WO2019013664A1

WO2019013664A1 - A labyrinth sealing arrangement with micro-cavities formed therein

Info

Publication number: WO2019013664A1
Application number: PCT/RU2017/000523
Authority: WO
Inventors: Mikhail Sergeevich GRITCKEVICH; Sergey Igorevich IGOLKIN
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-07-14
Filing date: 2017-07-14
Publication date: 2019-01-17

Abstract

A labyrinth sealing arrangement including a first part, a second part, and an axial series of seal fins is presented for rotating equipment such as a gas turbine. The first and the second parts are relatively rotatable within the rotating equipment. The seal fins are distributed along either the first part or the second part and each seal fin extends towards the other of the first and the second part to a tip so as to form a circumferential barrier against a flow of a working fluid between the first part and the second part. At least one of a surface of the first part, a surface of the second part and a surface of at least one of the seal fins includes a plurality of micro-cavities.

Description

A LABYRINTH SEALING ARRANGEMENT WITH MICRO-CAVITIES FORMED

THEREIN

The present invention relates to labyrinth sealing arrangements . It is widely acknowledged to use various seals as a part of the Secondary Air Systems (SAS) , which are aimed at providing the maximum operational efficiency of various rotating equipment by preventing a leakage fluid flow between two relatively rotating parts e.g. in gas and steam turbines, compressors, pumps etc.

A conventionally known seal 99, as shown in FIG 3, generally includes successively arranged seal fins 3 and caverns 4 formed between two adjacent seal fins 3. The seal fins 3 are positioned between a surface 91 of a first part 1 and a surface 92 of a second part 2. The first part 1 and second part 2 are relatively rotatable within a rotating equipment or machine such as a gas turbine. The first part 1 may be for example a stationary part of the gas turbine such as a fixed housing and the second part 2 may be for example a rotatable part of the gas turbine such as a rotating shaft of the gas turbine. The seal fins 3 are positioned on one of the first part 1 and the second part 2. FIG 3 depicts the seal fins 3 to be positioned on the second part 2, particularly on the surface 92 of the second part 2. The seal fins 3 extend towards the other part, i.e. in example of FIG 3 the seal fins 3 extend towards the first part 1, and particularly towards the surface 91 of the first part 1. The seal fins 3 are either angled or slanted with respect to a direction 9 of fluid flow as shown in FIG 4, or alternatively the seal fins 3 may extend normally from the surface 92 on which the seal fins 3 positioned as shown in FIG 5. The conventionally known seal 99, i.e. the conventionally known labyrinth seal 99, is employed in the rotating equipment to form a fluid barrier between areas of a high and low fluid pressure in order to retard a fluid 7, for example air 7, flowing through the labyrinth seal 99 to a desired level. Generally, the desired retardation is achieved by forcing a high-velocity fluid 7, for example air to pass sequentially through annular slitlike orifices, which are formed between the seal fins 3 and the surface 91 of the first part 1, i.e. of the stationary part in the example of FIG 3, with the successive entering of the flowing fluid 7 into the caverns 4, where energy of the flowing fluid 7 is largely dissipated into turbulence.

Several reasons of the aforementioned turbulence generation in the fluid 7 are present within the labyrinth seal 99. One of the reasons is the friction between the high-velocity fluid 7 and the adjacent seal surfaces, i.e. the surface 91 and/or the surface 92. A second reason of turbulence is the result of intense free shear layer friction between a high velocity fluid jet discharging from an orifice, i.e. openings formed between the seal fins 3 and the surface 91 of the first part 1, and a relatively slow moving fluid in the cavern 4 immediately downstream of the orifice.

Efficiency of such conventionally known labyrinth seal 99 is improved by reducing the leakage of fluid flow from the space of the seal 99, i.e. by reducing flow of the fluid 7 from the space between the first surface 91 and the second surface 92. Some conventional techniques attempt to reduce the leakage by decreasing the radial clearances between the stationary and the rotatable parts or members, i.e. between the first part 1 and the second part 2, and particularly between the surface 91 and the surface 92 by introducing the seal fins 3. However, the radial clearance can only be reduced to a limited extent so as to avoid contact between the stationary part and the rotatable part during operation of the rotating equipment, which can result in damage to the parts of the rotating equipment. The contact can be caused by many factors such as the rotor eccentricity, centrifugal growth due to non concentric alignment, variations of the operational conditions, vibrations, manuf cturing tolerances, misalignment during assembling etc. As a result, a radial clearance has to be maintained with adequate buffer so as to avoid accidental contact between the stationary and the rotating parts, and this in turn results in impairment or reduction in the sealing efficiency of the conventionally known labyrinth seals 99.

Moreover, when installed within the rotating equipment, rotation of the parts of the conventionally known seal 99 causes a rise in the total temperature of the fluid 7 because of the windage heating effect due to the viscous work generated by the relatively rotating components or parts of the conventionally known labyrinth seals 99. Minimization of the temperature rise of the fluid 7, especially in gas turbines, is of a high importance because the fluid 7 is subsequently passed into the main gas flow and thus the temperature of the fluid 7 contributes to increase in the temperature of the main gas flow path resulting in lower efficiency of the gas turbine, and also due to the influence of the fluid 7 on the intensity of the heat transfer to the surrounding structure while being passed onto the main gas flow. Particularly, the thermal expansion of the turbine parts is one of the factors, which significantly affects the temperature distributions inside the solid members, which inevitably cause the change of the radial clearance of the conventionally known labyrinth seal 99 with the consequent increase in probability of contact between the stationary and the rotating parts of the gas turbine . Thus, the object of the present invention is to provide a technique for increasing sealing efficiency for rotary seals and particularly for labyrinth seals by reducing leakage of the fluid through the seal. It is desirable that the present technique provides reduction in abovementioned windage heating.

The above objects are achieved by a labyrinth sealing arrangement for a rotating equipment according to claim 1 of the present technique and a gas turbine according to claim 11 of the present technique. Advantageous embodiments of the present technique are provided in dependent claims. Features of claim 1 can be combined with features of dependent claims, and features of dependent claims can be combined together.

In an aspect of the present technique, a labyrinth sealing arrangement for rotating equipment is presented. The labyrinth sealing arrangement, hereinafter also referred to as the seal, includes a first part and a second part. The first part and the second part are configured to be relatively rotatable within _the rotating equipment, such as a gas turbine and more particularly an axial flow turbine. The seal also includes an axial series of seal fins that are distributed along either the first part or the second part. The axial direction referred to hereinabove is the axial direction of the rotating equipment, for example a direction along an axis of rotation of a gas turbine. Each seal fin extends towards other of the first part and the second part to a tip of that seal fin so as to form a circumferential barrier against a flow of a working fluid between the first part and the second part. According to the present technique at least one of a surface of the first part, a surface of the second part and a surface of at least one of the seal fins includes a plurality of micro-cavities. In one embodiment of the labyrinth sealing arrangement, at least two of the surface of the first part, the surface of the second part and the surface of at least one of the seal fins include the micro-cavities. In another embodiment of the labyrinth sealing arrangement, at least two of the surface of^' the first part, the surface of the second part and the surfaces of all the seal fins include the micro-cavities. In yet another embodiment of the labyrinth sealing arrangement, all of the surface of the first part, the surface of the second part and the surfaces of all the seal fins include the micro-cavities .

In an embodiment of the labyrinth sealing arrangement, the first part is configured to be stationary within the rotating equipment and the second part is configured to be rotatable within the rotating equipment, for example the first part may be, but not limited to a rotor segment of a gas turbine whereas the second part may be, but not limited to, a stator segment of the gas turbine. Alternatively, in another embodiment of the labyrinth sealing arrangement the first part is configured to be rotatable within the rotating' equipment and the second part is configured to be stationary within the rotating equipment, for example the first part may be, but not limited to a stator segment of a gas turbine whereas the second part may be, but not limited to, a rotor segment of the gas turbine.

The micro-cavities may be formed by laser. A depth of the micro-cavities may be between 0.001 mm and 1.0 mm, and preferably between 0.01 mm and 0.2 mm. At least one of the surface of the first part, the surface of the second part and the surface of the at least one seal fin includes an area having between 50 and 250,000 micro-cavities per square cm. The micro-cavities may be formed as cylindrical holes, conical holes, dome shaped holes, spherical dome shaped holes, conical holes with rounded top, and so on and so forth. Furthermore, the micro-cavities may circumferentially extend along the surface on which the micro-cavities are formed. Due to presence of micro-cavities, additional recirculation zones are formed within each micro-cavity. Consequently, within the space between the first and the second part the viscous sub-layer, where the maximal heat generation is typically observed, is at least partially isolated from the high-speed main flow of the working fluid within the space at least at some portions of the surface where the micro- cavities are formed. The isolation results from the free- shear layers formed between the recirculation zones within the micro-cavity and the high-speed main. flow. As the result, the total windage heating of the seal is effectively reduced, resulting in the lower total temperature when the flow from the seal re-enters the main gas path of the rotating equipment such as the gas turbine.

In another aspect of_, the present technique a gas turbine is presented. The gas turbine includes a labyrinth sealing arrangement. The labyrinth sealing arrangement is according to the aforementioned aspect of the present technique.

The above mentioned attributes and other features and advantages of the present technique and the manner of attaining them will become more apparent and the present technique itself will be better understood by reference to the following description of embodiments of the present technique taken in conjunction with the accompanying drawings, wherein: FIG 1 shows part of a gas turbine engine in a sectional view and in which a labyrinth sealing arrangement of the present technique is to be incorporated, FIG 2 shows a turbine section of a gas turbine engine in a sectional view and in which labyrinth sealing arrangements of the present technique are incorporated, FIG 3 schematically illustrates the conventionally known labyrinth seal,

FIG 4 schematically illustrates an exemplary embodiment of the conventionally known labyrinth seal depicting slanted seal fins, FIG 5 schematically illustrates another exemplary embodiment of the conventionally known labyrinth seal depicting normally aligned seal fins,

FIG 6 schematically illustrates an exemplary embodiment of the labyrinth sealing arrangement of the present technique,

FIG 7 schematically illustrates another exemplary

' embodiment of the labyrinth sealing arrangement of the present technique depicting positioning of the micro-cavities, FIG 8 schematically illustrates an effect of the micro- cavities of the labyrinth sealing arrangement,

FIGs 9a to 9e schematically illustrate different types of micro-cavities and their mutual orientation, and

FIGs 10a to 10c schematically illustrates different ways of forming the micro-cavities; in accordance with aspects of the present technique.

Hereinafter, above-mentioned and other features of the present technique are described in details. Various embodiments are described with reference to the drawing, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be noted that the illustrated embodiments are intended to explain, and not to limit the invention. It may be evident that such embodiments may be practiced without these specific details.

It may be noted that in the present disclosure, the terms "first", "second", etc. are used herein only . to facilitate discussion, and carry no particular temporal or chronological significance unless otherwise indicated.

FIG. 1 shows an example of a gas turbine 10, also referred to as the gas turbine engine 10, in a sectional view. The gas turbine engine 10 comprises, in flow series, an inlet 12, a compressor or compressor section 14, a combustor section 16 and a turbine section 18 which are generally arranged in flow series and generally about and in the direction of a longitudinal or rotational axis 20. The gas turbine engine 10 further comprises a shaft 22 which is rotatable about the rotational axis 20 and which extends longitudinally through the gas turbine engine 10. The shaft 22 drivingly connects the turbine section 18 to the compressor section 1 .

In operation of the gas turbine engine 10, air 24, which is taken in through the air inlet 12 is compressed by the compressor section 14 and delivered to the combustion section or burner section 16. The burner section 16 comprises a longitudinal axis 35 of the burner, a burner plenum 26, one or more combustion chambers 28 and at least one burner 30 fixed to each combustion chamber 28. The combustion chambers 28 and the burners 30 are located inside the burner plenum 26. The compressed air passing through the compressor 14 enters a diffuser 32 and is discharged from the diffuser 32 into the burner plenum 26 from where a portion of the air enters the burner 30 and is mixed with a gaseous or liquid fuel. The air/fuel mixture is then burned and the combustion gas 34 or working gas from the combustion is channeled through the combustion chamber 28 to the turbine section 18 via a transition duct 17.

This exemplary gas turbine engine 10 has a cannular combustor section arrangement 16, which is constituted by an annular array of combustor cans 19 each having the burner 30 and the combustion chamber 28, the transition duct 17 has a generally circular inlet that interfaces with the combustor chamber 28 and an outlet in the form of an annular segment. An annular array of transition duct outlets form an annulus for channeling the combustion gases to the turbine 18. The turbine section 18 comprises a number of blade carrying discs 36 attached to the shaft 22. In the present example, two discs 36 each carry an annular array of turbine blades 38. However, the number of blade carrying discs could be different, i.e. only one disc or more than two discs. In addition, guiding vanes 40, which are fixed to a stator 42 of the gas turbine engine 10, are disposed between the stages of annular arrays of turbine blades 38. Between the exit of the combustion chamber 28 and the leading turbine blades 38 inlet guiding vanes 44 are provided and turn the flow of working gas onto the turbine blades 38.

The combustion gas from the combustion chamber 28 enters the turbine section 18 and drives the turbine blades 38 which in turn rotates the shaft 22. The guiding vanes 40, 44 serve to optimize the angle of the combustion or working gas on the turbine blades 38.

The turbine section 18 drives the compressor section 14. The compressor section 14 comprises an axial series of vane stages 46 and rotor blade stages 48. The rotor blade stages 48 comprise a rotor disc supporting an annular array of blades. The compressor section 14 also comprises a casing 50 that surrounds the rotor stages and supports the vane stages 48. Tlie guide vane stages include an annular array of radially extending vanes that are mounted to the casing 50. The vanes are provided to present gas flow at an optimal angle for the blades at a given engine operational point. Some of the guide vane stages have variable vanes, where the angle of the vanes, about their own longitudinal axis, can be adjusted for angle according to air flow characteristics that can occur at different engine operational conditions.

The casing 50 defines a radially outer surface 52 of the passage 56 of the compressor 14. A radially inner surface 54 of the passage 56 is at least partly defined by a rotor drum 53 of the rotor which is partly defined by the annular array of blades 48.

The present technique is described with reference to the above exemplary turbine engine having a single shaft or spool connecting a single, multi-stage compressor and a single, one or more stage turbine. However, it should be appreciated that the present technique is equally applicable to two or three shaft engines and which can be used for industrial, aero or marine applications. The terms axial, radial and circumferential and related phrases are made with reference to the rotational axis 20 of the gas turbine 10, unless otherwise stated.

FIG 2 schematically presents a part of a rotating equipment 10 for example the turbine section 18 of the gas turbine engine 10 of FIG 1 within which a labyrinth sealing arrangement 100, shown in FIG 6, of the present technique is incorporated. FIG 2 shows a few exemplary locations, with the gas turbine engine 10, hereinafter also referred to as the turbine 10, at which the labyrinth sealing arrangement 100, hereinafter also referred to as the seal 100 is incorporated. FIG 2 depicts a first stage nozzle 71 which is held in position with the turbine 10 by a retaining ring 72 and a supporting ring 73. Downstream of the first stage nozzle 71 are sequentially arranged a first turbine blade 64, a second stage nozzle 76, a second stage turbine blade 65, a third stage nozzle 77 and a third stage turbine blade 66. As may be appreciated by one skilled in the art, the turbine 10 may include more turbine blades and nozzles than depicted in FIG 2. The turbine blades 64,65,66 of FIG 2 may be understood to be same as the turbine blades 38 of FIG 1. The first stage nozzle 71 of FIG 2 may be understood to be same as the inlet guiding vane 44, whereas the second stage and the third stage nozzles 76,77 may be understood to be same as the guiding vane 40 of FIG 1.

The first, second and third stage turbine blades 64,65,66 are supported on first, second and third stage turbine wheels 67,68,69 respectively. The turbine wheels 67,68,69 are same as the blade carrying discs 36 of FIG 1. The turbine blades 64,65,66 along with the turbine wheels 67,68,69 form a rotor or part of the rotor in the turbine 10. The turbine blades 64,65,66 supported on their respective turbine wheels 67,68,69 extend radially towards a stator of the turbine 10. The stator may include a first stage shroud 61, a second stage shroud 62 and a third stage shroud 63 corresponding to the first stage turbine blade 64, the second stage turbine blade 65, and the third stage turbine blade 66. The first, second and third stage shrouds 61,62,63 form stationary member or part of the turbine 10. As shown in FIG 2, the seal 100 may be present between the rotor or parts of the rotor and the stator or parts of the stator, for example one seal 100 is depicted to be present between the second stage turbine blade 65 and the corresponding second stage shroud 62 and another seal 100 is depicted to be present between the third stage turbine blade 66 and the corresponding third stage shroud 63. Similarly one seal 100 is shown to be present between a second stage diaphragm segment 74 extending from the second stage nozzle 76 and a part 60 of the rotor, and another seal 100 is shown to be present between a third stage diaphragm segment 75 extending from the third stage nozzle 77 and a part 60' of the rotor. It may be noted that the aforementioned locations depicted for the positioning of the seal 100 are presented for exemplary purposes and not as a limitation.

FIG 6 presents structural details of the seal 100. The seal 100 includes a first part 1 and a second part 2 and an axial series of seal fins 3. The seal 100 is similar to the conventionally known seal 99 depicted in FIGs 3,4, and 5 and additionally essentially includes micro-cavities 5.

The seal 100 includes successively arranged seal fins 3 and caverns 4 formed between adjacent seal fins 3. The seal fins 3 are positioned between the surface 91 of the first part 1 and the surface 92 of the second part 2. The first part 1 and second part 2 are relatively rotatable within the gas turbine 10 and when the gas turbine 10 is operational. One from the first part 1 and the second part 2 is a stationary part of the gas turbine 10 such as the part formed by the nozzles 76,77 and the corresponding diaphragm segments 74,75 depicted in FIG 2 or the shrouds 61,62,63 depicted in FIG 2, whereas the other from the first part 1 and the second part 2 is a rotatable part of the gas turbine 10 such as the blades 64,65,66 or the parts 60,60' of the rotor as shown in FIG 2.

Although the seal fins 3 may be positioned or may extend from either the first part 1 or the second part 2 and may extend towards the other of the first part 1 and the second part 2, hereinafter the first part 1 is assumed to be stationary part whereas the second part 2 is assumed to be the rotatable part. Furthermore, although the seal fins 3 are shown in FIG 6 to be located on the ' second part 2 and extending towards the first part 1, it may be appreciated by one skilled in the art that it is well within the scope of the present technique that the seal fins 3 are present on the first part 1 and extend towards the second part 2.

The seal fins 3 form an axial series i.e. the seal fins 3 are axially arranged i.e. along the axis 20 (also shown in FIG 1) . FIG 7 schematically depicts a perspective view of one such seal fin 3. The seal fin 3 arises out of or is formed integrally on the surface 92 and culminates at a tip 95. The seal fin 3 extends towards the first part 1, in other words the tip 95 of the seal fin 3 faces the surface 91 and is closer to the surface 91 than distance between the surface 91 and the surface 92. Thus the seal fin 3, along with the tip 95 of the seal fin 3, forms a circumferential barrier against a flow 9 of a working fluid 7 that intends to flow between the first part 1 and the second part 2 i.e. between the surfaces 91 and 92.

In the seal 100 of the present technique, at least one of the surface 91 of the first part 1, the surface 92 of the second part 2 and a surface 93 of the seal fin 3 includes a plurality of micro-cavities 5. Thus, as depicted in FIGs 6 and 7, the micro-cavities 5 may be present either on the surface 92 or on the surface 93 or on both. When present on the surface 93 the micro-cavities 5 may be present on the tip 95 or one or both sides 96 of the seal fin 3, as shown in FIG 7. The micro-cavities 5 may also be present on a surface 94 i.e. at a base of the caverns 4 or in other words on part of the surface 92 that is bound by two adjacent seal fins 3. Alternatively in another embodiment (not shown) the micro- cavities 5 may be present on the surface 91.

In yet another embodiment of the seal 100, at least two of the surface 91, the surface 92 and the surface 93 include the micro-cavities 5, as shown in FIGs 6 and 7. In a further embodiment (not shown) all of the surface 91, the surface 92 and the surface 93 include the micro-cavities 5.

As aforementioned in an embodiment of the seal 100, the first part 1 is configured to be stationary within the turbine 10 and the second part 2 is configured to be rotatable within the turbine 10. Alternatively, in another embodiment of the seal 100 the first part 1 is configured to be rotatable within the turbine 10 and the second part 2 is configured to be stationary within the turbine 10. The micro-cavities 5 may be formed by laser 6, 6', 6" as shown in FIGs 10a, 10b and 10c. As shown in FIG 10a, the laser 6 may be directed perpendicular to the surface 91,92,93 on which the micro-cavities 5 are formed, or as shown in FIG 10b, the laser 6 may be directed at an angle to the surface 91,92,93 on which the micro-cavities 5 are formed. Alternatively, as shown in FIG 10c, a first laser 6' may be directed to the surface 91,92,93 on which the micro-cavities 5 are formed and then subsequently a second laser 6" is directed to the so formed micro-cavities 5 to create a complex geometry of the micro-cavities 5 as shown in FIG 10c. The different shapes of the micro-cavities 5 determined formation of different types of recirculation zones and also determine the volume of the recirculation zones. A depth h of the micro-cavities 5 may be between 0.001 mm and 1.0 mm, and preferably between 0.01 mm and 0.2 mm. The depth h for the micro-cavities 5 of FIG 10c may be a sum of a depth h' and a depth h" created by the corresponding lasers 6' , 6" respectively. Furthermore the micro-cavities 5 may have different sized openings L at the surface 91,92,93 on which the micro-cavities 5 are formed.

FIGs 9a, 9b and 9c schematically show different types of the micro-cavities 5 and their arrangement on the surface 91,92,93 on which the micro-cavities 5 are formed. As shown in FIG 9a the micro-cavities 5 may be formed as circular holes and arranged in rows and columns that are circumferentially and axially arranged. The micro-cavities 5 of successive rows and columns axially arranged linearly. As shown in FIG 9a the micro-cavities 5 may be formed as circular holes and arranged in rows and columns that form a zigzag pattern on the surface 91,92,93 on which the micro- cavities 5 are formed. As shown in FIG 9c the micro-cavities 5 may be formed as oblong holes and arranged in alternating orientation. In an embodiment of the seal 100, as shown in FIG 9a one or more of the surfaces 91,92,93 on which the micro-cavities 5 are formed includes an area 98 having between 50 and 250,000 micro-cavities per square cm.

FIGs 9d and 9e depict another type of the micro-cavities 5. As shown in FIGs 9d and 9e the micro-cavities 5 may circumferentially, i.e. tangentially along the surface, extend along the surface 91,92,93 on which the micro-cavities 5 are formed. The circumferential extension of the micro- cavities 5 may be perpendicular to the axial direction 20 as shown in FIG 9d or may be at an angle to the axial direction 20 as shown in FIG 9e .

FIG 8 schematically depicts an exemplary embodiment of working of the micro-cavities 5. Due to presence of micro- cavities 5, additional recirculation zones 8 are formed within each micro-cavity 5. Consequently, within the space between the first part 1 and the second part 2 the viscous sub-layer, i.e. the surface 92 in the example of FIG 6, where the maximal heat generation is typically observed, is at least partially isolated from the high-speed main flow 79 of the working fluid 7 within the space at least at some portions of the surface 92 where the micro-cavities 5 are formed. The isolation results from the free-shear layers 70 formed between the recirculation zones 8 formed within the micro-cavities 5 and the high-speed main flow 79.

While the present technique has been described in detail with reference to certain embodiments, it should be appreciated that the present technique is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves, to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

List of Reference Characters

1 first part

2 second part

3 seal fins

4 cavern

5 micro-cavity

6 laser

6' first laser

6" second laser

7 working fluid

8 recirculation zone

9 direction of fluid flow

10 gas turbine engine

12 inlet

14 compressor section

16 combustor section or burner section

17 transition duct

18 turbine section

19 combustor cans

20 rotational axis

22 shaft

24 air

26 burner plenum

28 combustion chamber

30 burner

32 diffuser

34 combustion gas or working gas

35 longitudinal axis of the burner

36 blade carrying discs

38 turbine blades

40 guiding vanes

42 stator

44 inlet guiding vanes

46 vane stages 48 rotor blade stages

50 casing

52 radially outer surface

53 rotor drum

54 radially inner surface

56 passage

60 part of rotor

60' part of rotor

61 first stage shroud

62 second stage shroud

63 third stage shroud

64 first turbine blade

65 second turbine blade

66 third turbine blade

67 first stage turbine wheel

68 second stage turbine wheel

69 third stage turbine wheel

70 free-shear layer

71 first stage nozzle

72 retaining ring for first stage nozzle

73 supporting ring for the first istage nozzle

74 second stage diaphragm segment

75 third stage diaphragm segment

76 second stage nozzle

77 third stage nozzle

79 high-speed main flow

91 surface of the first part

92 surface of the second part

93 surface of the seal fin

94 surface between the seal fins

95 tip of the seal fin

96 side of the seal fin

98 area

99 conventionally known labyrinth seal 100 labyrinth sealing arrangement

Claims

Patent claims

1. A labyrinth sealing arrangement (100) for a rotating equipment (10) , the labyrinth sealing arrangement (100) comprising:

- a first part (1) and a second part (2) wherein the first part (1) and the second part (2) are configured to be relatively rotatable,

- an axial series of seal fins (3) , distributed along one of the first part (1) and the second part (2) , wherein each seal fin (3) extends towards other of the first part (1) and the second part (2) to a tip (95) so as to form a circumferential barrier against a flow (9) of a working fluid (7) between the first part (1) and the second part (2) ,

characterized in that at least one of a surface (91) of the first part (1) , a surface (92) of the second part (2) and a surface (93) of at least one of the seal fins (3) comprises a plurality of micro-cavities (5) .

2. The labyrinth sealing arrangement (100) according to claim 1, wherein the first part (1) is configured to be stationary within the rotating equipment (10) and wherein the second part (2) is configured to be rotatable within the rotating equipment (10) .

3. The labyrinth sealing arrangement (100) according to claim 1, wherein the first part (1) is configured to be rotatable within the rotating equipment (10) and wherein the second part (2) is configured to be stationary within the rotating equipment (10) .

4. The labyrinth sealing arrangement (100) according any of claims 1 to 3, wherein the micro-cavities (5) are laser- formed micro-cavities (5) .

5. The labyrinth sealing arrangement (100) according any of claims 1 to 4, wherein a depth (h) of the micro-cavities (5) is between 0.001 mm and 1.0 mm.

6. The labyrinth sealing arrangement (100) according claim 5, wherein the depth (h) of the micro-cavities (5) is between

0.01 mm and 0.2 mm.

7. The labyrinth sealing arrangement (100) according any of claims 1 to 6, wherein at least one of the surface (91) of the first part (1) , the surface (92) of the second part (2) and the surface (93) of the at least one seal fin (3) comprises an area (98) having between 50 and 250,000 micro- cavities (5) per square cm.

8. The labyrinth sealing arrangement (100) according any of claims 1 to 7, wherein the micro-cavities (5) circumferentially extend along one of the surface (91) of the first part (1), the surface (92) of the second part (2) and the surface (93) of the at least one seal fin (3) , on which the micro-cavities (5) are formed.

9. The labyrinth sealing arrangement (100) according any of claims 1 to 8, wherein the rotating equipment (10) is a gas turbine .

10. The labyrinth sealing arrangement (100) according claims 9, wherein the gas turbine is an axial flow gas turbine.

11. A gas turbine (10) comprising a labyrinth sealing arrangement (100) , wherein the labyrinth sealing arrangement

(100) is according to any of claims 1 to 10.