VANE

Description

[0001] The invention relates to a guide vane for a guide wheel of a pump or turbine, comprising a guide vane body with a leading edge, an exit edge, a profile chord and at least one, preferably two, pivot pins, wherein the guide vane is rotatably mounted about an axis of rotation defined by the pivot pin, wherein the profile chord of the guide vane is at least partially spaced from the axis of rotation, wherein the guide vane body forms different flow profiles along an axial extent, which differ at the leading edge and / or at the exit edge.

[0002] Guide vanes are known from the prior art for directing a working fluid at an optimal angle onto the rotor blades of a turbine, particularly in turbines. Unlike the rotor blades, which rotate with the turbine, guide vanes are generally stationary but can be rotated within an inlet casing to influence the flow and, if necessary, restrict mass flow. For example, in Kaplan or Francis turbines, the guide vanes can be arranged regularly along a circle coaxial with the turbine within the inlet casing, resulting in a so-called guide vane assembly, also known as a guide ring.

[0003] Guide vanes known from the prior art are mounted in the guide vane assembly by one or two pivot pins, thus creating an axis of rotation around which the guide vanes can be turned. These guide vanes have a guide vane body with a flow profile that is essentially constant along an axial extent, for example, a NACA profile. Guide vanes with flow profiles that vary along an axial extent are also known; these are also known as profiled guide vanes or sculpted guide vanes. In this case, for example, the tail angle of the guide vane's skeletal curve can be varied along an axial extent.

[0004] Furthermore, methods for designing guide vanes for hydropower plants are also known from the prior art. According to the prior art, a flow profile is usually selected, and only minor modifications to this flow profile are made, such as, in particular, a fairing, in order to determine the most favorable guide vane design.

[0005] Guide vanes and guide plates are known from documents DE 33 45 234 A1 and DE 77 31 451 U1. Furthermore, guide plates of the prior art are known from documents WO 2020 / 035452 A1, DE 199 50 227 A1, and US 2018 / 0313320. Documents WO 95 / 10705 A1 and JP 2015 10569 A disclose hydraulic turbomachines with guide plates and impeller blades.

[0006] However, it has been shown that in many cases only an unsatisfactory level of efficiency is achieved with guide vanes known from the prior art, which is why there is a need for guide vanes with which a higher level of efficiency can be achieved.

[0007] This is where the invention comes in. The object of the invention is to provide a guide vane of the type mentioned above, with which a particularly high efficiency can be achieved when used in a hydroelectric power plant.

[0008] This problem is solved according to the invention by a guide vane of the type mentioned at the outset, in which the axis of rotation is positioned at least partially outside the guide vane body.

[0009] Within the scope of the invention, it was recognized that a favorable flow control is possible by using a guide vane body arranged eccentrically to the axis of rotation, in which the profile chord of the guide vane is at least partially, preferably along its entire axial extent, spaced away from the axis of rotation. This is particularly relevant when modernizing existing hydropower plants where the positions of the pivot pins or the axes of rotation of the guide vanes can no longer be changed. Eccentrically arranged guide vane bodies allow for adjustments to the distances between the guide vanes and the rotor blades. Specifically, reducing the distance between the guide vanes and the rotor blades, i.e., shifting the guide vanes radially inwards towards the machine axis, often results in favorable flow control and an increase in efficiency.

[0010] On the other hand, it was recognized within the scope of the invention that particularly favorable flow conditions can be achieved with a guide vane body that has a surface formed by a freeform surface, at least in some areas. The background to this is that conventional guide vanes, which generally have a constant flow profile along an axial extent, optionally with a strake, cause local turbulence, particularly in edge regions, due to boundary layer effects, leading to unfavorable efficiencies. When using a freeform surface for the guide vane, there is no limitation to a single flow profile, so that the guide vane can, for example, be designed differently at the axial end, where boundary layer effects play a role, than in an axially central region, where no boundary layer effects are present.

[0011] A better efficiency can be achieved either with only an eccentric guide vane or with only a guide vane having a freeform surface, although it is preferred that both features be implemented in order to achieve a particularly high efficiency.

[0012] According to the invention, the axis of rotation is positioned outside the guide vane body, at least partially, preferably along its entire axial extent. The axial extent is defined as the axis of rotation along the pivot pins. The longitudinal direction is defined as the direction along the chord line, which is defined by a direct connection between the leading and trailing edges. The thickness or width of the airfoil is defined along a transverse direction in a plane normal to the axial direction or normal to the axial extent and normal to the longitudinal direction.

[0013] It is particularly advantageous if the axis of rotation has a distance from the guide vane body, at least in certain areas, preferably along the entire axial extent of the guide vane body, that corresponds to at least 50%, preferably at least 75%, of the maximum thickness of the guide vane. This allows for good alignment of the guide vanes with the rotor blades, resulting in a short flow path between the guide vanes and the rotor blades, which has proven to be advantageous from a fluid mechanics perspective.

[0014] It has proven advantageous for the profile chords to have a distance to the axis of rotation, at least in a partial area of ​​the guide vane, preferably along the entire axial extent of the guide vane body, which corresponds to at least 15%, preferably at least 30%, of the length of the profile chords.

[0015] The guide vane body is defined here as the portion of the guide vane exhibiting a flow profile, which, when the guide vane is used as intended in a guide ring or guide vane assembly of a hydroelectric power plant, is surrounded by a fluid flow. It is understood that the guide vane body may have a rounded end or similar feature at its connection to the pivot pin, in which case, of course, a smaller distance between the guide vane body and the axis of rotation may be provided in the area of ​​this rounded end. Furthermore, it is also possible that the guide vane body has no distance to the axis of rotation in the area of ​​the end rounded end.

[0016] The distance of the airfoil chord from the axis of rotation can also be specified relative to the length of the airfoil chord. It has proven advantageous if the airfoil chord, at least in a partial region of the guide vane, preferably along the entire axial extent of the guide vane body, has a distance from the axis of rotation that corresponds to at least 25%, preferably at least 30%, of the airfoil chord length. Such a guide vane design has proven particularly advantageous for use in a Francis turbine.

[0017] It is advantageous if the profile chord, at least in a partial area of ​​the guide vane, preferably along the entire axial extent of the guide vane body, has a distance to the axis of rotation which corresponds to at least 50%, preferably at least 75%, of the maximum thickness of the guide vane.

[0018] It has been shown that boundary layer effects, particularly in the leading edge region, have a comparatively large influence on efficiency. Therefore, it has proven advantageous for the guide vane body to develop different flow profiles along its axial extent, which differ at the leading edge. The leading edge can thus be optimized along the axial direction or along the axial extent of the guide vane according to the local flow conditions, so that, for example, flow profiles adapted to the boundary layers can be provided in a marginal or end region.

[0019] It is advantageous if the flow profiles have a greater thickness axially at the leading edge than in the area in between. This has been shown to enable beneficial flow control.

[0020] Preferably, the flow profiles have axial chords at their leading edge that are longer than the chords of intermediate flow profiles, thus forming end-face protrusions at the leading edge. These end-face protrusions at the leading edge can positively influence the inflow, resulting in higher efficiency.

[0021] It is particularly preferred that the chord lines of the end-side airfoils at the leading edge are angled to the chord lines of airfoils in between. This has been shown to result in different flow conditions at the axial end and beginning of the guide vane due to boundary layer effects. With a guide vane of constant angle along its axial extent, these conditions lead to turbulence and a reduction in efficiency. Therefore, differently inclined chord lines at the beginning and end of the guide vane can be very beneficial for efficiency. It is understood that the inclination of the chord line at the axial end and beginning is typically determined by the flow in this region or by the effect of boundary layers, which can be determined, in particular, by flow simulation.Accordingly, a skeleton line can also be inclined differently at axial end regions than in axially middle regions of the guide vane, especially at the leading edge.

[0022] According to the invention, the guide vane body is designed to form different flow profiles along an axial extent, which differ at the leading edge and / or the trailing edge. Thus, it is possible, for example, to adapt the flow profile of the guide vane body to boundary layer effects, even at the trailing edge.

[0023] Furthermore, the guide vane can then be designed to be so wide in the area of ​​the exit edge that sufficient space remains for a seal on the front face of the guide vane.

[0024] It is particularly advantageous if flow profiles in a region close to the trailing edge have a greater axial thickness at the end than in an intermediate region, thus forming a thickening. This allows for optimal positioning of a seal on the end face of the guide vane body, close to the trailing edge, thereby reducing efficiency losses caused by flow around the guide vanes at the axial ends. A region positioned close to the trailing edge can be understood as a region located less than 30%, particularly less than 20%, preferably less than 10%, and most preferably less than 5% of the length of the skeleton line from the trailing edge. The thickening can extend to the trailing edge or terminate before it, for example, at a distance of 1% to 10% of the skeleton line length before the trailing edge, so that the trailing edge itself does not exhibit any thickening.This allows for a particularly good front-side seal of the guide vane body.

[0025] The thickening can be provided at one axial end of the guide vane or at both axial ends to enable a particularly good seal at the corresponding end face.

[0026] Preferably, seals are arranged on the end faces of the guide vane body. These seals are typically positioned in grooves located on the end faces. These seals seal a flow channel against boundary surfaces in the guide vane assembly. The grooves and seals can extend into the area of ​​the thickened sections, particularly along the entire length of the thickened sections, to achieve the best possible seal.

[0027] It has proven advantageous for the pivot pins to have an end face that is approximately perpendicular to the axis of rotation and to which the pivot pins are connected to the guide vane body. Such a guide vane design is also referred to as a disc design, since the ends of the pivot pins are perpendicular to the axis of rotation and are approximately disc-shaped.

[0028] It is advantageous to have a fillet at the transition between the guide vane body and the end face, with the fillet having different radii of curvature along the longitudinal direction of the guide vane. This achieves favorable flow conditions, which contribute to a higher efficiency. By applying different radii of curvature along the longitudinal direction of the fillet, local flow conditions can also be taken into account, which can be determined, for example, in a flow simulation. Generally, a small radius of curvature is advantageous to achieve a large cross-section for the flowing fluid; however, a larger radius of curvature may be necessary in certain areas to meet requirements, for example, regarding strength or stiffness.

[0029] Both goals can be achieved by applying different radii of curvature along the longitudinal direction of the guide vane.

[0030] In particular, it can be provided that the radius of curvature along the longitudinal direction of the guide vane initially increases, then decreases, and finally increases again. Furthermore, it can be provided that the rounding along the longitudinal direction has one or more inflection points.

[0031] It has proven advantageous for the guide vane body to have axial end radii extending from the leading edge to the trailing edge, particularly concave radii. These radii can thus extend longitudinally beyond the pivot points. This avoids sharp corners in the flow profile that could otherwise occur at a contact surface between the guide vane body and a surrounding wall.

[0032] In the case of a guide wheel for a pump or turbine, in particular for a Kaplan or Francis turbine, which is formed by several guide vanes, it is preferred if the guide vanes are designed according to the invention.

[0033] It is advantageous if the blade bodies of the guide vanes are arranged eccentrically to the axes of rotation of the respective guide vanes in such a way that the profile chords of the blade bodies have a smaller distance to the machine axis than the axes of rotation.

[0034] Further features, advantages, and effects of the invention will become apparent from the exemplary embodiment described below. The drawings referenced therein show: Fig. 1 bis 6 a guide vane designed according to the invention in different views; Fig. 7 a cut through the in Fig. 5 Guide vane shown along line VII-VII.

[0035] Fig. 1 bis 6 show a guide vane 1 according to the invention in different views, wherein Fig. 1 A view looking along a rotation axis 7 shows about which rotation axis 7 the guide vane 1 can be rotatably arranged in a guide vane assembly and which rotation axis 7 is defined by two pivot pins 6 attached to the end face of a guide vane body 2. It is understood that a design is also possible in which only one pivot pin 6 is provided and the rotation axis 7 is defined by only one pivot pin 6.

[0036] The guide vane body 2 does not have a constant flow profile 12 along the axial direction 8. Instead, individual areas of the guide vane body 2 are fluid-mechanically optimized for the flow along the axial direction 8, whereby, for example, boundary layer effects at the axial beginning and end are taken into account by a modified shape of the flow profile 12 in these areas. This complex surface shape is referred to here as a freeform surface, since the surface cannot simply be formed by extruding a flow profile 12 along the axial direction 8.

[0037] As in Fig. 1 As can be seen, the guide vane body 2 is arranged eccentrically to the axis of rotation 7 or spaced apart from the axis of rotation 7. A distance 11 of a profile chord 5, which forms a connection between a leading edge 3 and a trailing edge 4 of the guide vane body 2, is here more than 25% of a length 9 of the profile chord 5 or a length 9 of the guide vane 1.

[0038] The guide vane body 2 forms a flow profile 12 between the leading edge 3 and the trailing edge 4, whereby the flow profile 12 changes along an axial direction 8, such that sections normal to the axial direction 8 show different flow profiles 12. For illustration, profile chords 5 of two different flow profiles 12 are shown in Fig. 1 The figure shows the profile chords 5 of a flow profile 12 in an axially end region and of a flow profile 12 in an axially middle region, which are at an angle to each other as shown. In the illustrated embodiment, the profile chords 5 intersect at the trailing edge 4, although in principle an embodiment would also be possible in which the flow profiles 12 in an axially end region also differ at the trailing edge 4 from flow profiles 12 in an axially middle region, so that the position of the trailing edge 4 changes along the axial direction 8 or the trailing edge 4 does not run parallel to the axial direction 8.

[0039] In the illustrated embodiment, a distance 11 of the profile chord 5 from the axis of rotation 7 corresponds approximately to 1.2 times the maximum thickness 10 of the profile in a transverse direction 21, which is oriented perpendicular to the longitudinal direction 20 and perpendicular to the axis of rotation 7 or to the axial direction 8. The distance 11 can also be expressed in relation to the length 9 of the profile chord 5, where the distance 11 corresponds here to approximately 20% of the length 9 of the profile chord 5. As can be seen, a flow profile 12 of the guide vane body 2, and thus also the guide vane body 2 itself, is spaced from the axis of rotation 7 in a central region.

[0040] This eccentric arrangement of the guide vane 1 relative to the axis of rotation 7 allows for a small distance between the guide vane 1 and the impeller blades, resulting in a short flow path between the guide vane 1 and the impeller blades and thus reducing turbulence between the guide vanes 1 and the impeller blades, thereby achieving high efficiency.

[0041] Fig. 2 and 3Figure 1 shows the leading edge 3 of the guide vane 1 in detail. As can be seen, the guide vane 1 has protrusions 13 at its beginning and end, viewed in the axial direction 8, which extend further in the longitudinal direction 20 than the leading edge 3 in the region between the beginning and end. The reason for this is that the corresponding protrusions 13 achieve a design of the guide vane 1, or rather the guide vane body 2, at the axial beginning and end, which can accommodate the flow conditions present in a corresponding boundary layer. A flow profile 12 of the guide vane body 2 thus changes along its axial extent and, in the region of the leading edge 3, is also a skeletal line oriented differently at the beginning and end than in between, in order to capture the flow particularly well in this region.

[0042] As can be seen in Fig. 3 As a result, the leading edge 3, viewed in the transverse direction 21, is thus approximately U-shaped or forms end-end noses 13 for flow optimization.

[0043] Fig. 4 Figure 1 shows a side view of the guide vane 1. Besides the leading edges 13 on the leading edge 3, a transition 22 from a rounding 19 to the guide vane body 2 is visible. This transition is determined by flow simulations and exhibits different curvatures along a longitudinal direction 20 of the guide vane 1, which allows for particularly good adaptation to local flow conditions in order to achieve a very high efficiency. In particular, in Fig. 4 It is evident that the transition 22 of the rounding 19 to the part of the guide vane body 2, which has a cross-section that is approximately constant in the axial direction, has an inflection point 23 in a front third of the guide vane 1.

[0044] Fig. 5 and 6Further views of the guide vane 1 are shown, with the trailing edge 4 clearly visible. As can be seen here, the guide vane body 2 also has a non-continuous or variable cross-section along the axial direction at the trailing edge 4, so that the thickness 10 of the profile is greater at the axial beginning and end than between these areas. This leaves more space on the end faces 16 of the guide vane body 2 for a groove 14 in which a seal 17 can be arranged.

[0045] Fig. 5 and 6Furthermore, the plate design of the guide vane 1 is shown, wherein the pivot pins 6 have end faces 18 which are oriented approximately perpendicular to the axis of rotation 7. A rounding 19 is arranged between the end faces 18 of the pivot pins 6 and the guide vane bodies 2, which has different curvatures along the longitudinal direction 20 of the guide vane 1 and extends from the leading edge 3 to the trailing edge 4, i.e. beyond the pivot pin 6 or the plate.

[0046] Fig. 7 shows a section through the guide vane body 2 along line VII-VII in Fig. 5In this not-to-scale drawing, the axial end thickening 15 is particularly visible. This thickening allows the end-face groove 14 to extend to a region near the exit edge 4, thus preventing flow at the end face almost to the exit edge 4 and achieving a particularly high efficiency. As can be clearly seen, without the thickening 15, a groove 14 would no longer be possible in this region near the exit edge 4.

[0047] With a guide vane 1 according to the invention, a particularly favorable flow can be achieved when used in a hydropower plant, which leads to a high efficiency.

Claims

1. A guide vane (1) for a guide wheel of a pump or turbine, having a guide vane body (2) with a leading edge (3), an outlet edge (4), a chord (5) and at least one pivot (6), wherein the guide vane (1) can be mounted in a rotatable manner about an axis of rotation (7), which is defined by the pivot (6), wherein the chord (5) of the guide vane (1) is spaced from the axis of rotation (7) at least in some regions, wherein the guide vane body (2) forms different flow profiles (12) along an axial extent, which differ at the leading edge (3) and / or at the outlet edge (4), characterized in that the axis of rotation (7) is positioned outside the guide vane body (2) at least in some regions.

2. The guide vane (1) according to Claim 1, characterized in that the axis of rotation (7) is positioned outside the guide vane body (2) along an entire axial extent of the guide vane body (2).

3. The guide vane (1) according to Claim 1 or 2, characterized in that the axis of rotation (7) has a spacing (11) from the guide vane body (2) at least in some regions, preferably along an entire axial extent of the guide vane body (2), which spacing corresponds to at least 50%, preferably at least 75%, of a maximum thickness (10) of the guide vane (1).

4. The guide vane (1) according to any one of Claims 1 to 3, characterized in that the chord (5) has a spacing (11) from the axis of rotation (7) at least in a subregion of the guide vane (1), preferably along an entire axial extent of the guide vane body (2), which spacing corresponds to at least 15%, preferably at least 30%, of a length (9) of the chord (5).

5. The guide vane (1) according to any one of Claims 1 to 4, characterized in that the chord (5) has a spacing (11) from the axis of rotation (7) at least in a subregion of the guide vane (1), preferably along an entire axial extent of the guide vane body (2), which spacing corresponds to at least 50%, preferably at least 75%, of a maximum thickness (10) of the guide vane (1).

6. The guide vane (1) according to any one of Claims 1 to 5, characterized in that the flow profiles (12) on the leading edge (3) have a larger thickness (10) axially at the ends than in a region therebetween.

7. The guide vane (1) according to any one of Claims 1 to 6, characterized in that the flow profiles (12) have chords (5) on the leading edge (3) axially at the ends, which chords are longer than chords (5) of flow profiles (12) therebetween, so that end-side noses (13) are formed on the leading edge (3).

8. The guide vane (1) according to any one of Claims 1 to 7, characterized in that the chords (5) of the end-side flow profiles (12) on the leading edge (3) are at an angle to chords (5) of flow profiles (12) therebetween.

9. The guide vane (1) according to any one of Claims 1 to 8, characterized in that flow profiles (12) in a region which is close to the outlet edge (4) have a larger thickness (10) axially at the ends than in a region therebetween, so that a thickening (15) is formed.

10. The guide vane (1) according to any one of Claims 1 to 9, characterized in that seals are arranged at end faces (16) of the guide vane body (2).

11. The guide vane (1) according to any one of Claims 1 to 10, characterized in that the pivots (6) have an end face (18) which is formed approximately normal to the axis of rotation (7) and at which the pivots (6) are connected to the guide vane body (2).

12. The guide vane (1) according to Claim 11, characterized in that a rounding (19) is arranged at a transition region between guide vane body (2) and end face (18), wherein the rounding (19) has different radii of curvature along a longitudinal direction (20) of the guide vane (1).

13. The guide vane (1) according to any one of Claims 1 to 12, characterized in that the guide vane body (2) has roundings (19) axially at the ends, which roundings extend from the leading edge (3) to the outlet edge (4).

14. A guide wheel for a pump or turbine, particularly for a Kaplan or Francis turbine, which guide wheel is formed by a plurality of guide vanes (1), characterized in that the guide vanes (1) are formed according to any one of Claims 1 to 13.

15. The guide wheel according to Claim 14, characterized in that the vane bodies of the guide vanes (1) are arranged eccentrically to the axes of rotation (7) of the respective guide vanes (1) in such a manner that the chords (5) of the vane bodies have a smaller spacing (11) from the machine axis than the axes of rotation (7).