Fluid machinery blade having a notched blade tip on the surface of a wear-resistant film and method for manufacturing the same

Abstract

The present invention relates to a blade (1) for a fluid machine, the blade (1) being formed along a radial axis and having a blade cross-sectional portion with a blade tip (4), a discharge side (5) and a suction side (6), the blade (1) having a blade tip surface (7) that faces an inner wall of a housing during operation, the blade tip surface (7) having an abradable coating (8), the abradable coating (7) being formed such that peeling of the abradable coating (8) occurs when the abradable coating (7) comes into contact with the inner wall of the housing during operation, the abradable coating (8) having an abradable coating surface (11) is formed, and a notch (12) is arranged in the abradable coating surface (11).

Description

Technical Field

[0001] The present invention relates to a blade for a fluid machine, in which the blade is formed along a radial axis and has a blade tip and a blade cross-sectional profile with a discharge side and a suction side, and further the blade has a blade tip surface facing the inner wall of the housing during operation, and this blade tip surface has a wear-resistant coating.

[0002] Furthermore, the present invention relates to a method for manufacturing a wear-resistant coating.

Background Art

[0003] In fluid machines for processing and treating liquid and / or gaseous fluid media, it is often necessary to seal the gap between the moving member and the stationary member against the fluid medium. Examples of fluid machines include steam turbines, gas turbines, compressors, and the like.

[0004] In a steam turbine, the gap between the rotor and the housing surrounding it is sealed to block the path of the steam through the blade ring. The accuracy of this seal has a significant impact on the efficiency of such fluid machines.

[0005] In fluid machines, the principle of changing the swirl is used to convert the internal energy of the working fluid into mechanical energy of the rotating member. Since the fluid guiding member is usually closed so that the working fluid does not become uninvolved in the process, internal flow may occur.

[0006] In order to enable a disturbance-free swirl of fluid machine parts in the fluid guiding geometry, a radial gap is absolutely necessary between the stationary member and the rotating member. This radial gap must be made as small as possible to reduce losses, and from the perspective of integrity, it must be made as large as necessary.

[0007] Generally, in fluid machines, the radial clearance between the moving blade tips of the blades and the housing facing them is designed so that an over-bridge of the radial clearance is avoided in important operating cases.

[0008] In a low-pressure steam turbine, which is an example of a fluid machine, there is also a problem of corrosion by droplets. In these fluid machines, the expansion often ends in the two-phase region of steam, imposing a large corrosion load on the rotating member and the stationary member adjacent thereto.

[0009] In fluid machines such as steam turbines, self-supporting low-pressure blades are mainly used in the low-pressure region. Structurally, such fluid machines have a relatively large radial gap between the blade tips and the housing. Nevertheless, in order to prevent the losses from becoming too large, it is known to arrange a peelable coating on the housing facing the blade tips. When the blade tips come into contact with the housing, only the peelable coating easily peels off, thus creating a relatively small radial gap.

[0010] Basically, while considering the principles of dynamics (increase in the radial length of the blades under the influence of centrifugal force and temperature), the radial play is minimized mainly by passive design means. For example, in addition to minimizing the ovalization of the housing and the vibration of the shaft, blades shortened in a cylindrical shape that minimize the influence of the axial expansion difference are used.

[0011] Actively, in a rotor for blades shortened in a conical shape, a (hydraulic) mechanical device for influencing the axial position of the rotor is used.

[0012] In the housing, active, semi-passive, and passive solutions are taken to influence the radial play.

[0013] As an active solution, there is a "retractable sealing segment" that closes only when a flow is formed and reduces the radial play at the rated rotational speed. In the case of an overbridge, the shape of the housing can be expanded by a circumferential spring structure.

[0014] A semi - passive "elastic seal segment" in which a radial spring structure enables expanding the geometric shape of the housing functions similarly.

[0015] As passive solutions, there are easily removable insert / attachment members and components as well as peelable coatings.

[0016] On the opposing housing side surfaces, there are often wear - resistant peelable coatings.

[0017] However, in fluids with droplets, these functional coatings cannot be used because they cannot functionally withstand the high mechanical forces caused, for example, by droplet impingement corrosion.

[0018] As an auxiliary means, there is a so - called honeycomb seal segment, which has anisotropic peeling characteristics and can be embedded in the housing wall. The practical problem here is that a hollow structure may be formed and solid particles contained in the working medium may fill it, potentially losing the original positive anisotropic characteristics.

[0019] In some cases, seal - tip - shaped structures that also serve to reduce gap losses are provided on the opposing housing side surfaces even for self - supporting rotating blades.

[0020] Turbine blades with wear - resistant coatings are disclosed in the following prior art documents.

Prior Art Documents

Patent Documents

[0021]

Patent Document 1

[0022] An object of the present invention is to provide a blade for a fluid machine that can be used in a fluid machine and has less gap loss during operation. [Means for Solving the Problems]

[0023] This problem is solved by a blade having a blade cross-sectional shape formed along a radial axis, having a blade tip, a discharge side surface, and a suction side surface, having a blade tip surface facing the inner wall of the housing during operation, the blade tip surface having a wear-resistant coating, the coating being formed so as to peel off when contacting the inner wall of the housing during operation, the wear-resistant coating (8) having a wear-resistant coating surface (11), and notches (12) being arranged on the coating surface (11).

[0024] Thus, the present invention proposes a measure of applying a wear-resistant coating to the blade tip. This wear-resistant coating is formed so that when the wear-resistant coating contacts the housing, the wear-resistant coating peels off or becomes peelable, that is, the material peeling of the wear-resistant coating occurs, so that the radial gap is optimized.

[0025] The individual pieces of material that are formed by the peeling action and remain in the fluid machine during operation are configured such that they do not cause any damage in the fluid machine. Furthermore, the individual pieces of material are relatively small, which is achieved by the configuration of the wear-resistant coating according to the invention.

[0026] The solution according to the invention is a novel method, since hitherto, if necessary, the inner wall of the housing was formed with a release coating, whereas here the residual elliptical shape of the housing contour can be compensated at low cost.

[0027] Compared with the coating of the stationary part, the coating of the blades has advantages in the following situations. That is, even if there are fluctuations in the radial length of the blades and / or the ellipticity of the housing, in the case of wear, only the coating of the longest blade is removed by peeling. The gaps of the remaining blades remain unchanged.

[0028] According to the invention, the wear-resistant coating has a wear-resistant coating surface, and notches are arranged on this coating surface.

[0029] In this way, even if material peeling occurs due to contact with the inner wall of the housing, it is achieved that the individual pieces of the peeled material do not become too large. The notches basically act like intended breaking points, and the peeling of the material pieces reaches the notches. As a result, the notches act as the boundary lines where the wear-resistant coating can be peeled off, so to speak.

[0030] The wear-resistant coating, so to speak, is usually segmented along the chord line (Chord line = Skelettlinie) of the blade tip profile. As a result, in the event of chipping, partial loss or peeling is limited. In this case, the segmentation can be created by cutting or can already be formed during the layering process. or chord line (Chord line=Skelettlinie) is segmented. As a result, in the event of chipping, partial loss or peeling is limited. In this case, the segmentation can be created by cutting or can already be formed during the layering process.

[0031] Advantageous embodiments are specified in the dependent claims.

[0032] For example, in the first embodiment, a lubricant is provided on the wear-resistant coating.

[0033] This lubricant has abrasiveness. This means that material detachment of the wear-resistant coating occurs when the inner wall of the housing comes into contact with the wear-resistant coating. In this case, since the material properties of the wear-resistant coating are such that the individual material pieces are sufficiently small, the risk of damage due to the flying of the detached material pieces is minimized.

[0034] In a further advantageous embodiment, the lubricant contains graphite and / or hexagonal boron nitride.

[0035] Precisely, graphite and / or hexagonal boron nitride have ideal material properties for use as a detached coating or a component of a detached coating in a fluid machine. The crystal structure and bonding force in graphite and / or hexagonal boron nitride cause detachment of the material of the wear-resistant coating, but the individual material pieces to be detached are sufficiently small.

[0036] In a further advantageous embodiment, the blade cross-sectional profile can be described by a cord line, and the wear-resistant coating is arranged along the cord line.

[0037] In a further advantageous embodiment, the blade has an inlet edge and an outlet edge, and the wear-resistant coating is arranged from the inlet edge to the outlet edge.

[0038] In an advantageous embodiment, the cord line has a length D, and the wear-resistant coating is arranged only in the region before the outlet edge, where d = (0.4 to 0.9) × D, and d is the length of the wear-resistant coating along the cord line to the outlet edge.

[0039] According to this advantageous embodiment, it is proposed that, in principle, the wear-resistant coating is provided only in the region before the outlet edge without providing it on the entire surface of the blade tip.

[0040] Similarly advantageously, the notch is formed substantially perpendicular to the cord line.

[0041] Similarly, the notches are preferably formed at equal intervals from each other.

[0042] In another advantageous embodiment, the wear-resistant coating is formed continuously from the discharge side surface to the suction side surface.

[0043] In another advantageous embodiment, the wear-resistant coating peels off due to wear with the inner wall of the housing occurring during operation, thereby forming a contact surface by the peeling, and this contact surface becomes wider radially toward the blade leg portion by further peeling.

[0044] This measure enables an initial process in which the wear-resistant coating so to speak wears down. This means that the contact surface between the wear-resistant coating and the inner wall of the housing becomes larger and larger during further contact between the wear-resistant coating and the inner wall of the housing.

[0045] For this reason, it is advantageous if the wear-resistant coating is formed on the blade tip surface such that, when viewed in cross-section, the wear-resistant coating shows an obtuse-angled tip.

[0046] In other words, the wear-resistant coating faces the inner wall of the housing like an obtuse-angled tip. When the coating on the inner wall of the housing wears, first the tip peels off. As the contact increases, the contact surface becomes wider and wider.

[0047] In a particularly advantageous embodiment, the wear-resistant coating has a slit, and this slit is arranged such that the peeling of the wear-resistant coating reaches a measurable length L of the slit, and the height of the coating can be measured by this length.

[0048] Therefore, this slit provides an indicator for judging how much the wear-resistant coating has peeled off or what the thickness of the wear-resistant coating is.

[0049] The slit can be provided across the entire width of the wear-resistant coating and also across a part of the width of the wear-resistant coating.

[0050] In an advantageous embodiment, a plurality of slits can also be arranged in the wear-resistant coating for each blade.

[0051] These slits are processed from the edge of the blade surface on the suction side or discharge side to the tip chip. When a chip peels off during operation, the in-plane slit length can be measured in the plan view of the wear-resistant coating, and thereby the thickness of the wear-resistant coating can be calculated based on geometric characteristics and trigonometric considerations.

[0052] The slits can serve the function of notches and can also serve as a role of a set breaking point. Therefore, the size of the break can be limited by the slits.

[0053] The problem regarding the method is solved by a method for manufacturing a wear-resistant coating on a blade surface, in which the wear-resistant coating is applied to the blade tip by a thermal spraying coating method such as APS or HVOF, a lubricant such as graphite and / or hexagonal boron nitride is applied to this wear-resistant coating, the wear-resistant coating (8) is formed together with the wear-resistant coating surface (11), and a notch (12) is arranged on this wear-resistant coating surface (11).

[0054] It is advantageous to add a polymer to the wear-resistant coating in order to form a porous structure in the wear-resistant coating.

[0055] In a particularly advantageous embodiment, before the application of the wear-resistant coating to the blade, a first heat treatment for hardening the blade is performed, the wear-resistant coating is applied after the first heat treatment, and after the application of the wear-resistant coating, a second heat treatment is performed at a temperature at which the blade is stress-relieved annealed, and this temperature is selected such that the polymer melts within the sprayed wear-resistant coating, thereby resulting in a porous structure of the wear-resistant coating.

[0056] By this advantageous method, it is achieved that the polymer melts and is removed from the wear-resistant coating during the second heat treatment, whereby the wear-resistant coating is given a porous structure in a simple and cost-effective manner.

[0057] In another advantageous embodiment, notches are provided on the wear-resistant coating along the code line, and the notches are formed by a cutting method such as milling, for example, during or after the coating process.

[0058] The present invention will be described in detail below with reference to the drawings based on specific exemplary embodiments.

[0059] The above-described characteristics, features, and advantages of the present invention, and the manner in which they are achieved, will become more clearly understood and easier to understand in connection with the following description of the embodiments described in detail with reference to the drawings.

[0060] The same member or members having the same function are here designated with the same reference numerals.

[0061] Examples of the present invention will be described below with reference to the drawings. These do not illustrate the exemplary embodiments to scale, and the drawings used for the description are schematic and / or slightly exaggerated. With regard to the supplementation of the teachings directly distinguishable in the drawings, reference shall be made to the relevant prior art.

Brief Description of the Drawings

[0062]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0063] Figure 1 shows the overall view of blade 1. Blade 1 has a blade leg 2 suitable for fixing to a rotor (not shown). This blade leg 2 has a leg shape like that of a so-called Christmas tree. Other embodiments such as plug-in and saddle legs, Laval legs, sheath legs or T legs are known for the blade leg 2. Such a blade 1 can be used in fluid machines such as steam turbines, gas turbines or compressors. Blade 1 is formed along the radial axis 3 and has a blade tip 4 and a blade body with a discharge side surface 5 and a suction side surface 6.

[0064] Blade 1 has blade cross-sectional profiles formed variously along the radial axis 3.

[0065] Figure 2 is an enlarged view of the blade tip 4 of blade 1. This blade tip 4 has a blade tip surface 7 facing the inner wall of the housing (not shown) during operation.

[0066] The blade tip surface 7 is inclined at a constant angle with respect to the radial axis 3, and as a result, the blade tip surface 7 is formed substantially parallel to the inner wall of the housing.

[0067] A wear-resistant coating 8 is disposed on the blade tip surface 7. This wear-resistant coating 8 is applied to the blade tip surface 7 mainly for further improvement of gap loss. This wear-resistant coating 8 is formed as a peelable wear-resistant coating to minimize the risk of damage when contacting the inner housing. Therefore, the wear-resistant coating 8 is formed such that peeling of the wear-resistant coating 8 occurs when it contacts the inner wall of the housing during operation.

[0068] To enable the peeling of the wear-resistant coating 8, the wear-resistant coating 8 is made of a lubricant. This lubricant contains graphite and / or hexagonal boron nitride.

[0069] In order to improve the peeling characteristics of the wear-resistant film 8 and enable peeling of the wear-resistant film 8, the wear-resistant film 8 is formed to be porous. This means that a relatively large number of small cavities are formed in the wear-resistant film 8.

[0070] The cavities that form the porosity of the wear-resistant film 8 are formed as described below.

[0071] In the first step, a method for making the wear-resistant film 8 is executed on the blade surface 7. The wear-resistant film 8 is applied to the blade tip surface 7 by a thermal spraying film formation method such as APS or HVOF, where the wear-resistant film 8 is applied with a lubricant such as graphite and / or hexagonal boron nitride.

[0072] Furthermore, a polymer is added to the wear-resistant film 8 to form a porous structure of the wear-resistant film 8.

[0073] In the next step, a first heat treatment is performed before attaching the wear-resistant film 8 to harden the blade 1.

[0074] After the first heat treatment, the wear-resistant film 8 is attached, and after attaching the wear-resistant film 8, a second heat treatment is performed at a temperature at which the blade 1 is stress-relieved annealed. The temperature in this case is selected so that the polymer melts in the wear-resistant film 8 to which it has been sprayed. This results in small cavities in the wear-resistant film 8, which ultimately gives rise to the porous structure of the wear-resistant film 8.

[0075] The blade 1 can also be manufactured from steel, titanium, or composite materials.

[0076] Figure 4 shows the blade tip 4 as seen in the direction of the inlet edge 9.

[0077] The blade cross-sectional profile of blade 1 can be described by the chord line (Chord line = Skelettlinie) currently used in fluid machine structures. The wear-resistant coating 8 is arranged along the chord line here. In the first embodiment, the wear-resistant coating 8 thus covers the entire blade tip surface 7.

[0078] Blade 1 further has an inlet edge 9 and an outlet edge 10, and in the first embodiment, the wear-resistant coating 8 is arranged from the inlet edge 9 to the outlet edge 10.

[0079] In another alternative embodiment, when the wear-resistant coating 8 is arranged only in the region before the outlet edge 10, the length of the chord line is D, and d=(0.4 - 0.9)×D holds, where d is the length of the wear-resistant coating 8 along the chord line up to the outlet edge 10.

[0080] Therefore, in this alternative embodiment, it is not necessary for the entire blade 1 to be formed of the wear-resistant coating 8, and only the region before the outlet edge 10 is sufficient.

[0081] The wear-resistant coating 8 has a wear-resistant coating surface 11, and notches 12 are arranged on this wear-resistant coating surface 11.

[0082] These notches 12 are made on the wear-resistant coating surface 11, and in this way, during operation, the peeling of the wear-resistant coating 8 occurs only in the segment 13 arranged between the two notches 12. The notches 12 can thus be regarded as set breaking points when the operating conditions under which the wear-resistant coating 8 is subjected to the material peeling condition occur at the positions where the destruction of the wear-resistant coating 8 is intended.

[0083] The notches 12 are formed substantially perpendicular to the chord line here, so the manufacturing cost is reduced. Furthermore, the notches 12 are arranged at equal intervals along the chord line.

[0084] The notch 12 is formed by using a cutting method such as milling during or after the coating process.

[0085] When manufacturing the wear-resistant coating 8 on the blade tip surface 7, the wear-resistant coating 8 is continuously formed from the discharge side surface 5 to the suction side surface 6.

[0086] The wear-resistant coating 8 is formed such that contact with the inner wall of the housing occurring during operation causes peeling of the wear-resistant coating 8. As a result, a contact surface (not shown) is formed due to the peeling, and further peeling causes the contact surface to become wider in the direction of the blade leg 2 along the radial axis 3.

[0087] For this purpose, the wear-resistant coating 8 is formed on the blade tip surface 7 so as to exhibit an obtuse-angled tip 14 when viewed in cross-section.

[0088] In order to enable detection of the state of the wear-resistant coating 8, a wear-resistant coating 8 having a peeling indicator 15 is formed. For this purpose, the wear-resistant coating 8 has a slit 16, and this slit is arranged such that peeling of the wear-resistant coating 8 becomes a measurable length L of the slit, and the height of the wear-resistant coating 8 can be determined via the length L.

[0089] For this purpose, the slit 16 is provided from the edge of the discharge side surface 5 to the tip 14 as shown in FIG. 3. A side view of the peeling indicator 15 is shown in FIG. 2.

[0090] Since the wear-resistant coating 8 can be peeled off during operation, the contact surface indicated by the dashed line 17 in FIG. 2 becomes wider. This line 17 is arranged substantially parallel to the blade tip surface 7.

[0091] In this state, a measurable slit 16 of length L can be seen. Therefore, by determining L, the height H of the wear-resistant coating 8 can be detected by considering a simple triangular geometry. Thus, the state of the wear-resistant coating 8 can be inferred simply by looking at the length L of the slit 16.

[0092] Figures 5 and 6 schematically show the release indicator 15 in more detail, and FIG. 6 shows a cross-sectional view of FIG. 5 along line 17.

[0093] The curved blade tip 4 can be advantageously used for the low-pressure final-stage blades of a low-pressure steam turbine. The peripheral speed of the blade tip 4 here can be a value greater than Mach 1. As a result, it can be used in the aerodynamic regions of subsonic, transonic, and supersonic flows.

[0094] The above characteristics of the blade 1 can be varied within the blade row in a fluid machine.

[0095] The blade 1 is used in a wet steam flow.

[0096] Furthermore, the above characteristics can be changed from blade row to blade row and from turbine flow to turbine flow in relation to the mechanical structure and operating requirements.

[0097] Since the present invention can minimize the distance of the blade tip 4 from the measuring instrument by means of the wear-resistant coating 8, it can be combined with a non-contact blade vibration measurement system.

Claims

1. The blade (1) is formed along a radial axis (3) and has blade tips (4) and a blade cross-sectional profile having a discharge side surface (5) and a suction side surface (6), the blade (1) has a blade tip surface (7) facing the inner wall of the housing during operation, the blade tip surface (7) has a wear-resistant coating (8), the wear-resistant coating (8) is formed such that peeling of the wear-resistant coating (8) occurs when it comes into contact with the inner wall of the housing during operation In a blade (1) for a fluid machine, the wear-resistant coating (8) has a wear-resistant coating surface (11), and notches (12) are arranged on the wear-resistant coating surface (11), A blade (1) for a fluid machine, characterized in that.

2. The blade (1) according to claim 1, wherein the wear-resistant coating (8) is provided with a lubricant.

3. The blade (1) according to claim 2, wherein the lubricant contains graphite and / or hexagonal boron nitride.

4. The blade (1) according to claim 1, wherein the blade cross-sectional profile can be described by a chord line, and the wear-resistant coating (8) is arranged along the chord line.

5. The blade (1) according to claim 1, wherein the blade (1) has an inlet edge (9) and an outlet edge (10), and the wear-resistant coating (8) is arranged from the inlet edge (9) to the outlet edge (10).

6. The blade cross-sectional profile can be described by a chord line, the length of the chord line is D, the wear-resistant coating (8) is arranged only in the region before the outlet edge (10), where d = (0.4 to 0.9) × D, and d is the length of the wear-resistant coating (8) along the chord line to the outlet edge (10). The blade (1) according to claim 5.

7. The blade (1) according to claim 4, wherein the notches (12) are formed substantially perpendicular to the chord line.

8. The blade (1) according to claim 1, wherein the mutual spacing of the notches (12) is equidistant.

9. The blade (1) according to claim 1, wherein the wear-resistant coating (8) is continuously formed from the discharge side surface (5) to the suction side surface (6).

10. The wear-resistant coating (8) peels off due to wear with the inner wall of the housing generated during operation, and as a result, a contact surface generated by the peeling is formed. The contact surface becomes wider toward the blade leg portion (2) in the direction of the radial axis (3) due to further peeling. The blade (1) according to claim 1

11. The wear-resistant coating (8) is formed on the blade tip surface (7) so as to be a chip (14) with an obtuse angle when viewed in cross section. The blade (1) according to claim 1

12. The wear-resistant coating (8) has a slit (16). The slit is arranged so that the peeling of the wear-resistant coating (8) becomes a measurable length L of the slit (16), and the height of the wear-resistant coating (8) is obtained through this length L. The blade (1) according to claim 1

13. The wear-resistant coating (8) is applied to the blade tip surface (7) by a thermal spraying coating process such as APS or HVOF. The wear-resistant coating (8) includes a lubricant such as graphite and / or hexagonal boron nitride. The wear-resistant coating (8) is formed to have a wear-resistant coating surface (11), and a notch (12) is arranged on the coating surface (11). A method of forming a wear-resistant coating (8) on a blade tip surface (7).

14. Adding a polymer to the wear-resistant coating (8) to form a porous structure of the wear-resistant coating (8). The method according to claim 13

15. Before attaching the wear-resistant coating (8) to the blade (1), a first heat treatment is performed to harden the blade (1). After the first heat treatment, the wear-resistant coating (8) is attached. After the attachment of the wear-resistant coating (8), a second heat treatment is performed at a temperature at which the blade (1) is stress-relieved annealed. The temperature is selected so that the polymer melts in the sprayed wear-resistant coating (8), and as a result, a porous structure of the wear-resistant coating (8) is formed. The method according to claim 14

16. The blade cross-sectional profile can be described by a chord line. A front notch (12) arranged along the chord line is formed on the wear-resistant coating (8). The notch (12) is formed by a cutting method such as milling during or after the coating process. The method according to claim 13

Images