JANUARY 2012
SET 1
1. (a) Differentiate between speed Ratio and jet ratio in a Pelton wheel. What are the ranges of these ratios.
(b) What is Hydraulic Brake in a Pelton wheel? What for it is used?
(c) How do you design the size of the buckets and number of buckets in a Pelton wheel? [5+5+5]
2. (a) Obtain an expression for the work done by impeller of a centrifugal pump on water per second per unit weight of water.
(b) A centrifugal pump is to discharge 0.12m3/s at a speed of 1400 r.p.m. against a head of 30 m. The diameter and width of the impeller at outlet are 25 cm and 5 cm respectively. If the manometric efficiency is 75% determine the vane angle at outlet. [7+8]
3. (a) Explain the working of a Servo-motor with a neat sketch.
(b) A turbine develops 7300KW power under a head of 25m and at 135rpm speed.What is its specific speed? What would be the normal speed and output under a head of 29m. [7+8]
SET 4
4. (a) A Kaplan turbine generates 45 MW under a head of 22 m. The overall efficiency is 90% and the ratio of outlet to hub diameter is 2.85. Calculate the speed, specific speed and diameter of the runner.
(b) A Pelton wheel has a tangential velocity of buckets of 15 m/sec. The water is being supplied under a head of 36m at the rate of 20 lit/sec. The bucket deects the jet through an angle of 1600. If the coefficient of velocity of the nozzle is 0.98, and the power produced by the turbine. [7+8]
5. (a) What is the significance of Unit Power, Unit speed and unit discharge? Explain.
(b) Prove that for s single jet Pelton wheel, the specific speed is given by the relation:NS = 250d/D*n Where NS = Specific speed d = diameter of the jet in metres, D = diameter of the runner in metres n= overall efficiency of the wheel. Take coefficient of velocity for the nozzle as 0.98 and bucket speed as 0.46times the speed of the jet. [7+8]
6. (a) Define specific speed of a centrifugal pump. What is its significance..
(b) A centrifugal pump discharges 1200 lit/minute against a head of 16.5m when the speed is 1500 rpm. The diameter of the impeller is 35 cm and the power required is 6 h.p. A geometrically similar pump of 45 cm is to run at 1750 rpm. Assuming equal efficiencies, and i. the head developed ii. the discharge iii. power developed by 45 cm pump.
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