Power Plant Engineering MCQ

21. The function of a surge tank is to

(a) supply water at constant pressure.
(b) relieve water hammer pressures in the penstock pipe.
(c) produce surge in the pipeline.
(d) none of the above.

22. Water hammer occurs in

(a) surge tank.
(b) penstock.
(c) turbine casing.
(d) draft tube.

23. In a medium or high head hydroelectric power station a surge tank is provided to

(a) reduce the length of the penstock pipes.
(b) augment water at the forebay.
(c) control the pressure variations in the penstock pipes due to sudden load changes.
(d) control the Water flow through the turbine.

24. Where is the draft tube of a hydropower station that is an airtight pipe located?

(a) Near the surge tank.
(b) In between the penstock and the runner.
(c) In between the runner exhaust and the tailrace.
(d) At the beginning of penstock.

25. The draft tube is provided to

(a) raise the water surface of the stream to create an artificial head.
(b) reduce the effect of water hammer.
(c) increase the acting head on the water wheel.
(d) none of the above.

26. For variable heads of near about but less than 30 metres, which type of turbines is used in hydropower stations?

(a) Pelton.
(b) Kaplan.
(c) Francis.
(d) None of the above.

27. For harnessing lower variable water heads, the suitable hydraulic turbine with high percentage of reaction and runner adjustable vanes is

(a) Kaplan
(b) Francis
(c) Pelton
(d) Impeller

28. For high head and low discharge the water turbine used is

(a) Pelton wheel.
(b) Kaplan turbine.
(c) Francis turbine.
(d) propeller turbine.

29. The specific speed (N_s) of a turbine is given by the equation

(a) N_s = N√P ÷ H^0.75
(b) N_s = P√N ÷ H^3/2
(c) N_s = N√P ÷ H^1.25
(d) N_s = N√P ÷ H^2/3

30. The “specific speed” of a water turbine is the speed at which the turbine develops

(a) maximum horse power.
(b) unit horse power at all heads.
(c) unit horse power at unit head.
(d) minimum horse power.

31. The specific speeds of Kaplan, Francis and Pelton turbines are in

(a) the increasing order.
(b) the decreasing order.
(c) neither increasing nor decreasing order.

32. An impulse turbine

(a) is most suited for low head and high discharge power plants
(b) operates by initial complete conversion to kinetic energy.
(c) makes use of a draft tube.
(d) always operates submerged.

33. Turbines installed at Bhakra Nangal are

(a) Pelton wheels.
(b) Francis turbines.
(c) Kaplan turbines.
(d) Propeller turbines.

34. In water turbines, the runaway speed of Pelton wheel is

(a) 1.8 times rated speed.
(b) 2 – 2.2 times rated speed.
(c) 2.5 – 3 times rated speed.
(d) full load speed.

35. The number of buckets (Z) for a Pelton wheel in terms of jet ratio(m) is given by empirical relation

(a) Z = 15 m + 0.5
(b) Z = 0.5 m + 15
(c) Z = 2 m + 15
(d) Z = 2 + 15 m

36. In a reaction turbine, the function of draft tube is to

(a) reduce water hammer.
(b) increase flow rate of water.
(c) convert kinetic energy of water to potential energy by a gradual expansion in divergent part.
(d) none of the above.

37. In Francis turbine runner, the number of blades is usually of the order of

(a) 16 – 24
(b) 8 – 10
(c) 6 – 8
(d) 3 – 6

38. The maximum head of a Kaplan turbine is limited to

(a) 25 m
(b) 70 m
(c) 125 m

39. Which of the following statements is/are correct? In pumped storage power plants,

(a) water is re-circulated through water turbines.
(b) reversible turbines are used which operate as turbines for power generation during peak load hours and as pumps for pumping water during peak-off hours.
(c) plain Francis turbines are used.
(d) both (a) and (c) above are employed.

40. Consider the following statements regarding pumped storage plants:

1. A pumped storage plant is a base load plant.
2. The starting time of a pumped storage plant is very short.
3. Reversible turbines and pumps are highly suitable for pumped storage plants.

Which of the statements given above are correct?
(a) 1 and 2.
(b) 1 and 3.
(c) 2 and 3.
(d) 1, 2 and 3.