FRANCIS TURBINE 



495 



race tunnel is 366 square feet, this gives a velocity of efflux of 24 feet per 

 second. 



With the Francis turbine and cylindrical gate regulation, the full-load 

 efficiency may be as high as 88 per cent., but this efficiency falls rather 



regulating 



FIG. 234E. Oil Pressure Relay Governor for 10.250 H.P. Turbine. 



rapidly as the gate opening is diminished, and does not in general 

 exceed 75 per cent, at half gate. Two Francis turbines installed at 

 Schaffhausen in an open water chamber, and developing at full load 

 434 H.P. at 169 revolutions and under 13'6 feet head, gave the following 

 efficiencies : 



