Turbine with a sealing system for nozzle guide vanes

Abstract

A turbine includes a sealing system for nozzle guide vanes (2). The sealing system comprises at least two inner platforms (1) and at most one inner platform for each nozzle guide vane. Each inner platform is adapted to be coupled with a hub (3) of the turbine and comprises a main portion (11) faced to at least one nozzle guide vane and a coupling portion (12) adapted to be coupled with a housing (31) of the hub. At least a part of the coupling portion comprises at least two protrusions coupled to respective undercut grooves of the housing, respectively a leading protrusion (1211) coupled with a leading undercut groove (311') and a trailing protrusion (121") coupled with a trailing undercut groove (311"). At least one interspace (122) is present between a leading side and a trailing side of the coupling portion and the leading side and the trailing side of the housing. At least one passage (13) fluidically connects the leading area upstream of the sealing system and the at least one interspace (122, 122a, 122b).

Description

Turbine with a sealing system for nozzle guide vanesDescriptionTECHNICAL FIELD

[0001] The present disclosure concerns a turbine with a sealing system for nozzle guide vanes. Embodiments disclosed herein specifically concern a sealing system for nozzle guide vanes for limiting leakage flow in the nozzle guide vane stages.BACKGROUND ART

[0002] The development of advanced machinery and technology in the areas of energy production places an enormous demand on the components involved. In particular, turbines are subjected to extreme conditions of heat and pressure, which can lead to erosion or damage over time. The efficiency and performance of such turbines are often determined by the efficacy of their design and construction, especially regarding the sealing systems in place within these machines.

[0003] Sealing systems within turbines serve a vital role in ensuring the effective operation of these machines. In a turbine, a core part is played by the nozzle guide vanes, which control the flow of steam through the turbine. The inner platform of these nozzle guide vanes must be designed for optimal coupling with the hub of a steam turbine while mitigating potential leakage issues that could lead to decreases in overall efficiency.

[0004] In general, friction can occur between the nozzle guide vane and the hub of the steam turbine. To solve this problem, a radial clearance of approximately 1 mm must be provided between the nozzle guide vane and the turbine casing. However, this solution generates leakage in the nozzle guide vane, resulting in a loss of efficiency of this component.

[0005] Accordingly, an improved sealing system for nozzle guide vanes to address the issues of leakage in turbine would be beneficial and would be welcomed in the technology.SUMMARY

[0006] In one aspect, the subject matter disclosed herein is directed to a turbine with a sealing system for nozzle guide vanes that limits leakage flow. The sealing system comprising at least two inner platforms and at most one inner platform for each nozzle guide vane. In particular, the inner platform comprises a main portion faced to at least one nozzle guide vane and a coupling portion adapted to be coupled with a housing of the hub.

[0007] A feature of the sealing system is that the coupling portion comprises two protrusions, specifically a leading protrusion and a trailing protrusion. These protrusions are coupled to respective undercut grooves of the housing, with the leading protrusion coupled with a leading undercut groove and the trailing protrusion coupled with a trailing undercut groove.

[0008] Another aspect of the sealing system is the presence of at least one interspace in the coupling portion between the leading side and the trailing side.

[0009] A further feature of the sealing system is the presence of at least one passage configured to fluidly connect the leading area upstream of the sealing system and the interspace. This passage allows for controlled flow between the upstream area and the interspace.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. l illustrates a perspective sectional view of a hub and a nozzle guide vane incorporating a sealing system, according to a first embodiment;Fig. 2 illustrates a perspective sectional view of a hub and a nozzle guide vane incorporating a sealing system comprising a spring, according to a second embodiment;Fig. 3 illustrates a perspective sectional view of a hub and a nozzle guide vane incorporating a sealing system, according to a third embodiment;Fig. 4 illustrates the same view of Fig. 3 with a schematization of flows;Fig. 5 illustrates a top view of a hub and a nozzle guide vane incorporating a sealing system, according to a fourth embodiment;Fig. 6 illustrates a sectional view of a hub and a nozzle guide vane incorporating a sealing system, according to a fifth embodiment; andFig. 7 illustrates a perspective sectional view of a hub and a nozzle guide vane incorporating a sealing system comprising a spring, according to a sixth embodiment.DETAILED DESCRIPTION OF EMBODIMENTS

[0011] According to one aspect, the present subject matter is directed to a turbine with a sealing system for limiting leakage flow in the nozzle guide vane stages. By providing a controlled flow path from the upstream area to the interspace via the passage, and by securing the coupling between the inner platform and the hub through the protrusions and undercut grooves, the sealing system can effectively limit undesired leakage flows. The spring provides an additional means to maintain the sealing engagement while accommodating operational dynamics.

[0012] Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase “in one embodiment” or “in an embodiment” or “in some embodiments” in various places throughout the specification is not necessarily referring to the same embodiment s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0013] When introducing elements of various embodiments the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. Theterms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0014] Referring now to the drawings, Fig.1 shows a sealing system of a turbine, the turbine comprising an inner platform 1 for each nozzle guide vane 2. Each inner platform 1 is adapted to be coupled with a hub 3 of the turbine. Each inner platform 1 comprises a main portion 11 faced to the one or more nozzle guide vanes 2 and a coupling portion 12 adapted to be coupled with a housing 31 of the hub 3. Additionally, the inner platform 1, as well as the portions thereof, and specifically the coupling portion 12, has a leading side and a trailing side, respectively at the leading side and the trailing side of the one or more nozzle guide vanes 2.

[0015] A feature of the sealing system is that the coupling portion 12 comprises two protrusions 121’, 121”, specifically a leading protrusion 121’ and a trailing protrusion 121”. These protrusions 121’, 121” are coupled to respective undercut grooves of the housing 31, with the leading protrusion 121’ coupled with a leading undercut groove 311’ and the trailing protrusion 121” coupled with a trailing undercut groove 311”.

[0016] A further feature of the sealing system is that it comprises means pushing the coupling portions 12 in a radial direction far from the axis of rotation of the turbine.

[0017] In further embodiments not shown, the sealing system comprises a seal between the trailing side of the coupling portion and the trailing side of the housing of the hub. In particular, the seal can be a labyrinth seal or a gasket.

[0018] Another aspect of the sealing system is the presence of one or more interspace 122 in the coupling portion 12 between the leading side and the trailing side thereof. According to this embodiment, a recess 122a of the coupling portion 12 defines an enlargement of the interspace between the inner platform 1 and the hub 3.

[0019] A further feature of the sealing system according to this embodiment is the presence of at least one passage 13 to fluidly connect the leading area upstream of the sealing system and the one or more interspaces 122. This passage 13 allows for controlled flow between the upstream area and the interspace 122.

[0020] With continuing reference to Fig.1, Fig. 2 illustrates another embodiment of the sealing system. The same reference numbers designate the same or correspondingparts, elements or components already illustrated in Fig.l and described above, and which will not be described again. In particular, in the sealing system of Fig.2, the interspace between the leading side and the trailing side of the coupling portion 12 and the leading side and the trailing side of the housing 31 of the hub 3 comprises both a recess 122a of the coupling portion 12 and / or a recess 122b of the housing 31 of the hub 3. The means pushing the coupling portion 12 is a spring 15 situated in the recess 122. In particular, the spring 15 shown in Fig. 2 is an U-shaped spring 15. This spring 15 is adapted to couple the hub 3 and the coupling portion 12. In particular, the spring elastic force is negligible in pressurized condition. However, the spring 15 is essential to keep in position the inner platform 1 in depressurized condition and to absorb the effect of the impact of a possible contact, due to thermal distortion, between the nozzle guide vane 2 and the inner platform 1, on the hub 13. In particular, the spring 15 comprises two ends 15’ respectively coupled to the ends of the coupling portion 12. In a further embodiment not show, the spring could be a leaf spring.

[0021] With continuing reference to Figs.1 and 2, Figs. 3 and 4 illustrate a third embodiment of the sealing system. According to this embodiment, at least a part of the coupling portion 12 comprises a channel 123 facing the leading undercut groove 311’, so that a leading portion of the at least one channel 13 has a greater width than a trailing portion of said channel 13” In particular, the channel 123 allows a high pressure Phigh in the interspace 122. In fact, the channel 123 acts as a pressure equalizer hole that guarantees minimum pressure losses of the controlled flow between the upstream area and the interspace 122.

[0022] In fact, referring to Fig. 4, the inner platform 1 is pushed radially outward and axially downstream by the pressure resultant force, thus closing the gap between the walls of the housing 31 of the hub 3 and the inner platform 1 itself. An additional radially outward pressure resultant force is obtained by pressurizing the interspace 122. The pressure drop of the controlled flow between the upstream area and the interspace 122 shall be minimized by axial and radial contact to avoid aerodynamic efficiency penalty. This flow is controlled by contact pressures that can be maximized by guarantying the maximum pressure in the interspace 122.

[0023] With continuing reference to Figs.1, 2, 3 and 4, Fig. 5 illustrates a fourth embodiment wherein a seal 14 is placed between adjacent inner platforms 1 of a turbinein order to limit flow leakage. In particular, each inner platform 1 comprises two flshaped housings arranged respectively on the side walls of the inner platform 1 and the seal 14 is arranged between adjacent L-shaped housings of adjacent inner platforms 1.

[0024] With continuing reference to Fig. 5, a further feature of the sealing system is the presence of a symmetry plane TI in the inner platform 1 passing through the axis of rotation of the turbine. In particular, the at least one interspace 122 is symmetrical with respect to the symmetry plane TI.

[0025] With continuing reference to Figs. l, 2, 3, 4 and 5, Fig. 6 illustrates a fifth embodiment of the sealing system comprising an L-shaped seal 14 placed between adjacent inner platforms 1 of the turbine. In particular, said L-shaped seal 14 deviates intersectional flow to avoid a penalisation of aerodynamic efficiency.

[0026] Finally, with continuing reference to Figs.1, 2, 3, 4, 5 and 6, Fig. 7 illustrates a sixth embodiment of the sealing system. According to this embodiment, the spring situated in the interspace 122 is an U-shaped spring 15. In particular, the U-shaped spring comprises two ends respectively coupled to the ends of the coupling portion 12.

[0027] While the invention has been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without departing form the spirt and scope of the claims. In addition, unless specified otherwise herein, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

Claims

Turbine with a sealing system for nozzle guide vanesCLAIMS1. Turbine with a sealing system for nozzle guide vanes, wherein the sealing system comprising at least two inner platforms (1) and at most one inner platform (1) for each nozzle guide vane (2), each inner platform (1) being adapted to be coupled with a hub (3) of the turbine and comprising a main portion (11) faced to at least one nozzle guide vane (2), a coupling portion (12) adapted to be coupled with a housing (31) of the hub (3), at least a part of the coupling portion (12) comprising at least two protrusions (121’, 121”) coupled to respective undercut grooves of the housing (31), respectively a leading protrusion (121’) coupled with a leading undercut groove (311’) and a trailing protrusion (121”) coupled with a trailing undercut groove (311”), at least one interspace (122) being present between the leading side and the trailing side of the coupling portion (12) and the leading side and the trailing side of the housing (31), and at least one passage (13) fluidically connecting the leading area upstream the sealing system and the at least one interspace (122, 122a, 122b).

2. Turbine according to the preceding claim, wherein the interspace (122, 122a, 122b) between the leading side and the trailing side of the coupling portion (12) and the leading side and the trailing side of the housing (31) comprises a recess (122a) of the coupling portion (12) and / or a recess (122b) of the housing (31) of the hub (3).

3. Turbine according to the preceding claim, wherein each inner platform (1) has a symmetry plane TI) passing through the axis of rotation of the turbine and the at least one recess (122a) of the coupling portion (12) is symmetrical with respect to the symmetry plane TI).

4. Turbine according to any one of the preceding claims, wherein the leading side of the coupling portion (12) comprises a channel (123) configured to fluidly connect the leading area upstream the sealing system and the at least one interspace (122, 122a, 122b).

5. Turbine according to any one of the preceding claims, wherein the sealing system comprises a seal between the trailing side of the coupling portion (12) and the trailing side of the housing (31) of the hub (3).

6. Turbine according to claim 5, wherein said seal is a labyrinth seal.

7. Turbine according to claim 5, wherein said seal is a gasket.

8. Turbine according to any one of the preceding claims, wherein the sealing system comprises means pushing the coupling portion (12) in a radial direction far from the axis of rotation of the turbine.

9. Turbine according to claim 8, wherein the means pushing the coupling portion in a radial direction far from the axis of rotation of the turbine comprise at least one spring (15) in the recess (122).

10. Turbine according to claim 9, wherein the spring (15) is a U-shaped spring (15).

11. Turbine according to claim 9 or 10, wherein the spring is a leaf spring.

12. Turbine according to any one of claims 9-11, wherein the spring (15) comprises at least one end coupled to the coupling portion (12).

13. Turbine according to claim 12, wherein the spring (15) comprises two ends (15’) respectively coupled to the ends of the coupling portion (12).

14. Turbine according to any one of the previous claims, wherein each inner platform (1) comprises two housings arranged respectively on the side walls of each inner platform (1) and a seal (14) arranged between adjacent housings of adjacent inner platforms (1).

15. Turbine according to claim 14, wherein said housings are L-shaped housings.

16. Turbine according to the preceding claim, wherein the seal is an L- shaped seal (14).

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