Turbine with an internal secondary space equipped with fins for correcting the rotation of the air flow

Abstract

The invention relates to a turbine, comprising: a rotor (27) surrounded by a stator, a first movable stage comprising a set of rotating blades, a second movable stage comprising a second set of rotating blades, a nozzle guide vane (33) comprising a set of fixed blades, the blades having platforms (34, 36, 37) which together define a gap between a main space (EA) in which a heat flow passing through the blades circulates and a secondary space (E1, E2) surrounding the hub of the rotor. The rotor (27) has an opening (48) through which air (AP) is blown toward the secondary space (E1, E2), and the air (AP) is discharged toward the main space (EA). The invention provides straightening fins (51, 58) carried by the nozzle guide vane (33) in the secondary space (E1, E2) to straighten the air flow to change the rotation of the air flow.

Description

Technical Field

[0001] The invention relates to a seal in a turbine of a turbomachine between a rotatably movable element and a stationary element, for example a rotor element and a stationary distributor wheel surrounding the rotor element. Background Art

[0002] The turbine of a turbomachine generally comprises a hub rotating about a main axis carrying movable stages of blades spaced apart from one another along the axis, and a stationary rotating casing surrounding the assembly.

[0003] Between two consecutive movable stages a stage of fixed blades, called a distributor, is inserted for straightening the air longitudinally before it passes through the next movable stage.

[0004] exist Figure 1 In the figure, a part 1 of the turbine of the turbomachine comprises a rotor 2 rotating about a longitudinal axis AX, the rotor comprising a first disk portion 3 carrying a first series of radially rotating blades 4 forming a first movable stage 6 and a second disk portion 7 carrying a second series of radially rotating blades 8 forming a second movable stage 9.

[0005] This part comprises a fixed distributor stage 11 inserted longitudinally between the two movable stages 6 and 9 and comprising a series of fixed vanes 12 carried at their radially outer ends by a fixed casing, not shown, surrounding the assembly and forming a stator therewith.

[0006] Each stationary vane 12 comprises a platform 13 at its radially inner end, and the platforms of different vanes 12 adjoin one another in the circumferential direction to jointly form an inner shroud of the distributor 11 .

[0007] Similarly, each rotating blade 4 also includes a platform 14 at its radially inner end, and each rotating blade 8 includes a platform 16 at its radially inner end. Figure 1 It can be seen that the platforms of the different blades together form a wall, which is shaped roughly like a section of a cone. This wall separates the main annular space (called the main flow channel and indicated as VP), which is occupied by the blades 4, 8, 12 and through which the hot flow passes, from a secondary internal space (called the sub-distributor cavity) surrounding the rotor, which is kept at a lower temperature than the hot flow.

[0008] Each platform 13 of the distributor 11 comprises a body 17 shaped substantially like a portion of a cylinder carrying ribs 18 extending radially towards the axis AX. Thus, a set of ribs 18 of a platform 13 has a planar annular shape coaxial with the axis AX.

[0009] A set of ribs 18 carries an inner shroud 19 which carries on its inner surface a wearable element 21 facing the axis AX against which a lip 22 carried by the rotor 2 rubs. The lip 22 is located between the first disk 3 and the second disk 7 to provide a barrier between an internal upstream secondary space E1 located between the first disk 3 and the shroud 19 and an internal downstream secondary space E2 located between the shroud 19 and the second disk 7.

[0010] like Figure 1 It can be seen that the lip 22 and the two disks 3 and 7 are part of the rotor 2. The flow of leakage air AP is blown into the space E1 through the holes 24 of the rotor 2 to cool this space. A part of this air is discharged through the gap l1 separating the platform 14 of the blade 4 from the platform 13 of the fixed blade 12. Another part of this air passes through the barrier formed by the lip 22 and the wearable element 21 to leak to the downstream secondary space E2, and this other part is discharged through the gap l2 separating the platform 13 of the fixed blade 12 from the platform 16 of the blade 8.

[0011] The leakage air AP makes it possible to limit the ingress of air from the heat flow through the gaps 11 and 12 to limit the leakage of air from the heat flow and enable the secondary spaces E1 and E2 to be maintained at a desired temperature.

[0012] However, when the leakage air AP is discharged through the gaps l1 and l2, the leakage air locally generates vortices in the heat flow, which results in a decrease in efficiency, also known as mixing loss.

[0013] The object of the present invention is to provide a solution to remedy this disadvantage. Summary of the invention

[0014] To this end, an object of the invention is a turbine of a turbomachine extending about an axis, comprising a rotor provided with a sealing lip and a stator surrounding the rotor, the rotor being rotatably mounted in the stator, the stator comprising a distributor provided with a platform from which at least one fixed vane extends in radial direction, the platform carrying a main abradable sealing element cooperating with the lip, the platform radially delimiting a division between a main space through which the flow of hot air passes and a secondary air circulation space extending radially between the lip and the main space, the rotor comprising holes through which the air is blown in order to pass through the secondary space and reach the main space, characterized in that the distributor comprises a mainly radially extending flange carrying straightening fins located in the secondary space for straightening the air flow passing through the secondary space in order to change the rotation of the air flow before it is discharged towards the main space.

[0015] By means of this solution, the rotation of the leakage flow reinjected into the heat flow through the gap is close to the rotation of the heat flow, so as to reduce the so-called mixing losses.

[0016] The invention also relates to a turbine as defined herein, wherein the secondary space comprises an upstream secondary space and a downstream secondary space separated from each other by a primary sealing barrier, the primary sealing barrier comprising at least a lip which slides along a primary wearable element arranged opposite the lip, the bore of the rotor opening into the upstream secondary space, the turbine comprising on the one hand upstream straightening fins carried by the distributor and situated in the upstream secondary space, and on the other hand downstream straightening fins carried by the distributor and situated in the downstream secondary space, in order to straighten the air flow passing through the downstream secondary space in order to change the rotation of the air flow before it is discharged towards the primary space.

[0017] The invention also relates to a turbine as defined herein, wherein the upstream straightening fins are arranged to reduce the swirl of the flow through the upstream secondary space, and wherein the downstream straightening fins are arranged to increase the swirl of the flow through the downstream secondary space.

[0018] The invention also relates to a turbine as defined herein, comprising an upstream secondary sealing barrier located in the upstream secondary space, upstream of the upstream fins, the holes of the rotor communicating between the upstream secondary sealing barrier and the main sealing barrier, so that most of the air entering through the holes is straightened by the upstream fins before leaving the upstream secondary space and entering the main space.

[0019] The invention also relates to a turbine as defined herein, comprising a downstream secondary sealing barrier located in the downstream secondary space, downstream of the downstream straightening fins, and wherein the downstream secondary space is supplied with air from a bore of the rotor, the air passing through the primary sealing barrier to enter the primary space.

[0020] The invention also relates to a turbine as defined above, wherein the upstream secondary sealing barrier comprises an upstream lip carried by the rotor and arranged opposite an upstream abradable element carried by the distributor.

[0021] The invention also relates to a turbine as defined above, wherein the downstream secondary sealing barrier comprises a downstream lip carried by the rotor and arranged opposite a downstream abradable element carried by the distributor.

[0022] The invention also relates to a turbine as defined above, wherein the main abradable sealing element is connected to the upstream abradable sealing element by an upstream straightening fin and wherein the main abradable sealing element is connected to the downstream abradable sealing element by a downstream straightening fin.

[0023] The invention also relates to a turbine as defined above, wherein the straightening fins have a blade shape.

[0024] The invention also relates to a turbomachine comprising a turbine as defined above. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a longitudinal cross-sectional view of a known turbine portion;

[0026] Figure 2 is a longitudinal cross-sectional view of a turbine portion according to the present invention;

[0027] Figure 3 is a more detailed view of a turbine section according to the invention. DETAILED DESCRIPTION

[0028] exist Figure 2 In the figure, a part 26 of the turbine of the turbomachine comprises a rotor 27 rotating about a longitudinal axis AX, the rotor comprising a first disk portion 28 carrying a first series of rotating blades (not shown) forming a first movable stage 29 and a second disk portion 31 carrying a second series of rotating blades (not shown) forming a second movable stage 32.

[0029] This portion comprises a fixed distributor stage 33 inserted longitudinally between the two movable stages 29 and 32 , comprising a series of fixed vanes, not shown, carried at their radially outer ends by a fixed casing, not shown, which surrounds the assembly and forms a stator with the distributor 33 .

[0030] Each stationary vane comprises a platform 34 at its radially inner end, and the platforms of different vanes adjoin one another in the circumferential direction to jointly form an inner shroud of the distributor 33 .

[0031] Each rotating blade of the first stage also comprises a platform 36 at its radially inner end, and each rotating blade of the second stage comprises a platform 37 at its radially inner end. The platforms together form a wall, which is shaped generally like a portion of a cone. The wall separates the main annular space EA (called the main flow channel), which is occupied by the blades and through which the hot flow passes, from a secondary internal space (called the sub-distributor cavity) surrounding the rotor, which has a temperature lower than that of the hot flow.

[0032] Each platform 34 of the distributor 33 comprises a body 38 shaped substantially like a portion of a cylinder carrying ribs 39 extending radially towards the axis AX. Thus, a set of ribs 39 on a platform 34 has a planar annular shape coaxial with the axis AX.

[0033] A set of ribs 39 carries an inner support 41 which carries, on its inner surface, a main abradable sealing element 42 facing the axis AX, against which two lips 43, 44 carried by the rotor 27 rub. These lips 44 are located between the first disk 28 and the second disk 31 and slide along the main abradable element 42 to form with it a central main barrier B0 which separates an internal upstream secondary space E1 between the first disk 28 and the inner support 41 from an internal downstream secondary space E2 between the inner support 41 and the second disk 31.

[0034] The lips 43, 44 are carried by a hub 47 which is part of the rotor 27 by being rigidly integral with the two disks 28 and 31 of the rotor. A flow of leakage air AP is blown through holes 48 of the rotor formed in the hub 47, coming from the inner area of ​​the rotor to circulate towards the secondary space E1.

[0035] Due to the rotation of the rotor, the air AP entering the space E1 has a high gyration, ie the circumferential component of the air has a greater speed than the radial component of the air.

[0036] According to the invention, the distributor 33 here carries, at a flange 49 attached to the upstream edge of the support 41, a series of straightening fins 51 arranged to centrifuge the leakage air AP so as to reduce the whirl of this leakage air. More specifically, these fins straighten the flow as it travels towards the gap l1 so as to increase the radial component of the flow and / or reduce the circumferential component of the flow.

[0037] like Figure 2 and Figure 3 It can be seen that the annular flange 49, having a substantially planar shape and an orientation perpendicular to the axis AX, and the fins 51 carried on this ring extend perpendicularly to this ring, while having a general orientation inclined by about 45° relative to the circumferential direction C1. These fins 51 are uniformly spaced from one another in the circumferential direction on the upstream face of the flange 49.

[0038] In the example of the figure, the end closest to the axis AX of each fin 51 has a circumferential orientation Cl, and the opposite end closest to the gap l1 of each fin has a radial orientation RA. Advantageously, these fins 51 are curved in the form of an arc to increase the centrifugal effect of these fins. The curvature is oriented in a direction corresponding to the movement of the central fin area close to the central axis. Therefore, the fin 51 is arranged to reduce the swivel of the airflow when the rotor rotates along the forward direction represented by D in the figure. More generally, each fin 51 has a blade shape having a span axis EV oriented orthogonally.

[0039] Complementarily, in order to better direct the air AP to be centrifuged, another upstream flange 52, parallel to the flange 49, is attached to the upstream edge of the fin 51 so as to delimit, together with the flange 49, an upstream annular channel 53 circumferentially delimited by the fin 51. This upstream flange 52 also carries an upstream abradable element 54 which cooperates with an upstream lip 56 carried by the hub 47 to form an upstream secondary sealing barrier B1.

[0040] Thus, the inlet hole 48 for the leakage air AP opens into the annular space delimited upstream by the barrier B1 and downstream by the main barrier B0. Therefore, most of the leakage air AP is discharged through the upstream annular channel 53 so as to be effectively centrifuged to form a flow with reduced rotation when the leakage air leaves the upstream secondary space E1 through the gap l1, as shown by the dotted arrows.

[0041] exist Figure 2 and Figure 3 In the example of , the downstream secondary space E2 is supplied with leakage air coming from the holes 48 and having passed through the main barrier B0 , which is dimensioned so as to enable the passage of air calibrated therefor.

[0042] As can be seen, the downstream leakage air has low rotation once it passes through the main barrier. According to the present invention, when the air leaves the downstream internal secondary space through the gap 12, the air is straightened by other fins to increase the rotation of the air.

[0043] To this end, the downstream edge of the main abradable element 42 carries an annular downstream flange 57 , having a substantially planar shape and an orientation perpendicular to the axis AX, which carries a series of straightening fins 58 .

[0044] The fins 58 carried by the other ring extend downstream perpendicularly to the other ring, with a general orientation inclined by about 45° relative to the circumferential direction C1. These fins 58 are evenly spaced from each other circumferentially on the downstream surface of the flange 57.

[0045] Therefore, in the example of the figure, the end closest to the axis AX of each fin 58 has a radial orientation RA, and the opposite end of each fin (i.e., the end closest to the gap l2) has a circumferential orientation Cl. Advantageously, these fins 58 are curved in the form of an arc to increase the straightening effect of these fins. The curvature is oriented in a direction corresponding to the separation of the central fin area and the central axis. Therefore, the fin 58 is arranged to increase the rotation of the airflow when the rotor rotates along the forward direction represented by D in the figure. More generally, each fin 58 is shaped like a blade having a span axis EV oriented orthogonally.

[0046] Furthermore, in order to better guide the air AP to be straightened, another downstream flange 59, parallel to the flange 57, is attached to the downstream edge of the straightening fin 58 so as to delimit, together with the flange 57, a downstream annular channel 61 circumferentially delimited by the fin 58. This downstream flange 59 also carries a downstream abradable element 62 which cooperates with a downstream lip 63 carried by the hub 47 so as to form a secondary downstream sealing barrier B2.

[0047] Therefore, the leakage air passing through the main barrier B0 reaches the downstream annular space defined downstream by the downstream barrier B2. Therefore, most of the leakage air reaching this space is discharged through the downstream annular channel 61 so as to be effectively straightened to increase the rotation of the leakage air. More specifically, the fins 58 straighten the air to increase the circumferential component of the air and / or reduce the radial component of the air so that the air has a greater rotation when it passes through the gap l2 and leaves the downstream secondary space E2, as shown by the dotted arrows.

[0048] As will be understood, the invention makes it possible to reduce the generally strong swirl of the leakage air discharged through the gap 11 situated upstream of the distributor and to increase the generally lower swirl of the leakage air discharged through the gap 12 situated downstream of the distributor.

[0049] The rotation of the leakage air exiting through the two gaps l1 and l2 is therefore close to the rotation of the heat flow passing through the distributor vanes, which makes it possible to reduce the disturbances caused by this reintroduction into the heat flow, also known as mixing losses.

[0050] This optimization of the return of the leakage air reintroduced through the gaps l1 and l2 also makes it possible to improve the flow of the leakage air through these gaps, with reduced turbulence in this flow, which makes it possible to limit the flow of hot air that may enter through the gaps l1 and l2.

[0051] In the example shown in the figures, upstream straightening fin 51 is carried by flanges 49 and 52 to form an upstream straightening wheel portion, and downstream straightening fin 58 is carried by flanges 57 and 59 to form a downstream straightening wheel portion. Upstream barrier B1 and downstream barrier B2 provide secondary sealing to increase the slewing correction by ensuring that all or at least most of the leakage flow is straightened by the fins before being discharged through the gap.

[0052] Other straightening fin arrangements are conceivable without departing from the scope of the present invention, as long as they make it possible to change the turn of the flow of leakage air before it leaves the internal secondary space.

[0053] Furthermore, the invention is illustrated in the figures according to an embodiment, in which the main barrier as well as the upstream and downstream barriers are formed by labyrinth seals, i.e. comprising one or more lips arranged opposite to the wearable element. The invention is applicable to overall similar structures, in which the sealing barriers can also be obtained by other technical solutions. In particular, the upstream barrier, the downstream barrier and the main barrier can be formed by so-called brush seals, i.e. one surface of the brush seal carries the strands, the ends of which bear on the other surface to ensure the required sealing.

Claims

1. A turbine of a turbomachine, the turbine of the turbomachine extending around an axis (AX), comprising a rotor (27) provided with a sealing lip and a stator surrounding the rotor (27), the rotor (27) being rotatably mounted in the stator, the stator comprising a distributor (33) provided with a platform (34), from which at least one fixed vane extends in radial direction, the platform (34) carrying a main wearable sealing element (42) cooperating with the sealing lip, the platform (34) radially delimiting a division between a main space (EA) and a secondary air circulation space (E1, E2) through which a flow of hot air passes, the secondary air circulation space extending radially between the sealing lip and the main space (EA), the rotor (27) comprising holes (48) through which air (AP) is blown in to pass through the secondary air circulation space (E1, E2) and to the main space (EA), characterized in that The distributor (33) comprises a mainly radially extending flange (49, 57) carrying straightening fins (51, 58) extending into the secondary air circulation space (E1, E2) to straighten the air flow passing through the secondary air circulation space (E1, E2) in order to change the turn of the air flow before it is discharged towards the main space (EA).

2. The turbine according to claim 1, wherein: The secondary air circulation space comprises an upstream secondary air circulation space (E1) and a downstream secondary air circulation space (E2) separated from each other by a main sealing barrier (B0), the main sealing barrier comprising the sealing lip and the main wearable sealing element (42) arranged opposite to the sealing lip, the hole (48) of the rotor (27) leading to the upstream secondary air circulation space (E1), the turbine comprising, on the one hand, upstream straightening fins (51) carried by the distributor (33) and located in the upstream secondary air circulation space (E1), and on the other hand, downstream straightening fins (58), the upstream straightening fins being carried by the distributor (33) and located in the downstream secondary air circulation space (E2) to straighten the air flow passing through the downstream secondary air circulation space (E2) so as to change the rotation of the air flow before the air flow is discharged toward the main space (EA).

3. The turbine according to claim 2, wherein: The upstream straightening fin (51) is arranged to reduce the turning of the flow passing through the upstream secondary air circulation space (E1), and wherein the downstream straightening fin (58) is arranged to increase the turning of the flow passing through the downstream secondary air circulation space (E2).

4. A turbine according to claim 2 or 3, comprising an upstream secondary sealing barrier (B1) located in the upstream secondary air circulation space (E1) and upstream of the upstream straightening fin (51), the hole (48) of the rotor (27) being connected between the upstream secondary sealing barrier (B1) and the main sealing barrier (B0), so that most of the air entering through the hole (48) is straightened by the upstream straightening fin (51) before leaving the upstream secondary air circulation space (E1) and entering the main space (EA).

5. The turbine according to claim 4, comprising a downstream secondary sealing barrier (B2) located in the downstream secondary air circulation space (E2), downstream of the downstream straightening fin (58), and wherein, The downstream secondary air circulation space (E2) is supplied with air from the holes (48) of the rotor (27), and the air passes through the primary sealing barrier (B0) to enter the main space (EA).

6. The turbine according to claim 4, wherein: The upstream secondary sealing barrier (B1) comprises an upstream lip (56) carried by the rotor (27) and arranged opposite an upstream abradable element (54) carried by the distributor (33).

7. The turbine according to claim 5, wherein: The downstream secondary sealing barrier (B2) comprises a downstream lip (63) carried by the rotor (27) and arranged opposite a downstream abradable element (62) carried by the distributor (33).

8. The turbine according to claim 7, wherein: The upstream secondary sealing barrier (B1) comprises an upstream lip (56) carried by the rotor (27) and arranged opposite an upstream abradable element (54) carried by the distributor (33), the main abradable sealing element (42) being connected to the upstream abradable element (54) via the upstream straightening fin (51), and wherein the main abradable sealing element (42) is connected to the downstream abradable element (62) via the downstream straightening fin (58).

9. A turbine according to any one of claims 1 to 3, wherein: The straightening fins (51, 58) have a blade shape.

10. A turbomachine comprising the turbine according to any one of claims 1 to 9.

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