Sealing assembly for turbomachine

Abstract

The invention relates to a turbine engine comprising an air compression stage comprising at least one movable compressor wheel, an air inlet duct coupled to said air compression stage, a first sealing device, which is arranged between a front portion of the movable compressor wheel and the air inlet duct and comprising at least one seal, a channel for conveying the air compressed by the movable wheel and a second sealing device, which is arranged between a rear portion of the movable compressor wheel and the conveying channel and is configured to receive an airflow coming from the conveying channel, the turbine engine being remarkable in that the second sealing device is configured to allow some of the air passing therethrough to be bled and in that the bleed air is conveyed to the seal of the first sealing device so as to keep it under pressure.

Claims

1. A turbine engine, comprising: an air compression stage which comprises at least one movable compressor wheel, an air inlet duct which is coupled to said air compression stage, a first sealing device, which is arranged between a front portion of the movable compressor wheel and the air inlet duct, comprising at least one seal, a channel for conveying the air compressed by the movable wheel, a second sealing device, which is arranged between a rear portion of the movable compressor wheel and the conveying channel and is configured to receive an airflow coming from the conveying channel, wherein the second sealing device is configured to allow some of the air passing therethrough to be bled, the bleed air being conveyed to the at least one seal of the first sealing device so as to keep the at least one seal of the first sealing device under pressure, wherein the second sealing device comprises a front seal and a rear seal, the air being bled between the front seal and the rear seal of the second sealing device, wherein the rear seal of the second sealing device is configured such that the flow rate of bleed air is sufficient to keep the at least one seal of the first sealing device under pressure, and wherein the front seal of the second sealing device is configured so as to reduce the flow rate of air passing therethrough as much as possible so as to avoid disturbing the flow of air in a rear part of the movable compressor wheel onto which said front seal of the second sealing device opens.

2. The turbine engine according to claim 1, wherein the second device comprises at least one block of abradable material and a labyrinth seal which comprises an assembly of sealing strips which cooperate with the at least one block of abradable material.

3. The turbine engine according to claim 1, wherein the rear seal of the second device comprises between one and three sealing strips.

4. The turbine engine according to claim 1, wherein the front seal of the second device comprises at least two sealing strips.

5. The turbine engine according to claim 1, wherein the rear seal of the second sealing device and the front seal of the second sealing device are spaced apart by a distance which is greater than or equal to 2 mm, so as to form a pressurised air pocket in which the air can be bled in order to be conveyed to the seal of the first sealing device.

6. The turbine engine according to claim 1, said turbine engine comprising a second movable compressor wheel of which a front portion is connected to a rear portion of the first movable compressor wheel in the region of the second sealing device by a coupling, in which a passage is made, the air which is bled as the airflow passes through the second sealing device flowing through said passage before being conveyed towards the seal of the first device in order to keep the seal of the first sealing device under pressure.

7. A method for keeping at least one seal under pressure by bleeding air in a turbine engine, the turbine engine having: an air compression stage comprising at least one movable compressor wheel, an air inlet duct coupled to said air compression stage, a first sealing device, which is arranged between a front portion of the movable compressor wheel and the air inlet duct, comprising at least one seal, a channel for conveying the air compressed by the movable wheel, a second sealing device, which is arranged between a rear portion of the movable compressor wheel and the conveying channel and is configured to receive an airflow coming from the conveying channel, wherein the second sealing device comprises a front seal and a rear seal, the method comprising: bleeding some of the air passing through the second sealing device, the air being bled between the front seal and the rear seal of the second sealing device; conveying the air which is thus bled to the at least one seal of the first sealing device so as to keep the at least one seal of the first sealing device under pressure; and reducing the flow rate of air passing through the front seal of the second sealing device to avoid disturbing the flow of air in a rear part of the movable compressor wheel onto which said front seal of the second sealing device opens.

8. The turbine engine according to claim 3, wherein the rear seal of the second device comprises two sealing strips.

9. The turbine engine according to claim 4, wherein the front seal of the second device comprises four sealing strips.

10. The turbine engine according to claim 6, wherein said the front portion of the second movable compressor wheel is connected to the rear portion of the first movable compressor wheel in the region of the second sealing device by a curvic coupling.

Description

DESCRIPTION OF THE DRAWINGS

(1) The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a longitudinal section through a turboshaft engine;

(3) FIG. 2 is a partial sectional view of a turboshaft engine according to the disclosure;

(4) FIG. 3 is a partial sectional view of the seal of the second sealing device of the turboshaft engine in FIG. 2; and

(5) FIG. 4 is a partial sectional view of the seal of the first sealing device of the turboshaft engine in FIG. 2.

DETAILED DESCRIPTION

(6) The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed. Embodiments of the disclosure are described hereinafter in relation to an aircraft turboshaft engine, but it may of course be used more generally in a turbine engine, in particular for an aircraft, comprising any type of compressor, for example a centrifugal compressor, a dual-centrifugal compressor or a mixed compressor.

(7) The terms front and rear refer to the position of elements which are located relative to the direction of the central axis XX of rotation of the parts of the turboshaft engine, in particular of the compression and expansion rotors, which corresponds to the overall direction of the airflow passing through the turboshaft engine during operation. Likewise, the terms upstream and downstream are understood in relation to the direction of the airflow circulating in the turbine engine.

(8) FIG. 1 schematically shows a helicopter turboshaft engine 1 comprising a first compression stage or compressor 2. In such a turboshaft engine, air (arrow F1) is introduced into an air inlet 3 and is carried into an air inlet duct 4 which forms a channel which opens onto the first compression stage 2. The air compressed by the first compression stage 2 is conveyed towards a second compression stage 5.

(9) The air compressed by the second stage 5 discharges via a radial diffuser 6 and is then injected into a combustion chamber 7 in order to be mixed with fuel therein and to supply, after combustion, kinetic energy to set into rotation turbines 8, 9 and 10. The turbine 8 in turn drives the compressors 5 and 2 via the shaft 10b. The turbines 9 and 10 transmit power via the shaft 10a in order to drive via a speed reduction unit 11, for example, a helicopter rotor and/or equipment (pump, alternators, load compressor, etc.).

(10) Each compression stage comprises a movable compressor wheel, which may be axial (axial compressor), radial (centrifugal impeller) or mixed. The turboshaft engine shown comprises two compression stages, but of course the turbine engine according to the disclosure may also comprise a single compression stage or more than two compression stages.

(11) The compressor 2 comprises a first movable wheel 20 which is intended to rotate within a casing 30 and comprises fins 22 for guiding the airflow (with reference to FIG. 2). In this example, the compressor comprises a bladed diffuser 40 which is inclined in the extension of the movable wheel 20.

(12) An air conveying channel 45, which is coupled to the diffuser 40, extends between the first compression stage 2 and the second compression stage 5 onto which it opens and allows the air compressed by the first compression stage 2 to be conveyed to the second compression stage 5. The second compression stage 5 comprises a second movable compressor wheel 50 which opens onto the diffuser 6 and comprises fins 52 for guiding the airflow (with reference to FIG. 2).

(13) As shown in FIG. 2, the turboshaft engine 1 comprises a first sealing device 54, which is arranged between a front portion 56 of the movable compressor wheel 20 and an axial portion 58 of the air inlet duct 4. This first sealing device 54 comprises a front seal 60 and a rear seal 62, between which an air passage 77 is made.

(14) A bearing 63 for guiding the rotor relative to the stator is arranged in front of the first sealing device 54 and comprises lubricating oil which is kept in the bearing 63 by the pressure of the air in the region of the front seal 62 of the first sealing device 54.

(15) The turboshaft engine 1 comprises a second sealing device 64, which is arranged between a rear portion 66 of the movable compressor wheel 20, a front portion 67 of the second movable wheel 50 and a portion 68 of the channel 45 for conveying air compressed by the movable wheel 20, all three extending substantially in a direction parallel to the axis XX.

(16) This second device 64 comprises a front seal 70, which is arranged between the portion 68 of the conveying channel 45 and the rear portion 66 of the first movable wheel 20, and a rear seal 72, which is arranged between the portion 68 of the conveying channel 45 and the front portion 67 of the second movable compressor wheel 50.

(17) According to the disclosure, the second sealing device 64 is configured to allow some of the air passing therethrough to be bled, the bleed air in this case being conveyed to the front seal 60 of the first sealing device 54 so as to keep it under pressure.

(18) In this example, the seals of the devices are labyrinth seals which each comprise an assembly of annular sealing strips which are arranged consecutively in a direction parallel to the axis XX and cooperate in a known manner with a block of abradable material to form the seal.

(19) As shown in FIG. 3, the airflow F3 which keeps the front seal 60 of the first device 54 under pressure is bled between the rear seal 72 and the front seal 70 of the second device 64.

(20) In order to obtain a flow rate of bleed air which is sufficiently high to keep the rear seal 62 of the first device 54 under pressure, the rear seal 72 of the second device 64 comprises, as shown in FIG. 3, two sealing strips 80 and 81 which cooperate with a block of abradable material 90 which is fixed to the portion 68.

(21) The front seal 70 of the second device 64 comprises four sealing strips 82, 83, 84 and 85 which cooperate with the block of abradable material 90 and make it possible to make the flow rate of the airflow passing through the front seal 70 very low or almost zero and to thus avoid disturbances in the rear part 86 of the first movable compressor wheel 20.

(22) During operation of the turboshaft engine 1, as shown in FIG. 2, the airflow F1 enters the air inlet duct 4, is compressed by the first movable compressor wheel 20 and is then conveyed towards the second movable compressor wheel 50. Some F2 of this airflow which is compressed by the first movable compressor wheel 20 penetrates into the second sealing device 64.

(23) As shown in FIG. 3, the airflow F2 passes, from the rear to the front, through the rear seal 72 to a pressurised air pocket P which extends over an axial distance D between the front seal 70 and the rear seal 72.

(24) Some F4 of the flow F2 which has passed through the rear seal 72 to the pressurised air pocket P passes through the front seal 70 to a space 86 located behind the first movable compressor wheel 20. The flow rate of the airflow F4 which has passed through the front seal 70 is relatively low or almost zero, given that the air has passed through both the rear seal 72 and then the front seal 70, which in this case is configured specifically to greatly reduce the flow rate of the flow F4. This makes it possible to greatly limit the flow rate of the airflow F4 which returns, via a passage 73, into the airflow which is compressed by the first movable wheel 20, thus improving the efficiency of the compression.

(25) The remainder F3 of the flow F2 which has passed through the rear seal 72 to the pressurised air pocket P is bled in order to be conveyed through a passage 75 towards the front seal 60 of the first device 54 so as to keep it under pressure.

(26) In this example, the passage 75 extends between a rear portion 66 of the first movable compressor wheel 20 and a front portion 67 of the second movable compressor wheel 50. The connection between the rear portion 66 of the first movable compressor wheel 20 and the front portion 67 of the second movable compressor wheel 50 may be produced, for example, by curvic coupling, such that the passage 75 is thus made between the teeth of the gears.

(27) Referring to FIG. 4, once it has passed through the passage 75, the airflow F3 which has been bled between the two seals 70 and 72 of the second sealing device 64 is conveyed to a second passage 77 through which it passes in order to reach the front portion of the rear seal 62 of the first sealing device 54. The rear seal 62 is thus kept under pressure by the bleed airflow F3, so as to prevent the oil which is inside the first device from leaking through the passage 77 into the air inlet duct 4 and/or into the compression stage 2.

(28) Embodiments of the disclosure therefore make it possible to keep the seal or seals of the first sealing device under pressure and to thus prevent oil leaks which are linked to a reduction in pressure of one of the seals of the first device, for example of the rear seal, in particular in the case of a reduction in pressure in the air inlet duct of the turbine engine.

(29) The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure, as claimed.