RADIAL FLOW RUNNER FOR A HYDRAULIC MACHINE
A runner of the Francis type including a crown, a plurality of blades, each blade being defined by a pressure surface, a suction surface, an edge adjoining the high pressure side and a spaced apart edge adjoining the low pressure side. The crown includes a seal to seal the space above the crown against water from the high pressure side. The further runner includes at least one passage being capable to drain high pressure leakage water to the low pressure side. The passage includes an inlet aperture located in a portion of the crown which is exposed to high pressure leakage water. The passage is located within a blade and leads from the inlet aperture to the edge of the same blade adjoining to the low pressure side. The passage is shaped to form a continuous opening in the same edge adjoining to the low pressure side.
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This is a continuation of PCT application No. PCT/EP2017/081659, entitled “RADIAL FLOW RUNNER FOR A HYDRAULIC MACHINE”, filed Dec. 6, 2017, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION 1. Field of the InventionThe present invention relates generally to hydroelectric turbine or pump installations with a radial flow runner of the Francis type.
2. Description of the Related ArtHydraulic machines including a radial flow runner of the Francis type are suffering from axial thrust applied to the runner of the hydraulic machine. Since the sealing between the runner and the high pressure side of the water passage cannot be made perfectly tight, water can get in the space between the head cover of the hydraulic machine and the runner crown resulting in a high axial thrust. To reduce the axial thrust prior art has proposed several concepts. One concept comprises balancing pipes draining the water passing the seals to the low pressure side of the water passage (see e.g. U.S. Pat. No. 1,820,150 to Moody). Another concept comprises balance holes within the runner crown leading to the runner hub or to the space between the blades of the runner (see e.g. U.S. Pat. No. 4,086,020 to Seiichi and Syoji). Balancing pipes are generally expensive. The effectiveness of the prior art balancing holes depends on the revolution speed of the runner and the blade geometry and therefore leading not always to satisfactory results concerning thrust reduction. Especially in the case of modernization projects when an existing runner relying on balancing holes has to be replaced by a new runner the situation can occur that the modern blade geometry cannot be accommodated by balancing holes of the known type and the installation of balancing pipes is impractical since the existing hydraulic machine is embedded in concrete. It is desirable in many modernization projects to have new runners with blades which extend closer to the axis of rotation at the trailing edge near runner crown. This geometry provides improved performance characteristics but in many cases makes the use of balancing holes in the runner crown less effective at reducing thrust due to radial pumping effects within the runner crown space below the shaft flange. In some cases where the flange connecting the runner to the shaft is at a relatively low elevation, there may no longer be sufficient space available in the runner crown flange to accommodate balancing holes of the known type and so an alternative solution for thrust reduction is necessary.
What is needed in the art is an alternative concept for reducing the axial thrust being less expensive than balancing pipes and easily applicable within modernization projects.
SUMMARY OF THE INVENTIONThe present invention provides a runner of the Francis type for a hydraulic turbine or pump. The runner has a low pressure side and a high pressure side. The runner also has a crown including a seal for sealing a space above the crown against water from the high pressure side, a plurality of blades, and each blade of the plurality of blades being defined by a pressure surface, an oppositely facing suction surface, an edge adjoining the high pressure side of the runner, and a spaced apart edge adjoining the low pressure side of the runner. The runner further includes at least one passage being capable to drain high pressure leakage water passing the seal to the low pressure side. The at least one passage includes an inlet aperture located in a portion of the crown which during operation is exposed to high pressure leakage water. The at least one passage is located within a respective blade of the plurality of blades and leads from the inlet aperture to the edge adjoining to the low pressure side of the same respective blade. The passage is shaped to form a continuous opening in the edge adjoining to the low pressure side.
The axial thrust can be reduced by a runner that includes at least one passage leading from the runner crown to the trailing edge of at least one of the runner blades. Having leakage water exiting the trailing edge may reduce drag forces as the runner rotates and result in an improvement in hydraulic efficiency.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTIONThe spacer pieces 10 may form an obstacle to the leakage water flow. Therefore it may be favorable that the spacer pieces are of aerodynamic shape.
It is clear that the embodiments shown in the figures are examples of a much broader variety of embodiments each employing the inventive ideas. For example there could be several separate passages through one blade leading from separate inlet apertures to several separate continuous openings located at different portions of the edge adjoining the low pressure side. The different passages could also be located in different blades.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Claims
1. A runner of the Francis type for a hydraulic turbine or pump, comprising:
- a low pressure side and a high pressure side;
- a crown comprising a seal for sealing a space above the crown against water from the high pressure side;
- a plurality of blades, and each blade of the plurality of blades being defined by a pressure surface, an oppositely facing suction surface, an edge adjoining the high pressure side of the runner, and a spaced apart edge adjoining the low pressure side of the runner; and
- at least one passage being capable to drain high pressure leakage water passing the seal to the low pressure side, and the at least one passage includes an inlet aperture located in a portion of the crown which during operation is exposed to high pressure leakage water, and the at least one passage is located within a respective blade of the plurality of blades and leads from the inlet aperture to the edge adjoining to the low pressure side of the same respective blade, and wherein the passage is shaped to form a continuous opening in the edge adjoining to the low pressure side.
2. The runner of claim 1, wherein the continuous opening extends over at least 15% of the developed length of the edge adjoining to the low pressure side.
3. The runner of claim 1, wherein the location of the continuous opening is at an equal or larger radial distance from the axis of rotation of the runner than the inlet aperture.
4. The runner of claim 1, wherein in the region of the continuous opening, the pressure surface of the respective blade extends further than the suction surface measured from the edge adjoining the high pressure side along a camberline of the respective blade.
5. The runner of claim 1, wherein the respective blade in which the at least one passage is located comprises a base part and a cover part where the base part is of a single piece construction including the entire edge adjoining the high pressure side, the entire pressure surface of the respective blade, as well as a portion of a surface of the edge adjoining the low pressure side, and wherein the base part contains a cavity and the cover part is attached to the base part above the cavity to form the at least one passage.
6. The runner of claim 1, wherein the respective blade in which the at least one passage is located comprises a base part and a cover part, wherein the base part is of a single piece construction including the entire edge adjoining the high pressure side, the entire suction surface of the respective blade, as well as a portion of a surface of the edge adjoining the low pressure side, and wherein the base part contains a cavity and the cover part is attached to the base part above the cavity to form the at least one passage.
7. The runner of claim 6, further comprising at least one spacer piece that is located between the base part and the cover part within the at least one passage.
Type: Application
Filed: Jul 24, 2019
Publication Date: Nov 14, 2019
Applicant: Voith Patent GmbH (Heidenheim)
Inventors: Stuart Coulson (Seven Valleys, PA), Kenneth Dunbar (Manchester, PA), Benjamin Kotzman (New Oxford, PA), John Seifarth (York, PA), Daniel Mc Ginnis (Hanover, PA)
Application Number: 16/521,110