Patent Application
20180142567
The present invention relates to a sealing system for an axial turbomachine. The present invention further relates to an axial turbomachine.
In axial turbomachines, in particular in multistage axial turbomachines, the pressure of the operating medium (or conveyed medium) changes from stage to stage. In a turbomachine designed as a gas turbine, the pressure in the compressor is, as a rule, higher downstream of a row of blades or vanes than the pressure upstream; in the turbine, in contrast, the pressure is lower downstream than the pressure upstream. In order to achieve a high efficiency of the turbomachine, it is necessary for the operating medium to be conveyed through the blading of the individual stages and not to circumvent the row of blades or vanes as a leakage flow (or bypass flow) without output of work. For this purpose, a sealing system, which is designed as a labyrinth system, for example, is provided in the region of an outer boundary of an annular space.
Sealing systems of this kind have the task of minimizing a leakage flow through a sealing gap between the rotating blading and a housing and hence to enable a stable operating behavior at high efficiency. Usually, the rotating components of a turbine have sealing fins or sealing tips, which can graze or run in against honeycomb seals. In this case, the seals are designed as abradable and run-in coatings. Through minimization of the radial gaps above the sealing fins, it is attempted to minimize the leakage flows through the cavities into these regions, in particular into regions above shrouds of rotating blades, and the losses in efficiency that thereby ensue. Nonetheless, when leakage flows enter into the so-called main flow of the turbomachine, mixing losses result due to different directions and speeds of the main flow and leakage flow.
An object of the present invention is to provide a sealing system for an axial turbomachine. Furthermore, it is an object of the present invention to provide an axial turbomachine having the sealing system according to the present invention.
The object in accordance with the invention is achieved by a sealing system in accordance with the present invention. It is further solved by an axial turbomachine with the features of the present invention.
Proposed in accordance with the invention is accordingly a sealing system for an axial turbomachine, wherein the sealing system comprises at least one rotor with a shroud arranged radially outside and a housing surrounding the rotor. A gap is arranged between the shroud and the housing. The gap is bounded, on one side, by a seal that is joined to the housing and, on the other side, by at least one sealing tip that is arranged at the shroud. This sealing tip arranged at the shroud may be referred to as a rotating sealing tip, because it rotates together with the rotor. The seal, as viewed in the radial direction, is arranged opposite to the shroud. The bounding of the gap by way of the seal and the shroud can reduce the flow losses of the gap flow. Arranged at the downstream end region of the housing-side seal is another static sealing tip that is joined to the housing. By this static sealing tip, the flow through the gap is influenced and, in particular, is reduced. Alternatively or additionally, the flow downstream of the static sealing tip is influenced by the static sealing tip.
An influence on and, in particular, a reduction of the flow through the gap by the static sealing tip can be caused by flow losses of the static sealing tip.
Alternatively or additionally, it is possible for the static sealing tip to influence any potential eddy formation downstream of the static sealing tip. The gap flow between the static sealing tip and the shroud can bring about or cause an eddy or an eddy region downstream, the direction of rotation of which primarily has the same direction of flow as the adjacent main flow. In this way, it is possible to reduce the flow losses and/or the disruption of the main flow due to this eddy. This can advantageously increase the efficiency of the axial turbomachine by way of the sealing system according to the invention.
A reduction in the disruption of the main flow due to the described direction of rotation of the eddy may be referred to as a low-loss mixing with the main flow. In contrast to this, a sealing system without a static sealing tip can lead to an eddy formation, the primary direction of rotation of which is opposite to the main flow. This would lead to a high-loss mixing with the main flow and could contribute to a reduction in the efficiency of the turbomachine.
The radially outer shroud arranged at the rotor may be referred to as an outer shroud or as a rotating blade outer shroud.
The gap arranged between the shroud and the housing may be referred to as a rotor gap.
The axial turbomachine according to the invention comprises at least one low-pressure turbine stage with a sealing system according to the invention. In addition, the axial turbomachine can have at least one high-pressure turbine stage, one low-pressure compressor stage, and one high-pressure compressor stage. Each of the mentioned stages can have a sealing system according to the invention.
The axial turbomachine can be a gas turbine, in particular an aircraft gas turbine or an aircraft engine.
Advantageous enhancements of the present invention are each the subject matter of dependent claims and embodiments.
Exemplary embodiments in accordance with the invention can have one or more of the features mentioned below.
A static and/or a rotating sealing tip may be referred to as a sealing fin.
In some exemplary embodiments according to the invention, the seal, which is joined to the housing, can be a run-in seal. A run-in seal may be referred to as an abradable seal. A run-in seal can have a run-in coating or a run-in layer, into which, for example, a sealing tip can penetrate for creation of a sealing gap. This sealing gap can be designed to be small through the penetration or run-in of a sealing tip, in particular during a provided operating state, and is thus advantageous for optimizing the efficiency of the turbomachine. The run-in seal can comprise a honeycomb structure for penetration of a sealing tip.
The run-in seal can be joined to the housing in a material-bonded manner and/or in a form-fitting manner. The run-in seal can be adhesively attached, soldered, riveted, or clamped, or fastened in a different way to the housing.
In some exemplary embodiments in accordance with the invention, the run-in seal is fastened only to the housing. In this embodiment, no run-in seal is fastened to the rotor, in particular to the shroud of the rotor. Accordingly, the run-in seal is arranged only on one side of the gap.
In some exemplary embodiments in accordance with the invention, the shroud can have at least two sealing tips. Two sealing tips can engage in two opposite-lying run-in seals at the housing and form a sealing gap. The at least two sealing tips can be arranged axially in succession on a radius or at a height radially. Alternatively, the two sealing tips can be arranged in succession axially at different radii or at radially different heights, that is, radially offset.
In some exemplary embodiments in accordance with the invention, the shroud has no seal and, in particular, no run-in seal.
In some exemplary embodiments in accordance with the invention, the shroud has three or more sealing tips. The sealing tips can be arranged radially at one height or at different heights. For example, two sealing tips that are arranged axially in succession can have the same radius, whereas a third sealing tip is radially arranged further outward.
In some exemplary embodiments in accordance with the invention, the at least one sealing tip of the shroud is arranged upstream at a tilt. The angle of tilt between the radial direction and the axial direction can be, for example, at least 15 degrees. The angle of a sealing tip that is not tilted in the radial direction would be zero degrees. A tilted sealing tip can influence advantageously the flow losses due to a smaller flow through the gap. A tilted sealing tip can also be advantageous in terms of the shroud configuration—for example, in the case of an arrangement of a plurality of sealing tips at the shroud. Likewise, the structural strength of the shroud can advantageously be greater with a tilted sealing tip. In particular, the frontmost upstream sealing tip of the shroud can be tilted. The tilt can be twenty degrees, twenty-five degrees, thirty degrees, or more.
In some exemplary embodiments in accordance with the invention, the shroud has a wear protection in the opposite-lying region of the static sealing tip. The wear protection can advantageously prevent any direct contact of the static sealing tip with the base material of the shroud. A direct contact could damage the shroud and hence cause major damage.
In some exemplary embodiments in accordance with the invention, the wear protection of the shroud extends over the opposite-lying region of the static sealing tip, in particular at least to the adjoining end of the shroud. The wear protection can extend over additional regions of the shroud.
In some exemplary embodiments in accordance with the invention, the wear protection is a coating, at least in sections, of the shroud. Alternatively, however, the wear protection layer can also be understood to mean a lamellar element that is fastened at the shroud in a material-bonded or force-fitting manner, such as, for example, an element made of a material with the trade name “Stellit.”
In some exemplary embodiments in accordance with the invention, the wear protection is arranged in regions over the periphery of the shroud. For example, the wear protection can be arranged at individual points of the shroud.
In some exemplary embodiments in accordance with the invention, the material of the static sealing tip has a lesser hardness in comparison to the hardness of the wear protection layer. The hardness of the material can be a measure of the resistance of the material to wear. The material of the wear protection layer preferably differs from the base material of the shroud and, in particular, likewise has a greater hardness in comparison to this base material. The term “greater hardness” in terms of the present invention means, in particular, a “greater wear resistance.”
In some exemplary embodiments in accordance with the invention, the wear protection is elevated in comparison to the remaining shroud surface or, in other words, the wear protection extends outward in its height above the surface. The wear protection thickness can be, for example, 5 μm, 10 μm, 20 μm, or another thickness.
In some exemplary embodiments in accordance with the invention, a wear protection is produced by a local edge layer hardening, in particular by a laser-assisted method.
In some exemplary embodiments in accordance with the invention, the static sealing tip is fastened with a form-fitting component, in particular a retaining element, at the housing. The static sealing tip can be joined to the retaining element in a material-bonded manner.
In some exemplary embodiments in accordance with the invention, the static sealing tip is fastened to the housing with a form-fitting component, in particular a retaining element, at the downstream guide vane assembly or at the connection to the guide vane assembly. The static sealing tip can be joined to the retaining element in a material-bonded manner.
In some exemplary embodiments in accordance with the invention, the rotor is a turbine rotor, in particular a low-pressure turbine rotor.
In some exemplary embodiments in accordance with the invention, the shroud is segmented over the periphery of the rotor. In particular, the segments are designed as Z-shroud segments. By Z-shroud segments, the rotating blades can be tensioned advantageously with respect to one another.
In some exemplary embodiments in accordance with the invention, the contact regions of the shroud segments have a wear protection in the peripheral direction. This wear protection can be designed as a wear protection in the opposite-lying region of the static sealing tip. In particular, this wear protection projects outward as a wear protection layer over the shroud surface, so that, in the event of a contact of the static sealing tip with the shroud, initially only the wear protection layer is touched. In particular, the hardness of the wear protection layer is greater than the hardness of the static sealing tip. As a result of this, the shroud can be protected advantageously against any contact with the static sealing tip. Such a contact could damage the shroud.
The wear protection can be joined to the shroud in a material-bonded manner, for example by welding (for example, by laser deposition welding). The material of the wear protection can be a hard alloy based on cobalt, such as, for example, a cobalt-chromium alloy, or can comprise such an alloy. The hardness of the wear protection layer can be, purely by way of example, greater than 600 Vickers hardness units (abbreviated HV).
In some exemplary embodiments in accordance with the invention, the static sealing tip is joined to the housing by a retainer element in a form-fitting and/or material-bonded manner.
In some exemplary embodiments in accordance with the invention, the static sealing tip has a variable and, in particular, wavy structure in the peripheral direction at the side lying opposite to the shroud. By the variable or wavy structure, an axially larger region of a contact surface of the sealing tip can be utilized, when the sealing tip contacts the shroud or when there is a wear protection layer on the shroud, in comparison to a non-variable or non-wavy, that is, straight structure over the periphery. By an axially larger region of the contact surface, it is advantageously possible during a contact process or a frictional process to distribute the heat input between the sealing tip and the shroud (or the wear protection layer) over a larger surface area and a greater material volume. In this way, it is possible to reduce the load locally, in particular, the thermal material load, of the wear protection layer.
Many or all of the embodiments in accordance with the invention can have one, a plurality of, or all of the advantages mentioned above and/or below.
By the sealing system according to the invention, it is possible advantageously to reduce the leakage, that is, the bypass flow or the gap flow. The leakage may be referred to as primary losses. In particular, it is possible by the static sealing tip to reduce the gap flow.
Furthermore, it is possible by the sealing system according to the invention to disrupt the main flow to a lesser extent and thus to increase the efficiency of the turbomachine. The disruptions of the main flow may be referred to as secondary losses. In particular, the eddy formation downstream of the static sealing tip can be influenced and hence the direction of rotation of an eddy can be matched to the main flow direction. In this way, it is possible to achieve a low-loss mixing of the eddies, which result from the gap flow, with the main flow.
The present invention will be explained below by way of example on the basis of the appended drawings, in which identical reference characters indicate identical or similar components. In the respective, highly schematically simplified figures:
Illustrated between an upstream guide wheel or stator 1 and a downstream guide wheel or stator 2 on the housing side is a housing section 10, in which a seal carrier 11 is mounted. The housing section 10 could be referred to as a static seal part. The run-in seal 12 is fastened at the seal carrier 11, for example, in a material-bonded manner by soldering or adhesive attachment. Two sealing tips 5, which may be referred to as sealing fins, engage in the run-in seal 12. A rotor gap 6 between the run-in seal 12 and the sealing tips 5 is created or generated by running-in or cutting-in of the sealing tips 5. The sealing tips 5 are arranged at a radially outer shroud 4, which, in turn, is joined to a rotating blade 3. The shroud 4 can be joined integrally to the rotating blade 3, for example by a laser sintering production process.
The direction of flow of a leakage flow (the leakage flow may be referred to as a gap flow or as a bypass flow) is indicated by the arrow for the reference numeral of the rotor gap 6. In a turbine stage illustrated here, the pressure of the flow medium decreases in the flow-through direction of the main flow H, that is, in
Downstream of the second sealing tip 5 (right in
Furthermore, a reinforcement structure 13 on the shroud 4 is illustrated optionally.
The rotating blade 3 is clearly positioned opposite to the run-in seal 12 and hence opposite to the surrounding housing 30 and the guide wheels 1, 2, which may be referred to as stators. However, the rotor (not illustrated in
The arrangement of the upstream guide wheel or stator 1, the downstream guide wheel or stator 2, the rotating blade 3, the housing section 10, and the seal carrier 11 (which is designed differently in
Furthermore, a so-called baffle 22 is incorporated in the housing 30 on the inside. The baffle 22 can contribute, for example, to reducing flow losses.
The additional static sealing tip 20 can advantageously reduce the leakage resulting from the rotor gap 6. Furthermore, the direction of rotation of the eddy W forming downstream of the static sealing tip 20 with respect to the direction of rotation of the sealing system 100′ from
The static sealing tip 20 forms, together with the rear section of the shroud 4, a sealing point that is additional to the two sealing points formed by the sealing tips 5 and the run-in seal 12.
The front, upstream sealing tip 5 is tilted, in relation to the radial direction r, opposite to the main flow direction, which is aligned in the axial direction. The tilt is about 30 degrees. By a tilted sealing tip 5, it is possible, for example, to influence the leakage flow through the rotor gap 6.
The two sealing tips 5 are arranged radially offset and hence form approximatively the widening flow channel of the turbine stage.
The shroud 4 is designed in segments over the periphery u. The segments are often designed as so-called Z shrouds (see
In the radial direction r, the wear protection layer 8 projects over the surface of the shroud 4. This has the advantage that, when there is an undesired contact of the static sealing tip 20 with the shroud 4, for example when an aircraft equipped with the turbomachine as an engine makes a hard landing, the static sealing tips 20 do not touch the shroud 4 itself, that is, the base material of the shroud, and possibly damage it, but rather solely touch the wear protection layer 8. When the material of the wear protection layer 8 has a greater hardness than the material of the static sealing tip 20, the static sealing tip 20 is abraded or ground down by the rotating blade 3 of the rotor. The static sealing tip 20 can easily be shortened in the radial direction r, for example. In this way, any damage at the rotor 3 is prevented. A grinding down of the static sealing tip 20 by the wear protection layer 8 is, in contrast, far less critical and, in addition, the static sealing tip 20 can be replaced relatively easily and cost-effectively.
The shroud 4 is segmented. The so-called Z shroud has wear protection layers 7, 8 at the contact points of segments that abut one another. In particular, the wear protection layer 8, which extends further downstream in the axial direction than the wear protection layer 7, projects slightly above the radial extension of the shroud surface. This is illustrated in
The sealing tips 5 of the shroud 4 project out of the plane of the illustration. The wear protection layers 7, 8 are located at the contact surfaces of the Z shroud to the segments of additional blade shrouds (not illustrated) that are adjoined in the peripheral direction. The shadowed illustrated wear protection layer 8 was already shown in the sectional plane of
It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 222 720.3 | Nov 2016 | DE | national |
