Rotor with partially coated turbine blades and methods

Abstract

The invention relates to a turbine blade (1, A) with support vanes, which has a coating (18) on its upper half, wherein the coating (18) extends to a maximum of 40% of the radial length of a blade (10) of the turbine blade (1, A).

Description

[0001] The invention relates to a rotor with partially coated turbine blades and a method.

[0002] A problem in the operation of turbines with turbine blades is self-excited vibrations (flutter) at the blade tip of the turbine blade.

[0003] To date, the common strategy to suppress flutter has been to change the vibration behavior of some blades in the wheel by changing, for example, their stiffness or damping properties.

[0004] EP 1 813 773 A2 discloses a blisk in which a coating is applied in different ways at different locations for balancing purposes.

[0005] US 2020 / 0032659 A1 discloses a rotor in which the turbine blades have support wings. This also results in flutter.

[0006] It is therefore an object of the invention to solve the above-mentioned problem.

[0007] The object is achieved by a turbine blade according to claim 1, a rotor according to claim 11 and a method according to claim 12.

[0008] The subclaims list further advantages which can be combined with each other in any way to achieve further advantages.

[0009] The description and the figures represent only exemplary embodiments of the invention.

[0010] What is new is the partial coating according to the invention for changing the mass of blades that have a coupling, in particular in turbine blades with a cover blade.

[0011] The Figure 1 shows a turbine blade according to the invention and partly a rotor according to the invention, and Figure 2 shows a cross section through a turbine blade according to the invention.

[0012] In Figure 1Two types A, B of turbine blades 1 are shown, with one turbine blade A having an additional coating 18 and the other turbine blade B not having one as the only difference.

[0013] Otherwise, they are trained or manufactured in the same way.

[0014] These are preferably turbine blades for a gas turbine. However, the idea is applicable to all types of turbines, compressors, or machines with blades.

[0015] A turbine blade 1, A, B has a blade root 4 which preferably has a fir tree structure.

[0016] The blade root 4 is later inserted into a speaking groove of a turbine disk or rotor disk to form a rotor for a rotor stage.

[0017] A blade platform 7 is connected to the blade root 4 in the radial direction 21.

[0018] After the blade platform 7, a blade 10 extends in the radial direction 21 towards the radial end of the blade 10.

[0019] At the end of the blade 10, a shroud 13 is preferably present.

[0020] The shroud 13 represents a coupling between adjacent turbine blades 1, A, B.

[0021] Another type of coupling is represented by supporting blades, whereby such turbine blades in particular do not have a shroud.

[0022] There are also turbine blades with shrouds and supporting wings.

[0023] Other coupling types are conceivable for this invention.

[0024] The turbine blade of type A according to the invention has the coating 18 on its upper half of the blade airfoil 10, in particular at the radial end.

[0025] The coating 18 is preferably metallic.

[0026] The coating 18 represents an overlay coating.

[0027] A NiCoCrAlX coating is preferably used.

[0028] X preferably corresponds to yttrium (Y), rhenium (Re), tantalum (Ta) and / or silicon (Si).

[0029] Preferably it is a NiCoCrAlY, NiCoCrAlYTa or NiCoCrAlYRe, NiCoCrAlYSi coating.

[0030] Otherwise, the turbine blades A, B in particular have no coatings on the blade airfoil 10.

[0031] However, the turbine blades of type A, B can also have a coating on the blade airfoil 10 outside the area for the coating 18, in particular on the entire blade airfoil 10.

[0032] This can be a diffusion coating, for example an aluminide coating, preferably produced by alitization.

[0033] In this case, the coating 18 is applied over the diffusion coating.

[0034] Likewise, the turbine blades A, B may already have a coating on the blade airfoil 10, in particular on the complete blade airfoil 10.

[0035] If the turbine blade of type A, B already has a coating on the blade airfoil, the turbine blade of type A is then only made thicker at the radial end by the coating 18, in particular by the same coating material as on the rest of the blade airfoil 10.

[0036] The coating 18 extends only at the radial end of the blade 10 and therefore has a maximum length of at most 40%, in particular up to a maximum of 30%, of the length of the blade 10.

[0037] Preferably, the coating 18 extends up to the cover strip 13.

[0038] In particular, the coating 18 is only present on the blade, i.e. not also on the inside of the shroud 13.

[0039] In turbine blades with support vanes, the coating 18 is present particularly up to the blade tip. The support vanes may be covered with the coating 18 except for their contact surfaces.

[0040] The coating 18 preferably has a thickness of at least 0.01 mm and preferably up to 0.8 mm at most. Preferably, the layer thickness is at most 0.6 mm.

[0041] The area from the coating 18 to the uncoated part or thinner coated part of the blade 10 is preferably designed as a transition area in order not to create steps on the blade 10.

[0042] In Figure 2 a section CC through the turbine blade A with the coating 18 is shown.

[0043] Preferably, the coating 18 represents a circumferential coating around the blade 10.

[0044] Variations of this are conceivable, such as only a coating on the suction or pressure side of the turbine blade A.

[0045] A rotor has multiple stages: two, three, or more. Type A turbine blades are preferably used for the third and / or fourth stage of the turbine, or preferably for the last two stages.

[0046] A rotor with such turbine blades of type A is formed as follows: The natural frequencies of the turbine blades 1 are measured preferably according to the ping method (ping frequencies of the free-standing blade for the flutter-relevant mode) and sorted according to the size of the measured natural frequency.

[0047] The frequencies of the turbine blades 1 are measured individually and not in the installed state.

[0048] The influence on the natural frequency in the coupled / installed state is calculated in advance.

[0049] Then the sorting is divided into two groups of equal size, in which a group with small and a group with larger natural frequencies is formed, so that the group with the smaller natural frequencies always has a natural frequency less than or equal to any natural frequency from the group with the larger natural frequencies.

[0050] The group of turbine blades with the lower natural frequencies receive the coating 18 according to the invention.

[0051] The rotor is assembled and therefore does not constitute a blisk.

[0052] The installation of the turbine blades A, B is carried out with the aim of minimizing the imbalance of the rotor and the maximum frequency differences between the turbine blades A and B.

[0053] Preferably, one half of the turbine blades for a rotor disk / stage are turbine blades of type A and the other half are turbine blades of type B.

[0054] A division other than half is also conceivable.

[0055] The coating 18 is preferably designed identically on all such turbine blades of type A, i.e. same thickness or same thickening, same extension, same material.

[0056] Thereafter, the blades are preferably installed in a specific order, in particular in the order ABAB, ... into the corresponding grooves of a rotor disk and thus form a stage as part of a rotor.

[0057] Other sequences such as AABAAB, ... or ABBABB, ... or AABB- ... are also conceivable due to different selection regarding the natural frequencies.

Claims

1. Rotor with at least two stages, in particular with at least three stages, very particularly with at least four stages, wherein at least the last stage, in particular at least the last two stages, very particularly only the last two stages, have a plurality of turbine blades (A) with supporting wings and with a coating (18), wherein the turbine blades (A) have a coating (18) on the upper half of their blade airfoil (10), in particular have a coating (18) on their radial end, very particularly only have a coating at their radial end, the coating (18) which is in particular metallic, wherein the coating (18) extends at most up to 40%, in particular at most up to 30%, of the radial length of a blade airfoil (10) of the turbine blade (A).and also turbine blades (B) without the coating (18), wherein in particular one half of the turbine blades of a stage is formed by coated or locally thickened turbine blades of type A and the other half by uncoated or non-locally thickened turbine blades of type B.

2. Rotor according to claim 1, wherein the turbine blades (A) coated or locally thickened by the coating (18) and the turbine blades (B) are arranged in a specific radial sequence in the disk of the rotor, in particular in the sequence ABAB, ....

3. Rotor according to claim 1, wherein the coating (18) is present only on the blade (10).

4. Rotor according to one or both of claims 1 or 3, wherein the coating (18) extends directly below the cover band (13), in particular extends only directly below the cover band (13).

5. Rotor according to one or more of claims 1, 3 or 4, wherein the coating (18) of a turbine blade (A) with support vane extends to the blade tip.

6. Rotor according to one or more of claims 1, 3, 4 or 5, wherein the coating (18) comprises a NiCoCrAlX alloy, where X is selected from the group: yttrium (Y), rhenium (Re), tantalum (Ta), silicon (Si).

7. Rotor according to one or more of claims 1, 3, 4, 5 or 6, wherein the coating (18) has a layer thickness of up to 0.8 mm, in particular up to 0.6 mm.

8. Rotor according to one or more of claims 1, 3, 4, 5, 6 or 7, wherein the coating (18) extends completely over the circumference of the blade (10).

9. Rotor according to one or more of claims 1, 3, 4, 5, 6, 7 or 8, wherein only the coating (18) is present on the blade (10).

10. Rotor according to one or more of claims 1, 3, 4, 5, 6, 7 or 8, wherein the coating (18) on the blade (10) represents a thickening of an already existing coating on the blade (10).

11. Rotor according to one or more of claims 1, 3, 4, 5, 6, 7, 8, 9 or 10, in which the region from the coating (18) to the uncoated part or thinner coated part of the turbine blade (A) is designed as a transition region in order not to produce steps on the blade (10).

12. A method for producing a rotor with turbine blades (A) according to one or more of the preceding claims 1 to 11, in which the natural frequencies of turbine blades (1) are measured and divided into two groups (A, B), in particular groups (A, B) of equal size, in which a group (A) with small natural frequencies and a group (B) with larger natural frequencies are formed, wherein the group (A) with the smaller natural frequencies always has a natural frequency less than or equal to any natural frequency from the group (B) with the larger natural frequencies, wherein the group of turbine blades (A) with the smaller natural frequencies then receives the coating (18) according to the invention.

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