Hydraulic Machines Most Imp Mcq

Hydraulic Machines Most Imp Mcq

1. A Kaplan turbine is preferred for a specific speed of

 

Ans.300 to 1000 r.p.m.

2. The specific speed of a turbine is the speed of an imaginary turbine, identical with the given turbine, which

Ans. develops unit power under unit head

3. The runaway speed of a hydraulic turbine is the speed

Ans. at which the turbine will run freely without load

4. If the net positive suction head (NPSH) requirement for the pump is not satisfied, then

Ans. cavitation will be formed

6. The ratio of quantity of liquid discharged per second from the pump to the quantity of liquid passing per second through the impeller is known as

Ans. volumetric efficiency

7. Discharge of a centrifugal pump is

Ans. Inversely proportional to (diameter)² of its impeller

8. The static head of a centrifugal pump is equal to the __________ of suction head and delivery head.

Ans. sum

9. The ratio of actual work available at the turbine to the energy imparted to the wheel is known as

overall efficiency.

10. Geometric similarity is said to exist between the model and the prototype, if both of them

Ans. are identical in shape, but differ only in size

11. The power produced by the reaction turbine is directly proportional to the

head of water.

12. Slip of a reciprocating pump is defined as the

Ans. difference of theoretical discharge and the actual discharge

13. The efficiency of a centrifugal pump will be maximum when the blades are

Ans.bent backward.

14. Multi-stage centrifugal pumps are used to

Ans. produce high heads

15. Which of the following pump is preferred for flood control and irrigation applications?

Ans. Axial flow pump

16. The unit discharge through the turbine is

Ans :- Q / √ H

17. The discharge of a double acting reciprocating pump is (where L = Length of stroke, A = Cross-sectional area of piston, and N = Speed of crank in r.p.m.)

Ans .2 L.A.N/ 60

18. Which of the following turbine is preferred for 0 to 25 m head of water?

Ans. Kaplan turbine

19. Discharge (Q) of a centrifugal pump is given by (where D = Diameter of impeller at inlet, b = Width of impeller at inlet, and Vf = Velocity of flow at inlet)

Ans.Q = π.D.b.Vf

20. A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to the

Ans. Manometric head

21. A Francis turbine is used when the available head of water is

Ans. 25 m to 250 m

22. A hydraulic coupling belongs to the category of

Ans. energy transfer machines

23. The principle of jet propulsion is used in driving the.

Ans. ships and Aeroplan’s

24. In the casing of a centrifugal pump, the kinetic energy of the water is converted into pressure energy

Ans. before the water leaves the casing.

25. The speed of an imaginary turbine, identical with the given turbine, which will develop a unit power under a unit head, is known as

Ans. specific speed

26. For centrifugal pump impeller, the maximum value of the vane exit angle is

Ans. 20° to 25°

27. Power required to drive a centrifugal pump is directly proportional to fourth power of diameter of its

 impeller.

28. The mechanical efficiency of an impulse turbine is

Ans. ratio of the actual work available at the turbine to the energy imparted to the wheel

29. In a Kaplan turbine runner, the number of blades are generally between

Ans. 4 to 8

30. The impeller of a centrifugal pump may have A.volute casing

B.volute casing with guide blades

C.vortex casing

D.any one of these

31. A reciprocating pump is suitable for.

Ans.less discharge and higher heads

Note:-

A reciprocating pump is a class of positive-displacement pumps which includes the piston pump, plunger pump and diaphragm pump.

32. The cavitation in a hydraulic machine is mainly due to

Ans. low pressure

33. The unit speed of the turbine runner is

Ans. N / √ H

34. Which of the following pump is sucessfully used for lifting water to the boilers?

Ans. Jet pump

35. Which of the following pump is successfully used for lifting water from deep wells?

Ans. Air lift pump

36. The Thomson's turbine is an inward flow

reaction turbine.

37. The overall efficiency for a Pelton wheel lies between

Ans. 0.85 to 0.90

38. A reciprocating pump is also called a

positive displacement pump.

39. The head available at the inlet of the turbine is known as

Ans.  net or effective head.

40. A double overhung Pelton wheel has

Ans. two runners

41. Which of the following hydraulic unit is used for transmitting increased or decreased torque to the driven shaft?

Ans. Hydraulic torque converter

42. If the ratio of all the corresponding linear dimensions are equal, then the model and the prototype are said to have

Ans. geometric similarity

43. Which of the following pump is suitable for small discharge and high heads?

Ans. Reciprocating pump

44. In an outward flow reaction turbine

Ans. the water enters at the center of the wheel and then flows towards the outer periphery of the wheel

45. A hydraulic press is a device used

Ans. to lift larger load by the application of a comparatively much smaller force

46. Which of the following turbine is preferred for a specific speed of 60 to 300 r.p.m.?

Ans. Francis turbine

Note:-

It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today. They operate in a water head from 40 to 600 m (130 to 2,000 ft) and are primarily used for electrical power production.

47. The jet ratio is defined as the ratio of the

Ans. diameter of Pelton wheel to the diameter of jet

48. Mechanical efficiency of a centrifugal pump is the ratio of

Ans. energy available at the impeller to the energy supplied to the pump by the prime mover

49. Slip of a reciprocating pump is negative, when

Ans. suction pipe is long and delivery pipe is short and the pump is running at high speeds.

Note:-

Slip is the quantity of fluid that leaks from the higher-pressure discharge to the lower-pressure suction. Slip occurs because all rotary pumps require clearances between the rotating elements and pump housing.

50. The Furneyron turbine is an outward flow

Ans. reaction turbine.

51. Which of the following pump is successfully used for lifting water to the turbines?

Ans. Jet pump

52. The width of the bucket for a Pelton wheel is generally five times the

Ans. diameter of jet.

53. For 450 m head of water, Pelton wheel

 shall be used.

54. Impulse turbine is generally fitted

little above the tail race

Note:-

a fast-flowing stretch of a river or stream below a dam or watermill.

44. The angle of taper on draft tube is

less than 8°.

Note:-

function of a draft tube

Draft tube: The draft tube is a conduit which connects the runner exit to the tail race where the water is being finally discharged from the turbine. The primary function of the draft tube is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the outlet.

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