece,
characterized in that it comprises a stop ring, mounted on the fixed structure of the turbomachine to cooperate with the support part of the first bearing and ensure, in case of displacement of the rotor relative to the fixed structure, a function axially retaining the rotor, homogeneously, without effect of angle between the axis of the turbomachine and the axis of the drive shaft.

Thanks to the invention, the axial retention of the rotor, for example in the case of a rupture of the compressor shaft following the loss of a blade of the fan, if the rotor is a fan rotor, is homogeneous regardless of the angle between the axis of the compressor and the axis of the turbomachine at the time of retention. This angle, which can vary due to the unbalance suffered by the tree, does not affect the restraint axial rotor.

Preferably, the support part of the first bearing has a bearing intended to cooperate with the surface of a bead of the stop ring.

Advantageously in this case, the scope is of frustoconical shape.

Advantageously, the surface of the bead of the stop ring presents in axial section a curved shape, symmetrical of revolution around the axis of the turbine engine.

In this case, preferably, the curved shape is an arc of a circle.

Preferably, the stop ring longitudinally belts the downstream portion of the bearing part of the first bearing, without contact in normal operating mode of the turbomachine.

According to one embodiment, the drive shaft being supported by a second bearing, the second bearing being mounted on the fixed structure of the turbomachine by a bearing support part, the support part of the first bearing is attached to the supporting part of the second bearing by means of fusible screws allowing its decoupling of the support part of the second bearing.

According to one embodiment, the drive shaft being supported by a second bearing, the second bearing being mounted on the fixed structure of the turbomachine by a bearing support part, fixed by screws, the stop ring has longitudinal recesses allowing the passage of said screws to ensure fixing the stop ring to the fixed structure of the turbomachine.

According to one mode of operation, the support piece of the first bearing being mounted on the fixed structure of the turbomachine by a device allowing its decoupling with respect to the fixed structure of the turbomachine, the stop ring is arranged so as not to interfere with the decoupling phase.

According to another mode of operation, the support part of the first bearing being mounted on the fixed structure of the turbomachine by a device allowing its decoupling with respect to the fixed structure of the turbomachine, the stop ring is arranged to limit the deflections of the compressor shaft during the phase of decoupling.

According to a particular embodiment, the second bearing is mounted on the fixed structure of the turbomachine by a device allowing its decoupling by relative to the fixed structure of the turbomachine.

Preferably, finally, the support part of the first bearing being mounted on the fixed structure of the turbomachine by a device allowing its decoupling by compared to the fixed structure of the turbomachine, the stop ring ensures in particular the axial retention of the rotor in case of breakage of the drive shaft after decoupling the first landing.

The invention is particularly applicable to a double-body turbojet engine, whose second bearing is a bearing supporting the low pressure rotor, but the applicant does not intend to limit the scope of its rights to this application.

• la figure 1 représente une vue en coupe axiale, de profil, de la forme de réalisation préférée de l'invention ;
• la figure 2 représente une vue agrandie de la zone de la figure 1 contenue dans le cadre C ;
• la figure 3 représente une vue en coupe axiale, de profil, de la zone du deuxième palier du turboréacteur de la forme de réalisation préférée de l'invention, pendant une phase de découplage, et
• la figure 4 représente une vue en coupe axiale, de profil, de la zone du deuxième palier du turboréacteur de la forme de réalisation préférée de l'invention, après rupture de l'arbre de compresseur.

The invention will be better understood thanks to the following description of the preferred embodiment of the turbojet engine of the invention, with reference to the appended drawings, in which:

• Figure 1 shows an axial sectional view, in profile, of the preferred embodiment of the invention;
• FIG. 2 represents an enlarged view of the area of FIG. 1 contained in frame C;
• FIG. 3 represents an axial sectional view, in profile, of the zone of the second bearing of the turbojet engine of the preferred embodiment of the invention during a decoupling phase, and
• FIG. 4 represents an axial sectional view, in profile, of the zone of the second bearing of the turbojet engine of the preferred embodiment of the invention, after rupture of the compressor shaft.

With reference to FIG. 1, the turbojet engine 1 of the invention comprises a blower 2, whose rotor comprises blades 3 extending radially around the axis 4 of the turbojet. The fan shaft 2 is fixed, downstream of the blades 3, to the shaft of the compressor 5. This is the low pressure compressor shaft. We will designate in following the entire shaft of the blower 2 and the compressor shaft 5 per shaft compressor 5, or drive shaft 5. The compressor shaft 5 is supported by a first bearing 6 and a second bearing 7, located downstream of the first bearing 6.

The first bearing 6 comprises an inner ring 8 and an outer ring 9, between which are mounted balls 10 or other rolling members. The ring internal 8 is mounted integral with the compressor shaft 5 and the integral outer ring a bearing support member 11, referred to in the following support of the first bearing 11. The balls 10 allow the rotation of the inner ring 8, therefore of the shaft of the compressor 5, with respect to the outer ring 9, thus to the support of the first bearing 11.

The support of the first bearing 11 extends, from the first step 6, towards the downstream; it is of slightly frustoconical shape, its diameter increasing downstream.

The second bearing 7 comprises an inner ring 14 and an outer ring 15, between which are mounted rollers 16 or other rolling members. The ring internal 14 is mounted integral with the compressor shaft 5 and the outer ring 15 is fixed mounting of the fixed structure of the turbojet engine 1. The rollers 16 are mounted parallel to the axis 4 of the turbojet engine 1, in a groove extending at the circumference of the inner ring 14, and are held spaced from each other by a cage, although known to those skilled in the art. They allow the rotation of the inner ring 14 by relative to the outer ring 15, and therefore via the compressor shaft 5 with respect to the fixed structure of the turbojet engine 1.

The second bearing 7 is supported by a bearing support piece 19, named thereafter support of the second bearing 19, presenting generally in the form a flange extending transversely to the axis 4 of the turbojet engine 1. The outer ring 15 of the second bearing 7 comprises, on its outer face, a radial flange 20 fixed to the supporting the second bearing 19 by screws 21.

With reference to FIG. 2, the support of the second bearing 19 is fixed by a radial flange 22, to the fixed structure of the turbojet engine 1, here to a housing 23 said crankcase intermediate 23, by screws 24.

The support of the first bearing 11 has at its downstream end a portion stop 26, here of greater thickness than its upstream portion. This stop portion 26 presents in axial section a section in the shape of a right triangle. The inner wall 27 of this stop portion 26 is of cylindrical shape, its downstream wall 28 extends transversely to the axis 4 of the turbojet engine, the inner 27 and downstream 28 walls being connected by a wall 29 having a generally frustoconical surface, the diameter of which increases downstream, and which corresponds to the hypotenuse of the right triangle defined by the portion stop 26 in axial section. The support of the first landing 11 thus presents, in its downstream part, a frustoconical bearing surface 29 constituted by the frustoconical wall 29.

The stop portion 26 has longitudinal recesses 26 'allowing the passage of fusible screws 25 for fixing the support of the first bearing 11 to the flange 22 of the support of the second bearing 19. These fusible screws 25 are radially located between the axis 4 of the turbojet engine 1 and the screws 24 for fixing the support of the second bearing 19 to the intermediate housing 23. These fusible screws 25 comprise a portion of lower section 25 ', having a determined tensile strength which causes them to break in cases of excessive effort, especially when an imbalance appears on the tree of the compressor 5, following for example the loss of a blade 3.

The intermediate casing 23 supports a stop ring 30, which extends around the stop portion 26 of the support of the first bearing 11, longitudinally encircling it, without any contact between them during normal operation of the turbojet engine 1. This stop ring 30 is of frustoconical shape, its diameter increasing towards the rear, its inner walls 30 'and outer 30 "being here approximately parallel over the majority of its length. It comprises, at its downstream end, a radial flange 31 by which it is fixed to the intermediate casing 23, here by the screws 24 for fixing the support of the second bearing 19 to intermediate casing 23.

The stop ring 30 has, at its upstream end, a bead 32 making protruding radially inwards. The inner surface 33 of the bead 32 is of a shape convex curve, in axial section, according to a curve schematized in FIG. curve portion 33 '.

The stop ring 30 is arranged so that the surface of the reach frustoconical 29 of the support of the first bearing 11 can abut on the surface 33 of its bead 32, if the support of the first bearing 11 is made to be driven axially forward. The function of the stop ring 30 is to block axially, through the support of the first bearing 11, the compressor shaft 5 into case of rupture, so that the blower 2 which is attached to it is not driven towards forward in this case, as will be explained later.

The operation of the turbojet engine 1 of the invention during the loss of a Blower dawn 3 will now be explained in more detail.

The loss of a blade 3 during operation of the turbojet engine 1, so in rotation of the fan 2, causes an unbalance on the compressor shaft 5. With reference to FIG. 3, the induced forces cause the fusible screws to rupture. fixing the support of the first bearing 11 to the support of the second bearing 19, level of their weakened portion 25 '. The fusible screws 25 do not all break at the same time time, but usually gradually. In FIG. 3, a fusible screw 25 is broken, on the underside of the figure, while the fusible screw 25 on the higher is still intact. In this situation, the unbalance induced a flexion of the compressor shaft 5, whose axis 5 'is inclined relative to the axis 4 of the turbojet engine 1. This bending of the compressor shaft 5 is allowed by a sliding of rolls of the second bearing 7 on their outer ring 15, with that said a probable deterioration of this level 7.

The support of the first bearing 11, integral with the compressor shaft 5, is same stroke also inclined with respect to the axis 4 of the turbojet engine 1. The surface of the frustoconical bearing 29 of the first bearing 11 can then abut on the surface of the wall 33 of the bead 32 of the stop ring 30, in the regions where the fusible screws 25 broke. Due to the duly optimized shape of the surface 33 of the bead 32, the angle has no effect on this contact, which is homogeneous regardless the angle considered. Thus, during the decoupling phase of the support of the first level 11 of the fixed structure of the turbojet engine 1, the stop ring 30 allows, in the form of described here, to limit somewhat the bending of the compressor shaft 5, homogeneous way. This flexion can also be limited, as is generally the case, because of the consumption of the game between the ends of the blades 3 of the blower 2 and their retention housing.

According to another embodiment, the longitudinal distance between the span frustoconical 29 of the support of the first bearing 11 and the bead 32 of the stop ring 30 can be dimensioned so that the surfaces of the frustoconical wall 29 and the bead 32 never come into contact during the decoupling phase, in order not to not interfere with it. It is besides this form of realization which will be preferred, in which the stop ring 30 provides only an axial stop function and not Radial movement limitation function.

Whatever the embodiment, once the set of fusible screws 25 broken, the support of the first bearing 11 is decoupled from the support of the second bearing 19, therefore of the intermediate casing 23, that is to say that it is decoupled from the fixed structure of the turbojet engine 1. The forces are no longer transmitted to the fixed structure of the turbojet by the support of the first bearing 11 and the compressor shaft 5 can freely rotate on its axis 5 ', the frustoconical bearing surface 29 of the support of the first bearing 11 and the bead 32 of the stop ring 30 not being in contact.

However, the continued rotation of the blower 2 can lead to constraints on the compressor shaft 5 and the turbine shaft, which are integral, and cause the rupture of one or both of them. We speak then, as it was seen previously, breakage of the compressor shaft 5. In this case, the rotation of the blower 2 drives the latter, and the compressor shaft 5 which is solidary, forward.

The support of the first bearing 11 is then also driven forward, and the rollers 16 of the second bearing 7, which slide on their outer ring 15. In reference to FIG. 4, this forward leakage is stopped thanks to the stop ring 30, integral with the fixed structure of the turbojet engine 1. Indeed, during the flight towards the front of the support of the first bearing 11, the frustoconical bearing surface 29 of the support of the first bearing 11 abuts on the wall 33 of the bead 32 of the stop ring 30, which thus ensures the axial stop of the support of the first bearing 11 and therefore of the fan 2, which is not expelled from the turbojet. The rotation of the blower 2 can be prolonged somewhat, before stopping by friction.

The curve 33 'defining the inner surface 33 of the bead 32 is optimized so that the abutment of the bearing surface 29 of the first bearing 11 on this surface 33, and therefore the axial stop of the blower 2, is done homogeneously, independent of the angle that can exist between the axis 5 'of the compressor shaft 5 with the axis 4 of the turbojet engine 1. This curved shape of the inner surface 33 of the bead 32 is a meridian curve, in an axial plane, symmetrical of revolution around the axis 4 of the turbojet. The curve 33 'is here, in axial sectional view, of circular shape. This curve 33 'could be of more complex shape, for example to respect the different phases of decoupling - with or without contact depending on the steps.

In fact, the continued rotation of the fan 2 after decoupling the support of the first bearing 11 is not necessarily around the axis 4 of the turbojet engine 1, since precisely the compressor shaft 5 is no longer centered by the first bearing 6. At the moment of rupture of the compressor shaft 5 and its forward leakage, the angle of its axis 5 'with the axis 4 of the turbojet 1 is random. This hazard does not disturb the shutdown of the blower 2 by the retaining ring 30 due to the optimized shape of the wall 33 This allows, moreover, with the continuation of the rotation of the fan 2 related to its advance, to put the blower 2 and the shaft of the compressor 5 in the axis 4 of the turbojet 1, as is the case in FIG.

The invention has been described in connection with the support of the first level fixed to the fixed structure of the turbojet engine via the support of the second bearing, while the stop ring is fixed to the fixed structure of the turbojet engine by the fixing screws of the second bearing support to this fixed structure. It goes without saying that the first support of bearing, the second bearing support and the stop ring could be attached to the fixed structure of the turbojet independently of one another and to fill the same functions that have been described.

In addition, in the case where the stop ring is attached to the fixed structure of the turbojet engine independently, the support of the second bearing could be fixed at this structure by fusible screws. Thus, the decoupling of the two levels would be possible, the axial stop by the stop ring intervenes only in case of breakage of the shaft of the compressor.

The downstream bearing 29 of the first bearing 11 has here been described with a frustoconical shape. It goes without saying that it could also have a curved shape, in sectional view axial shape, this shape being optimized in correlation with the curve 33 'that the 33 surface of the bead 33 of the stop ring 30 so that the stop of the blower is do it in a homogeneous way, without angle effect.

It may be noted that the stop ring 30 could also provide a function an emergency bearing, acting as a bearing for the compressor shaft 5, in case of rupture of the latter after decoupling of the first bearing 6.

The invention has been described in relation with a turbojet engine, in particular a double-body turbojet engine, the second bearing of which is a bearing supporting the rotor low pressure. The invention applies to other types of turbomachines, such as a turboprop, an industrial turbocharger or an industrial turbine, the rotor not being then a fan rotor but simply a rotor.

Claims (13)

Turbomachine, extending longitudinally along an axis (4), comprising a rotor (2), integral with a drive shaft (5), arranged to rotate about an axis (5 '), supported by at least one first bearing (6), mounted on the fixed structure of the turbomachine by a bearing support member (11), characterized in that it comprises a stop ring (30), mounted on the fixed structure of the turbomachine for cooperate with the support part of the first bearing (11) and ensure, in case of movement of the rotor (2) relative to the fixed structure, an axial retention function of the rotor (2), homogeneously, without effect of angle between the axis (4) of the turbomachine and the axis (5 ') of the drive shaft (5). A turbomachine according to claim 1, wherein the support piece the first bearing (11) has a bearing surface (29) intended to cooperate with the surface (33) a bead (32) of the stop ring (30). A turbomachine according to claim 2, wherein the span (29) is frustoconical shape. Turbomachine according to one of claims 2 or 3, in which the surface (33) of the bead (32) of the stop ring (30) has in axial section a curved shape (33 '), symmetrical of revolution about the axis (4) of the turbomachine. Turbomachine according to Claim 4, in which the curved shape (33 ') is an arc of a circle. Turbomachine according to one of claims 1 to 5, wherein the ring stopping longitudinally the downstream part of the support part of the first bearing (11), without contact in normal operating mode of the turbomachine. Turbomachine according to one of claims 1 to 6 wherein the shaft drive (5) being supported by a second bearing (7), the second bearing (7) being mounted on the fixed structure of the turbomachine by a bearing support piece (19), the support part of the first bearing (11) is fixed to the support part of the second bearing (19) by fusible screws (25) allowing its decoupling of the piece of support of the second bearing (19). Turbomachine according to one of claims 1 to 7 wherein the piece supporting the first bearing (11) being mounted on the fixed structure of the turbomachine by a device (25) allowing its decoupling with respect to the fixed structure of the turbomachine, the stop ring (30) is arranged not to interfere with the phase of decoupling. Turbomachine according to one of claims 1 to 7 wherein the piece supporting the first bearing (11) being mounted on the fixed structure of the turbomachine by a device (25) allowing its decoupling with respect to the fixed structure of the turbomachine, the stop ring (30) is arranged to limit the deflections of the shaft compressor (5) during the decoupling phase. Turbomachine according to one of claims 1 to 9 wherein the shaft drive (5) being supported by a second bearing (7), the second bearing is mounted on the fixed structure of the turbomachine by a device allowing its decoupling with respect to the fixed structure of the turbomachine. Turbomachine according to one of claims 1 to 9 wherein the shaft drive (5) being supported by a second bearing (7), the second bearing (7) being mounted on the fixed structure of the turbomachine by a bearing support piece (19), fixed by screws (24), the locking ring (30) has recesses longitudinal members (26 ') allowing the passage of said screws (24) to ensure the fixing of the stop ring (30) to the fixed structure of the turbomachine. Turbomachine according to one of claims 1 to 11, which is an element of the assembly consisting of a double-body turbojet, comprising a second bearing (7) which is a bearing supporting the low pressure rotor, a turboprop, a turbocharger and a turbine. Turbomachine according to one of claims 1 to 12 wherein the piece supporting the first bearing (11) being mounted on the fixed structure of the turbomachine by a device (25) allowing its decoupling with respect to the fixed structure of the turbomachine, the stop ring (30) ensures in particular the axial retention of the rotor (2) in case of breakage of the drive shaft after decoupling the first bearing (6).

Images