Blade with simplified root geometry

Abstract

The invention relates to a blade (01) of a compressor, having a blade aerofoil (02) and a blade root (03). The latter comprises a retaining portion (04), which extends along a blade axis (11), a connection portion (05), which is arranged between the blade aerofoil (02) and retaining portion (03), and a base portion (06) on the side facing away from the blade aerofoil (02). The retaining portion (04) is delimited laterally by planar, inclined retaining surfaces (14) located opposite one another, and the base portion (06) is delimited by planar, inclined base surfaces (16) located opposite one another. Provision is also made for the underside to have on it a planar fitting surface (08) at a distance from the ends of the blade root.

Description

Description TITLE Shovel with simplified foot geometry TECHNICAL FIELD

[0001] The invention relates to a blade of a turbomachine with a blade airfoil and a blade root, wherein the blade root has a geometry which enables simple manufacture. BACKGROUND TO THE INVENTION

[0002] Turbomachines of this type feature alternating rows of guide vanes and rows of rotor blades. The guide vanes are arranged vertically in the casing, while the rotor blades are mounted on a rotor. Typically, the guide vanes and rotor blades are attached individually, allowing for simpler manufacturing and the use of the optimal material and manufacturing process for both the blades and the blade-supporting components.

[0003] The blades are typically secured in specific retaining grooves via blade roots. In the simplest case, grooves similar to a dovetail groove are used. The blade has a radially extending blade airfoil and a blade root, which, in the simplest case, has opposing retaining surfaces extending along the retaining groove, depending on the shape of the retaining groove. The retaining surfaces are inclined relative to the radial direction.

[0004] Typically, generous roundings are provided on the blade root on the side facing away from the blade. To ensure a seat in the retaining groove with as little play as possible, a central shoulder is provided on the underside of the blade root facing away from the blade. This allows for the blade root to be installed in the retaining groove with as little play as possible. The rounded edges, in conjunction with the shoulder, ensure a small amount of clearance at the rounded edges.

[0005] Although the well-known designs of shovels with simple foot geometries have proven themselves, their production requires special tools and increased effort.

[0006] A simpler geometry for a blade root reveals the EP 2569514 B1 . In this case, rounding is omitted and instead the blade root is provided with inclined, flat surfaces on both sides.

[0007] Furthermore, a clearance-free installation of the blade root in the retaining groove is preferred. For this purpose, the simplified blade root design provides a groove on the underside of the blade root and a groove on the groove base, corresponding to the retaining groove. With the blade root installed, a C-shaped clamping element is inserted into the space between the groove on the underside and the groove base.

[0008] Although this ensures that the blade root is securely positioned in the retaining groove and also enables axial fixation in an inclined orientation, the limited installation space between two rows of blades makes assembly and disassembly of the necessary clamping elements more difficult.

[0009] Another disadvantage is the effort required to produce the groove on the underside and the groove base, particularly taking into account the tolerance to be maintained, particularly in the direction of the blade root. SUMMARY OF THE INVENTION

[0010] The object of the present invention is therefore to enable a more cost-effective production and assembly / disassembly of the blades.

[0011] The stated object is achieved by an embodiment according to the teaching of claim 1. Advantageous embodiments are the subject of the subclaims.

[0012] The blade according to the invention comprises a radially extending blade airfoil and a blade root. The blade root extends along a blade axis and has a holding section extending over a profile length. On the side facing away from the blade airfoil, it has a base section and a connecting section, which represents the connection between the holding section and the blade airfoil. The holding section defines a root width of the blade root transversely to the blade axis.

[0013] The holding section is bounded on both sides by planar, mutually inclined holding surfaces, opposite each other (perpendicular to the blade axis). Similarly, the base section is bounded on both sides by planar, mutually inclined base surfaces.

[0014] The manufacturing costs with a simpler assembly are achieved by providing a planar mating surface on the side of the base section facing away from the blade, spaced from the opposite ends of the blade root. DESCRIPTION OF THE INVENTION

[0015] A generic blade is used in a turbomachine. The turbomachine comprises a rotor and a stator, thus defining a rotor axis and a radial direction perpendicular to the rotor axis. The blade comprises an airfoil and a blade root arranged at one end of the airfoil, with the airfoil extending in the radial direction.

[0016] Furthermore, it can be provided that at the other end of the blade opposite the blade root a second device for mounting the Blade is present. An airfoil does not usually have straight surfaces, but consists of curved surfaces. Thus, an airfoil extends in both the axial and tangential directions. At one end of the airfoil is the blade root, which is used for attachment to the turbomachine. The blade root defines a blade axis. This extends transversely to the radial direction in the tangential direction and / or in the direction of the rotor axis. Measured in the direction of the blade axis, the blade root has a profile length. Measured transversely to the blade axis and transversely to the radial direction, the blade root has a blade width.

[0018] The blade root, in turn, comprises a holding section extending in the direction of the blade axis. The holding section serves in particular to fix the blade in the turbomachine. For this purpose, opposing holding surfaces extending along the blade axis are arranged on the holding section. Accordingly, the holding section is delimited by the holding surfaces in a direction transverse to the blade axis and transverse to the radial direction. For the generic embodiment, it is provided that the holding surfaces are planar, i.e. flat, and are inclined with respect to the radial direction. The holding angle resulting between the holding surfaces opens away from the blade airfoil.

[0019] Preferably, the holding angle between the two opposing holding surfaces is between 25° and 60°. A holding angle of at least 35° is particularly preferred. In contrast, the holding angle should particularly preferably be no more than 50°.

[0020] Advantageous fixation in the turbomachine while ensuring the necessary stability is advantageously achieved when the radial height of the holding section is at least 0.3 times the root width. This results in a sufficient cross-section for power transmission to the rotor blade and a sufficient size of the holding surface. It is particularly preferred if the radial height of the holding section is at least 0.35 times the root width.

[0021] In contrast, an oversized blade root should be avoided. Therefore, it is advantageous if the radial height of the holding section is no more than 0.6 times the root width. It is particularly advantageous if the radial height of the holding section corresponds to a maximum of 0.5 times the root width.

[0022] Furthermore, the blade root comprises a base section which is arranged on the side of the holding section facing away from the blade and extends equally along the blade axis.

[0023] For further analysis, the end of the blade root on both opposite sides in the direction of the blade axis is considered to be the end of the holding section and the base section. Any other sections of the blade root that may extend beyond the end of the blade root, i.e., the end of the holding section and the base section, are initially irrelevant.

[0024] Furthermore, it is provided that the base section is delimited by two opposing base surfaces extending along the blade axis, which are also planar, i.e., flat. The base surfaces are thus arranged opposite one another on the base section and extend along the blade axis. The base surfaces are aligned at an angle to one another.

[0025] By omitting the otherwise standard rounding at the blade root, the blade can be manufactured more simply. Any clearance that may arise at the blade root during installation in the turbomachine is accepted, thus achieving a cost advantage.

[0026] A cost-effective and at the same time play-free installation is made possible according to the invention by the blade root having a fitting surface on the base section on the side facing away from the blade. The fitting surface is designed as a planar, i.e. flat, surface. It is intended that the fitting surface does not extend in the direction of the blade axis to the opposite ends of the blade root. Consequently, opposite transverse edges of the mating surface are spaced from the respective corresponding end of the blade root. Preferably, a base angle between the two opposite base surfaces has a value between 60° and 120°. A base angle of at least 70° is particularly preferred. In contrast, the base angle should particularly preferably be at most 100°. Advantageous production of both the blade root and the corresponding receptacle in the turbomachine is advantageously enabled if the radial height of the base section is at least 0.15 times the root width. It is particularly preferred if the radial height of the base section is at least 0.2 times the root width.

[0029] An oversized blade root should be avoided. Therefore, it is advantageous if the radial height of the root section does not exceed 0.35 times the root width. It is particularly advantageous if the radial height of the root section corresponds to a maximum of 0.3 times the root width. It is equally advantageous if the width of the base section on the side facing away from the blade is approximately equal to or slightly smaller than the smallest width of the holding section. Accordingly, the smallest width of the base section should be at least 0.6 times the smallest width of the holding section. Conversely, the smallest width of the base section should not be greater than 1.2 times the smallest width of the holding section.

[0031] It is particularly advantageous if the smallest width of the base section corresponds to at least 0.8 times and / or a maximum of 1.0 times the smallest width of the holding section.

[0032] The smallest width of the holding section results from the distance between the two opposite holding surfaces on the blade facing edges. Analogously, the smallest width of the base section can be determined as the distance between the two edges of the opposite base surfaces facing away from the blade.

[0033] The mating surface can be provided at various locations between the ends of the blade root. However, it is advantageous if the mating surface is located in the center of the blade root. The mating surface does not have to be positioned at exactly the same distance from the ends—although this is preferred. At a minimum, it is necessary for the mating surface to intersect a transverse plane, with the transverse plane being the same distance from both ends of the blade root.

[0034] Viewed in the transverse direction (transverse to the blade axis and transverse to the radial direction), it can be provided that opposite longitudinal edges of the mating surface are equally spaced from the longitudinal sides of the blade root, i.e., from the base surfaces. Preferably, the mating surface extends to the base surfaces. This means that the respective longitudinal edge of the mating surface is also, in sections, the edge of the corresponding base surface.

[0035] If the transverse edges of the mating surface are spaced from the ends of the blade root, the transverse edges can initially have any desired shape (e.g., curved, serrated). However, the shape is primarily determined by the geometry intended for the end of the blade root. A straight transverse edge shape is obvious and preferred. (0036J However, the transverse edges should preferably be aligned at an angle to the transverse direction. In a particularly preferred embodiment, an angle between the blade axis and the respective transverse edge of between 30° and 60° is selected. Furthermore, it is advantageous if the transverse edges run parallel to one another.

[0038] To enable the blade root to be fitted into a corresponding receptacle in the turbomachine, it is sufficient if the advantageous fitting surface extends only over a part of the blade root. For this purpose, the distance between the transverse edges of the mating surface is advantageously selected to be between 0.05 and 0.3 times the profile length of the blade root. Particularly preferably, the distance between the transverse edges corresponds to at least 0.1 times the profile length. In contrast, the particularly preferred distance between the transverse edges corresponds to a maximum of 0.2 times the profile length.

[0039] To create a mating surface spaced from the ends of the blade root, a shoulder can be provided on both sides of the mating surface.

[0040] Particularly preferably, an inclined mounting surface adjoins the mating surface on both sides. The mounting surface should also be planar, i.e., flat. An angle between the mounting surface and the mating surface of between 0.03° and 2° is preferred. An angle between the mounting surface and the mating surface of between 0.5° and 1.5° is particularly preferred.

[0041] Due to the particularly advantageous design of the blade root with the holding section and the base section, limited on the opposite sides and on the underside facing away from the blade by several preferably planar, i.e. flat, surfaces, a particularly cost-effective production can be made possible and at the same time the function of the blade root is made possible with a precise installation and secure hold in a corresponding holder.

[0042] In this regard, it is irrelevant whether small rounded portions or phases without any further function are present to avoid sharp edges. Also included is a design in which a section, for example, the width of the blade, without any further function is arranged between the holding section with the holding surfaces and the base section with the base surfaces.

[0043] The blade can be either a rotor blade on a rotor of the turbomachine or, preferably, a guide vane attached to a stator of the turbomachine.

[0044] The use of the described solution is particularly preferred for a guide vane of a compressor of a gas turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG 1 shows an exemplary embodiment of a blade according to the invention with a simplified blade root.

[0046] FIG 2 outlines the installation of a blade root according to the state of the art.

[0047] FIG 3 outlines the installation of the blade root for the embodiment in Fig. 1 .

[0048] FIG 4 shows a longitudinal view of a blade root according to the state of the art.

[0049] FIG 5 shows a longitudinal view of the blade root for the embodiment shown in Fig. 1.

[0050] FIG 6, like Fig. 5, sketches the blade root with the angles.

[0051] FIG 7 shows a perspective view from below of the blade root for the embodiment in Fig. 1 .

[0052] FIG 8 shows a side view of the blade root for the embodiment shown in Fig. 1. DESCRIPTION OF THE EMBODIMENT

[0053] Figure 1 shows a perspective view of an example of a blade according to the invention. This can be either a rotor blade or a guide blade. The blade comprises at least first the blade 02 and the blade root 03, by means of which the blade can be attached in the turbomachine.

[0054] In the case of a guide vane, in many cases a fastening device is also arranged opposite the blade root 03 at the other end of the blade airfoil 02. Although the blade according to the invention is preferably used as a guide vane, the depiction of the corresponding conventionally present devices opposite the blade root 03 has been omitted here.

[0055] It can already be seen from the perspective view in Fig. 1 that the blade root 03 has a shape that is easy to manufacture compared to the usual embodiments.

[0056] For comparison, Figure 2 and Figure 4 show the usual design of a blade root 23 from the prior art.

[0057] The blade root 23 comprises a holding section 24, which is defined by opposing, planar, mutually inclined holding surfaces. These holding surfaces secure the blade root in the turbomachine 10.

[0058] Adjacent to the holding section 24 is the connecting section 25, via which the blade 22 is connected.

[0059] Opposite the connecting section 25 is the base section 26, which features generous roundings on both sides. The receiving groove in the turbomachine 10 has approximately the same rounding, leaving only a very small clearance. This minimizes undesirable flow along the blade root. On the side facing away from blade 22, there is a small shoulder adjacent to the fillet, which secures the blade to the turbomachine mount. This shoulder typically extends the entire length of the blade root.

[0061] In contrast, Figures 3 and 5 show the blade root 03 from the example in Figure 1 in comparison to the prior art.

[0062] The blade root 03 similarly comprises the holding section 04 and, on one side, the connecting section 05, which establishes the connection to the blade 02. The area of ​​the holding section 04 and the connecting section 05 essentially corresponds to the prior art design with the holding section 24 and connecting section 25. To simplify production, the otherwise required rounding is omitted and instead the base section 06 adjacent to the holding section 03 opposite the blade root 02 is provided with planar bevels.

[0064] Figure 6 again shows the blade root 03 of the exemplary blade 01.

[0065] The upper side of the illustration shows a partial view of the blade 02. The connecting section 05 adjoins it. The holding section 04 is bounded on each of the two opposite sides by a holding surface 14. The holding surfaces 14 are planar, with a holding angle 15 defined between the two holding surfaces 14 due to the inclination relative to the radial direction 07. In this exemplary embodiment, a holding angle 15 of 45° is selected. On the side facing away from the blade is the base section 06, which, according to the invention, is defined on both opposite sides by a base surface 16. The base surfaces 16 are designed to be planar, i.e., flat. Due to the existing inclination relative to the radial direction 07, the base surfaces 16 define a base angle 17. In this exemplary embodiment, a base angle 17 of 85° is selected. [0CS7] Furthermore, the shape of the holding section 06 defines a blade width 13 measured transversely to the radial direction 07 and transversely to the blade axis 11.

[0068] On the underside of the blade root 03 facing away from the blade 02 there is a fitting surface 08 which enables the blade 01 to be installed in the turbomachine without any play. Figure 7 shows the embodiment from Figure 1 again in perspective, looking at the blade root 03 from the underside. The straight extension of the blade root 03 along a blade axis 11 can be seen.

[0070] The retaining section 04 with the retaining surface can be seen again. The blade 02 is connected via the connecting section 05.

[0071] The base section 06 has three separate surfaces on its underside. The mating surface 08 is located in the center of the blade root 03. This 08 extends parallel to the blade axis and perpendicular to the radial direction 07. On both sides of the mating surface 08 there is a mounting surface 09 which is inclined relative to the mating surface 08.

[0072] Thus, the mating surface 08 is bounded in the transverse direction by longitudinal edges as a section of the border of the respective base surface 16. The transverse edges of the mating surface 08 adjacent to the mounting surfaces 09 do not extend transversely to the blade axis 11, but rather at an angle of 45° to the blade axis from one base surface 16 to the opposite base surface 16.

[0073] Furthermore, it can be seen that the mating surface 08 extends in the direction of the blade axis 11 only over a short section of the profile length of the blade root 03. In this exemplary embodiment, the distance between the two transverse edges of the mating surface 08 corresponds approximately to 0.15 times the profile length of the blade root.

[0074] The arrangement of the mating surface 08 and, relative thereto, the mounting surfaces 09 is shown again in Figure 8, looking in the direction of the transverse edges of the mating surface 08. Between the mating surface 08 and the mounting surface 09 is the mounting angle 18, which in this exemplary embodiment is approximately 1° (not to scale in the view).

Claims

Claims The following is claimed:

1. Blade (01) for use in a turbomachine, which defines a rotor axis and a radial direction (07), - with a blade (02) extending in the radial direction (07); and - with a blade root (03), which (03) defines a blade axis (11) and has a root width (13) transverse to the blade axis (11) and a holding section (04) extending along the blade axis (11) over a profile length and on the side facing the blade (02) a connecting section (05) and on the side facing away from the blade (02) Side comprises a base section (06), wherein the holding section (04) is delimited transversely to the blade axis (11) by planar, opposite, inclined holding surfaces (14) and the base section (06) is delimited by planar, opposite, inclined base surfaces (16); characterized in that the base section (06) has, on the side facing away from the blade (02), a planar fitting surface (08) spaced from the opposite ends of the blade root (03).

2. Blade (01) according to claim 1, wherein a holding angle (15) between the holding surfaces (14) is at least 25°, in particular at least 35°, and a maximum of 60°, in particular a maximum of 50°; and / or wherein the radial height of the holding section (04) is at least 0.3 times, in particular at least 0.35 times, and a maximum of 0.6 times, in particular a maximum of 0.5 times, the base width (13).

3. Blade (01) according to claim 1 or 2, wherein a base angle (17) between the base surfaces (16) is at least 60°, in particular at least 70°, and a maximum of 120°, in particular a maximum of 100°; and / or wherein the radial height of the base section (06) is at least 0.15 times, in particular at least 0.2 times, and a maximum of 0.35 times, in particular a maximum of 0.3 times, the base width (13).

4. Shovel (01) according to one of claims 1 to 3, wherein the smallest width of the base section (06) corresponds to at least 0.6 times, in particular at least 0.8 times, and at most 1.2 times, in particular at most 1.0 times, the smallest width of the holding section (04).

5. Blade (01) according to one of claims 1 to 4, wherein the mating surface (08) is arranged centrally in the direction of the blade axis (11); and / or wherein opposite longitudinal edges of the mating surface (08) adjoin the respective base surfaces (16).

6. Blade (01) according to one of claims 1 to 5, wherein opposite transverse edges of the mating surface (08), in particular parallel to one another, are aligned at an angle between 30° and 60° to the blade axis (11); and / or wherein the axial distance between opposite transverse edges of the mating surface (08) corresponds to at least 0.05 times, in particular at least 0.1 times, and at most 0.3 times, in particular at most 0.2 times, the profile length.

7. Blade (01) according to one of claims 1 to 6, wherein in the direction of the blade axis (11) a planar mounting surface (09) inclined relative to the fitting surface (08) adjoins the fitting surface (08) on both sides.

8. Blade (01) according to claim 7, wherein a mounting angle between the mating surface (08) and the mounting surface (09) is at least 0.3°, in particular at least 0.5°, and a maximum of 2°, in particular a maximum of 1.5°.

9. Blade (01) according to one of claims 1 to 8, wherein it is a guide vane of a compressor, in particular of a gas turbine.

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