POKHARA UNIVERSITY

Level: Bachelor Semester – Spring Year : 2010Programme: BE Full Marks : 100

Pass Mark : 45Course: Power Plant Equipment Time : 3 hrs

Candidates are required to give their answers in their own words as far as practicable.The figures in the margin indicate full marks.Attempt all the questions.

1. a. With the help of a simple diagram, explain the working of a hydropower plant. Deduce an expression for the power available from the plant in terms of head (H) and discharge (Q).

b. A Kaplan turbine has the outer diameter of 8m and the inner diameter of 3 m. The turbine develops a power of 29400 kW at 80 rpm under a head of 12 m. The discharge through the runner is 300m3/sec. If the hydraulic efficiency of the turbine is 95%, determine i) the inlet and outlet blade angles, ii) the mechanical efficiency of the turbine and iii) the overall efficiency of the turbine.

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2. a. What is meant by "Water Hammer"? Deduce an expression for the rise of pressure in a pipe when the water flowing in the pipe is brought to rest by gradually closing the valve fitted at the end of the pipe. Assume that the pipe is rigid.

b. A diesel engine has a compression ratio of 15:1 and the fuel is cut-off at one-tenth of the stroke. If the calorific value of the fuel is 33,496kJ/kg, calculate the amount of fuel required in kg/kWh. Take for both, air and gas.

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3. a. With the help of a simple diagram, explain the working of a combined cycle plant employing steam and gas turbines. How does the combined cycle plant improve the thermal efficiency of the plant?

b. A gas turbine power plant takes in air at 150C, the pressure ratio is 4:1 and the maximum temperature in the cycle is 5600C. Assuming efficiencies of 0.86 and 0.83 for the turbine and compressor respectively, determine the overall efficiency of the plant for the following cases.

i. Without using heat exchanger

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ii. With heat exchanger making the use of 75% of the heat available.

4. a. What is meant by "Nuclear Chain Reaction"? Explain how is the nuclear reaction controlled in a reactor?

b. The steam leaves the nozzles of an impulse turbine with a velocity of 375 m/sec and the nozzle angle is 200. The blade speed is 165 m/sec. Find suitable inlet and outlet angles for the blades in order that the axial thrust is zero. The relative velocity of steam as it flows over the blades is reduced by 15% by friction. Determine the power developed by the turbine, if the steam flow rate is 10kg/sec.

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5. a. Discuss the methods of increasing the thermal efficiency of a simple Rankine cycle.

b. Estimate the electric energy that could theoretically be produced by fissioning of 1 gm of U235 per day.

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6. a. Elaborate the importance of earthing system in a power plant. What are the factors to be taken into consideration while designing an earthing system?

b. Name the different types of bus-bar schemes usually adopted in outdoor switchyards. Explain the ring bus-bar arrangement in detail.

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7. Write short notes on any two:a. Cooling of Diesel power plantb. Starting of gas turbine power plantc. Use synchronous machine as synchronous condenser

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