Radial flow runner for a hydraulic machine

Abstract

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.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]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 INVENTION1. Field of the Invention[0002]The present invention relates generally to hydroelectric turbine or pump installations with a radial flow runner of the Francis type.2. Description of the Related Art[0003]Hydraulic 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 ...

AI Technical Summary

Benefits of technology

The patent is about a device called a runner that reduces drag and improves hydraulic efficiency by allowing water to leak out of its blades. This helps the device rotate more smoothly and reduces the amount of force needed to move it.

Problems solved by technology

Hydraulic 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.

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.

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.

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