570 HYDKAULICS AND ITS APPLICATIONS 



(6) A Jonval turbine works under a head of 13*5 feet. The mean 

 diameter is 8 feet, the width of buckets = 17f inches, the number of 

 revolutions 46 per minute, and the turbine develops 266 horse power with 

 an efficiency of 86 per cent. The number of vanes is thirty-eight, these 

 being -f^ inch thick. Assuming guide angles of 18, and a coefficient of 

 discharge of *9, determine the velocity of exit from the guides, and the 

 inlet and outlet angles of the wheel vanes for entry without shock and 

 for rejection of water without velocity of whirl. Assume a coefficient of 

 discharge of '9 for the discharge orifices. 



(7) The following are details of an outward flow reaction turbine : 

 a = 28; /3 = 90; y = 22; 



r 2 = 3-875 feet ; r s = 4'146 feet ; 



61 = -971 feet ; b z = -937 feet ; 1 3 = '932 feet ; 



wi = 88 ; n 2 = 44; ti = '0083 feet; * 2 = '0117 feet. 



Measured outflow area of guide passages = 6'537 square feet. 

 ,, buckets = 7'687 



The available head is 13 feet. Determine the number of revolutions 

 for maximum efficiency, and determine the hydraulic efficiency under 

 such conditions. 



(8) The following are details of a 800 H.P. outward radial flow Girard 

 turbine : 



a = 20; /3 = 36; y = 30; r 2 = 4'1 feet; r 3 = 4'71 feet; bi = b 2 = 

 4'91 inches ; 6 3 = 16'14 inches. The effective head is 595'5 feet, and the 

 coefficient of discharge from the guide passages is found to be "85, the 

 coefficient of velocity being '92. Calculate the speed of rotation (actually 

 200 per minute) for maximum efficiency. 



