Blisk

Abstract

The invention relates to a blade-platform connection (3) and a compressor blisk (2) in a gas turbine (1), comprising a blade (10) with a blade (11) and a blade root (14), a platform (20), in particular a rotor hub platform, wherein the blade (10) is integrally attached to the platform (20), a fillet (30) at the blade root (14) and between the blade (11) and the platform (20), wherein the fillet (30) extends with a longitudinal extent (L) around the blade root (14) and a transverse extent (Q) from the platform (20) to the blade (11), wherein the fillet (30) has a variable radius (r) along the transverse extent (Q).According to the invention, such a bucket-platform connection (3) is characterized in that the variable radius (r) has, at least in a first section (36a) of the fillet (30), a minimum radius (rm in) which is spaced at least 30% of the transverse extent (Q) of the fillet relative to the platform. This improves the safety behavior in the event of damage or extreme loading.

Description

[0001] The invention relates to a blisk for a gas turbine, comprising at least one blade, with a blade and a blade root, a platform, in particular a rotor platform, wherein the blade is integrally attached to the platform, a fillet at the blade root and between the blade and the platform, wherein the fillet extends with a longitudinal extent around the blade root and a transverse extent from the platform to the blade, wherein the fillet has a variable radius along the transverse extent.

[0002] Rotor blades in turbomachinery are subject to high mechanical loads, primarily caused by centrifugal forces, vibrations, and thermal gradients. Localized overloading can lead to cracks in the blade material, which propagate into the component under the influence of mechanical and thermal stresses. Particularly in integrally bladed rotors, such as blisks (bladed disks) or blings (bladed rings), the blades and disk or ring form a single, integral or monolithic component. Furthermore, it must be considered that foreign particles can enter the turbine and, upon impact with the blades, cause damage, especially cracking. It is primarily due to the combination of these factors that cracks can propagate from the blades into the disk or ring body, potentially even leading to failure of the entire component. This crack propagation is undesirable.

[0003] To counteract this failure, so-called double fillets are known, for example, from EP 3 473 431 A1. These fillets connect two concave areas with an intermediate platform, so that crack growth occurs away from the rotor disk and into the blade. This fillet shape is not suitable for all applications. For example, boundary conditions due to aerodynamic considerations can prevent the use of such fillets.

[0004] Concave fillets with variable radius profiles are already known from EP 4 019 741 A1. The blades shown therein are part of turbine blades with an outer and an inner shroud, wherein an inner fillet connecting the blade and the inner shroud has a minimum radius in a transverse area of ​​the fillet near the platform. Furthermore, the blades have a root area that serves for connection to a rotor disk. Towards the outside, the radius essentially increases to a maximum value and then decreases again, with maximum values ​​of the radius profile being located near the blade but spaced away from it. Fillets designed in this way reduce the stress on the blades, but not on the connection between the blade and the platform.

[0005] EP 4 239 163 A1 discloses a blisk section for a gas turbine, comprising at least a first blade with a wing surface, a leading edge, a trailing edge, a blade root, a suction side and a pressure side, a platform, and a first fillet with a crack control device. The robustness of the gas turbine is improved by the fact that a first surface structure is arranged at least on the leading edge of the first blade and on the first fillet, which interacts with the crack control device for crack control and flow control.

[0006] Rotors and / or blisks are mounted on an engine shaft, rotating around an engine axis. To describe the geometries found in these engines, three principal axes are defined. The first principal axis runs in the direction of the engine's axis of rotation and is also called the longitudinal axis. This axis defines a front and a rear for the geometry under consideration, with the front being the inlet and the rear the outlet for the exhaust gas. The second axis runs along a direction perpendicular to the engine's axis of rotation and is also called the radial axis. This axis defines an outside and an inside for the engine, with the engine axis being the inside and the radial direction extending outwards from the engine axis.The third principal axis runs circumferentially perpendicular to the other two principal axes and connects the meridian sections formed by the first two principal axes. Together, the three principal axes define three principal planes: meridian planes spanned by the longitudinal axis and each radial axis; circumferential planes lying on a cylindrical surface around the axis of rotation; and cross-sectional planes of the engine, arranged perpendicular to the engine's axis of rotation.

[0007] Blades with complex spatial geometry are typically described by stacked blade profiles, whose profile area extensions do not necessarily lie in only one circumferential plane, but can also intersect the other principal planes as curved blade profiles. This design is primarily due to the aerodynamic construction of the blades and the requirements of the main flow channel, whose edges, especially the inner shroud, do not have to run parallel to the main axis. The final shape, particularly in the hub or shroud region, also deviates from this aerodynamically optimized, especially ideal, blade profile for structural mechanical reasons; in most cases, so-called fillets are arranged in this shroud region. The geometric centers of gravity of the aerodynamically optimized blade profiles form a stacking line, with the stacking line being a measure of the slope (or inclination)."pitch" represents the shovel.

[0008] Blade profiles are further described by a camber line running from the leading edge to the trailing edge of the blade profile, as well as by the boundary lines on the blade surface that encircle the blade profile and typically form a teardrop shape with suction and pressure sides.

[0009] The skeleton line is the profile centerline from the leading edge to the trailing edge of the blade and corresponds to a line connecting all the centers of circles inscribed in the blade profile. This connecting line can be described, in the simplest approximation, by a series of straight lines, but also by splines or other polynomial curves through the centers. If the blade is axially subdivided into one hundred or more parts, for example, by one hundred axially equidistant inscribed circles and their centers connected by straight lines, sufficient accuracy is achieved for the course of the skeleton line to serve as at least a first indication in determining the geometric positions of the points involved.

[0010] The leading and trailing edges can also be formed by circular segments, since sharp edges are undesirable in turbomachinery, especially in the main gas channels of these machines. However, in the following discussion, the leading and trailing edges will be reduced to a line, that is, a series of points on the blade surface. The following procedure is used to define a point on this leading edge line or trailing edge line on a profile as the leading edge point or trailing edge point, respectively. Inscribed circles can be drawn up to the leading or trailing edge of the blades. At the leading and trailing edges, the skeleton line runs from the center point of the leading edge circle or the center point of the trailing edge circle, respectively, directly towards the leading or trailing edge.To a good approximation, this direction corresponds to the direction of the line connecting the penultimate and last centers of the respective inscribed circles, because a continuous and converging skeletal line can be expected in this region if the centers of the circles are sufficiently close together, that is, if the spacing of the considered geometric points is sufficiently fine. This definition serves to determine the leading and trailing edges, particularly when the blade geometry is unknown, i.e., when data on the blade geometry is not available from the design. A straight line spanning from the leading edge to the trailing edge is called the blade chord. Unless otherwise specified, references to the chord length are to be understood as surface points of the structure above or below projected onto the chord length, respectively, in the circumferential direction.

[0011] For determining the quantitative dimensions, it is considered sufficiently approximate if the position of the points to be determined for the corresponding blade size (axial extent, radial extent, circumferential extent) can be determined to an accuracy of at least one-twentieth of the blade's extent in the corresponding spatial direction. If there are indications that a finer resolution would be necessary, or if the geometries under consideration closely approximate this description and the values ​​specified in the claims, this approximation should be refined accordingly.

[0012] The maximum thickness of an airfoil is defined as the largest possible diameter of a circle between the suction side and pressure side of the airfoil, with the center of this largest circle located on the wing's skeletal line. A surface connecting to a rotor hub or rotor shroud is called a blade root.

[0013] Since efforts are made to minimize turbulence and thus losses in engines, and to avoid or distribute unwanted stresses in the material of the blades and the rotor platform (also referred to as hub, rotor hub, shroud, or inner shroud) so that these unwanted stresses are harmless, the transitions from the blade to the platform in the area of ​​the blade root are designed to be as smooth as possible by incorporating a fillet. This results in geometries that deviate from the aerodynamically ideal or optimized blade profile, meaning that the exact position of the leading and trailing edges may no longer be unambiguously determined by the procedure described above, as the circular shapes of the blade tips at the leading and trailing edges are disrupted by the presence of a fillet, i.e., a blade shape that deviates from an aerodynamically optimized form.To complicate matters further, the blade profiles calculated during the design process are not defined along a cylindrical circumferential plane, but can intersect it. Furthermore, in the area of ​​the blade root, the platform, hub, or endwall contouring of the rotor body can be adapted to the flow, which in turn makes it more difficult to locate the start of the fillet.

[0014] When determining the dimensions of a blade to be measured, especially a connecting structure such as a fillet, the surfaces of the blade and the platform, as well as the transition between the blade and the platform (the fillet), can be measured optically, for example. However, the exact position of the leading and trailing edges, the precise connection area from the aerodynamically ideal airfoil to the fillet, and the connection area from the fillet to the rotor disk platform are still difficult to determine. Internal dimensions are generally unknown, and the surface transitions from the blade to the fillet (hereinafter referred to as the blade connection) and further to the platform of the blisk or rotor disk (hereinafter referred to as the platform connection) are usually continuous due to the aerodynamic shape of the blade.This means that determining a precise transition point without knowledge of the flow and the design point of the blades is also difficult.

[0015] In order to enable a sufficiently good approximation of the quantitative dimensions of blades to be measured when the aerodynamic conditions and design considerations are unknown, sections through the blade are used that lie in one of the main planes, whereby the distances for the approximate determination of the geometries under consideration are staggered along the three main axes by at least one hundredth of the greatest longitudinal extent of the blade, the greatest radial extent of the blade and the greatest circumferential extent of the blade.In other words, a grid (analogous to a grid in a finite element method, abbreviated FEM) is laid with a fineness of at least twenty steps in all three principal directions, namely between the foremost and rearmost point of the blade, the innermost and outermost points of the blade, and between the points of the blade that are furthest apart in the circumferential direction.

[0016] The greatest circumferential and axial extensions of the blade are to be expected at the platform, because that is where the connection area, the fillet, from the blade root to the rotor body takes place and the blade root has the greatest extent.

[0017] To determine the axial start and end points, i.e., the attachment points, of the fillet in the axial direction, the contour of the surface in the area of ​​the platform must be considered. If there is a depression in the platform adjacent to the attachment area in or against the axial direction, then the attachment point of the fillet to the platform will be an inflection point of the surface.

[0018] If the platform has a raised section in or against the axial direction, the attachment point will be a minimum radial distance between the surface and the rotor axis of rotation. If the platform has a straight extension in the plane under consideration, the attachment point will be defined by the beginning of a curve.

[0019] To determine the circumferential start or end point of the fillet, the surface contour in the platform area must be considered. A transition from the platform surface to a connecting structure, such as a fillet, can be expected in an area where the surface curvature changes. If a depression exists adjacent to the expected transition area in the circumferential direction, the transition point of the fillet onto the platform will be an inflection point of the surface. If there is a raised section of the platform in the circumferential direction, the transition point will be a minimum radial distance of the surface from the rotor axis. If the platform extends in a straight line in the considered plane, the transition point will be defined by the beginning of a curve.

[0020] The axial start and end points of the fillet, as well as the circumferential start and end points of the fillet, are points that each have a radial distance from the axis of rotation of the turbomachine. A circumferential plane can be defined as a cylindrical surface over the point with the smallest radial distance. This surface subsequently defines an auxiliary cover band of the platform and serves as a reference point for determining the radial extent of the blade, including, to a first approximation, its maximum radial extent.

[0021] The greatest radial extent of the blade can then be determined, as an alternative, by forming another cylinder around the engine's axis of rotation, whose outer surface intersects only a single point, namely the outermost point of the blade.

[0022] From these maximum dimensions, the scales or grids for determining all blade dimensions as described above can be derived, in particular grids whose edge lengths are each one-twentieth or less of the maximum longitudinal, radial, and circumferential dimensions of the blade. The resolution of the grids should depend on the dimensions under consideration in order to be able to make a comparison with these dimensions with sufficient confidence.

[0023] To determine the attachment point of the airfoil to a connecting structure, for example, a fillet, or of the airfoil to the platform under unknown flow conditions or without knowledge of the underlying structural mechanics, the airfoil is enclosed in a grid subdivision of meridian planes, cross-sectional planes, and circumferential planes, as described above. Then, to determine the attachment points of the airfoil to the connecting structure, those points on the airfoil surface in the region where the start of the connecting structure is expected are identified as having a greater change in curvature compared to at least one radially outer and inner neighboring point along the surface.The connection points between the attachment structure and the platform are determined analogously, whereby both the axially and circumferentially adjacent points on the surface of the blade and the platform, respectively, are used to compare the change in curvature. After determining the connection areas, the measured surfaces as well as the beginning and end of the attachment structure in the radial direction should now be known. In the respective circumferential plane of the leading and trailing edges, an extension line, also called an extrusion line, can be generated from the straight line used to determine the leading and trailing edges. From this extension line, a line can be projected radially onto the attachment structure up to the blade root, which will subsequently serve as the leading and trailing edges on the attachment structure.In cases where the blades and their attachment structures are intersected in the axial direction due to a geometric limitation of the disk, there can be two leading or trailing edges in this area, from which the corresponding other parameters for describing the attachment structure are to be determined. Along each of the attachment areas, at least twenty grid points can be placed between the leading and trailing edges, with two opposite points of the two attachment areas located on either the suction side or the pressure side being connected along the measured surface, thus enabling a correspondingly fine subdivision of the attachment structure. From this, the extents of the areas of the attachment structure described in this application, i.e., the fillet, and its variants, can be determined at least to a first approximation.

[0024] The methods described above for determining the dimensions and positions are initial approximations for classifying an unknown blade. If necessary, a further verification should be carried out, ideally using the precise geometry and knowledge of the connections. More accurate results can be obtained by using actual dimensions, for example, from engineering drawings.

[0025] The object of the invention is to provide a blisk whose safety behavior in the event of damage or extreme stress is improved.

[0026] This task is accomplished according to the invention by a blisk according to claim 1.

[0027] Such a blisk according to the invention in a gas turbine comprises at least one blade with a blade and a blade root, a platform, in particular a rotor disk platform, wherein the blade is integrally attached to the platform, a fillet arranged at the blade root and between the blade and the platform, wherein the fillet transitions into the blade at a blade joint and into the platform at a platform joint. The fillet extends longitudinally around the blade root and transversely from the platform joint on the platform to the blade joint on the blade, wherein the fillet has a variable radius along the transverse extent.The fillet, comprising at least one blade, the platform and the corresponding connection, forms a blade-platform connection, whereby different blade-platform connections may also be provided on a blisk.

[0028] The problem is solved by the blisk according to the invention in that the variable radius has a minimum radius, at least in a first section of the fillet, which is spaced at least 15%, preferably at least 30%, away from the platform along the transverse extent of the fillet. This distance to the platform advantageously prevents cracking in the platform and thus the rotor disk in the event of damage. Such a distance of the minimum radius to the platform therefore constitutes a crack control device. This advantageously introduces a first decoupling means of static and dynamic stresses in the blade into the geometry. This significantly reduces the risk of disk failure. It can be provided that the distance to the platform is at least 35%, in particular at least 40%, and most preferably at least 45% of the transverse extent of the fillet.This allows for a favorable influence on crack propagation into the blade and away from the rotor disk in the event of blade damage. Additionally, the minimum radius can be designed not only linearly but also as a band. The minimum radius can be constant over a central portion of the transverse extent, at least in the first section. Similarly, the variable radius can be considered a function that may also exhibit constant values ​​along certain sections. The resulting structural band of a minimum radius can extend along the longitudinal extent of the fillet, with the fillet itself exhibiting a radius with a constant minimum value or a straight line along the transverse extent within this structural band. The first section of the fillet can comprise 5% of the fillet's longitudinal extent. However, it is also possible for the first section to be larger or smaller.The first section can comprise 2%, 3%, or 4% of the longitudinal extent of the fillet, but it can also comprise 10%, 15%, or 20% of the longitudinal extent of the fillet. Furthermore, at least in the first section, the ratio of the minimum radius to the maximum radius on the blade and / or the platform is at least 1.5, particularly at least 3, and most preferably at least 5. Such a radius distribution along the transverse extent in at least one section along the longitudinal extent of the fillet allows for a controlled increase in stress to influence cracking.

[0029] Further features of the invention are described in the dependent claims and the drawings. These features represent further aspects of the crack control device described above.

[0030] In a preferred embodiment of the invention, the minimum radius along the transverse extent of the fillet can be spaced at least 30% of the transverse extent from the blade. This advantageously ensures that even damage occurring at a low radial height of the blade does not lead to crack propagation into the disk, but rather propagates within the blade. This advantageously introduces a second decoupling mechanism for static and dynamic stresses in the blade geometry. It can be provided that the distance to the blade is at least 35%, in particular at least 40%, and most preferably at least 45% of the transverse extent of the fillet. The resulting structure of the fillet radius along the transverse extent is trough-shaped or U-shaped.

[0031] In another preferred embodiment of the blisk, the fillet is completely concave along its transverse extent, at least in the first section. By eliminating convex or straight areas, the component stresses can be distributed favorably, resulting in reduced aerodynamic effects and lower mechanical stress peaks.

[0032] Furthermore, it can be provided that the radii of the fillet along its transverse extent are also completely concave, at least in the first section. That is, the radii have a monotonically increasing first derivative along the transverse extent with a zero crossing at the minimum radius.

[0033] Furthermore, in a further embodiment of the blisk, the minimum radius in at least the first section can be 5 mm or less, in particular 3 mm or less, and most preferably 2 mm or less. Such small radii allow for targeted control of the material stresses, thus advantageously reducing or preventing crack propagation into the disk. This provides a particularly advantageous third decoupling element, allowing static and dynamic stresses to be controlled separately. It can be provided that the minimum radius is at most 5 mm, and in particular at most 4 mm. This means that the remaining radius profile has larger values, allowing for a particularly good distribution of surface stresses.

[0034] In a further embodiment of the blisk, the variable radius exhibits a maximum radius at the blade and / or the platform, at least in the first section. Specifically, the variable radius along the transverse extent of the fillet displays a monotonically decreasing profile between the maximum and minimum radii. This allows for a blade connection with a maximum radius between the fillet and the blade, and / or a platform connection with a maximum radius between the fillet and the platform. Because the maximum radius is located at the blade connection and / or the platform connection, there are no local stress concentrations along the transverse extent of the fillet that could contribute to component failure.

[0035] In a supplementary or alternative embodiment of the blisk, wherein the blade has a blade chord extending from a leading edge to a trailing edge, the ratio of the maximum radius to the minimum radius on the blade and / or on the platform can be maximized at a maximum point of the fillet located between 5% and 95% of the blade chord. The projected distance of this maximum point on the blade chord to the leading edge is at least 5% of the blade chord length. This can favorably influence crack propagation into the blade and away from the rotor disk in the event of blade damage. The distance to the platform can be at least 5%, 10%, 15%, 20%, preferably at least 25%, 30%, 35%, particularly at least 40%, or most preferably at least 45% of the transverse extent of the fillet.It can be provided that the distance to the blade is at least 5%, 10%, 15%, 20%, preferably at least 25%, 30%, 35%, particularly at least 40%, or most preferably at least 45% of the transverse extent of the fillet. It can be provided that the maximum point is located in the first section.

[0036] In a further embodiment, the fillet may have a second section spaced apart from or adjacent to the first section, wherein, at least in the second section, the ratio of the maximum radius to the minimum radius on the blade and / or on the platform is at most 1.5, in particular at most 1.2, and most preferably at most 1.1. In particular, this allows for the targeted creation of areas that can withstand one of the static or dynamic stresses. This advantageously provides a fourth decoupling means that allows static and dynamic stresses to be controlled separately from one another.

[0037] According to another aspect of the invention, the ratio of the maximum radius (r max ) to the minimum radius (r min ) on the suction side can be larger than on the pressure side of the blade; in particular, the ratio on the suction side can be on average twice as large, preferably three times as large, as on the pressure side.

[0038] In a preferred further embodiment, the first section extends from a leading edge to a trailing edge of the blade. However, it is also possible for the first section to extend between 30% and 70% of the blade chord of the fillet. Furthermore, other or smaller local sections are proposed that exhibit the properties of the first section. For example, such a section can be located at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45% of the chord length from the leading edge. Similarly, such a section can also be located at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45% of the chord length from the trailing edge.

[0039] Furthermore, in another embodiment, the first section can be additionally arranged on the pressure side and / or the suction side of the blade. Arranging the first section on the suction and / or pressure side can be used to specifically compensate for static stresses resulting from blade tilt. This provides a fifth decoupling means that allows static and dynamic stresses to be controlled separately.

[0040] In a further advantageous embodiment, the blisk can be designed such that the first section is arranged on the suction side of the blade and the second section is arranged on the pressure side of the blade. This opposing arrangement of the two different sections of the fillet allows stresses arising from blade tilt to be particularly effectively mitigated.

[0041] Another preferred embodiment of a blisk according to the invention in a gas turbine, which may be claimed independently, comprises at least one blade with a blade and a blade root, a platform, in particular a rotor disk platform, wherein the blade is integrally attached to the platform, and a fillet arranged at the blade root and between the blade and the platform, wherein the fillet transitions into the blade at a blade joint and into the platform at a platform joint. The fillet extends longitudinally around the blade root and transversely from the platform joint on the platform to the blade joint on the blade, wherein the fillet has a variable radius along the transverse dimension.The fillet, comprising at least one blade, the platform and the corresponding connection, forms a blade-platform connection, whereby different blade-platform connections may also be provided on a blisk.

[0042] The problem is solved by a composite fillet. Here, the radial offset / distance of the blade connection from the platform connection ABdist is greater than the circumferential offset of the platform connection relative to the blade connection EBdist. The more precise definition of the boundary curves (in addition to the already filed patent for qualitative radius profiles) represents a further means of influencing the static and dynamic load distribution of the component. This element also contributes to an increase in damage tolerance (preventing crack growth into the disk).

[0043] During the structural engineering design work, it was shown that so-called "composite blends" have a positive effect on the separation of static and dynamic loads.

[0044] In addition to the radius profiles of the fillet contour, the definitions of the rotor-side boundary curve (Endwall Boundary / platform connection) and the blade-side boundary curve (Airfoil Boundaryn / blade connection) are also of crucial importance.

[0045] According to the present part of the invention, the boundary curves can be defined parametrically based on the maximum profile thickness (tmax0) of the blisk blade or the alrfoil.

[0046] The platform connection / endwall boundary can be created by a rolling ball, a variable rolling ball, or an offset of the blade surface by a constant / variable value.

[0047] The range of values ​​for the area to be protected is EBdist = 0.70 ... 1.35 * tmax0

[0048] The blade connection / airfoil boundary can be created by a rolling ball, a variable rolling ball, or an offset of the annular space surface by a constant / variable value.

[0049] The range of values ​​for the area to be protected is ABdist = 0.8 ... 2.0 * tmax0

[0050] Additionally, the requirement ABdist > EBdist applies in all areas to guarantee an elliptical shape of the composite blend.

[0051] In other words, the radial offset / distance of the blade connection from the platform connection can be in a range ABdist = 0.8 ... 2.0 * tmax0 and the circumferential offset of the platform connection relative to the blade connection EBdist can be 0.70 ... 1.35 * tmax0, where ABdist is greater than EBdist.

[0052] Another aspect of the invention relates to a blisk in a gas turbine, comprising at least one blade with a blade and a blade root, a platform, in particular a rotor disk platform, wherein the blade is integrally attached to the platform, and a fillet connecting the blade to the platform at the blade root and between the blade and the platform. The fillet extends longitudinally around the blade root and transversely from the platform to the blade, the fillet having a variable radius along the transverse extension. This further blade-platform connection achieves the objective in that the fillet provides a decoupling means, in particular a structural and / or geometric one, for static and dynamic stresses occurring in the blade-platform connection during operation.

[0053] The invention is explained in more detail with reference to the following drawings and some preferred embodiments of the invention. Fig. 1 shows an embodiment of a compressor blister according to the invention. Fig. 2a shows a first embodiment of a blade-platform connection according to the invention on a suction side of a blade. Fig. 2b shows the first embodiment of a blade-platform connection according to the invention with exemplary radius profiles. Fig. 3a shows a second embodiment of a blade-platform connection according to the invention on a pressure side of a blade. Fig. 3b shows the second embodiment of a blade-platform connection according to the invention with exemplary radius profiles.

[0054] In Fig. 1 Figure 1 shows a segment of an embodiment of a blisk 2 according to the invention in perspective. The blisk 2 is arranged in a gas turbine 1 for an aircraft engine, wherein the gas turbine 1 is located in the Fig. 1 The structure is indicated by its three main axes Ax, R, and U. These three main axes run axially (Ax), radially (R), and circumferentially (U). The blisk 2 serves as a rotor in a compressor of gas turbine 1.

[0055] The blisk 2 comprises a blisk disk 4 and a plurality of blades 10, referred to as rotor blades, arranged on the blisk disk 4. The blades 10 are spaced apart from one another in the circumferential direction U on a platform surface 22 of a platform 20 of the blisk disk 4. The blades 10, the platform 20, and a fillet 30 connecting each blade 10 to the platform 20 together form a blade-platform connection 3. The blades 10 have a blade 11 for absorbing aerodynamic forces, a blade root 14 for attachment to the platform surface 20, and a blade tip 15 pointing towards an annular space wall of the gas turbine 1. The blisk 2 rotates in the circumferential direction U, with a suction side 16 of each blade 10 facing opposite to the direction of rotation and a pressure side 17 of each blade 10 facing in the direction of rotation of the blisk 2.The suction and pressure sides 16, 17 each extend from a front edge 12 to a rear edge 13 of the respective blade 10.

[0056] The Blisken 2 exhibit a particularly robust crack growth behavior, whereby cracks can hardly or not at all penetrate the disk, but rather the blades 10 are separated from the platform 20 beforehand.

[0057] The bucket-platform connections 3 are described below using two exemplary embodiments. Fig. 2a , 2b and Fig. 3a , 3b explained in more detail.

[0058] Fig. 2a Figure 1 shows a first embodiment of a blade-platform connection 3 according to the invention in a spatial, schematic representation on a suction side 16 of a blade 10. The blade-platform connection 3 comprises the blade 10, a platform 20, and a fillet 30, which connects the blade 10 and the platform 20. The blade 10 has, as shown in Figure 1, a Fig. 1 A bucket blade 11 and a bucket root 14 are described. The fillet 30 surrounds the bucket root 14 along its longitudinal extent L and extends transversely to its longitudinal extent L along its transverse extent Q from the platform 20 to the bucket blade 11.

[0059] In this embodiment, the fillet 30 extends around and from a leading edge 12 to a trailing edge 13 of the blade 10, with a longitudinal extent L of the fillet 30 defined from the leading edge 12 to the trailing edge 13. In this embodiment, the trailing edge 13 is formed by a section of the blisk 2, so that the blade 10 has two trailing edges 13 in a region of the blade root 14, which converge at the blade 11. The fillet 30 therefore terminates at the trailing edges 13 and does not extend around them. The fillet 30 is connected to the blade 10 or the blade 11 by a blade connection 32 and to the platform 20 by a platform connection 34. In its transverse extent Q, the fillet 30 is concave over its entire longitudinal extent L and has a variable radius r.

[0060] The variable radius r is a minimum radius rmin in a central region 38 of the fillet 30 along the transverse extent Q. Conveniently, the longitudinal extent L is measured at the height of the minimum radius rmin of the fillet. The central region 38 is band-shaped and extends around the blade 10, with the minimum radius rmin potentially extending at a point, over part, or across the entire width of the central region 38. Thus, a surface with the minimum radius can be formed. The central region 38 is at least 20%, 25%, or 30% of the transverse extent Q of the fillet 30 away from the blade joint 32. Furthermore, the central region 38 is at least 30% of the transverse extent Q of the fillet 30 away from the platform joint 34. In the longitudinal extent L of the fillet 30, the minimum radius r min is spaced from the leading edge 12 at least 5%, 10%, 15%, 20%, 25% or 30% of the longitudinal extent L of the fillet 30.Furthermore, the minimum radius r min is spaced from the trailing edge 13 at least 10%, 15%, 20%, 25% or 30% of the longitudinal extent L of the fillet 30.

[0061] This means that the minimum radius r min is advantageously located in a central area of ​​the fillet 30 on the suction side 16 of the blade 10. This enables the targeted separation of static and dynamic stress maxima and is therefore beneficial for the damage tolerance of the component.

[0062] Fig. 2b Figure 1 shows the first embodiment of the bucket-platform connection 3 according to the invention, with exemplary radius profiles r shown. For the sake of clarity, not all reference numerals are shown again.

[0063] In the present embodiment, the variable radii r exhibit a maximum radius rmax along the longitudinal extent L in all cases, both on the outside and inside of the bucket transition 32 and the platform transition 34. Combined with the minimum radius rmin in the central region 38, this results in a trough-shaped or U-shaped transverse profile of the fillet 30 along its longitudinal extent L.

[0064] Both in Fig. 2a as well as in Fig. 2b A first section 36a of the fillet 30 is shown, which may have the aforementioned properties. In particular, at a maximum point M, the ratio of the larger maximum radius rmax to the minimum radius rmin may be maximal. The maximum point M, projected from the leading edge 12 and / or the trailing edge 13 onto a chord S of the blade 10 at the radial height of the maximum point M, may be at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45% away. The first section 36a may be located at a position on the fillet 30 that is closest to an adjacent blade 10 on the blisk 2.

[0065] In the first embodiment in Fig. 2a and 2bThe ratio of the maximum radius rmax to the minimum radius rmax decreases along the longitudinal extent L towards the leading edge 12 and the trailing edge 13. In this embodiment, the trough shape or U-shape is maintained between the leading edge 12 and the trailing edge 13 of the blade, but is less pronounced at these points, thus advantageously allowing for improved force transmission in the front and rear regions of the blade 10. To achieve this, at least one of the two maximum radii rmax can decrease towards the leading edge and / or the trailing edge, particularly by a monotonically decreasing curve. Alternatively or additionally, the minimum radius rmin can increase towards the leading edge 12 and / or the trailing edge 13.

[0066] The embodiment shown avoids further stress concentrations in statically highly stressed areas, for example in the fillet between the blade and the platform, by introducing a larger radius.

[0067] Fig. 3a and 3b Figure 1 shows a second embodiment of a blade-platform connection 3 according to the invention in a spatial, schematic representation on a suction side 16 of a blade 10. Only differences from the first embodiment are described below. Further details and differences from the first embodiment may become apparent from the figures.

[0068] On the pressure side 17 of the blade 10, a first section 36a with the properties described above for the first embodiment is arranged in a front region of the blade-platform connection 3 in close proximity to the leading edge 12 of the blade 10. The distance to the leading edge 12 along the longitudinal extent of the fillet is 20% or less. This means that a maximum ratio between the maximum radius rmax and the minimum radius rmin is located near the leading edge 12.

[0069] A second section 36b of the fillet 30, with properties differing from those of the first section 36a, is arranged in a central region along the longitudinal extent L of the fillet 30. This second section 36b is located on the pressure side and has a ratio of the maximum radius rmax to the minimum radius rmin of less than 1.5. The radius along the transverse extent Q of the fillet 30 is particularly preferably constant in the second section 36b. The second section 36b can preferably be projected onto the blade chord S and spaced at least 30% of the blade chord length from the leading edge 12 and / or the trailing edge 13. This advantageously results in a uniform radius profile in the center of the blade along the longitudinal extent L of the fillet 30.

[0070] It may be provided that a third section 36c of the fillet is provided in a rear area of ​​the fillet 30 near the trailing edge 13 of the blade 10, which is similar to the first section but has a lower ratio of maximum radius r max to minimum radius r min.

[0071] Finally, in a further embodiment, it can be provided that a fillet 30 according to the first embodiment is arranged as shown in the illustrations in the Fig. 2a and 2b , which describes the fillet flow on the suction side 16 of the blade 10 and that a fillet 30 according to the second embodiment according to the illustrations of the Fig. 3a and 3bThe first section, which describes the fillet path on the pressure side 17, is combined. The first section can be arranged at the same height or with a maximum deviation of 10% along the chord S of the blade 10 as the second section 36b. This directs crack propagation to one side of the blade, thus advantageously reducing the probability of a disc crack on the more heavily loaded pressure side 17 of the blade 10. Bezugszeichenliste

[0072] 1 Gas turbine 2 Blisk 3 Blade platform connection 10 Bucket 11 Bucket blade 12 Leading edge 13 Trailing edge 14 Bucket foot 15 Bucket tip 16 Suction side 17 Pressure side 20 Platform 22 Platform interface 30 Fillet 32 ​​Bucket connection 34 Platform connection 36 First section 36 Second section 38 Middle area r variable radius r min minimum radius r max maximum radius S blade chord M maximum point

Claims

1. Blisk (2), in particular a compressor blisk, for a gas turbine (1), comprising at least one blade (10) having an airfoil (11) and a blade root (14), a platform (20), the blade (10) being integrally attached to the platform (20), a fillet (30) which is arranged at the blade root (14) and between the airfoil (11) and the platform (20), the fillet (30) transitioning into the airfoil (11) at a blade connection (32) and the fillet (30) transitioning into the platform (20) at a platform connection (34), the fillet (30) extending with a longitudinal extent (L) around the blade root (14) and with a transverse extent (Q) from the platform (20) to the airfoil (11), the fillet (30) having a variable radius (r) along the transverse extent (Q), wherein, in a first portion (36a) which is a region of the fillet (30) that is arranged along the longitudinal extent (L) of the fillet (30), the variable radius (r) along the transverse extent (Q) has a minimum radius (r min) which, in the transverse extent (Q) of the fillet (30), has a distance from the platform (20) of at least 15%, preferably at least 30%, of the transverse extent (Q) of the fillet (30), characterized in that the variable radius (r), at least in the first portion (36a), has a maximum radius (rmax) on the airfoil (11) and / or on the platform (20); and in that, at least in the first portion (36a), a ratio of the maximum radius (rmax) to the minimum radius (rmin) on the airfoil (11) and / or on the platform (20) is at least 1.5, in particular at least 3, particularly preferably at least 5.

2. Blisk (2) according to claim 1, characterized in that the minimum radius (rmin) along the transverse extent (Q) of the fillet (30) is spaced apart from the airfoil (11) by at least 30% of the transverse extent (Q).

3. Blisk (2) according to either of the preceding claims, characterized in that the fillet (30) is completely concave along its transverse extent (Q) at least in the first portion (32a).

4. Blisk (2) according to any of the preceding claims, characterized in that the minimum radius (rmin), at least in the first portion, is 5 mm or less, in particular 3 mm or less, particularly preferably 2 mm or less.

5. Blisk (2) according to any of the preceding claims, characterized in that the variable radius (r) has a monotonically falling gradient between the maximum radius (rmax) and the minimum radius (rmin).

6. Blisk (2) according to any of the preceding claims, the blade having a blade chord (S) which extends from a leading edge (12) to a trailing edge (13), characterized in that a ratio of the maximum radius (rmax) on the airfoil (11) and / or on the platform (20) to the minimum radius (rmin) is maximum at a maximum point (M) of the fillet (30) that is arranged between 30% and 70% of a blade chord (S).

7. Blisk (2) according to any of the preceding claims, characterized in that the fillet (30) has a second portion (36b) which is spaced apart from or adjacent to the first portion (36a), a ratio of a maximum radius (rmax) to the minimum radius (rmin) on the airfoil (11) and / or on the platform (20), at least in the second portion (36b), being at most 1.5, in particular at most 1.2, particularly preferably at most 1.1.

8. Blisk (2) according to any of the preceding claims, characterized in that the first portion (36a) extends from a leading edge (12) to a trailing edge (13) of the blade (10).

9. Blisk (2) according to any of the preceding claims, characterized in that the first portion (36a) is arranged on the pressure side (16) and / or the suction side (17) of the blade (10).

10. Blisk (2) according to claim 8, characterized in that the first portion (36a) is arranged on the suction side (16) of the blade (10) and the second portion (36b) is arranged on the pressure side (17) of the blade.

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