220 



HYDRAULIC EQUIPMENT 



is imagined to be cut by a plane perpendicular to the paper and 

 intersecting the paper in an ordinate at any given value of 0, 

 the resulting intersection would be a performance curve such as 

 one of those plotted in Fig. 109. 



In Fig. 109, of course, the horse-power has been stepped up to 

 represent a large runner operating under a given head. The 

 performance curves can be conveniently plotted from the </>- 

 efficiency and <t>-HP\ curves by finding the corresponding values 

 of HP\ and efficiency for certain required values of < which are 

 determined by the head and speed in a given installation. 



Speed Regulation. 1 The most generally used method for 

 governing the speed of reaction turbines is by means of wicket 

 gates or guide vanes which change the amount of water supplied 

 by simply altering the water passages (see Fig. 113). The vanes 



j"'"i.-' : ^. : -'. ! -:-j 



FIG. 113. Typical Arrangement of Vertical Reaction Turbine, Showing 

 Relation of Wicket Guide Vanes to Casing and Runner. 



rotate about pivots and are fastened to a shifting ring by link 

 motion, the ring being operated by pressure cylinders, actuated 

 by the governor. If the velocity of the water is checked too 

 suddenly dangerous pressures may be set up in the pipe lines and 

 the speed regulation may be affected. In order to avoid this, 

 1 See also sections on " Governors " and " Waterhammer." 



