SYSTEM FOR SEALING AND DRAINING OIL LEAKS FOR A TURBOMACH BEARING HOUSING

Description

TECHNICAL FIELD

[0001] The invention relates to a drainage cavity dedicated to collecting oil that may leak through a seal that this cavity adjoins, in a sealing system integrating this seal and this cavity. PREVIOUS STATE OF THE ART

[0002] On the figure 1 , a turbofan engine 1 with a double flow has at its upstream AM an inlet sleeve 2 into which outside air is admitted before passing through a fan 3 comprising a series of rotating blades, to then be split into a central primary flow and a secondary flow surrounding the primary flow.

[0003] The primary flow passes through a low-pressure compressor 4 and then a high-pressure compressor 5 before entering a combustion chamber 6. It then expands through a high-pressure turbine 7 and then a low-pressure turbine 8 before being discharged downstream AV. The secondary flow is propelled directly downstream by the fan 3 into a channel defined by the casing 9 to generate thrust. Such an engine comprises a rotor rotating around its longitudinal axis AX, and including several discs, each bearing a series of blades or vanes around its periphery. These discs correspond to the fan, compressors, and turbines.

[0004] In the case of a twin-spool turbofan engine, the high-pressure compressor and high-pressure turbine are part of a high-pressure housing that surrounds a low-pressure shaft and rotates at a different speed. This low-pressure shaft carries the low-pressure compressor and the low-pressure turbine. The shaft and the high-pressure housing are supported by bearings housed in lubrication chambers that isolate them from the rest of the engine.

[0005] Such an enclosure is defined by walls rotating relative to one another, with a seal between these walls that limits the oil leakage area. Additionally, such an enclosure is said to be pressurized, which in practice means that the inside of the enclosure is at a lower pressure than its surroundings. Thus, the oil is kept away from the seal by means of a continuous flow of air entering through this seal, from the outside to the inside of the enclosure.

[0006] On the figure 2 A stator 11 has on its inner face a circumferential seal 12 and an internal circumferential groove 13 facing the axis of rotation AX of the motor and attached to the downstream face of this seal 12. This groove 13 is connected to a drain 14 carried by the stator and located in its lower part relative to the vertical direction. A rotor 16 is engaged in this stator 11 with its outer face sliding against the seal 12; this rotor 16 has an external circumferential groove 17 located radially opposite the groove 13.

[0007] Grooves 13 and 17 define a drainage cavity 18 connected to drain 14 to form, together with seal 12, a sealing system for enclosure E1 located upstream of this system. This drainage cavity 18 is adjacent to seal 12 to collect oil that might leak through seal 12 as it flows from upstream AM to downstream AV from enclosure E1, preventing it from reaching a space E2 outside enclosure E1. When the engine is horizontal, as in the figure 2 The oil H, flowing downstream through seal 12 along rotor 16, is centrifuged by this rotor into groove 13, and then collected in the lower part of the stator by drain 14. As can be seen on the figure 2, the oil centrifuged in the groove 13 in the upper part of the engine can flow vertically along the downstream face of the groove 13 to be collected by the groove 17 and centrifuged again, so that it eventually reaches the lower part of the groove 13 to be collected by the drain 14.

[0008] In case of engine tilting, as in the figure 3 , for example at takeoff of the aircraft, the oil centrifuged in the upper part of the groove 13 which flows down the downstream face of this groove 13 is likely to exit this groove 13 through the gap I radially separating this stator groove 13 from the rotating groove 17.

[0009] As seen on the figure 3This oil leakage is due to gravity, which tends to cause it to flow vertically, while the downstream face of groove 13 has an oblique orientation due to the engine's tilt. In other words, it is because of the engine's tilt relative to the vertical that the oil is forced through gap I to leak out of cavity 18, and the fact that it is a pressurized chamber is not sufficient to prevent this type of leakage.

[0010] Leaks can also occur in situations where the enclosure is not sufficiently pressurized, during a transient phase of operation, for example when the engine is idling or stopped, or in the event of a seal failure.

[0011] The aim of the invention is to provide a sealing system solution that reduces or even eliminates leakage of oil collected in the drainage cavity to the outside.

[0012] A similar sealing gasket is known from DE 103 22 027 A1, according to the preamble of claim 1. DESCRIPTION OF THE INVENTION

[0013] To this end, the invention relates to an oil leak sealing and drainage system for a turbomachine bearing housing, this bearing comprising a stator carrying a rotor rotating around an axis of rotation, this system comprising a seal carried by the stator and surrounding the rotor, an external circumferential groove carried by the stator and contiguous to the seal to collect leaking oil traveling along the rotor through the seal and which is centrifuged by the rotor towards this circumferential groove, a drain located in the lower part of the turbomachine to collect the oil recovered by the circumferential groove, this circumferential groove being open towards the axis of rotation by being delimited by a bottom extended by two lateral walls, the lateral wall opposite the seal being terminated by a channel opening towards the bottom.

[0014] Thanks to the channel carried by the side wall opposite the seal, the oil centrifuged towards the bottom of the external groove is necessarily collected by this channel instead of falling back onto the rotor and risking continuing its progression beyond the sealing system.

[0015] The invention thus allows for better channeling of oil leaks towards the drain, preventing them from contaminating the rest of the engine, by adapting an existing part. The invention also relates to a sealing system defined as follows, in which the groove is absent in the lower part of the circumferential groove.

[0016] The invention also relates to a sealing system defined as follows, in which the bottom is formed by a frustoconical wall whose internal diameter decreases as it moves away from the joint.

[0017] The invention also relates to a sealing system thus defined, comprising an internal circumferential groove formed in the rotor opposite the external circumferential groove, this internal circumferential groove having a length along the axis of rotation which is less than the length of the external circumferential groove along the axis of rotation.

[0018] The invention also relates to a sealing system thus defined, in which the internal circumferential groove has a truncated conical bottom whose internal diameter decreases as it moves away from the seal.

[0019] The invention also relates to a sealing system defined as follows, in which the rotor has a circumferential rib terminating the internal circumferential groove. The invention also relates to a sealing system defined as follows, comprising flaps attached to the rotor that slide along a radially internal face of the groove, which is provided with abradable elements, to form a labyrinth seal.

[0020] The invention also relates to a turbomachine comprising a bearing housing which is equipped with a sealing system as defined above.

[0021] The invention also relates to a turbojet engine comprising a bearing housing which is equipped with a sealing system as defined above. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] There [ Fig. 1 ] is a longitudinal cross-sectional view of a turbojet engine; The [ Fig. 2] is a longitudinal cross-sectional view of a known sealing system when the engine it equips is horizontal; The [ Fig. 3 ] is a longitudinal cross-sectional view of a known sealing system when the engine it equips is inclined; The [ Fig. 4 ] is a longitudinal cross-sectional view of a sealing system according to the invention when the engine it equips is horizontal; The [ Fig. 5 ] is a schematic view showing three examples of possible profiles for the external throat groove; The [ Fig. 6 ] is a cross-sectional view of the motor at the external groove; The [ Fig. 7 ] is a longitudinal cross-sectional view of a sealing system according to the invention when the engine it equips is inclined. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0023] The idea behind the invention is to improve the external groove so that it better captures the oil leaking through the seal.

[0024] On the figure 4A sealing system 21 provides a seal between a stator 22 surrounding a rotor 23 of a turbojet engine with axis of rotation AX. This system prevents the passage of oil from a bearing enclosure E1 located upstream AM of this sealing system 21, through a drainage cavity 24 which it comprises, to a space E2 of the turbojet engine located outside the enclosure E1 and which is located downstream AV of this system 21 in the example of the figures.

[0025] This system 21, which constitutes a sealing barrier, includes a seal 25 carried by the stator 22 and surrounding the rotor 23, which is here a segmented radial seal, and an external groove 26 carried by the stator 22 and located immediately downstream of the seal 25, this external groove 26 being open towards the axis AX.

[0026] The rotor 23 has a shape of revolution including a cylindrical portion 27 at the joint 25 which is extended downstream AV by a conical portion or shoulder 28 defining a diameter reduction, downstream of which extends an internal groove 29 located radially opposite the external groove 26 of the stator. Downstream of the groove 29, the rotor 23 has a circumferential rib 31 advantageously followed by a sealing portion provided with three flaps 32.

[0027] The external groove 26 has a bottom 33 extended by an upstream side wall 34 along the joint 25 and a downstream side wall 35 opposite the joint 25, the bottom and the side walls together delimiting a corresponding shape approaching that of the letter U which is open in the direction of the axis AX.

[0028] In addition, a drain 36 located at the lowest point of the bottom 33 opens into this bottom, so as to collect the oil that may accumulate in the lower part of the groove 26, so as to send it back for example to a dedicated recovery box.

[0029] The downstream side wall 35 comprises a body 37 having a crown shape oriented normal to the axis AX, and whose radially internal edge is extended by an internal skirt 38 extending towards the bottom 33. This internal skirt 38 comprises in the example of the figures a cylindrical portion 39 running along the rims 32, and which is terminated by a conical portion 41 bringing it radially closer to the bottom 33, so that it has a general annular shape which is flared in the direction of the enclosure E1.

[0030] The inner face of the cylindrical portion 39 has abradable elements so as to form, with the tabs 32, a labyrinth seal 42 preventing oil from passing into space E2. Other shapes of the sealing portion that includes the tabs 32 are possible. It is also possible to do without such a sealing portion, or even without the labyrinth seal 42 altogether, if the oil passage into space E2 remains minimal and acceptable.

[0031] The inner skirt 38, together with the downstream lateral wall 35, defines a channel 43 extending into the gorge 26. In the example of the figure 4 This channel 43 has a trapezoidal cross-section, but other shapes are possible as illustrated on the figure 5 such as a rounded, rectangular, triangular or other shape.

[0032] In the event of a failure, or operation with insufficient pressure in space E2 to prevent oil leakage outside the enclosure, the oil H, which flows through the seal 25 along the outer face of the cylindrical portion 27 of the rotor, travels downstream AV, i.e., towards the groove 29, in the direction of the drainage cavity 24 adjacent to this seal. During its journey towards or into the groove 29, this oil H is centrifuged by the rotation of the rotor 23, so that it is collected by the groove 26, at its bottom 33 and / or its lateral walls 34, 35.

[0033] As seen on the figure 4 , the bottom 33 has a truncated cone shape whose internal diameter decreases towards the downstream AV, so that in the upper part of the engine, gravity acts on the oil collected on this bottom 33 so that it progresses spontaneously towards the downstream AV.

[0034] In the upper part of the engine, the oil collected by the conical bottom 33 is thus conveyed by gravity downstream AV towards the side wall 35. After reaching the side wall 35, this oil flows down into the channel 43 by gravity, then it trickles circumferentially downwards in this channel 43. Once it reaches the lower part of the engine, this oil leaves the channel 43 to fall onto the bottom 33 and is collected in the drain 36, which is located at the lowest point of the groove 26.

[0035] In the lower part of the engine, the oil collected by the bottom 33 flows down this bottom 33, until it reaches the drain 36 through which it is evacuated.

[0036] On the figure 4The channel 43 is absent in the lowest part of the motor, because it is advantageously recessed over an angular range A, on either side of the lowest point of the motor around the axis AX. This angular range A, which appears on the figure 6 The angle can be between 5° and 60° and is advantageously around 40°. This angular range, free of grooves, ensures that any oil that may have accumulated on the rotor rib 31 can flow by gravity directly to the bottom 33 when the engine is tilted. This prevents the oil from being collected by the upstream face of the conical portion 41, which could then carry it downstream towards the labyrinth seal 42.

[0037] As illustrated in the figures, the groove 26 can be provided in the form of a circular profile which is attached to the inner face of the stator 22, this profile having a portion without a groove 43. Advantageously this profile is provided with an angular indexing so as to allow its proper angular positioning to ensure that the portion without a groove 43 is located in the lower part of the motor.

[0038] The invention makes it possible to limit oil losses even when the engine is tilted, for example during a takeoff phase, as illustrated in the figure 7In this case, the leaking oil that has passed through the seal 25 and is projected into the groove 26 in the upper part of the engine is first captured by the bottom 33 and by the side wall 35. It then progresses by gravity in the channel 43, and then descends in this channel 43 until it reaches a lower part of the groove 26 where it is collected by the bottom 33 and then discharged by the drain 36. This oil from the upper part cannot therefore be directed towards the labyrinth seal 42, and is therefore not likely to escape.

[0039] The oil which passes through the seal 25 in the lower part of the engine is collected almost directly by the bottom 33 and by the downstream side wall 35 to be recovered in the drain 36.

[0040] As seen in the lower part of the figure 7, the oil that may be present on the rib 31 in the lower part of the engine can drip vertically under the effect of gravity into the bottom of the groove 33 without being intercepted by the channel 43 which is absent in this region of the engine, so that it also does not risk passing through the labyrinth seal 42 to reach the external space E2.

[0041] In addition, to limit the amount of oil present on the rotor 23, the bottom of the internal groove 29 has a conical shape whose diameter decreases downstream, so that any oil that might be present in this groove is directed upstream by centrifugal force. Under these conditions, this oil is naturally directed towards the upstream face of the groove 29, which is perpendicular to the axis AX, so that it is spontaneously centrifuged and collected by the bottom 33 of the external groove 26. The internal groove 29 thus acts as a drip deflector at its upstream face.

[0042] More generally, the internal groove 29, along the AX axis, is shorter than the external groove 26, while being positioned opposite it, to ensure that the oil captured in the internal groove is centrifuged into the wider external groove. This centrifugation occurs either at the upstream face of the internal groove or at the rib 31 delimiting the downstream face of this internal groove.

Claims

1. System (21) for sealing and draining leaks of oil for a turbine-engine bearing chamber (E1), this bearing comprising a stator (22) carrying a rotor (23) rotating about a rotation axis (AX), this system (21) comprising a seal (25) carried by the stator (22) and surrounding the rotor (23), an external circumferential groove (26) carried by the stator (22) while being contiguous with the seal (25) to collect leaking oil (H) travelling along the rotor (23) through the seal (25) and which is centrifuged by the rotor (23) towards this circumferential groove (26), a drain (36) located at the bottom part of the turbine engine for collecting the oil (H) recovered by the circumferential groove (26), this circumferential groove (26) being open towards the rotation axis (AX) while being delimited by a bottom (33) extended by two lateral walls (34, 35), the lateral wall (35) opposite to the seal (25) terminating in a gutter (43) opening towards the bottom (33) characterized in that the gutter (43) is absent at the bottom part of the circumferential groove (26).

2. System according to claim 1, wherein the bottom (33) is formed by a frustoconical wall the inside diameter of which decreases on moving away from the seal (25).

3. System according to claim 1, comprising an internal circumferential groove (29) formed in the rotor (23) facing the external circumferential groove (26), this internal circumferential groove (29) having a length along the rotation axis (AX) that is less than the length of the external circumferential groove (26) along the rotation axis (AX).

4. System according to claim 3, wherein the internal circumferential groove (29) has a frustoconically shaped bottom the inside diameter of which decreases on moving away from the seal (25).

5. System according to claim 2, wherein the rotor includes a circumferential rib (31) terminating the internal circumferential groove (29).

6. System according to claim 1, including knife-edge seals (32) secured to the rotor (23) and sliding along a radially internal face of the gutter (43) that is provided with abradable elements, to form a labyrinth seal (42).

7. Turbine engine comprising a bearing chamber (E1) that is equipped with a sealing system according to claim 1.

8. Turbine engine comprising a bearing chamber (E1) that is equipped with a sealing system according to claim 1.