EXAMPLES 529 



EXAMPLES. 



1. Discuss the relative advantages and disadvantages of the impulse 

 and pressure turbine as regards 



(a) Applicability to high, medium, 01 low heads. 



(b) Applicability to suit local conditions. 



(c) Efficiency. 



(d) Speed regulation. 



(e) Speed of rotation. 



2. Sketch any device suitable for the speed regulation of 



(a) A Pelton wheel. 



(b) A Girard turbine. 



(c) An inward radial flow turbine. 



(d) An outward radial flow turbine. 



3. The nozzle circle of a Barker's mill has a diameter of 2 feet. The 

 nozzles, two in number, are J" diameter, and when working under a head 

 of 1 foot the wheel makes 240 revolutions per minute. Determine its 

 hydraulic efficiency, neglecting the effect of friction. 



Answer '982. 



4. In the wheel of the previous example, the weight of water used at 

 240 revolutions per minute, working head 6 feet, was 670 Ibs. The 

 brake horse power was '056. 



Determine the coefficient of frictional resistance inside the wheel ; the 

 hydraulic efficiency, the total efficiency, the speed for maximum possible 

 hydraulic efficiency, and this efficiency. 

 Answer : 



F = -2. 



Hydraulic efficiency = -522. 



Total efficiency == '46. 



Speed for maximum efficiency = 160 revolutions. 

 Maximum efficiency =; '593. 



