Quiznetik

Fluid Mechanics (FM) | Set 8

1. What is the water flow direction in the runner in a Francis turbine?

A. Axial and then tangential

B. Tangential and then axial

C. Radial and then axial

D. Axial and then radial

Correct : C. Radial and then axial

2. Which of the following is true in case of flow of water before it enters the runner of a Francis Turbine?

A. Available head is entirely converted to velocity head

B. Available head is entire converted to pressure head

C. Available head is neither converted to pressure head nor velocity head

D. Available head is partly converted to pressure head and partly to velocity head

Correct : D. Available head is partly converted to pressure head and partly to velocity head

3. Why does the cross sectional area of the Spiral casing gradually decrease along the circumference of the Francis turbine from the entrance to the tip?

A. To ensure constant velocity of water during runner entry

B. To prevent loss of efficiency of the turbine due to impulsive forces caused by extra area

C. To prevent leakage from the turbine

D. To reduce material costs in order to make the turbine more economical

Correct : A. To ensure constant velocity of water during runner entry

4. Which of the following profiles are used for guide vanes to ensure smooth flow without separation?

A. Rectangular

B. Bent Rectangular

C. Elliptical

D. Aerofoil

Correct : D. Aerofoil

5. In which of the following type of runners the velocity of whirl at inlet is greater than the blade velocity?

A. Such a case is practically impossible

B. Slow Runner

C. Medium Runner

D. Fast Runner

Correct : B. Slow Runner

6. Which of the following runner types will have the highest vane angle at inlet (β1 value)?

A. Slow Runner

B. Medium Runner

C. Fast Runner

D. Vane angle is defined only for Kaplan Turbines and not Francis turbines

Correct : C. Fast Runner

7. In case of a Medium runner, tan (α1) CANNOT be given by (α1 = Guide vane angle at inlet)?

A. Vf1 / Vw1

B. Vr1 / Vw1

C. Vr1 / u1

D. Vw1 / u1

Correct : D. Vw1 / u1

8. In the velocity diagrams for Francis turbine, which of the following velocity directions is along the blade curvature?

A. Vr1

B. Vw1

C. V1

D. u1

Correct : A. Vr1

9. In the figure shown below,which of the following angles replace the question mark?

A. Guide vane angle at inlet

B. Blade angle at inlet

C. Vane angle at inlet

D. Blade angle at outlet

Correct : A. Guide vane angle at inlet

10. In the figure shown below, which of the following type of runners has the blade curvature as shown in the above figure (The arrow denotes direction of blade motion)?

A. Information insufficient to determine

B. Slow Runner

C. Medium Runner

D. Fast Runner

Correct : B. Slow Runner

11. Francis turbine is typically used for which of the following values of available heads?

A. 300 m

B. 100 m

C. 30 m

D. 5 m

Correct : B. 100 m

12. Water flow velocity is given 10 m/s. The runner diameter is 3 m and the width of the wheel is 25 cm. Find the mass of water (kg) flowing across the runner per second.

A. 7500π

B. 50π

C. 300π

D. RPM of the turbine needs to be given

Correct : A. 7500π

13. Work done per second by a Francis turbine can be given by ρAVf (Vw1u1 + Vw2u2).

A. True

B. False

C. none

D. none

Correct : B. False

14. Which of the following terms is considered to be zero while deriving the equation for work done per second for Francis Turbine?

A. Vr1

B. Vw2

C. Vf2

D. Vr2

Correct : B. Vw2

15. Power developed by Francis turbine are calculated for a certain set of conditions. Now, the inlet whirl velocity is doubled, the blade velocity at inlet is doubled and the flow velocity is quartered. The power developed:

A. Is 4 times the original value

B. Is 2 times the original value

C. Is ½ times the original value

D. Is same as the original value

Correct : D. Is same as the original value

16. Volume flow rate of water in a Francis turbine runner is 25 m3/s. The flow velocity, whirl velocity and blade velocity are 11 m/s, 10 m/s and 5 m/s respectively, all values given at runner inlet. Find the power developed by the turbine.

A. 25 kW

B. 1.25 MW

C. 1.25 kW

D. 25 MW

Correct : B. 1.25 MW

17. The flow rate of the water flow in a Francis turbine is increased by 50% keeping all the other parameters same. The work done by the turbine changes by?

A. 50% increase

B. 25% increase

C. 100% increase

D. 150% increase

Correct : A. 50% increase

18. A student performs an experiment with a Francis turbine. He accidently set the RPM of Francis turbine to 1400 rpm instead of 700 rpm. He reported the power to be 1 MW. His teacher asks him to perform the same experiment using the correct RPM. The student performs the same experiment again, but this time the erroneously doubled the flow velocity. What does the student report the power to be?

A. 0.5 MW

B. 0.25 MW

C. 2 MW

D. 1 MW

Correct : D. 1 MW

19. The available head of a Francis Turbine is 100 m. Velocity of the flow at the runner inlet is 15 m/s. Find the flow ratio.

A. 0.33

B. 0.45

C. 0.67

D. 0.89

Correct : A. 0.33

20. How does the flow ratio (ψ) of a Francis turbine vary with available head (H)?

A. ψ α H

B. ψ α 1/H

C. ψ α sqrt (H)

D. ψ α 1/(sqrt (H))

Correct : D. ψ α 1/(sqrt (H))

21. What is the typical value for flow ratio in a Francis turbine?

A. 0.05 – 0.1

B. 0.15 – 0.30

C. 0.35 – 0.45

D. 0.50 – 0.60

Correct : B. 0.15 – 0.30

22. The available head of a Francis Turbine is 120 m. The blade velocity is given 35 m/s. Find the speed ratio of the turbine.

A. 0.56

B. 0.61

C. 0.71

D. 0.81

Correct : C. 0.71

23. The speed ratio (φ) varies directly with which of the following parameters?

A. Vw1

B. V1

C. N (RPM)

D. H (Available head)

Correct : C. N (RPM)

24. The typical value range of speed ratio for a Francis turbine is:

A. 0.3 – 0.6

B. 0.5 – 0.6

C. 0.1 – 0.4

D. 0.6 – 0.9

Correct : D. 0.6 – 0.9

25. Which of the following efficiencies for Francis Turbine is described as the ratio between the power produced by runner to the power supplied by water at the inlet?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : A. Hydraulic efficiency

26. Which of the following efficiencies for Francis Turbine is described as the ratio between total quantity of water over runner blades to total quantity of water supplied to turbine?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : B. Volumetric efficiency

27. Which of the following efficiencies for Francis Turbine is defined as the ratio between the power available at the shaft of the turbine to the power produced by the runner?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : C. Mechanical efficiency

28. Which of the following efficiencies for Francis Turbine is defined as the ratio between the power available at the shaft to the power supplied by water at the inlet?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : D. Overall efficiency

29. The whirl velocity at inlet of Francis turbine is given to be 20 m/s. The blade velocity is given as 35 m/s. What is the hydraulic efficiency for a head of 100 m?

A. 80%

B. 90%

C. 70%

D. 98%

Correct : C. 70%

30. The desired hydraulic efficiency of a turbine is 80% at a whirl velocity of 20 m/s and a head of 100 m. What should be the blade velocity of the turbine at inlet in m/s?

A. 40

B. 60

C. 80

D. 25

Correct : A. 40

31. The input water power of the Francis turbine is 1.25 times the runner power. What would be the hydraulic efficiency of the turbine (in %)?

A. 60

B. 70

C. 80

D. 90

Correct : C. 80

32. The volume flow rate into a Francis turbine is Q m3/s. 0.25Q m3/s volume of water do not flow over the runner blades. What is the mechanical efficiency of the turbine (in %)?

A. 65

B. 75

C. 80

D. Mechanical efficiency cannot be found out from the given information

Correct : D. Mechanical efficiency cannot be found out from the given information

33. The volumetric efficiency of a Francis turbine is given to be 90%. If the volume flow rate through the turbine is 25 m3/s. What is the flow rate of water over the runner blades (in m3/s)?

A. 20

B. 25

C. 22.5

D. 21.5

Correct : C. 22.5

34. The volumetric efficiency of a given turbine is 80%. If volume flow rate of water in given to be 30 m3/s, find the volume of water (m3) NOT flowing over the runner blades per second?

A. 5

B. 6

C. 10

D. 12

Correct : B. 6

35. The power available at the shaft of a Francis turbine is 1 MW. The volume flow rate of water in 25 m3/s, whirl velocity at inlet is 10 m/s and blade velocity is 5 m/s. Find the mechanical efficiency (in %)?

A. 65

B. 75

C. 80

D. 90

Correct : C. 80

36. The whirl velocity at inlet is 15 m/s and blade velocity is 10 m/s. The volume flow rate of water in 20 m3/s. Find the power output available at the shaft if the mechanical efficiency is 95% (in MW)?

A. 2.85

B. 3.075

C. 6.55

D. 0.285

Correct : A. 2.85

37. The power output of the shaft is 5 MW. The volume flow rate of water in 10 m3/s at an available head of 60 m. Find the overall efficiency of the turbine in % (g = 10 m/s2)?

A. 80

B. 82.5

C. 83.3

D. 85

Correct : C. 83.3

38. The volume flow rate of water in 10 m3/s at an available head of 60 m (g = 10 m/s3). Find the shaft power (in MW) if the overall efficiency of the turbine is 90%.

A. 54

B. 5.4

C. 540

D. 0.54

Correct : B. 5.4

39. The hydraulic efficiency of a Francis turbine is 90%, the mechanical efficiency is 95% and the volumetric efficiency is assumed to be 100%. Fine the overall efficiency (in %)?

A. 80

B. 85.5

C. 87.5

D. 83.3

Correct : B. 85.5

40. In a Kaplan turbine, what is the direction of water flow?

A. Axial and then axial

B. Radial and then axial

C. Tangential and then axial

D. Tangential and then radial

Correct : A. Axial and then axial

41. For which of the following values of available heads may Kaplan turbine be used?

A. 250 m

B. 100 m

C. 80 m

D. 50 m

Correct : D. 50 m

42. In this type of low head turbine, the guide vanes are fixed to the hub of the turbine and are not adjustable. What is this type of turbine called?

A. Francis turbine

B. Kaplan Turbine

C. Propeller Turbine

D. Pelton turbine

Correct : A. Francis turbine

43. The velocity of flow through a Kaplan turbine is 10 m/s. The outer diameter of the runner is 4 m and the hub diameter is 2 m. Find the volume flow rate of the turbine in m3/s?

A. 95

B. 75

C. 85

D. 105

Correct : A. 95

44. The velocity of the flow at the inlet of Kaplan turbine is V. In an experimental setup, what could be the possible value of the velocity of the flow at the outlet of Kaplan turbine?

A. V

B. 0.8V

C. 1.2V

D. 2V

Correct : B. 0.8V

45. Which of the following turbines will have the lowest number of blades in it?

A. Pelton turbine

B. Steam turbine

C. Francis turbine

D. Kaplan turbine

Correct : D. Kaplan turbine

46. The velocity of the flow through the Kaplan turbine is 25 m/s. The available head of the turbine is 60 m. Find the flow ratio of the turbine (take g = 10 m/s2).

A. 0.65

B. 0.72

C. 0.69

D. 0.75

Correct : B. 0.72

47. A Kaplan turbine requires a speed ratio of 2. The available head of the turbine is 5 m. What should be the blade velocity of the turbine such that a speed ratio of 2 is maintained (take g = 10 m/s2)?

A. 75.75 m/s

B. 63.25 m/s

C. 23.35 m/s

D. 50.00 m/s

Correct : B. 63.25 m/s

48. The flow ratio of a Kaplan turbine is given as 0.7. The available head is 30 m. The outer diameter of the runner is 3.5 m and the hub diameter is 2 m. Find the volume of water flowing through the turbine per second (m3/s)?

A. 90

B. 111

C. 125

D. 168

Correct : B. 111

49. In which of the following type of runners in a Kaplan turbine the velocity of whirl at inlet is smaller than the blade velocity?

A. Such a case is practically impossible

B. Slow Runner

C. Medium Runner

D. Fast Runner

Correct : D. Fast Runner

50. In the outlet velocity triangle of a Kaplan turbine, β2 = 30o. Vf2 = 5 m/s. What is the relative velocity of the flow at outlet?

A. 10 m/s

B. 5.77 m/s

C. 8.66 m/s

D. 2.88 m/s

Correct : A. 10 m/s

51. In the inlet velocity triangle of a Kaplan turbine, α1 = 45o. The velocity of flow at inlet = 10 m/s. Find the whirl velocity of water at the inlet of Kaplan turbine?

A. 5 m/s

B. 10 m/s

C. 12.5 m/s

D. 15 m/s

Correct : B. 10 m/s

52. The whirl velocity of water at the inlet of the Kaplan turbine is 15 m/s. The velocity of water at inlet of the turbine is 20 m/s. Find the guide vane angle at inlet (In degrees).

A. 53.13

B. 36.86

C. 45

D. 41.41

Correct : D. 41.41

53. The relative velocity of water at the inlet of the Kaplan turbine is 7 m/s. β1 = 75o. The whirl velocity of the water at inlet is 10 m/s. Find the blade velocity of the turbine?

A. 26.124 m/s

B. 40 m/s

C. 36.124 m/s

D. 60 m/s

Correct : C. 36.124 m/s

54. For the figure given below, find the missing terms in the order of (1), (2), (3) and (4).

A. Vr1, α1, β1, Vw1

B. Vw1, β1, α1, Vr1

C. Vw1, α1, β1, Vr1

D. Vr1, β1, α1, Vw1

Correct : C. Vw1, α1, β1, Vr1

55. Kaplan turbine works on

A. Electrical energy

B. Hydro energy

C. Thermal energy

D. Chemical energy

Correct : C. Thermal energy

56. Kaplan turbine is an reaction turbine

A. Inward flow

B. Outward flow

C. Radial

D. Axial

Correct : A. Inward flow

57. The Kaplan Turbine is an evolution of

A. Francis turbine

B. Pelton wheel

C. Parsons turbine

D. Curtis turbine

Correct : A. Francis turbine

58. What is the dimension of thermal efficiency of a Kaplan turbine?

A. kg

B. m

C. kg/m

D. Dimensionless

Correct : D. Dimensionless

59. A Kaplan turbine is used in

A. Turbomachinery

B. Pressure drag

C. Aerodynamics

D. Automobiles

Correct : A. Turbomachinery

60. The head of the Kaplan ranges from

A. 100 to 200 m

B. 250 to 300 m

C. 10 to 70 m

D. 0 m

Correct : C. 10 to 70 m

61. Nozzles in the Kaplan turbine move due to impact of

A. Water

B. Steam

C. Blade

D. Another nozzle

Correct : B. Steam

62. The power output of Kaplan turbine ranges from

A. 5 to 200 MW

B. 1000 to 2000 MW

C. 2000 to 3000 MW

D. 5000 and above

Correct : A. 5 to 200 MW

63. Kaplan turbines rotates at a rate

A. Increasing

B. Decreasing

C. Constant

D. Increasing and then decreasing

Correct : C. Constant

64. What type of turbine is Kaplan?

A. Impulse

B. Reaction

C. Energy

D. Hydro

Correct : B. Reaction

65. Kaplan turbine is needed to improve

A. Increase Pressure

B. Decrease temperature

C. Change volume

D. Increase efficiency

Correct : D. Increase efficiency

66. Kaplan turbine is an type turbine

A. Pressure

B. Inward flow

C. Outward flow

D. Velocity

Correct : B. Inward flow

67. The turbine does not have to be at the lowest point of water flow as long as the water in the draft tube is full.

A. True

B. False

C. none

D. none

Correct : A. True

68. The outlet of the Kaplan turbine is through

A. Vane Blades

B. Moving pipeline

C. Draft tube

D. Pump

Correct : C. Draft tube

69. Kaplan turbine is most commonly used in propeller turbines.

A. True

B. False

C. none

D. none

Correct : A. True

70. For a Kaplan turbine, the whirl velocity at inlet of the turbine is given to be 18 m/s. The blade velocity is given as 25 m/s. What is the hydraulic efficiency for a head of 50 m. Take g = 10 m/s2?

A. 80%

B. 90%

C. 70%

D. 98%

Correct : B. 90%

71. Which of the following efficiencies for Kaplan Turbine is described as the ratio between the power produced by runner to the power supplied by water at the inlet?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : A. Hydraulic efficiency

72. The desired hydraulic efficiency of a Kaplan turbine is 98% at a whirl velocity of 20 m/s and a head of 60 m. What should be the blade velocity of the turbine at inlet in m/s? Take g = 10 m/s2.

A. 40

B. 60

C. 80

D. 30

Correct : D. 30

73. It is given that the input water power of the Kaplan turbine is 1.10 times the runner power. What would be the hydraulic efficiency of the turbine (in %)?

A. 60.61

B. 70.71

C. 80.81

D. 90.91

Correct : D. 90.91

74. Which of the following efficiencies for Kaplan Turbine is described as the ratio between total quantity of water over runner blades to total quantity of water supplied to turbine?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : B. Volumetric efficiency

75. The volume flow rate into a Kaplan turbine is Q m3/s. 0.10Q m3/s volume of water do not flow over the runner blades. What further information is required to find the volumetric efficiency (numerical value) of the Kaplan turbine?

A. The numerical value of Q

B. The available head of the turbine

C. The RPM or the blade velocity of the turbine

D. No further information is required

Correct : D. No further information is required

76. A student reports the volumetric efficiency of a Kaplan turbine to be 95%. If he measures the volume flow rate through the turbine is 40 m3/s. What is the flow rate of water over the runner blades (in m3/s)?

A. 38

B. 40

C. 42.11

D. 45

Correct : A. 38

77. 95*40 = 38 m3/s. 358. In a Kaplan turbine experiment, the volumetric efficiency of a given turbine is 91%. If volume flow rate of water in given to be 35 m3/s, find the volume of water (m3) NOT flowing over the runner blades per second?

A. 4.05

B. 3.15

C. 3.30

D. 2.55

Correct : B. 3.15

78. Which of the following efficiencies for Kaplan Turbine is defined as the ratio between the power available at the shaft of the turbine to the power produced by the runner?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : C. Mechanical efficiency

79. The power available at the shaft of a Kaplan turbine is 0.75 MW. The volume flow rate of water in 15 m3/s, whirl velocity at inlet is 12 m/s and blade velocity is 5 m/s. Find the mechanical efficiency (in %)?

A. 66.66

B. 75.00

C. 83.33

D. 91.33

Correct : C. 83.33

80. The whirl velocity at inlet of a Kaplan turbine is 7.5 m/s and blade velocity is 5 m/s. The volume flow rate of water in 20 m3/s. Find the power output available at the shaft if the mechanical efficiency is 93% (in MW)?

A. 0.831

B. 0.697

C. 1.362

D. 0.298

Correct : B. 0.697

81. In a Kaplan Turbine experimental setup, the power output of the shaft is 4.325 MW. The volume flow rate of water in 15 m3/s at an available head of 50 m. Find the overall efficiency of the turbine in % (g = 10 m/s2)?

A. 57.66

B. 83.63

C. 81.33

D. 79.95

Correct : A. 57.66

82. The hydraulic efficiency of a Kaplan turbine is 95%, the mechanical efficiency is 93% and the volumetric efficiency is assumed to be 100%. Fine the overall efficiency (in %)?

A. 80.05

B. 93.15

C. 87.55

D. 88.35

Correct : D. 88.35

83. Which of the following efficiencies for Kaplan Turbine is defined as the ratio between the power available at the shaft to the power supplied by water at the inlet?

A. Hydraulic efficiency

B. Volumetric efficiency

C. Mechanical efficiency

D. Overall efficiency

Correct : D. Overall efficiency

84. In Kaplan turbine apparatus, the volume flow rate of water in 15 m3/s at an available head of 55 m (g = 10 m/s2). Find the shaft power (in MW) if the overall efficiency of the turbine is 95%.

A. 78.3

B. 7.83

C. 783

D. 0.783

Correct : B. 7.83

85. Draft tube is also called

A. Straight divergent tube

B. Simple elbow tube

C. Thermal tube

D. Elbow tube with varying cross section

Correct : A. Straight divergent tube

86. A draft tube helps in converting kinetic energy into

A. Electrical work

B. Mechanical work

C. Chemical work

D. Thermal work

Correct : B. Mechanical work

87. Most common application of the draft tube is

A. Rotor

B. Motor

C. Pump

D. Filter

Correct : C. Pump

88. Draft tube consists of conical diffuser with angles of

A. 10 deg

B. 20 deg

C. 30 deg

D. 40 deg

Correct : A. 10 deg

89. What is the purpose of a Draft tube?

A. To prevent flow separation

B. To avoid Pressure drag

C. To prevent rejection of heat

D. To increase efficiency

Correct : A. To prevent flow separation

90. What is the maximum value of efficiency in a draft tube?

A. 100

B. 50

C. 90

D. 40

Correct : C. 90

91. Turbine that consists of draft tubes is called as_

A. Impulse turbine

B. Curtis turbine

C. Rateau turbine

D. Reaction turbine

Correct : D. Reaction turbine

92. Which of the following is a 50 percent reaction turbine?

A. Parsons turbine

B. Curtis turbine

C. Rateau turbine

D. Pelton wheel

Correct : A. Parsons turbine

93. The simple elbow draft tube helps to cut down the cost of excavation.

A. True

B. False

C. none

D. none

Correct : A. True

94. The exit diameter for a simple elbow draft tube should be

A. Large

B. Small

C. Very small

D. Same

Correct : A. Large

95. Properties that do not affect a draft tube is

A. Pressure

B. Temperature

C. Pressure velocity

D. Velocity

Correct : B. Temperature

96. The other name for elbow with varying cross section tube is called

A. Pressure tube

B. Bent draft tube

C. Velocity tube

D. Sink tube

Correct : B. Bent draft tube

97. What is the efficiency of the simple elbow type draft tube?

A. 10

B. 30

C. 60

D. 90

Correct : C. 60

98. The horizontal portion of the draft tube is usually bent to prevent entry of air from the exit end.

A. True

B. False

C. none

D. none

Correct : A. True

99. The efficiency of the draft tube is ratio of

A. Pressure energy by kinetic energy

B. Kinetic energy by Pressure energy

C. Kinetic energy into mechanical energy

D. Pressure into mechanical

Correct : B. Kinetic energy by Pressure energy

100. Draft tubes are not used in which of the following turbines?

A. Francis

B. Reaction

C. Kaplan

D. Pelton

Correct : D. Pelton