680 



HYDRAULICS AND ITS APPLICATIONS 



kead of 20 feet. The discharge area = 8*33 square feet, and the discharge 

 angle y = 26. The ratio - = f . 



?*2 J- 



Determine the manometric efficiency, and, assuming a loss of 10 per 

 cent, in friction, the H.P. to drive the pump, and the speed at which 

 lifting commences. 



f Manometric efficiency = '592. 



Mechanical efficiency = '492. 

 Answer. < Hp = 306 



[_ Lifting commences at 198 revolutions. 



C2) The following are results obtained from tests of a centrifugal pump, 

 having the following dimensions : r 3 = 15'25 inches ; r 2 = 7*675 inches ; 

 b 3 = 3-0 inches ; 6 2 = 4'0 inches ; y = 30 



Determine from this the value of % for maximum efficiency in terms 

 of V g H f , and determine the hydraulic efficiency in each case. 



(3) A pump delivers 3 cubic feet per second against 60 feet head, and is 

 required to rotate at 500 revolutions per minute. Making/ = J V 2 g H', 

 and giving the vanes radial tips, settle the leading features of the design, 

 on the assumption that guides are fitted with a conversion efficiency of 

 65 per cent. 



(4) A pump has an inner radius of 1 foot, and an outer radius of 2 feet. 

 It is not fitted with vortex chamber or guide vanes. 



Determine the speed at which lifting will commence against heads of 

 10, 20, 40 and 60 feet respectively. 



Answer. 99 ; 140 ; 198 ; 242 revolutions per minute. 



(5) A pump is intended to lift 25 cubic feet per second against a head 



