CN113803119A

CN113803119A - Gas turbine stator vane with sealing member and method of modifying same

Info

Publication number: CN113803119A
Application number: CN202110660356.8A
Authority: CN
Inventors: G·嘉尔德拉
Original assignee: Ansaldo Energia SpA
Current assignee: Ansaldo Energia SpA
Priority date: 2020-06-15
Filing date: 2021-06-15
Publication date: 2021-12-17
Also published as: EP3926141B1; EP3926141A1

Abstract

Gas turbine stator vanes with sealing members and methods of modifying the same. The gas turbine stator vane comprises an airfoil (13) having a forward edge (13 a) and an aft edge (13 b), an outer platform (14) connected to an outer end of the airfoil (13), and an inner platform (15) connected to an inner end of the airfoil (13). The inner platform (15) has a leading edge (15 a) and a trailing edge (15 b) at a leading edge (13 a) and a trailing edge (13 b) of the airfoil (13), respectively, and comprises a stator aft seal portion (19) at the trailing edge (15 b), and at least one aft sealing rib (20) integral with the inner platform (15) and bounded by adjacent aft grooves (21) extending parallel to each other in the stator aft seal portion (19) all the way along the trailing edge (15 b), whereby in use the stator aft seal portion (19) contacts a respective adjacent rotor portion of the gas turbine rotor (3) in response to thermal expansion only at the at least one aft sealing rib (20).

Description

Gas turbine stator vane with sealing member and method of modifying same

Cross Reference to Related Applications

This patent application claims priority to european patent application No. 20425018.7 filed on 6/15/2020, the entire disclosure of which is incorporated herein by reference.

Technical Field

The invention relates to a gas turbine stator vane with a sealing member and a method for modifying a gas turbine stator vane.

Background

It is well known that gas turbines are provided with sealing systems that prevent the hot gases produced by combustion from leaking and reaching components outside the hot gas path. In fact, while the component directly facing the hot gas is designed to withstand extremely high temperatures, the other components are not because the manufacturing costs would be too high. The sealing system is typically configured to supply a sealed flow of relatively fresh air at high pressure through a narrow passage between the stator and rotor components. The sealing gas flow confines the hot gas within the hot gas path, thus protecting components that would be exposed to high temperatures.

To be effective, the rotor and stator components that define the sealing system need to be spaced apart by a small distance in order to form a sufficiently narrow passage and maintain a sealed condition under any operating conditions. However, gas turbine components surrounding the hot gas path may experience large thermal expansion because they may be exposed to temperatures ranging from room temperature to over 1000 ℃. It is thus possible that, in certain cases, the stator component and the rotor component forming the sealing system are in contact with each other. Although this need to be taken into account, the contact between the stationary and rotating parts may also cause damage and in any case friction, which leads to a loss of efficiency. The known solutions are not effective in meeting the conflicting requirements of reducing the contact of the stator and rotor parts and maintaining a sufficiently narrow passage to seal the air flow under all operating conditions. However, some solutions that produce more encouraging results are costly because they require additional components, such as brushes or honeycomb seals, to be assembled, welded or brazed.

Disclosure of Invention

It is therefore an object of the present invention to provide a gas turbine stator vane and a method for modifying a gas turbine stator vane that allows to overcome or at least alleviate the above limitations.

According to the present invention, there is provided a gas turbine stator vane comprising:

an airfoil having a forward edge and an aft edge;

an outer platform connected to an outer end of the airfoil, and an inner platform connected to an inner end of the airfoil, wherein the inner platform has a leading edge and a trailing edge at a leading edge and a trailing edge, respectively, of the airfoil, and comprises:

a stator rear seal portion at the rear edge; and

at least one aft sealing rib integral with the inner platform and defined by adjacent aft grooves extending parallel to each other along an aft edge all the way through the stator aft sealing portion, whereby in use the stator aft sealing portion contacts a respective adjacent rotor portion of the gas turbine rotor in response to thermal expansion only at the at least one aft sealing rib.

The contact area of the stator and the rotor is thus minimized. Thus, the risk of friction and damage is significantly reduced without affecting the sealing function of the rear sealing portion of the stator. The sealing rib is also provided as a sacrificial element, since it may be partly eroded by wear due to the small contact area, and just to the extent needed to accommodate thermal expansion. Erosion of the aft sealing rib does not significantly change the overall shape of the aft edge of the platform and the sealing effect is not altered.

Furthermore, the rear sealing rib is integral with the inner platform and no additional components need to be applied. And therefore less costly than known solutions.

According to one aspect of the invention, the at least one rear sealing rib has a thickness between 0.3mm and 3 mm.

According to one aspect of the invention, the depth of the back groove is between 3mm and 20 mm.

According to one aspect of the invention, at least a portion of the trailing edge is defined by the envelope surface, and the distal edge of the at least one trailing sealing rib is located in the envelope surface.

According to one aspect of the invention, at least a portion of the trailing edge is defined by the envelope surface, and the distal rim of the at least one trailing sealing rib projects outwardly from the envelope surface.

The shape of the trailing edge of the platform facilitates the transport of the sealing air as a film-like flow, which also facilitates the cooling of the rotor component in the hot gas path.

According to an aspect of the invention, the envelope surface is a surface of revolution having a radius of curvature between 3mm and 15mm, or the envelope surface is a flat surface.

According to one aspect of the invention, the stator vane comprises a plurality of parallel aft sealing ribs defined by respective pairs of adjacent aft grooves extending parallel to each other along the aft edge all the way through the stator aft sealing portion, whereby in use the stator aft sealing portion contacts adjacent rotor portions of the gas turbine rotor in response to thermal expansion only at the plurality of aft sealing ribs.

A flexible design can be achieved accordingly to meet the requirements of reduction of the contact area between the rotor and the stator and the sealing effect under special conditions that need to be compromised.

According to one aspect of the invention, the inner platform comprises:

a stator front seal portion at the front edge; and

at least one forward sealing rib bounded by adjacent forward grooves extending parallel to each other along a forward edge all the way in the stator forward sealing portion, whereby in use the stator forward sealing portion contacts a respective adjacent rotor portion of the gas turbine rotor in response to thermal expansion only at the at least one forward sealing rib.

According to an aspect of the present invention, there is also provided a gas turbine comprising:

a rotor having a plurality of rotor stages;

a stator having a plurality of stator stages alternating with rotor stages in an axial direction;

wherein at least one of the stator stages comprises a plurality of stator vanes as defined above.

According to one aspect of the invention, the gas turbine includes a seal structure between a stator vane of at least one of the stator stages and a corresponding adjacent rotor stage, wherein the seal structure is defined in part by a stator aft seal portion of the stator vane.

According to one aspect of the invention, the seal structure includes a rotor seal portion of one of the rotor stages facing at least one of the stator stages, and the stator aft seal portion is configured to contact the rotor seal portion in response to thermal expansion only at the at least one aft seal rib.

According to one aspect of the invention, the aft sealing ribs of adjacent stator vanes of at least one of the stator stages are joined to each other without discontinuities.

According to an aspect of the invention, there is also provided a method for modifying a gas turbine stator vane blade, the stator vane comprising:

an airfoil having a forward edge and an aft edge;

an outer platform connected to an outer end of the airfoil, and an inner platform connected to an inner end of the airfoil, wherein the inner platform has a leading edge and a trailing edge at a leading edge and a trailing edge, respectively, of the airfoil; and

a stator rear seal portion at the rear edge;

the method includes forming adjacent aft grooves extending parallel to each other along an aft edge all the way in the stator aft seal portion, whereby the adjacent aft grooves define at least one aft seal rib integral with the inner platform, and in use the stator aft seal portion contacts a respective adjacent rotor portion of a rotor of the gas turbine in response to thermal expansion only at the at least one aft seal rib.

The method allows existing stator vanes to be adjusted to reduce the limitations associated with relatively large contact areas between stator and rotor components of the sealing system.

Drawings

The invention will now be described with reference to the accompanying drawings, which illustrate some non-limiting embodiments of the invention, and in which:

FIG. 1 is a cross-sectional view of a gas turbine engine;

FIG. 2 is a side view of a stator vane according to an embodiment of the invention comprised in the gas turbine engine of FIG. 1;

FIG. 3 is an enlarged perspective view of a portion of the stator vane of FIG. 2;

fig. 4 is an enlarged sectional side view of a first detail of the stator vane of fig. 2;

fig. 5 is an enlarged sectional side view of a second detail of the stator vane of fig. 2;

FIG. 6 is a sectional side view of a detail of a stator vane according to another embodiment of the invention;

FIG. 7 is a sectional side view of a detail of a stator vane according to another embodiment of the invention;

FIG. 8 is a sectional side view of a detail of a stator vane according to another embodiment of the invention; and

fig. 9 is a sectional side view of a detail of a stator vane in an intermediate step of the method according to an embodiment of the invention.

Detailed Description

Referring to fig. 1, a gas turbine engine according to an embodiment of the invention is indicated by the numeral 1 and comprises a stator 2 and a rotor 3, which is rotatably coupled to the stator 2 about a machine axis a. The stator 2 and the rotor 3 form a compressor section 4 and an expansion or turbine section 5 of the gas turbine engine 1, which further comprises a combustor assembly 7. The burner assembly 7 may be of the annular type as in the example of fig. 1, or may be of the cartridge annular, can or silo type. Compressor section 4 supplies an externally drawn airflow to combustor assembly 7. Combustor assembly 7 mixes air from compressor section 4 with fuel from a fuel supply system (not shown) to form an ignited and combusted mixture. The gas turbine engine 1 may be configured to use different types of fuels, both gaseous and liquid. The turbine section 5 receives and expands the flow of hot gases from the combustor assembly 7 to extract mechanical work, which is transmitted to an external user, typically an electrical generator, not shown herein.

The stator 2 and rotor 3 of the gas turbine engine 1 have a plurality of stator stages 8, each comprising an array of radial stator vanes 11, and rotor stages 10, each comprising an array of radial rotor blades 12. The stator stages 8 and the rotor stages 10 alternate in the axial direction of the gas turbine engine 1.

Fig. 2 and 3 show the stator vane 11 of one of the stator stages 8 in the turbine section 5. It is understood that all stator vanes 11 of the same stator stage 8 have the same structure, and the features described below with respect to fig. 2 may also be applied to stator vanes 11 of other stator stages 8 according to design preference.

The stator vane 11 includes an airfoil 13 having a forward edge 13a and an aft edge 13b, an outer platform 14 connected to an outer end of the airfoil 13, and an inner platform 15 connected to an inner end of the airfoil 13. The outer platform 14 and the inner platform 15 are curved, in particular in the form of respective concentric annular sectors extending about a common axis coinciding with the machine axis a, while the airfoils 13 extend in radial directions. Here and in the following, the terms "inner" and "outer" should be understood in general relation to the common axis of the outer platform 14 and the inner platform 15, i.e. as meaning "closer to" and "further away from" the common axis, respectively.

The outer platform 14 is connected to a vane carrier (not shown) of the stator 2 and supports the stator vanes 11 in the operating position.

The inner platform 15 is configured to join the inner platforms 15 of adjacent stator vanes 11 such that the inner platforms 15 of all stator vanes 11 in the same stator stage 8 form a ring around the rotor 3 that defines the hot gas path internally and provides mechanical strength.

The inner platform 15 has a leading edge 15a and a trailing edge 15b at the leading edge 13a and the trailing edge 13b of the airfoil 13, respectively.

As shown in fig. 4, the sealing structure 16 is formed as an air passage between the inner platform 15 of the stator vane 11 of the stator stage 8 in question and the rotor 3 (in particular the corresponding adjacent rotor stage 10 in the downstream direction). High pressure seal air from compressor section 4 is fed into the hot gas path through seal structure 16 and prevents ingestion of hot gases that may cause damage to components that are not expected and designed to be exposed to high temperatures. On the rotor side, the sealing structure 16 is defined by a rotor sealing portion 18 adjacent to the stator vanes 11. On the stator side, the sealing structure 16 is defined by a stator rear sealing portion 19 of the inner platform 15 of each stator vane 11. The sealing structure 16 comprises at least one rear sealing rib 20, which is formed integrally with the inner platform 15 in the stator rear sealing portion 19, in particular in the region intended to first contact the adjacent rotor sealing portion 18 in the event of large thermal expansion. The rear sealing rib 20 is delimited by adjacent rear grooves 21 which extend parallel to one another all along the rear edge 15 b. Since there is no material at the rear groove 21, in use, the stator rear seal portion 19 may contact the adjacent rotor seal portion 18 in response to thermal expansion only at the rear seal rib 20.

In one embodiment, the thickness of the rear sealing rib 20 is between 0.3mm and 3mm and the depth of the rear groove 21 is between 3mm and 20 mm. At least a portion of the trailing edge 15b is defined by an envelope surface, such as a surface of revolution S1 having a radius of curvature between 3mm and 15mm, and a distal edge of the at least one trailing sealing rib 20 is located in the envelope surface. The aft sealing ribs 20 of adjacent stator vanes 11 of the stator stage 8 are considered to be joined to each other without discontinuities.

In one embodiment (fig. 5), the inner platform 15 of the stator vane 8 further comprises a stator front sealing portion 24 at the front edge 15a, and at least one front sealing rib 25 delimited by adjacent front grooves 26 extending parallel to each other in the stator front sealing portion 24 all along the front edge 15 a. In use, the stator front seal portion 24 contacts a respective adjacent portion of the rotor 3 in response to thermal expansion only at the at least one front seal rib 25.

In one embodiment shown in fig. 6, at least a portion of the trailing edge 15b is defined by an envelope surface (also here surface of revolution S1), and a distal edge (here indicated by 20') of the trailing sealing rib projects outwardly from the envelope surface.

In one embodiment (fig. 7), the envelope surface is a flat surface S2. The distal edge of the rear sealing rib 20 may be located in the envelope surface (as shown in fig. 8) or protrude outwardly therefrom.

In one embodiment shown in fig. 8, the inner platform 15 comprises a plurality of parallel rear sealing ribs 20 "delimited by respective pairs of adjacent rear grooves 21", which extend parallel to each other all along the rear edge 15b in the stator rear sealing portion 19. In use, the stator aft seal portion 19 contacts the rotor seal portion 18 in response to thermal expansion only at the plurality of aft seal ribs 20 ".

The stator vane according to the invention can be obtained directly by casting or by modifying an existing stator vane. In the latter case, the modification is achieved by forming adjacent rear grooves 21 (see fig. 9, dashed lines) in the initially solid stator rear seal portion 19 of the inner platform 15. The grooves 21 may be formed by any suitable technique, such as machining or electroerosion.

Finally, it is clear that changes and modifications can be made to the gas turbine and to the method described and illustrated without departing from the scope of protection of the accompanying claims.

Claims

1. A gas turbine stator vane comprising:

an airfoil (13) having a forward edge (13 a) and a rearward edge (13 b);

an outer platform (14) connected to an outer end of the airfoil (13), and an inner platform (15) connected to an inner end of the airfoil (13), wherein the inner platform (15) has a front edge (15 a) and a rear edge (15 b) at a front edge (13 a) and a rear edge (13 b) of the airfoil (13), respectively, and comprises:

a stator rear seal portion (19) at the rear edge (15 b); and

at least one aft sealing rib (20; 20 '; 20' ') integral with the inner platform (15) and delimited by adjacent aft grooves (21; 21' ') extending parallel to each other in the stator aft sealing portion (19) all along the aft edge (15 b), whereby in use the stator aft sealing portion (19) contacts respective adjacent rotor portions of a gas turbine rotor (3) in response to thermal expansion only at the at least one aft sealing rib (20; 20'; 20 '').

2. Stator vane according to claim 1, characterized in that the thickness of the at least one rear sealing rib (20; 20'; 20 ") is between 0.3mm and 3 mm.

3. Stator vane according to claim 1 or claim 2, characterized in that the depth of the rear groove (21; 21 ") is between 3mm and 20 mm.

4. Stator vane according to any of the preceding claims, characterized in that at least a part of the trailing edge (15 b) is defined by an envelope surface (S1; S2) and a distal edge of the at least one trailing sealing rib (20) is located in the envelope surface (S1; S2).

5. Stator vane according to any one of claims 1 to 3, characterized in that at least a part of the trailing edge (15 b) is defined by an envelope surface (S1; S2) and a distal rim of the at least one trailing sealing rib (20') protrudes outwardly from the envelope surface (S1; S2).

6. A stator vane according to claim 4 or claim 5, characterized in that the envelope surface is a surface of revolution (S1) having a radius of curvature between 3mm and 15mm, or the envelope surface is a flat surface (S2).

7. Stator vane according to any of the preceding claims, comprising a plurality of parallel aft sealing ribs (20 ") delimited by respective pairs of adjacent aft grooves (21"), which extend parallel to each other in the stator aft sealing portion (19) all along the aft edge (15 b), whereby in use the stator aft sealing portion (19) contacts adjacent rotor portions of a gas turbine rotor (3) in response to thermal expansion only at the aft sealing ribs (20 ").

8. Stator vane according to any of the preceding claims, characterized in that the inner platform (15) comprises:

a stator front seal portion (24) at the front edge (15 a); and

at least one forward sealing rib (25) delimited by adjacent forward grooves (26) extending parallel to each other in the stator forward sealing portion (24) all along the forward edge (15 a), whereby in use the stator forward sealing portion (24) contacts respective adjacent rotor portions of a gas turbine rotor (3) in response to thermal expansion only at the at least one forward sealing rib (25).

9. A gas turbine, comprising:

a rotor (3) having a plurality of rotor stages (10);

a stator (2) having a plurality of stator stages (8) alternating with rotor stages (10) in an axial direction;

wherein at least one of the stator stages (8) comprises a plurality of stator vanes (11) according to any one of claims 1 to 8.

10. The gas turbine of claim 9, comprising a sealing structure (16) between a stator vane (11) of at least one of the stator stages (8) and a corresponding adjacent rotor stage (10), wherein the sealing structure (16) is defined in part by a stator aft sealing portion (19) of the stator vane (11).

11. The gas turbine of claim 10, wherein the seal structure (16) comprises a rotor seal portion (18) of one of the rotor stages (10) facing at least one of the stator stages (8), and the stator aft seal portion (19) is configured to contact the rotor seal portion (18) in response to thermal expansion only at the at least one aft seal rib (20; 20'; 20 ").

12. The gas turbine according to claim 10 or 11, wherein the aft sealing ribs (20; 20'; 20 ") of adjacent stator vanes (11) of at least one of the stator stages (8) are joined to each other without discontinuities.

13. A method of modifying a stator vane (11) of a gas turbine, the stator vane (11) comprising:

an airfoil (13) having a forward edge (13 a) and a rearward edge (13 b);

an outer platform (14) connected to the outer end of the airfoil (13), and an inner platform (15) connected to the inner end of the airfoil (13), wherein the inner platform (15) has a front edge (15 a) and a rear edge (15 b) at a front edge (13 a) and a rear edge (13 b) of the airfoil (13), respectively; and

a stator rear seal portion (19) at the rear edge (15 b);

the method comprises forming adjacent aft grooves (21; 21 '') extending parallel to each other in the stator aft sealing portion (19) all along the aft edge (15 b), whereby the adjacent aft grooves (21; 21 '') define at least one aft sealing rib (20; 20 '; 20' ') integral with the inner platform (15), and in use the stator aft sealing portion (19) contacts a respective adjacent rotor portion of a rotor (3) of the gas turbine in response to thermal expansion only at the at least one aft sealing rib (20; 20'; 20 '').

14. Method according to claim 13, characterized in that the thickness of said at least one rear sealing rib (20; 20'; 20 ") is between 0.3mm and 3 mm.

15. Method according to claim 13 or claim 14, characterized in that the depth of the rear groove (21; 21 ") is between 3mm and 20 mm.