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.

What is claimed is: 
     
         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.