504 



HYDRAULICS AND ITS APPLICATIONS 



a three-bearing machine. The turbine runner is a steel casting whose 

 radial depth is very slightly greater than the vanes, the shaft being 

 enlarged into a disc of sufficient diameter to permit of bolting the vane 

 ring directly to it. The vanes are finished smooth by filing. 



Owing to the large diameter of the wheel and the high statical pressure 

 at entrance, special means were necessary to balance the considerable end 



FlG. 239C. Cross Section and End Elevation of Turbine for Snoqualmie Falls. 



thrust on the shaft. Owing to the leakage of pressure water into the 

 space behind the wheel, the rear face is subject to a pressure substantially 

 equal to that at entrance, while the front face is subject to a pressure 

 varying from that at entrance to that in the draught tube. This 

 produces a large excess of pressure towards the draught tube, and althougl 

 the axial discharge, by producing a change of momentum in an axial 

 direction, calls for a reaction on the wheel in the opposite direction, 

 yet the effect of this is small in comparison with that previous! 

 considered. 



