QUESTION FIVE (a) Moving from first principles, derive expressions for the power absorbed to overcome viscous resistance in; Hydraulic dynamometer (i) (ii) Journal bearing (iii) Thrust bearing (15 marks) (b) A thrust bearing consists of a 200 mm diameter pad rotating on another pad separated by an oil film of absolute viscosity = 0.125 Ns/ m and 0.75 mm thick. Calculate the power dissipated in the bearing if it rotates at 1500 revolutions per minute. QUESTION SIX (5 marks) (a) Explain what is meant by the specific speed of a centrifugal pump and show that its value is NQZ 3 H4 Where N is the rotational speed of the impeller, Q the discharge and H the operating head. (6 marks) (b). A centrifugal pump, having four stages in parallel, delivers 11 m/min of liquid against a head of 24.7 m, the diameter of the impeller being 225 mm and the speed 1700 rev/min. A pump is to be made up with a number of identical stages in series, of similar construction to those in the first pump, to run at 1250 rev/min and to deliver 14.5 m/min. find the diameter of the impellers and the number of stages required. QUESTION SEVEN (14 marks) (a) Define specific speed, unit power and unit speed as applied to a hydraulic turbine and develop expressions for them in terms of actual power, speed and supply head. State carefully the assumptions made. (8 marks) (b) Show that for a pelton wheel turbine, maximum energy transfer is achieved when u =- Vi Where u = mean runner or bucket speed V= the absolute velocity of jet at entry to the runner vane. =1 (10 marks) (c) If a turbine develops 3750 kilowatts at 300 rev/min. under a head of 18 metres, what is its specific speed? H.V.2 (2 marks) T 4= T -TM D