BLADE FOR SHROUDED RUNNER AND SHROUDED RUNNER COMPRISING SAID BLADE

Abstract

Embodiments of the present invention are related to a shrouded Kaplan and shrouded propeller-type hydraulic turbine. More in particular, the embodiments relate to a blade for such shrouded turbines. An object of the embodiments of the present invention is to add a winglet on the pressure side of a blade to eliminate a large gap between the blade and the shroud, in order to improve performances, decrease marginal cavitation, and improve fish friendliness.

Claims

1. A blade for a shrouded runner, comprising: a winglet extending upwards and located on a pressure side of the blade, wherein the blade is configured to rotate within an external shroud annularly located around the runner.

2. The blade according to claim 1, wherein the winglet is located in the proximity of a trailing edge of the blade.

3. The blade according to claim 1, wherein the winglet has a hydrodynamic profile.

4. The blade according to claim 1, wherein the winglet has a rounded leading edge.

5. The blade according to claim 1, wherein the winglet has a fillet junction with the blade.

6. A shrouded runner comprising a blade according to claim 1.

7. A method for rehabilitating a shrouded runner, comprising: providing a runner having one or more blades configured to rotate within a shroud annularly located around the runner; and providing the one or more blades with a winglet located on a pressure side of the blade and extending upwards.

8. The method according to claim 7, wherein the winglet is connected to the blade by welding.

9. The method according to claim 8, wherein the connection between blade and winglet establishes a fillet junction along a welding portion.

10. The method according to claim 7, wherein the winglet is included in a casting of the blade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The objects, advantages and other features of the present invention will become more apparent upon reading of the following non-restrictive description of embodiments thereof, given for the purpose of exemplification only, with reference to the accompany drawing, through which similar reference numerals may be used to refer to similar elements, and in which:

[0030] FIGS. 1, 2, 3, 4, 5, 6, and 7 show a blade comprising a winglet according to embodiments of the present invention in different perspective views.

DETAILED DESCRIPTION

[0031] With reference to FIG. 1, it is schematically shown a terminal portion of a blade of a runner (not shown) according to an embodiment of the present invention, generally indicated by numeral reference 1. The blade 1 is configured to rotate within an external shroud, schematically indicated with numeral reference 6, annularly located around the blade 1. As shown in the figure, blade 1 comprises a winglet 3 located on a blade pressure side 4 and extending upwards. The extent of the winglet 3 towards the shroud 6 is selected in such a way to provide a minimal gap 5 between a summit of the winglet 3 and the shroud, such to ensure tolerance necessary for the rotation of the blade within the volume delimited by the surrounding shroud.

[0032] According to an embodiment, winglet 3 has a rounded leading edge 7, and comprises a fillet junction 8 with the blade 1 along a connecting portion, to avoid stress concentrations, which might lead to breakage during prolonged usage.

[0033] In an embodiment, leading edge 7 is hydraulically smooth to avoid local flow accelerations.

[0034] With reference to next FIG. 2, blade 1 including the winglet 3 is more clearly shown in a perspective view. In an embodiment, as it may be appreciated from this view, winglet 3 has a hydrodynamic profile and is located in the proximity of a trailing edge of the blade.

[0035] The blade 1 according to an embodiment of the invention is also pictured, in different perspective views, in following FIGS. 3-7.

[0036] The height of the winglet 3 is designed such to effectively reduce the existing gap 5 between blade and shroud, when compared to known installations having blades of similar length. Moreover, the winglet is provided with a sufficient thickness in order to ensure mechanical integrity.

[0037] The winglet 3 may also be provided to an existing shrouded runner, in order to rehabilitate the turbine and to improve its performances.

[0038] The rehabilitating method of a shrouded runner according to an embodiment of the present invention includes providing the blades of the runner with the winglet 3 extending upwards and located on the blade pressure side 4.

[0039] The connection between the winglet and the existing blade may be carried out with a welding operation. In particular, the welding may be operated such to create the fillet junction 8 along a welding portion.

[0040] According to an alternative embodiment, the method for rehabilitating a shrouded runner may include the winglet in the casting of the blade, in order to obtain a blade comprising the winglet as a single-piece.

[0041] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.