Blade of Pelton Turbine

Abstract

The invention relates to a bucket (2) of a Pelton turbine, the bucket (2) having an outlet edge (6) curved at least in sections. According to the invention, in order to achieve particularly high efficiency, the outlet edge (6) forms, in a side view, a rear projection (7), the center of curvature of which lies below the outlet edge (6) in the side view, and the apex (10) of which is closer to the cup base (3) than to the bucket front (4).

Description

Technical Field

[0001] The invention relates to a bucket blade of a Pelton turbine, the bucket blade having an outlet edge which is at least partially curved. Background Art

[0002] Pelton turbines have long been part of the prior art and are known in particular from document CA 32 918 A. Although initially only buckets with straight outlet edges were used (as described, for example, in document DE 39 38 356 C2), Pelton turbines with curved outlet edges have also been known for some time, in particular from documents EP 1 386 076 B1 and EP 2 868 912 A1. The goal has thus always been to increase the efficiency by beneficially influencing the flow generated by the bucket shape. Summary of the invention

[0003] It is therefore also an object of the invention to specify a Pelton bucket of the initially named type with which particularly high efficiencies can be achieved.

[0004] According to the invention, this object is achieved by a bucket of the type named at the outset, in which the outlet edge forms a rear ridge in side view, wherein the center of curvature of the ridge is located below the outlet edge in side view and the apex of the ridge is closer to the base of the cup than to the bucket front.

[0005] In the course of the present invention it was found that in this way the exit height of the water jet can be increased, whereby a better control of the exit flow is achieved, which in turn leads to an increase in efficiency.

[0006] Embodiments according to the present invention enable the design of innovative bucket profiles with more geometric possibilities in terms of position, curvature and angles in order to:

[0007] -Optimize energy transfer to the runner to improve hydraulic efficiency;

[0008] - Optimize the return flow of water from the cup in order to reduce the return flow to the nozzle and the rotor and change the impact point of the water on the nozzle or the housing;

[0009] -Optimize the thickness distribution in the rotor to improve the tension level in the rotor;

[0010] - Optimize the mass distribution in the runner to improve the dynamic characteristics of the axis.

[0011] The radially inner end of the bucket or cup is understood to be the cup base when the bucket is arranged on a Pelton wheel, and the radially outer end of the cup is understood to be the bucket front in the arrangement of the bucket on a Pelton turbine as intended. The rear ridge is therefore usually arranged in the radially inner half of the bucket and for the most part does not protrude beyond the pitch diameter. In particular, the apex of the ridge (that is, the point of the ridge at which the distance of the ridge from the theoretical straight outlet edge is the largest) is usually located radially within the pitch diameter.

[0012] It is beneficial if the ridge projects beyond the central splitter. The straight portion of the outlet edge (that is to say the area where the outlet edge forms a substantially straight connecting line between the bucket front and the cup base in a side view) can be arranged below the central splitter so that, in a preferred embodiment, the straight edge is located below the central splitter and only the ridge projects beyond the central splitter.

[0013] It has proven to be effective that the center of mass of the rear bulge is located between the cup base and the center between the cup base and the bucket front. In this way, a beneficial flow is achieved both in the radially outer region and in the rear region or the region of the cup further inward in the radial direction. Here, the part of the cup that protrudes beyond the direct straight connecting line of the cup base and the bucket front is understood as the bulge. Therefore, the center of mass of this part that protrudes beyond the straight edge is understood as the center of mass.

[0014] In this case, the expressions radially inner and radially outer naturally refer to a cylindrical coordinate system starting from the axis of rotation of the Pelton wheel on which the buckets are arranged or, as desired, can be arranged.

[0015] It is preferably provided that the rear ridge extends from the cup base to approximately the center between the cup base and the bucket front.

[0016] In principle, the ridge, which is part of the outlet edge, can be implemented in the most diverse ways. In order to achieve favorable flow conditions, it is preferably provided that the ridge comprises: a first concave area, which has a center of curvature located above the outlet edge in side view; a second convex area, which has a center of curvature located below the outlet edge in side view; and a third concave area, which has a center of curvature located above the outlet edge in side view. Preferably, the rear ridge thus comprises two turning points and a generally crown-shaped structure between them, and the first and third concave areas transition tangentially into the adjacent edge of the bucket, which edge thus generally corresponds in side view to a straight connecting line or a straight edge of the cup base and the bucket front.

[0017] Typically, it is provided that the rear ridge extends approximately to the cup base, but the cup comprises an outlet edge in the region of the cup base having a height corresponding to the straight edge. Here, the straight edge is considered to be the line forming a straight connection of the cup base and the bucket front in a side view.

[0018] In order to achieve a particularly advantageous flow rate and a high efficiency, it is preferably provided that the bucket comprises an additional front ridge which is at least sectionally curved, wherein the centre of curvature is located below the outlet edge in a side view, and wherein the apex of the front ridge is arranged closer to the bucket front than to the cup base.

[0019] The increase in the height of the flow outlet thus also results in a front region or radially outer region of the bucket.

[0020] The front ridge preferably also comprises a concave area, an adjacent convex area and another concave area adjacent to the convex area, so that the front ridge also preferably comprises two turning points and, as a rule, is located only above a theoretical straight edge or a straight connecting line from the base of the cup to the front of the bucket. The front ridge can extend to the front of the bucket, but it can also be provided that the front ridge does not completely extend to the front of the bucket at the front end, so that a straight or straight area is obtained between the front end of the front ridge and the front of the bucket.

[0021] It has proven to be particularly advantageous if the front elevation has a smaller height than the rear elevation. For example, the front elevation and the rear elevation can have a height of less than 30% of the maximum cup depth (according to the definition from DE 39 38 356 C2).

[0022] The invention can also be combined with a bucket comprising an outlet edge with a concave area, as described for example in document EP 1 386 976 B1. In this case, provision can be made that the outlet edge comprises a concave area, in particular between the rear bulge and the front bulge.

[0023] Buckets for Pelton turbines are usually arranged symmetrically about a central flow splitter. It has therefore proven to be beneficial if the ridges are arranged symmetrically on both sides of a theoretical center plane of the bucket (which center plane usually contains the central flow splitter).

[0024] It should be understood that the corresponding buckets are usually arranged on a Pelton wheel of a Pelton turbine, wherein the Pelton wheel preferably comprises only buckets implemented according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further features, advantages and effects of the invention are derived from the exemplary embodiments described below. In the accompanying drawings referenced thereby:

[0026] Figure 1A section of a Pelton wheel having three buckets according to the present invention is shown;

[0027] Figure 2 Another section of a Pelton wheel according to the invention having three buckets implemented according to the invention is shown;

[0028] Figure 3 Pelton wheel is shown;

[0029] Figure 4 The bucket blades of the Pelton wheel are shown;

[0030] Figure 5 A Pelton wheel is shown. DETAILED DESCRIPTION

[0031] Figure 1 A section of a Pelton wheel 1 according to the invention is shown, in which three buckets 2 are depicted. It can be seen that each bucket 2 comprises a bucket front 4, a cup base 3 and a central diverter 5. On both sides of the central diverter 5 and symmetrically about the center plane, the illustrated bucket 2 comprises a rear ridge 7 on the outlet edge 6, which extends beyond the illustrated straight edge 9, that is, in a side view beyond the straight connecting line of the cup base 3 and the bucket front 4. In this way, the outlet height of the flow is increased in the region of the rear ridge 7, which leads to more beneficial flow properties. In order to make this particularly clear, the straight edge 9 is illustrated as a dashed line in the region of the rear ridge 7. Outside the region of the rear ridge 7, the outlet edge 6 corresponds to the straight edge 9.

[0032] It can be seen that the rear ridge 7 comprises a first concave region 11, an adjacent second convex region 12 and another adjacent concave region 11, the second convex region 12 comprising an apex 10, wherein the concave region 11 transitions substantially continuously into the straight outlet edge 6. In the side view, it can be seen that the apex 10 of the rear ridge 7 is closer to the cup base 3 than to the bucket front 4 and is therefore located radially inside the center of the cup, or inside the steel ring.

[0033] Figure 2 A further exemplary embodiment of a Pelton wheel 1 with buckets 2 implemented according to the invention is shown, wherein a region comprising three buckets 2 is once again illustrated. Figure 1 In addition to the rear ridge 7 illustrated in the figure, these buckets 2 also include a front ridge 8. In this way, the height of the flow outlet is raised in some areas of the front region. It can be seen that both the rear ridge 7 and the front ridge 8 in this case each have a concave region 11, an adjacent convex region 12 and a further adjacent concave region 11, so that a substantially continuous transition to the outlet edge 6 of the adjacent ridge results.

[0034] It can also be seen that neither the front bulge 8 nor the rear bulge 7 extends completely to the front and rear ends of the bucket 2, respectively, or to the cup base 3 and the bucket front 4, even though this is possible in principle. Here, too, the apex 10 of the rear bulge 7 is closer to the cup base 3 than to the bucket front 4, while the apex 10 of the front bulge 8 is closer to the bucket front 4 than to the cup base 3. In the illustrated bulges, the center of mass of the rear bulge 7 is likewise closer to the cup base 3 than to the bucket front 4, and the center of mass of the front bulge 8 is closer to the bucket front 4 than to the cup base 3, respectively. The center of mass and the apex 10 of the rear bulge 7 are therefore located radially inside the steel ring, which is not illustrated here, and the apex 10 and the center of mass of the front bulge 8 are located radially outside the steel ring.

[0035] Figure 3 A further Pelton wheel 1 is shown with a bucket 2 implemented according to the invention. It can be seen that the bucket 2 comprises, on the one hand, a concave region 11 with a curvature, wherein the center of curvature is located above the outlet edge 6 in the side view. In addition, these buckets 2 also comprise a radially inner rear bulge 7 in order to positively influence the flow. The outlet edge 6 is thus located below the central flow divider 5 in the concave region 11.

[0036] Figure 4 A further bucket 2 of a Pelton turbine is shown, which again comprises, on either side of a central splitter 5, a rear ridge 7 and a front ridge 8, which rise above a straight edge 9, respectively, which coincides with the outlet edge 6 outside the rear ridge 7 and the front ridge 8. In this case, the straight connecting line of the bucket front and the cup base in the side view is again understood to be a straight edge. Here, the front ridge 8 extends to the bucket front 4 and is aligned with the outlet edge 6. Figure 2 In contrast to the front bulge 8 illustrated in the figure, it does not include a concave region 11 at the front end, but rather transitions convexly into the bucket front part 4. Therefore, the front bulge 8 in this case only includes one turning point, while the rear bulge 7 in this case is as shown in FIG. Figure 1 As in the exemplary embodiment illustrated in FIG. 1 , a concave region 11 , an adjacent convex region 12 and another concave region 11 adjacent to the convex region 12 are included, and thus two turning points are included.

[0037] Figure 5 Shown with Figure 4 The Pelton wheel 1 of the bucket blade 2 is illustrated in the figure.

[0038] By implementing the bucket 2 of a Pelton turbine according to the invention, a beneficial influence on the flow rate can be achieved and an increased efficiency can be obtained. In addition, previously impossible designs of innovative bucket profiles with more geometric possibilities in terms of position, curvature and angle can thus be achieved.

Claims

1. A bucket blade (2) of a Pelton turbine, the bucket blade (2) having an outlet edge (6) which is at least partially curved, characterized in that The outlet edge (6) forms a rear ridge (7) in a side view, wherein the center of curvature of the ridge is located below the outlet edge (6) in a side view, and the apex (10) of the ridge is closer to the cup base (3) than to the bucket front (4).

2. The bucket leaf (2) according to claim 1, characterized in that The raised portion protrudes beyond the central splitter (5).

3. The bucket leaf (2) according to claim 1 or 2, characterized in that The center of mass of the rear raised portion (7) is located between the cup base (3) and the center between the cup base (3) and the front portion (4) of the bucket.

4. Bucket leaf (2) according to one of claims 1 to 3, characterised in that The rear raised portion (7) extends from the cup base (3) approximately to the center between the cup base (3) and the bucket front portion (4).

5. Bucket (2) according to one of claims 1 to 4, characterised in that The raised portion comprises a first concave region (11), a second convex region (12) and a third concave region (11), wherein the first concave region (11) has a curvature center located above the outlet edge (6) in a side view, the second convex region (12) has a curvature center located below the outlet edge (6) in a side view, and the third concave region (11) has a curvature center located above the outlet edge (6) in a side view.

6. Bucket (2) according to one of claims 1 to 5, characterised in that The bucket (2) comprises an additional front ridge (8) which is at least partially curved, wherein the centre of curvature is located below the outlet edge (6) in a side view, and wherein the apex (10) of the front ridge (8) is arranged closer to the bucket front (4) than to the cup base (3).

7. The bucket leaf (2) according to claim 6, characterized in that The height of the front raised portion (8) is smaller than that of the rear raised portion (7).

8. Bucket (2) according to one of claims 1 to 7, characterised in that The outlet edge (6) comprises a concave region (11), in particular between the rear ridge (7) and the front ridge (8).

9. Bucket (2) according to one of claims 1 to 8, characterised in that The raised portions (7, 8) are symmetrically arranged on both sides of a theoretical center plane of the bucket (2).

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