This application is based upon and claims the benefit of priority from British Patent Application Number 1801296.3 filed 26 Jan. 2018, the entire contents of which are herein incorporated by reference.
The present disclosure concerns a circumferential seal, a stage of a gas turbine, a gas turbine engine, and a method of sealing a circumferential seal, a method of sealing a stage of a gas turbine engine, and a method of sealing a gas turbine engine.
Seals are used on a gas turbine engine for controlling airflow through the gaps between rotors and stators, or for example between two rotors rotating at different angular velocities.
Typically such seals comprise a tortuous path for airflow passing through the seal, such that pressure losses across the seal is as large as possible in order to minimise flow through it. Any flow through the seal can represent performance losses. For example there may be a performance loss if any working fluid escapes through the seal.
Typically such seals may be labyrinth seals. A labyrinth seal may create a tortuous path through the seal by, for example, the use of fins from either the rotor or the stator. In addition to the tortuous path, the labyrinth seal, for example the fins of the labyrinth seal, may be designed to minimise the gap between any part of the rotor and stator, in order to further minimise the airflow through the seal.
During operation of a gas turbine engine a rotor may experience deformation. This deformation may be caused by, for example, circumferential forces from rotation of the rotor, thermal expansion of the rotor, and/or vibration. As the rotor experiences deformation the gap can vary between the rotor and the stator. This can be detrimental to performance whereby in certain operational conditions a greater gap is formed between the rotor and the stator, compared to other operational conditions, such that a greater airflow can pass through the seal.
In order to minimise the airflow through a seal in a gas turbine across a range of operation conditions typically a liner material may be incorporated into the stator. During engine pass off and/or run-in, the rotor may cut into the stator liner material such that a tighter gap can be maintained during operation. However during the cutting of the liner material the rotor is worn. If the rotor wears too much then this may increase the gap between the rotor and stator as rotor material is worn away. Any wear to the rotor and/or stator may require maintenance.
It is therefore desirable to provide a seal for a rotating component, for example a gas turbine engine that minimises the airflow through the seal in order to increase component performance. It is desirable to provide a seal for a rotating component, for example a gas turbine engine, that minimise wear of the rotor and/or stator in order to prevent loss of performance and minimise maintenance costs.
According to an aspect there is provided a circumferential seal for a rotating component comprising a static seal part and a rotating seal part having a common central axis. The rotating seal part comprises a fin seal, wherein the fin seal comprises a protective coating. A first portion of the fin seal has a first sealing gap to the static seal part and a second portion of the fin seal has a second sealing gap to the static seal part. The first sealing gap has a greater radial dimension than the second sealing gap.
The fin seal may comprise a fin. The fin seal may comprise a plurality of fins. The protective coating may be for protecting the fin seal from wear. The protective coating may be for protecting the fin seal from wear due to rubbing against the static seal part.
The rotating component may impart energy onto a working fluid of the component. The circumferential seal may be for preventing working fluid escaping from a part of the rotating component.
The protective coating may be more wear resistant than the fin seal. The protective coating may be for resisting friction between the fin seal and the static seal part (for example during rub-in). The protective coating may be 10% or less, 20% or less, 30% or less, 40% or less, 50% or less, 60% or less, 70% or less, or more than 70% of the depth of the fin seal. The protective coating on the second portion may be a sacrificial coating.
The first portion may extend over a portion of the circumference. The first sealing gap and the second sealing gap may be average radial gaps, for example an average of the radial gaps across the first or second portion.
The first sealing gap and the second sealing gap may be both positive (e.g. to define a gap) and/or negative (e.g. during rubbing and/or cutting).
A fin of a fin seal may extend from the rotating seal part to a distal edge. A sealing gap (for example the first sealing gap or the second sealing gap) may be defined by the distance between the distal edge and the static seal part.
The protective coating may have a thickness greater than or equal to the difference in radial dimension between the first sealing gap and the second sealing gap.
The thickness may be 1.1, 1.2, 1.3, 1.4, 1.5, 1.75, 2 or more than 2 times the difference in radial dimension between the first sealing gap and the second sealing gap. The thickness may be less than the radial dimension between the first sealing gap and the second sealing gap. The thickness may be 0.9, 0.9, 0.7, 0.6, 0.5, 0.25 or less than 0.25 times the difference in radial dimension between the first sealing gap and the second sealing gap.
The static seal part may comprise an abradable liner. The static seal part may be static in relation to the rotating component. The static seal (e.g. slow seal) part may rotate at a slower rotational speed than the rotating seal part. The static seal part may be fixed in position. The static seal part may not rotate.
The rotating seal part may be arrangeable such that second portion of the fin seal contacts the static seal part.
The rotating seal part may be arrangeable such that the second sealing gap has a negative radial dimension.
The second portion may extend beyond the radially inner surface of the static seal part. The second sealing gap may be negative such that the second sealing gap defines an overlap between the second portion and the static seal part. In use the overlap will cause wearing of the second portion and the static seal part. An overlap may be when the fin seal cuts into the static seal part. The rotating seal part may be arrangeable due to deformation. Deformation may be caused by operation. Deformation may be caused by thermal and/or centrifugal effects during normal operation.
The first portion may have a first circumferential position and the second portion has a second circumferential position, and whereby the first circumferential position is different to the second circumferential position.
The circumferential seal may comprise a plurality of first portions and a plurality of second portions, wherein each first portion and each second portion are interspersed around the circumference of the circumferential seal.
Each first portion may be adjacent two second portions. Each second portion may be adjacent two first portions. The may be an equal number of first portions and an equal number of second portions. There may be one, two, three, four or more than four first portions. The circumferential seal may have an aspect of rotational symmetry.
The radial dimension of the first sealing gap may vary sinusoidally in the circumferential direction and the radial dimension of the second sealing gap may vary sinusoidally in the circumferential direction.
The first sealing gap, when adjacent the second sealing gap, may form a continuous profile. A sealing gap comprising a first sealing gap adjacent a second sealing gap may have a radial dimension that varies sinusoidally in the circumferential direction.
The fin seal may comprise a first fin and a second fin, wherein the first fin is axially offset from the second fin with respect to the common rotational axis, and wherein the first fin comprises the first portion and the second fin comprises the second portion.
The first portion may extend around the entire circumference of the circumferential seal and the second portion may extend around the entire circumference of the circumferential seal.
The fin seal may further comprises a third portion with a third sealing gap. The third sealing gap may be of different radial dimension to the first and/or second sealing gaps.
The fin seal may further comprises a fourth portion with a fourth sealing gap. The fourth sealing gap may be of different radial dimension to the first and/or second and/or third sealing gaps.
According to an aspect a stage of a gas turbine engine may comprise the circumferential seal as claimed herein.
According to an aspect a stage of a gas turbine engine may comprise the circumferential seal as claimed herein, the stage further comprising a set of blades, wherein the rotating seal part comprises a plurality of blade sealing parts, wherein each blade sealing part corresponds to, and is attached to, a blade of the set of blades, and wherein each blade sealing part comprises a first portion or a second portion.
The fin seal may comprise a plurality of blade fin seals, each blade fin seal corresponding to a blade of the set of blades. The first portion of the fin seal may correspond to a first blade fin seal and the second portion of the fin seal may correspond to a second blade fin seal. The blade fin seals may comprise a first blade fin seal and/or a second blade fin seal. The first blade fin seal may correspond to a first blade and/or a second blade fin seal may correspond to a second blade. A plurality of first blades and second blades may be interspersed.
The blades that comprise a first portion and blades that comprise a second portion may be interspersed.
According to an aspect a gas turbine engine may comprise the circumferential seal as claimed herein.
According to an aspect there is provided a method of sealing a circumferential seal (for example as claimed herein), the method comprising the step of rotating the rotating seal part such that second portion wears against the abradable liner for providing a tight seal, whilst the rotating seal part is arranged such that a positive first sealing gap is maintained.
According to an aspect there is provided a method of sealing a stage of a gas turbine engine comprises the method of sealing a circumferential seal as claimed herein.
The circumferential seal as described and/or claimed herein may improve performance of a rotating component. For example performance may be improved by providing a seal that minimises airflow through the seal across a range of operational conditions and/or across the life of a gas turbine engine.
The circumferential seal as described and/or claimed herein (for example comprising a rotating seal part and a static seal part) may minimise the gap between the rotor and the stator across a range of operational conditions. For example the operational conditions may include take-off, climb and/or cruise. The circumferential seal as described and/or claimed herein may minimise the gap between the rotor and the liner of the stator whilst minimising wear on the rotor. The circumferential seal as described and/or claimed herein may minimise the sealing gap between the rotor and the stator across the operational life of the gas turbine engine.
The circumferential seal as described and/or claimed herein may minimise wear to the rotor whilst minimising the thickness of protective coating on the rotor. The circumferential seal as described and/or claimed herein may minimise wear to the rotor when the maximum thickness of protective coating is limited by manufacturing techniques. The circumferential seal as described and/or claimed herein may minimise wear of the rotor when an unprotected portion of the rotor may wear faster than the protective coating.
The circumferential seal as described and/or claimed herein may minimise wear of the rotor when the rotor rubs against a different portion of the stator liner at different operational states, for example rub-in, idling, climb and/or cruise.
The circumferential seal as described and/or claimed herein may minimise heat generation in the seal. For example heat generation may be minimised by minimising the contact area between the rotor and stator. For example heat generation may be minimised by intermittent cutting. Heat generation may occur when a portion of the stator liner experiences cutting as the rotor rotates. For example heat generation may be minimised whereby when the rotor is in a first position a portion of the rotor is rubbing against a portion of the stator, whereas in a second position no part of the rotor is rubbing against the same portion of the stator.
The circumferential seal as described and/or claimed herein may minimise wear on the rotor when the seal is exposed to high temperatures during operation. For example high temperature operation the seal may require a liner material that is more robust and/or harder to cut.
The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.
Embodiments will now be described by way of example only, with reference to the Figures, in which:
With reference to
The principal rotational axis 11 defines axial, radial and circumferential directions of the gas turbine engine 10. The principal rotational axis 11 may be a common central axis for the components of the gas turbine engine 10. For example rotating components such as the rotating seal part 30 may rotate about the common central axis. Static components, such as the static seal part 36 may circumferentially surround the common central axis, for example the common central axis may be in the centre of the static seal part 36 (accounting for manufacturing tolerances and operational distortion).
Whilst the circumferential seal 26 is shown on a single stage of the intermediate pressure turbine 18, the circumferential seal 26 is not limited in its position on the gas turbine engine 10. For example the circumferential seal 26 can be positioned between any rotor and stator of the gas turbine engine 10. For example the circumferential seal 26 can be positioned on other turbine stages, for example the high-pressure turbine 17 or the low-pressure turbine 19. The circumferential seal 26 can be positioned on any rotor of the gas turbine engine, for example compressor stages or fan stages.
The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the air flow directed into it before delivering that air to the high pressure compressor 15 where further compression takes place.
The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.
Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.
The cutting and/or wearing force that wears the fin tips is predominantly defined by the mechanical and/or thermal effects on the rotor, which defines the extent of which the rotor sealing portion moves and/or extends towards the stator sealing portion. Therefore the force that causes the wear is only partially influenced by the number of fins. For example having two fins does not half the force that is wearing the fins.
The first fin 65 has a first fin body 67 and a first fin protective coating 68. The first fin 65 has a first fin tip 66. The first fin tip 66 has a first sealing gap 70 between the first fin tip 66 and the static seal part 69.
In other embodiments there may be further fins/portions, each with their own sealing gaps. For example there may be a third fin/portion with a third sealing gap. There may be a fourth fin/portion with a fourth sealing gap. There may be more than four sealing fins each with their own sealing gap dimensions. Where more than two portions, the wear may occur progressively along the portions, for example wearing the first portion first, then the second portion, then the third portion, then the fourth portion, in the method described herein.
In
In
The first fin 65 may be considered a first portion of the fin seal. The second fin 60 may be considered a second portion of the fin seal.
The second fin body 62, in the
The protective coating may extend across the whole of the radially outer surface of the rotating seal part 90, as shown in the
Whilst two rotor fins are shown in the fin seal 92 of
In
During the rotating parts of the embodiments shown in
The rotating seal part 100 may cut into the stator liner 107, for example the fin seal 102 may cut into the stator liner 107, in order to provide a better seal between the rotor and stator across a range of operating conditions. This is due to the fact that the sealing gap is zero or negative for a larger part of the operational life, compared to if the rotor fins were designed not to cut into the stator liner 107. The stator liner 107 is optional. For example the stator liner 107 may not be present and a seal is formed between the fin seal and the static seal part. For example the embodiment in
The first portion 114 may correspond to the first fin 65 of
The fin seal 112 comprises a single circumferential fin in the
The shape of the fin seal 112 in the
The second sealing gap 119, defined by the second portion 118 can be seen to have a radially smaller gap compared to the first sealing gap 115, defined by the first portion 114.
The fin seal 112 may have a protective coating. The protective coating may cover the first portion 114 and/or the second portion 118. The static seal part 116 may comprise a stator liner.
During operation the rotating seal part 110 rotates. The rotating seal part 110 may deform during operation, for example due to rotational forces, thermal expansion and/or vibration. The gap between the rotating seal part 110 and the static seal part 116 may decrease, for example according to the steps shown in
After a period of wear, the
Referring to
In a method of sealing a circumferential seal a rotating seal part 110, for example that shown in the
It will be appreciated that wear will first occur on the peaks of the fin seal 112, for example the second portion 118. In the
The depth of a protective coating may be limited by manufacturing techniques. For example if the protective coating is sprayed on, it may only be formed to a depth before it may fall off. That is to say, it cannot be sprayed on too deep.
Therefore the example arrangement shown in
The preferential and/or sacrificial wear of a portion of the protective coating is advantageous in minimising overall wear of a fin seal 112, 62. The preferential and/or sacrificial wear of a portion of the protective coating is advantageous in avoiding wear of unprotected fin seal 112, 62. Unprotected fin seal may be fin seal whereby there is portion of the fin seal that has protective coating at its radially outer profile. The preferential and/or sacrificial wear of a portion of the protective coating is advantageous when further wear occurs. Further wear may occur when a fin seal contacts different parts of a stator in different operating conditions, for example because the same fin portion has to cut a second part of the liner.
The first rotor sealing fin 134 and the second rotor sealing fin 138 may form a fin seal. The first rotor sealing fin 134 may be considered a first portion of the fin seal. The first rotor sealing fin 134 may correspond to the second fin 65 of
Each blade has a rotor sealing component 130 on its radially outermost end. The rotor sealing components form a complete sealing component around the circumference of the rotor. For example each rotor sealing component 130 abuts rotor sealing components 130 of adjacent blades. Each rotor sealing component 130 has a rotor fin 134, 138 extending radially outwardly from the radially outer surface of the rotor sealing component 130. A static seal part (not shown) may surround the rotor fins 134, 138 to form a seal. In the
In other embodiments a rotor sealing components 130 may comprise more than one sealing fin, for example two first sealing fins 134 or two sealing fins 138 or a first sealing fin 134 and second sealing 138. In other embodiments a rotor sealing component 130 may comprise more than two sealing fins. In other embodiments a different arrangement of first and second sealing fins may be present around the circumference of the rotor.
The gap between a first sealing fin 134 and a static seal part is smaller than a gap between a second sealing fin 138 and a static seal part. As such the first sealing fin 134 wears before a second sealing fin 138. Therefore after a first period of wear a second sealing fin 138 may still have an unworn protective coating. This reduces the risk of wear occurring on unprotected sealing fins. Advantageously the embodiment shown in
It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.
Number | Date | Country | Kind |
---|---|---|---|
1801296.3 | Jan 2018 | GB | national |