542 



HYDKAULICS AND ITS APPLICATIONS 



so that with radial tips the peripheral velocity at entrance is nearly that 



11' 



due to a fall through a height '-^ , while the supply water at this point 



has changed only approximately one half of its total store into kinetic 



energy. 



From the foregoing analysis, or from a consideration of the triangle of 



velocities a b c of Fig. 

 256, it is evident that 

 the speed of the wheel 

 is a function solely of 

 the velocity due to 

 the head, and of the 

 angle a. 



This being so, it re- 

 mains to decide upon 

 n '^ "" * some relation between 



the velocities of flow 

 and of whirl before 

 this angle, and the 

 wheel speed, can bo 

 settled. The precise 

 relations between 



FIG. 256.-Vane Angles for Inward Kadial Flow Turbine. these tw() velocitieg 



which shall conduce to the highest economic efficiency, can orjly be deducec 

 from experiment, and the following table shows the relationships whicl 

 modern practice has shown to be most successful : 



