SHELL OF A PELTON TURBINE

Description

[0001] The invention relates to a blade of a Pelton turbine with an exit edge that is curved at least in sections.

[0002] Pelton turbines have long been considered state of the art and are particularly well-known from document CA 32918 A. While initially only blades with flat trailing edges were used, as described, for example, in documents DE 39 38 356 C2 and DE 102 10 426 A1, blades for Pelton turbines with curved trailing edges have also been known for some time, particularly from documents EP 1 386 076 B1 and EP 2 868 912 A1. The aim is always to improve efficiency through favorable flow control achieved by the blade shape.

[0003] Accordingly, it is also an object of this invention to provide a Pelton blade of the type mentioned above with which a particularly high efficiency can be achieved. This object is achieved according to the invention by a blade of the type mentioned above according to claim 1.

[0004] Within the scope of the invention, it was recognized that in this way the exit height of the water jet can be increased, thereby achieving better control of the exiting flow, which in turn leads to an increase in efficiency.

[0005] The design according to the invention enables the creation of innovative blade profiles with more geometric possibilities in terms of positions, curvatures and angles, in order to: to optimize the energy transfer to the impeller for better hydraulic efficiency; to optimize the water backflow from the bucket to reduce backflow to the nozzles and the impeller and to change the points of impact of the water on nozzles or casing; to optimize the thickness distribution in the impeller to improve the stress level in the impeller; to optimize the mass distribution in the runner to improve the dynamic behavior of the shaft pipe.

[0006] The root of the blade or cup is understood to be the radially inner end of the blade or cup when the blade is mounted on a Pelton wheel, and the tip of the blade is understood to be the radially outer end of the cup when the blade is mounted on a Pelton turbine as intended. The trailing ridge is thus usually located in a radially inner half of the blade and generally does not extend beyond the diameter of the jet circle. In particular, the apex of the ridge, i.e., the point on the ridge where it has its maximum distance from an imaginary flat exit edge, is usually located radially within the diameter of the jet circle.

[0007] According to the invention, the hump projects above a central cutting edge. A flat part of the exit edge, i.e., an area in which the exit edge forms a substantially straight connecting line between the blade face and the cup root in a side view, can be arranged below the central cutting edge, so that in a preferred embodiment the flat edge lies below the central cutting edge and only the hump projects above the central cutting edge.

[0008] It has proven advantageous to position the center of gravity of the rear hump between the cup root and a midpoint between the cup root and the blade tip. This ensures favorable flow in both radially outer and radially inner regions of the cup. The hump is defined here as the portion of the cup that extends beyond a direct, straight line connecting the cup root and the blade tip. Consequently, the center of gravity is defined as the center of gravity of this portion extending beyond the flat edge.

[0009] The terms radial inside and radial outside naturally refer here to a cylindrical coordinate system starting from a rotation axis of the Pelton wheel, on which the blade is or can be arranged as intended.

[0010] Preferably, the posterior hump extends from the cup root to approximately a midpoint between the cup root and the blade face.

[0011] In principle, the hump, which is part of the trailing edge, can be designed in a variety of ways. To achieve favorable flow conditions, it is preferably provided that the hump has a first, concave region with a center of curvature positioned above the trailing edge in a side view, a second, convex region with a center of curvature positioned below the trailing edge in a side view, and a third, concave region with a center of curvature positioned above the trailing edge in a side view.Preferably, the rear hump thus has two turning points and an approximately dome-shaped formation in between, and the first concave area and the third concave area transition tangentially into the adjacent edge of the blade, which subsequently usually corresponds in a side view to a straight connecting line between the cup root and the blade face or to a flat edge.

[0012] The rear tubercle is generally designed to extend almost to the cup root, but the cup has a projection edge in the region of the cup root with a height corresponding to a flat edge. A flat edge is defined here as a line that, in a side view, forms a straight connection between the cup root and the blade face.

[0013] To achieve a particularly favorable flow and high efficiency, it is preferably provided that the blade has a further, front hump which is curved at least in sections, wherein a center of curvature is positioned below the trailing edge in a side view and wherein a vertex of the front hump is located closer to the blade front than to the cup root.

[0014] This also results in an increase in the height of the flow outlet in a front or radially outer area of ​​the blade.

[0015] The front hump preferably also has a concave region, a subsequent convex region, and a concave region adjoining the convex region, so that the front hump also preferably has two inflection points and is generally located exclusively above an imaginary flat edge or above a straight line connecting the cup root to the blade tip. The front hump can extend to the blade tip, although it is also possible that the front hump does not extend completely to the blade tip at one front end, resulting in a straight or flat region between the front end of the front hump and the blade tip.

[0016] It has proven particularly advantageous if the front hump has a lower height than the rear hump. For example, the front and rear humps can have a height of less than 30% of the maximum cup depth (according to the definition in DE 39 38 356 C2).

[0017] The present invention can also be combined with a shovel having a trailing edge with a concave region, as described, for example, in document EP 1 386 076 B1. In this case, the trailing edge can be provided to have a concave region, in particular between the rear hump and the front hump.

[0018] Blades for Pelton turbines are typically arranged symmetrically about a central cutting edge. Accordingly, it has proven advantageous to arrange ridges symmetrically on both sides of an imaginary central plane of the blade, which central plane usually contains the central cutting edge.

[0019] It is understood that the corresponding blades are usually arranged on a Pelton wheel of a Pelton turbine, the Pelton wheel preferably comprising exclusively blades designed according to the invention.

[0020] Further features, advantages, and effects of the invention will become apparent from the exemplary embodiments described below. The drawings referenced therein show: Fig. 1 a section of a Pelton wheel with three blades designed according to the invention; Fig. 2 a further section of a Pelton wheel according to the invention with three blades designed according to the invention; Fig. 3 a Pelton wheel; Fig. 4 a blade of a Pelton wheel; Fig. 5 a Pelton wheel.

[0021] Fig. 1 Figure 1 shows a section of a Pelton wheel 1 according to the invention, showing three blades 2. As can be seen, each blade 2 has a blade tip 4, a cup root 3, and a central cutting edge 5. The blades 2 shown have trailing ridges 7 on both sides of the central cutting edge 5 and symmetrically to a central plane at the exit edges 6. These ridges extend beyond the depicted flat edge 9, i.e., beyond a straight line connecting the cup root 3 and the blade tip 4 in a side view. This increases the exit height of the flow in the region of the trailing ridges 7, resulting in more favorable flow characteristics. To make this particularly clear, the flat edge 9 in the region of the trailing ridges 7 is shown with a dashed line. Outside the region of the trailing ridges 7, the exit edge 6 corresponds to the flat edge 9.

[0022] As can be seen, the rear humps 7 have a first, concave region 11, a subsequent second, convex region 12 which includes a vertex 10, and a further subsequent concave region 11, with the concave regions 11 transitioning approximately smoothly into the flat exit edge 6. As can be seen in a side view, the vertex 10 of the rear humps 7 is located closer to the cup root 3 than to the blade tip 4 and thus lies radially within a cup center or within a steel circle.

[0023] Fig. 2 Figure 1 shows a further embodiment of a Pelton wheel 1 with blades 2 designed according to the invention, again showing a section having three blades 2. In addition to the illustrations in Fig. 1 In addition to the rear humps 7 shown, these blades 2 also have front humps 8. In this way, the height of the flow outlet is also raised in certain areas at the front. As can be seen, both the rear humps 7 and the front humps 8 each have concave areas 11, a subsequent convex area 12, and then another concave area 11, resulting in a substantially continuous transition to the outlet edge 6 adjoining the humps.

[0024] Furthermore, it is evident that neither the anterior hump 8 nor the posterior hump 7 extend entirely to the front or rear end of the blade 2, or to the cup root 3 and blade face 4, respectively, although this is fundamentally possible. The apex 10 of the posterior hump 7 is again located closer to the cup root 3 than to the blade face 4, while the apex 10 of the anterior hump 8 is located closer to the blade face 4 than to the cup root 3. In the depicted humps, the center of gravity of the posterior humps 7 is also located closer to the cup root 3 than to the blade face 4, and the center of gravity of the anterior humps 8 is also located closer to the blade face 4 than to the cup root 3.The centers of gravity and vertices 10 of the rear humps 7 are thus radially within a steel circle not shown here, and the vertices 10 and centers of gravity of the front humps 8 are radially outside the steel circle.

[0025] Fig. 3 Figure 1 shows another Pelton wheel 1 with blades 2 designed according to the invention. As can be seen, the blades 2 have, on the one hand, a concave region 11 with a curvature, the center of curvature being located above the trailing edge 6 in a side view. Furthermore, these blades 2 also have radially inward rear humps 7 to favorably influence the flow. The trailing edge 6 is located in the concave region 11 below the central cutting edge 5.

[0026] Fig. 4 Figure 1 shows another blade 2 of a Pelton turbine, which again has rear humps 7 and front humps 8 on both sides of the central cutting edge 5. These humps each rise above a flat edge 9, which coincides with the trailing edge 6 outside of the rear humps 7 and front humps 8. Here, too, a flat edge is understood to be a straight line connecting the blade tip and the cup root in a side view. Here, the front humps 8 extend to the blade tip 4 and, unlike those in Figure 1, have a curved front end. Fig. 2 The depicted front humps 8 do not have a concave area 11, but rather transition convexly into the blade face 4. The front humps 8 thus only have one turning point here, while the rear humps 7, as in the one shown in Fig. 1 The illustrated embodiment has a concave region 11, a subsequent convex region 12 and a concave region 11 adjoining the convex region 12, and thus two inflection points.

[0027] Fig. 5 shows a Pelton wheel 1 with the in Fig. 4 shovels shown 2.

[0028] By designing the blades 2 of a Pelton turbine according to the invention, favorable flow control can be achieved and increased efficiency can be attained. Furthermore, this enables the design of innovative blade profiles with more geometric possibilities regarding positions, curvatures, and angles, which was previously impossible.

Claims

1. A blade (2) of a Pelton turbine with an exit edge (6) which is at least sectionally curved, wherein the exit edge (6) forms a rear hump (7) as viewed from the side, wherein a center of curvature of the hump is positioned below the exit edge (6) as viewed from the side, and an apex (10) of the hump is located closer to the cup root (3) than to the blade face (4), characterized in that the hump protrudes over a middle edge (5).

2. The blade (2) according to claim 1, characterized in that a center of gravity of the rear hump (7) is positioned between the cup root (3) and a midpoint between the cup root (3) and blade face (4).

3. The blade (2) according to claim 1 or 2, characterized in that the rear hump (7) extends from the cup root (3) to about a midpoint between the cup root (3) and blade face (4).

4. The blade (2) according to one of claims 1 to 3, characterized in that the hump has a first, concave area (11) with a center of curvature, which is positioned above the exit edge (6) as viewed from the side, a second, convex area (12) with a center of curvature, which is positioned below the exit edge (6) as viewed from the side, and a third, concave area (11) with a center of curvature, which is positioned above the exit edge (6) as viewed from the side.

5. The blade (2) according to one of claims 1 to 4, characterized in that the blade (2) has an additional, front hump (8), which is at least sectionally curved, wherein a center of curvature is positioned below the exit edge (6) as viewed from the side, and wherein an apex (10) of the front hump (8) is arranged closer to the blade face (4) than to the cup root (3).

6. The blade (2) according to claim 5, characterized in that the front hump (8) is not as high as the rear hump (7).

7. The blade (2) according to one of claims 1 to 6, characterized in that the exit edge (6) has a concave area (11), in particular between the rear hump (7) and front hump (8).

8. The blade (2) according to one of claims 1 to 7, characterized in that humps (7, 8) are symmetrically arranged on either side of an imagined center plane of the blade (2).