EP4185765A1

EP4185765A1 - Turbine with pressurised cavities

Info

Publication number: EP4185765A1
Application number: EP21752581.5A
Authority: EP
Inventors: Matthieu Simon; Ulysse Jacques Bernard DANTENY
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2020-07-23
Filing date: 2021-07-22
Publication date: 2023-05-31
Also published as: FR3112811A1; CN115885091A; FR3112811B1; WO2022018385A1; US20230296023A1

Abstract

The invention relates to a turbine (7) comprising a first rotor (25) and a second rotor (27) capable of pivoting about a longitudinal axis (X) in two opposite directions of rotation, the first rotor (25) comprising a radially outer drum (29) from which blades (26) extend radially inwards, the first rotor (25) and the second rotor (27) being surrounded by an annular stator part (31), characterised in that said annular stator part (31) delimits, with the drum (29), at least one upstream annular cavity (40) and one downstream annular cavity (42) separated from one another by sealing means (44).

Description

DESCRIPTION

TITLE: Pressurized Cavity Turbine

Technical field of the invention

This document relates to a cooling device in a turbine engine turbine, for example turbofan.

State of the prior art

FIG. 1 represents a turbomachine 1 with double flow and double body. The axis of the turbomachine is referenced X and corresponds to the axis of rotation of the rotating parts. In the following, the terms axial and radial are defined with respect to the X axis.

The turbomachine 1 comprises, from upstream to downstream in the direction of gas flow, a fan 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6 and a low pressure turbine 7.

The air from the fan 2 is divided into a primary flow 8 flowing in a primary annular vein 9, and a secondary flow 10 flowing in a secondary annular vein 11 surrounding the primary annular vein 10.

The low pressure compressor 3, the high pressure compressor 4, the combustion chamber 5, the high pressure turbine 6 and the low pressure turbine 7 are arranged in the primary stream 9.

The rotor of the high pressure turbine 6 and the rotor of the high pressure compressor 4 are coupled in rotation via a first shaft 12 so as to form a high pressure body.

The rotor of the low pressure turbine 7 and the rotor of the low pressure compressor 3 are coupled in rotation via a second shaft 13 so as to form a low pressure body, the fan 2 being able to be connected directly to the rotor of the compressor low pressure 3 or via an epicyclic gear train for example. As is best seen in Figure 2, the low-pressure turbine 7 comprises in particular different successive stages comprising movable wheels 14 and fixed parts. The impeller comprises a disc 15 at which blades 16 are mounted. The ends of the blades 16 are surrounded by a fixed ring 17 of abradable material, said ring 17 being fixed to the casing 18 of the turbine. Distributors 19 are located downstream of the impellers 14. The distributors 19 and the rings 17 are mounted on the casing by means of flanges or hooks 20 extending from the radially inner surface of the casing 18.

In order to guarantee a high efficiency of the turbomachine, it is necessary to limit the flow of air not passing through the moving wheels 14 of the various stages, that is to say to limit the leaks between the radially outer ends of the blades 16 and the ring 17 made of abradable material. For this, it is necessary to control the play at this interface, this play being dependent on the temperature of the casing 18, and in particular of the zones of said casing 18 comprising the hooks or flanges 20 supporting the ring 17.

The primary air flow from the combustion chamber 5 has a high temperature and heats the parts located downstream, such as the fixed and moving parts of the turbine 6, 7.

In order to control the aforementioned clearance and to avoid any premature degradation of the various fixed and moving parts of the turbine, it is necessary to provide effective cooling means that can be easily integrated into the environment of the turbomachine.

Patent application FR 3 021 700, in the name of the Applicant, discloses a device 21 for cooling a casing 18 of a low-pressure turbine 7, visible in FIG. 3, comprising manifold boxes 22 fixed to a fixed casing of the turbomachine, each manifold housing 22 forming a channel extending axially.

The device 21 further comprises tubes 23, also called ramps, extending circumferentially on either side of the collector boxes 22. Each tube 23 comprises an air inlet opening into the channel of the collector box 22 and orifices of ejection of air facing the casing 18, so that the cooling air can enter the collector housings 22 then the tubes 23 before emerging through the openings opposite the casing 18, so as to cool it. We speak in particular of cooling by impact since the air comes to impact the casing 18. Such a device is known under the name LPTACC (for “Low Pressure Turbine Active Clearance Control”).

Recent developments have led to the development of so-called contra-rotating turbines. Such a turbine comprises a first rotor comprising one or more stages formed by bladed wheels, rotating around the axis X of the turbomachine in a first direction of rotation, and a second rotor comprising one or more stages formed by bladed wheels, rotating around the X axis in a second direction of rotation, opposite to the first direction of rotation.

The first rotor has a radially outer drum, from which blades extend radially inward. The second rotor has a radially inner drum, from which blades extend radially outward.

It is necessary to ensure cooling of the rotors, in particular of the radially outer drum of the first rotor.

It turns out that it is not relevant to use a cooling device of the LPTACC type as described above. Indeed, the use of fixed ramps to cool a rotating drum by impact is not effective because, during the rotation of the drum, a layer of air boundary surrounds the drum, the airflow from the ramp orifices being sheared by the rotation of the drum and by said boundary layer, greatly reducing the cooling efficiency.

In the current technique, the radially outer drum delimits with an outer annular casing an annular space supplied with cooling air by air taken from the high pressure compressor, which reduces the efficiency of the compressor. In addition, a high piston effect exists because at the downstream end of the first rotor, there is a pressure difference equivalent to the total expansion of the turbine.

Summary of the invention

This document relates to a turbine comprising a first rotor and a second rotor capable of pivoting about a longitudinal axis in two opposite directions of rotation, the first rotor comprising a radially outer drum from which blades extend radially towards the interior, the first rotor and the second rotor being surrounded by an annular stator part, characterized in that the said annular stator part delimits with the drum at least one upstream annular cavity and one downstream annular cavity separated from each other by sealing means, the upstream annular cavity being connected to first means for supplying cooling air at a first pressure and the downstream annular cavity being connected to second means for supplying cooling air at a second pressure lower than the first press.

In this way, the upstream annular cavity is supplied with cold air via high pressure air in order to be able to purge the upstream annular cavity and also to pressurize it. This prevents hot air from the vein from flowing out of the drum. Given that a high pressure air supply penalizes the performance of a turbomachine since it is generally taken from a compressor, the objective is to provide the minimum and therefore to pressurize an annular cavity of low volume.

The downstream annular cavity is supplied with cooling air with air having a lower pressure, this air proving to be much less penalizing on the performance of the turbomachine. This cooling air is inexpensive and can be used in large quantities. However, the low supply pressure of this cooling air does not allow the purging of the entire annular space, that is to say the upstream annular cavity and the downstream annular cavity, which explains the separation of the two cavities by sealing means. Downstream of the external drum, the air is expanded and the slightly pressurized air coming from the secondary stream can still reach the primary stream.

The upstream annular cavity may be an annular cavity formed at the upstream end of the turbine. This upstream annular cavity surrounds the upstream end of the radially outer drum. The separation of the two annular cavities by sealing means makes it possible to limit the "piston" effect on the turbine. The positioning of sealing means immediately downstream of the annular row of blades of the first rotor achieves the best compromise between limiting the piston effect and purging the upstream annular cavity with high-pressure air. According to another characteristic, the first cooling air supply means have a first temperature lower than a second temperature of the second air supply means.

The upstream annular cavity can communicate fluidly with an annular air stream inside which the blades extend, the annular stream being delimited radially on the outside by the drum of the first rotor and being delimited radially on the inside by a radially inner drum of the second rotor.

The downstream annular cavity can communicate fluidly with the annular air stream inside which the blades extend.

The upstream end of the drum can delimit with the annular stator piece a first annular air passage with an annular air stream inside which the blades extend.

The downstream end of the drum of the first rotor can delimit with the annular stator piece a second annular passage with an annular air stream inside which the blades extend.

At least one annular housing may be formed at the junction of at least one blade of the first rotor with the drum of the first rotor.

A first annular housing can communicate fluidly with the upstream annular cavity. Said first housing can be arranged radially opposite the upstream annular cavity.

Said first annular housing can be formed at the level of the blade arranged at the upstream end of the drum of the first rotor. Said first housing can communicate fluidly with an annular air stream in which the blades extend radially.

A second annular housing can be arranged radially opposite the downstream annular cavity. The second housing(s) can be closed, i.e. be hermetic with respect to the air in the primary stream and the air in the downstream annular cavity.

The first and/or second air supply means may comprise means for controlling the opening/closing of the air supply.

The control means may comprise an air flow control valve, which air flow may be taken from an annular vein of secondary air. In this way, it is possible to carry out an active control of the clearances of the turbine in operation. Controlling a high flow of cold air in the downstream annular cavity, during the cruising phase, will make it possible to reduce the air temperature seen by the external annular drum and therefore by the external rotor via a reduction in the average temperature by enthalpy balance since more cold air flow is added from the second cooling air supply means than relatively warmer air flow from the first cooling air supply means cooling air, coming from the upstream annular cavity, and passing at the level of the sealing means. The first stage of the turbine, which does not benefit from this cooling due to the partitioning by the sealing means, will nevertheless see its temperature decrease and therefore its radial clearances close, via the phenomenon of conduction in the annular stator part from downstream to upstream. There is therefore a passive control at the level of the play(s) of the stages arranged radially at the level of the upstream annular air cavity and an active control of the plays of the downstream stages arranged radially at the level of the downstream annular cavity, when only the second means air supply are connected to air flow control means.

The drum of the first rotor can be tapered with a section increasing downstream.

This document also relates to a turbomachine, such as a turboprop or an aircraft turbojet, comprising at least one turbine as described above.

The turbomachine may be such that the first means for supplying cooling air are connected upstream to first means for taking air from a compressor, preferably high pressure, and/or in which the second means for supplying cooling air are connected upstream to second air bleed means in an annular secondary air stream of the turbomachine which is dual-flow with a primary air flow and the secondary air flow coaxial and external to the primary airflow. The annular vein of secondary air extends radially outside of said annular stator part.

It is understood that the air coming from the compressor only supplies the upstream annular cavity and/or that the air from the secondary annular air stream only supplies the downstream annular cavity. As the air in the secondary stream is cold, it is not necessary to bring air cooling to the level of the ends of the blades arranged in line with the downstream annular cavity.

The annular stream of secondary air refers here to the annular stream of air surrounding the annular stream of primary air and which is well known in the state of the art relating to dual-flow turbomachines. Thus, the turbomachine comprises a fan which blows air in a primary annular stream and in a secondary annular stream. The turbine blades according to this document extend into the primary stream and the air for the downstream cavity is taken from the secondary stream.

In another embodiment, the turbine may comprise three successive annular cavities along the longitudinal axis of the turbine, an upstream annular cavity, an intermediate annular cavity and a downstream annular cavity, the cavities being separated by sealing means. The intermediate annular cavity can be connected to third means for supplying cooling air, this air can be air coming from the compressor, preferably from the high pressure part of the compressor, and from a zone for taking off air in the compressor located upstream of the air bleed zone connected to the first air supply means. This makes it possible to have a more compressed purge air and makes it possible to prevent the stream air from going into the cavities outside the drum of the first rotor.

At least a third annular housing can communicate fluidly with the intermediate annular cavity. Said third annular housing can be arranged radially opposite the intermediate annular cavity and it can communicate fluidly with the annular primary air stream.

The annular stator part may be a casing of the turbine which may be a low pressure turbine of a turbomachine which may be turbofan.

The upstream end of the turbine casing can be connected to an intermediate casing interposed between a casing of an upstream high pressure turbine and the casing of the low pressure turbine. This intermediate casing may comprise substantially radial stationary vanes connecting an inner annular shroud and an outer annular shroud.

The downstream end of the turbine casing may be connected to an exhaust casing which may comprise an inner annular shroud and an outer annular shroud connected to each other by substantially radial stationary vanes.

The casing of the low pressure turbine can be connected to the outer annular shroud of the intermediate casing and for example at its downstream end and/or to the outer annular shroud of the exhaust casing and for example at its upstream end.

Brief description of figures

[Fig. 1], already described previously, is a schematic view in axial section of a turbomachine of the prior art,

[Fig. 2], already described previously, is a half-view in axial section of a turbine of the prior art,

[Fig. 3], already described above, is a perspective view of a prior art cooling device,

[Fig. 4],

[Fig. 5],

[Fig. 6], and

[Fig. 7] illustrate different embodiments of a turbine according to the present disclosure.

Detailed description of the invention FIGS. 4 to 6 illustrate a low-pressure turbomachine turbine 7 according to four possible embodiments.

The turbine 7 is of the counter-rotating type and comprises a first rotor 25 comprising one or more stages formed by bladed wheels 26, rotating around the longitudinal axis X of the turbine 7 in a first direction of rotation, and a second rotor 27 comprising one or more stages formed by bladed wheels 28, rotating around axis X in a second direction of rotation, opposite to the first direction of rotation.

The first rotor 25 has a radially outer drum 29, from which vanes 26 extend radially inward. The second rotor 27 has a radially inner drum 30, from which blades 28 extend radially outward. The first and second rotors 25, 27 are housed in an annular stator piece or fixed casing 31, said casing 31 comprising in particular a radially outer annular wall 32. The vanes 26, 28 extend in an annular primary air stream 34 The radially outer drum 29 has a frustoconical shape with a section increasing downstream. The upstream end of the radially outer annular wall 32 of the outer casing 31 is connected to the downstream end of an intermediate casing 36 inserted between the low pressure turbine and a high pressure turbine (not shown). The downstream end of the radially outer annular wall 32 of the outer casing 31 is connected to the upstream end of an exhaust casing 38. As indicated previously, it is necessary to ensure cooling of the rotors 25, 27, in particular of the radially outer drum 29 of the first rotor 25.

In the various embodiments, the radially outer drum 29 delimits with the radially outer annular wall 32 an upstream annular cavity 40 and a downstream annular cavity 42 which are separated from each other by sealing means 44. The annular cavity upstream 40 is formed at the upstream end of the turbine. This upstream annular cavity 40 surrounds the upstream end of the radially outer drum 29.

In the embodiments of Figures 4 and 5, only an upstream annular cavity 40 and a downstream annular cavity 42 are present, whereas in the embodiments of Figures 5 and 6, an intermediate annular cavity 46 is formed longitudinally between the upstream annular cavity 40 and the downstream annular cavity 42 and sealing means 44 separate the intermediate annular cavity 46 from the upstream annular cavity 40 and from the downstream annular cavity 42.

Although not shown in the figures, it would be possible to have more than three successive annular cavities.

The sealing means 44 comprise annular wipers 44a formed at the radially inner end of a radial annular wall 46 of the casing 31, this radial annular wall 46 being connected at its radially outer end to the radially outer annular wall 32 . The wipers 44a cooperate with the radially outer drum 29 in order to seal against the circulation of air. The upstream annular cavity 40 connected to first means 48 for supplying cooling air at a first pressure and at a first temperature and the downstream annular cavity is connected to second means 50 for supplying cooling air at a second pressure. lower than the first pressure and having a second temperature lower than the first temperature.

In the particular example of the low pressure turbine, the first means 48 for supplying cooling air are connected upstream to first means 52 for taking air from a compressor (not shown), for example high pressure, and the second means 50 for supplying cooling air are connected upstream to second means 54 for taking air from an annular stream of secondary air from a dual-flow turbomachine. Thus, the air supplying the upstream annular cavity 40 is at a pressure and a temperature respectively higher than the pressure and the temperature of the air supplying the downstream annular cavity 42.

The second air supply means 50 can comprise means 56 for controlling the opening/closing of the air supply to the downstream annular cavity 42. The control means 50 can for example comprise a flow control valve of air. The first air supply means 48 may have no control means, the flow of air entering the upstream annular cavity 40 not being regulated. The upstream end of the radially outer drum 29 delimits with the outer casing 31 a first annular air passage 56 with the primary air annular vein 34 inside which the blades 26, 28 extend. downstream of the radially outer drum 29 delimits with the outer casing 31 a second annular air passage 58 with the annular stream 34 of primary air inside which the blades 26, 28 extend.

Annular housings 60 can be formed at the junction of at least one blade 26 of the first rotor 29 with the radially outer drum 29. In practice, it is observed in the embodiments that each blade 26 includes such a housing 60.

In the embodiment of FIG. 4, a first housing 60a is formed at the level of the blade of the upstream end of the first rotor 25. This first housing 60a communicates with the annular stream 34 of primary air by means of an orifice emerging downstream and communicates with the upstream annular cavity 40. This first annular housing 60a is arranged radially at the level of the upstream annular cavity 40. Each annular row of blades 26 arranged radially opposite the annular cavity downstream 42 comprises a second annular housing 60b which is hermetic vis-à-vis the downstream annular cavity 42 and the primary annular vein 34, these second housings 60b not being able to receive air.

The arrival of cold air in the downstream annular cavity 42 can make it possible to reduce the air temperature seen by the external annular drum 29 and therefore by the external rotor via a reduction in the average temperature by enthalpy balance since one adds more cold air flow from second means 50 for supplying cooling air than relatively hotter air flow from the first means 48 for supplying cooling air, coming from the upstream annular cavity 40, and passing at the level of the sealing means 44. The first stage of the turbine, which does not benefit from this cooling due to the partitioning by the sealing means 44, will nevertheless see its temperature decrease and therefore its radial clearances close, via the phenomenon of conduction in the annular part stator 31 from downstream to upstream.

In this embodiment, it is observed that the cooling air of the upstream annular cavity 40 circulates in the first annular housing 60a then flows in the passage 34 making it possible to cool the annular row of blades 26 upstream and that 26 arranged immediately in downstream as shown in Figure 4. There is therefore a cascade cooling.

In the embodiment of FIG. 5, the sealing means 44 are arranged radially outside the first annular row of mobile blades of the second rotor. The presence of second hermetic annular housings 60b is observed but there is no first annular housing. The air entering the upstream annular cavity 40 flows directly through the first annular passage 56 and makes it possible to pressurize the upstream annular cavity 40. The cascade cooling mentioned with reference to FIG. 4 does not exist in this embodiment. This configuration makes it possible to minimize the air flow taken from the compressor. This solution is effective in the case of temperatures of the primary stream 34 that are quite cold and which does not require the need to cool the outer rotor 25. The air in the upstream cavity performs a purge to prevent the air from the primary stream flows radially over the outer drum while the air in the downstream cavity at a lower pressure is actually aimed at cooling the outer drum.

FIG. 6 corresponds to the embodiment of FIG. 4 in which the downstream annular cavity 42 has been separated into an intermediate annular cavity 46 and a new downstream annular cavity 42. First sealing means 44a separate the upstream annular cavities 40 and intermediate 46 and second sealing means 44b separate the intermediate 46 and downstream 42 cavities, these sealing means 44a, 44b possibly being identical to what has been described previously with reference to FIGS. 4 and 5.

The intermediate annular cavity 46 is connected to third means 62 for supplying cooling air, this air can here be air coming from the compressor, for example high pressure, and from an air bleed zone in the compressor located upstream of the air bleed zone connected to the first air supply means 48 . In this way, the air sampled is at a third pressure and a third temperature lower than the pressure and temperature of the first means 48 for supplying air but higher than the pressure and temperature of the second means 50 for supplying air. A first housing 60a is formed at the level of the blade 26 of the upstream end of the first rotor 25. This first housing 60a communicates fluidly with the annular stream 34 of primary air by means of an orifice emerging downstream and communicates fluidly with the upstream annular cavity 40. This first annular housing 60a is arranged radially at the level of the upstream annular cavity 40 The annular row of blades 26 arranged radially inside the intermediate annular cavity 46 comprises a third annular housing 60c which communicates fluidly with the intermediate annular cavity 46 and with the annular stream 34 of primary air. The annular row of blades 26 arranged radially inside the downstream annular cavity 42 comprises a second annular housing 60b which is hermetic and communicates neither with the annular stream 34 of primary air nor with the downstream annular cavity 42. The embodiment of Figure 7 corresponds to the embodiment of Figure 5 in which the downstream annular cavity 42 has been separated into an intermediate annular cavity 46 and a new downstream annular cavity 42. It still corresponds to the embodiment of Figure 6 in which the first sealing means 44a have been moved upstream and radially outside the annular row of blades of the upstream end of the second rotor 27. For the rest, the description made with reference to FIG. also applies to this figure.

In either of the embodiments of FIGS. 6 and 7, the third means 62 for supplying cooling air may comprise means 64 for controlling the opening/closing of the air supply to the annular cavity. downstream 42. The control means 64 can for example comprise an air flow control valve. The last two multi-cavity configurations make it possible to best adjust the needs in terms of cooling flow and associated pressure according to the expansion in the primary air stream.

Claims

1. Turbomachine, such as a turboprop or an aircraft turbojet, comprising a turbine (7) comprising a first rotor (25) and a second rotor (27) capable of pivoting about a longitudinal axis (X) along two opposite directions of rotation, the first rotor (25) comprising a radially outer drum (29) from which blades (26) extend radially inwards, the first rotor (25) and the second rotor (27) being surrounded by an annular stator part (31), characterized in that said annular stator part (31) delimits with the drum (29) at least one upstream annular cavity (40) and one downstream annular cavity (42) separated from one the other by sealing means (44), the upstream annular cavity (40) being connected to first means (48) for supplying cooling air at a first pressure and the downstream annular cavity being connected to second means (50) for supplying cooling air at a second pressure lower than the pr first pressure, the first means (48) for supplying cooling air being connected upstream to first means (52) for taking air from a compressor, preferably high pressure, and/or in which the second means ( 50) for supplying cooling air are connected upstream to second means (54) for taking air from an annular secondary air stream (34) which extends radially outside of said annular stator part (31).

2. Turbomachine according to claim 1, in which the upstream annular cavity (40) communicates fluidly with an annular stream (34) of air inside which the blades (26) extend, the annular stream (34) being delimited radially on the outside by the drum (29) of the first rotor (25) and being delimited radially on the inside by a drum (30) radially inside the second rotor (27).

3. Turbomachine according to claim 2, wherein the upstream end of the drum (29) of the first rotor (25) defines with the annular stator part (31) a first passage (56) annular air with the annular vein (34 ) of air inside which the blades (26) extend.

4. Turbomachine according to claim 2 or 3, in which the downstream annular cavity (42) communicates fluidly with the annular stream (34) of air inside which the blades (26) extend.

5. Turbomachine according to claim 4, in which the downstream end of the drum (29) of the first rotor (25) defines with the annular stator part (31) a second annular passage (58) of air with the annular vein (34 ) of air inside which the vanes (26) extend.

6. Turbomachine according to one of the preceding claims, wherein at least one annular housing (60a, 60b, 60c) is formed at the junction of at least one blade (26) of the first rotor with the drum (29) of the first impeller (25).

7. Turbomachine according to the preceding claim, wherein a first annular housing (60a) communicates fluidly with the upstream annular cavity (40).

8. Turbomachine according to the preceding claim, in which the first annular housing (60a) is formed at the level of the blade (26) arranged at the upstream end of the drum (29) of the first rotor (25).

9. Turbomachine according to one of claims 6 to 8, wherein a second annular housing (60b) is arranged radially opposite the downstream annular cavity (42).

10. Turbomachine according to one of claims 1 to 9, wherein the second air supply means (50) comprise control means (56) for opening/closing the air supply.

11. Turbomachine according to one of claims 1 to 10, wherein the drum (29) of the first rotor (25) is frustoconical with a section increasing downstream.