60 most asked Turbo Machines mcq questions

Q. 1. In a velocity triangle absolute velocity at inlet V1 has two components, Vf1 and Vw1. Vf1
is called as __________
A : Velocity of whirl at inlet
B : Velocity of flow at inlet
C : Velocity of vane at inlet
D : Velocity of flow at exit

Velocity of flow at inlet

Q. 2. Impulse turbine is generally fitted
A : At the level of tail race
B : Little above the tail race
C : Slightly below the tail race
D : About 2.5 m above the tail race to avoid cavitations

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Little above the tail race

Q. 3. Mass of 1 litre of water is equivalent to
A : 10 Kg
B : 100 Kg
C : 1000 Kg
D : 1000 gm

1000 gm

Q. 4. The runner passages of a reaction turbine are
A : partially filled with water
B : always completely filled with water
C : never filled with water
D : None of these.

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always completely filled with water

Q. 5. An impulse turbine is used for
A : Low head of water
B : High head of water
C : Medium head of water
D : High discharge

High head of water

Q. 6. Braking jet in an impulse turbine is used
A : to break the jet of water
B : to bring the runner to rest in a short time
C : to change the direction of runner
D : None of these

to bring the runner to rest in a short time

Q. 7. The cavitation in a hydraulic machine is mainly due to
A : Low velocity
B : High velocity
C : Low pressure
D : High pressure

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Low pressure

Q. 8. Which of the following draft tubes is suited
particularly for helical flow?

A : Conical type draft tube.
B : Elbow type draft tube.
C : Moody’s spreading draft tube.
D : None of these.

Moody’s spreading draft tube.

Q. 9. The equation F. dt = d (mv) is called as
A : Impulse momentum equation
B : Impulse reaction principle
C : Newton’s second law of motion.
D : None of these

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Impulse momentum equation

Q. 10. Gross head is the difference between
A : Head race and Tail race
B : Head race and Net head
C : Head race and Friction losses
D : Net head and Friction losses

Head race and Tail race

Q. 11. Which of the following turbines is least efficient
under part load conditions:

A : Propeller
B : Kaplan turbine
C : Pelton wheel
D : Francis turbine

Propeller

Q. 12. What is the general energy equation for transfer of energy between the fluid and
machine?
Where,
Vw1 = Tangential component of the velocity of fluid at the entry of the rotor
Vw2 = Tangential component of the velocity of fluid at the exit of the rotor
u1

A : E = ṁ (Vw1 – Vw2) x (u1 – u2)
B : E = ṁ (Vw1 – Vw2) / (u1 – u2)
C : E = ṁ (Vw1 u1 – Vw2 u2)
D : E = ṁ (Vw1 u1 – Vw2 u2)2

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E = ṁ (Vw1 u1 – Vw2 u2)

Q. 13. Axial width of Pelton wheel bucket lies between _____ Where d is diameter of jet
A : 2.5 d to 3 d
B : 3 d to 3.5 d
C : 3 d to 4 d
D : 3.5 d to 4.5 d

3 d to 4 d

Q. 14. In a velocity triangle at outlet, if angle β is 90 degrees , then Vf2= _________
A : U2
B : Vw2
C : V2
D : None

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V2

Q. 15. In a velocity triangle absolute velocity at inlet V1 has two components, Vf1 and
________

A : Vf2
B : Vw1
C : Vw2
D : Vri

Vw1

Q. 16. The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is
…………… of the jet velocity.

A : One-fourth
B : Half
C : Three-fourth
D : Double

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Half

Q. 17. Which of the following statements with respect
to a reaction water turbine is incorrect:

A : The spiral casing serves to uniformly
distribute water into guide blades
B : The water leaves the turbine at atmospheric
pressure
C : The draft tube allows setting of the
turbine above the tail race with minimum
reduction of available energy
D : The guide vanes direct the flow at proper
angle.

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The water leaves the turbine at atmospheric pressure

Q. 18. Efficiency of jet of water having velocity V , stiking series of vertical plates moving with
velocity U is maximum when ____.

A : U= 2V
B : U= V/2
C : U= V/3
D : U=V/4

U= V/2

Q. 19. The Jet of water after striking the stationary flat vertical plate will be deflected at an
angle of

A : 110 degrees
B : 45 degrees
C : 90 degrees
D : None of these

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90 degrees

Q. 20. Specific speed of a turbo-machine
A : relates the shape rather than the size of the
machine
B : remains unchanged under different
condi tions of operation
C : has the dimensions of rotational speed
D : is the speed of a machine having unit
dimensions.

relates the shape rather than the size of the machine

Q. 21. A hydraulic turbine converts the potential energy of water into
A : Kinetic energy
B : Heat energy
C : Thermal energy
D : Gravitational energy

Kinetic energy

Q. 22. The mechanical efficiency of an impulse turbine is
A : ratio of the actual power developed by the turbine to the energy actually supplied by the turbine
B : ratio of the actual work available at the turbine to the energy imparted to the wheel
C : ratio of the work done on the wheel to the energy of the jet
D : None of these

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

Q. 23. The value of flow ratio (Kf) in case of a Francis turbine varies from:
A : 0.1 to 0.14
B : 0.15 to 0.30
C : 0.35 to 0.5
D : 0.6 to 0.9

0.15 to 0.30

Q. 24. A turbo-machine becomes more susceptible to
cavitation if

A : velocity attains a high value
B : pressure become very high
C : temperature rises above the critical value
D : pressure falls below the vapour pressure.

pressure falls below the vapour pressure.

Q. 25. The gross or total head of the turbine is the ___________ of the water levels at the head
race and tail race

A : Sum
B : Difference
C : Product
D : None of these

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Difference

Q. 26. The force exerted by a jet impinging normally on a stationary fixed plate is
A : (ρAV)/4
B : (ρAV)
C : (ρAV2)/4
D : (ρAV2)

(ρAV2)

Q. 27. In a velocity triangle absolute velocity at inlet V2 has two components, Vf2 and Vw2,
Vw2 is called as __________

A : Velocity of whirl at inlet
B : Velocity of flow at inlet
C : Velocity of vane at inlet
D : Velocity of Whirl at at exit

Velocity of Whirl at at exit

Q. 28. What is runaway speed of the runner of Pelton wheel?
A : Maximum unsafe speed of the runner due to sudden increase in load on turbine
B : Minimum safe speed of the runner due to sudden increase in load on turbine
C : Maximum unsafe speed of the runner due to sudden decrease in load on turbine
D : Minimum safe speed of the runner due to sudden decrease in load on turbine

Maximum unsafe speed of the runner due to sudden decrease in load on turbine

Q. 29. The gross or total head of the turbine is the ………….. of the water levels at the head
race and tail race.

A : Sum
B : Difference
C : Product
D : Division

Difference

Q. 30. In a reaction turbine the function of a draft tube
is to

A : provide safety to turbine
B : prevent air from entering
C : reconvert the kinetic energy to flow energy
D : increase the rate of flow.

reconvert the kinetic energy to flow energy

Q. 31. Value of Cofficient of velocity Cv for nozzle in pelton wheel lies between
A : 0.85 to 0.9
B : 0.9 to 0.95
C : 0.95 to 0.97
D : 0.97 to 0.99

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0.97 to 0.99

Q. 32. The Francis turbine of runner diameter 0.484 m is running at 700 r.p.m.. Determine
velocity of wheel at inlet.

A : 17.73 m/s
B : 4.07 m/s
C : 6.56 m/s
D : 30.14 m/s

17.73 m/s

Q. 33. Mass of water striking per second , for a series of flat plates mounted on drum is
_______

A : ρaV
B : ρa(V-u)
C : ρa( V-u)/2
D : ρaV/2

ρaV

Q. 34. The depth of the bucket for a Pelton wheel is generally _________ the diameter of jet.
A : Equal to
B : 1.2 times
C : 1.8 times
D : Double

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1.2 times

Q. 35. The jet ratio of a pelton wheel lies between
A : 3 to 5
B : 6 to 10
C : 11 to 14
D : 20 to 25

11 to 14

Q. 36. When a steady water jet impinges on a fixed incline surface,
A : No force is exerted by the jet on the surface
B : The momentum in the direction parallel to the surface is unchanged
C : The flow is divided into two parts proportional to the angle of inclination of the surface
D : The speed is reduced for that portion of the jet that turns through more than 90 degree and increase
for the other position

The flow is divided into two parts proportional to the angle of inclination of the surface

Q. 37. The reaction turbine of runner diameter 1.08 m is running at 200 r.p.m.. Determine
peripheral speed at inlet.

A : 11.304 m/s
B : 3.84 m/s
C : 7.23 m/s
D : 30.97 m/s

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11.304 m/s

Q. 38. A Pelton wheel is ideally suited for
A : high head and low discharge
B : high head and high discharge
C : low head and low discharge
D : medium head and medium discharge

high head and low discharge

Q. 39. In a velocity triangle at outlet, if angle β < 90 degrees , then direction of Vw1 and Vw2
are________ _________

A : Same
B : Opposite
C : Perpendicular to each other
D : Parallel to each other

Opposite

Q. 40. In impulse Turbine, energy available at the inlet is in the form of
A : Potential Energy
B : Strain Energy
C : Kinetic energy
D : None of these

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Kinetic energy

Q. 41. A Pelton wheel working under a constant head and discharge, has maximum efficiency
when the speed ratio is

A : 0.26
B : 0.36
C : 0.46
D : 0.56

0.46

Q. 42. The maximum number of jets, generally, employed in an impulse turbine without jet
interference are

A : Two
B : Four
C : Six
D : Eight

Six

Q. 43. Power supplied to francis turbine is 15000 kW and having hydraulic efficiency of the
turbine 94 % Find the power developed to the turbine.

A : 14100 kW
B : 6204 kW
C : 3948 kW
D : 28764 kW

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14100 kW

Q. 44. when a jet of water strikes a vertical hinged plate, the angle of swing about the hinge is
given by ______________. Where, V=Velocity of the jet of water and W= weight of the hinged
plate

A : Sinθ= ρAV2/W
B : Cosθ= ρAV2/W
C : Tanθ= ρAV2/W
D : None of these

Sinθ= ρAV2/W

Q. 45. Jet of water strikes a stationary plate. Workdone by the jet will be
A : Negative
B : Positive
C : Zero
D : Unpredictable

Zero

Q. 46. A jet of water is striking at the centre of a curved vane moving with a uniform velocity
in the direction of jet. For the maximum efficiency, the vane velocity is ________ of the jet
velocity

A : One-half
B : One-third
C : Two-third
D : Three-fourth

One-third

Q. 47. A reaction turbine works under a head of 60 m. Assuming speed ratio as 0.6, find
tangential vlocity of blade.

A : 42.18 m/s
B : 20.58 m/s
C : 6.79 m/s
D : 6.58 m/s

20.58 m/s

Q. 48. In force exerted by jet on series of moving curves vanes, jet strikes tangentially, the
relative velocity is ____________, where, V is the Velocity of Jet and U is the velocity of the Plate.

A : V1-U
B : Vri
C : V1+U
D : None of these

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V1-U

Q. 49. A Kaplan turbine works under a head of 7.62 m. Assuming flow ratio as 0.95, find
vlocity of flow.

A : 11.61 m/s
B : 5.1 m/s
C : 2.78 m/s
D : 20.31 m/s

11.61 m/s

Q. 50. The runaway speed of a hydraulic turbine is the speed
A : At full load
B : At which there will be no damage to the runner
C : Corresponding to maximum overload permissible
D : At which the turbine will run freely without load

Corresponding to maximum overload permissible

Q. 51. A jet of water is striking at the centre of a curved vane moving with a uniform velocity
in the direction of the jet. For the maximum efficiency, the vane velocity is ______ of the jet
velocity.

A : Twice
B : One-Third
C : Two-Third
D : Three-Forth

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One-Third

Q. 52. In force exerted by jet on series of moving curves vanes, jet strikes tangentially, angle α
is called____________

A : guide vane angle at inlet
B : moving vane angle at inlet
C : angle made absolute velocity at inlet
D : moving vane angle at exit

angle made absolute velocity at inlet

Q. 53. In a reaction turbine, work done is 150 kW. Velocity of blade at inlet is 3.17 m/s and rate
of flow of water is 2.66 m3/s. Determine tangential velocity of whirl. Assume whirl velocity at
outlet as zero.

A : 3.86 m/s
B : 31.07 m/s
C : 4.96 m/s
D : 17.78 m/s

17.78 m/s

Q. 54. A jet of water of diameter 5 cm having a velocity of 30 m/sec strikes a curved vane
horizontally at one of its tip which is moving with a velocity of 15 m/sec in the direction of jet.
The jet leaves the vane at an angle of 60˚ to the direction of motion o

A : 7.12 kW
B : 9.94 KW
C : 12 kW
D : 10 kW

9.94 KW

Q. 55. The ratio of actual work available at the turbine to the energy imparted to the wheel is
known as ________ efficiency.

A : Hydraulic
B : Mechanical
C : Overall
D : None of these

Mechanical

Q. 56. The specific speed of a turbine is given by the equation
A : (NÖP)/H3/2
B : (NÖP)/H2
C : (NÖP)/H5/4
D : (NÖP)/H3

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(NÖP)/H5/4

Q. 57. A Pelton wheel develops 1750 kW under a head of 100 meters while running at 200
r.p.m. and discharging 2500 liters of water per second. The unit speed of the wheel is

A : 10 r.p.m.
B : 20 r.p.m.
C : 40 r.p.m.
D : 80 r.p.m.

20 r.p.m.

Q. 58. The relation between hydraulic efficiency (ηh), mechanical efficiency (ηm) and overall
efficiency (ηo) is

A : ηh = ηo × ηm
B : ηm = ηm × ηh
C : ηo = ηh × ηm
D : NONE

ηo = ηh × ηm

Q. 59. Ratio of forces exerted by water Jet, when it is made to strike a stationary flat plate held
normal to it and a flat plate moving in the direction of jet at one-third of the velocity of it would
be ___

A : 0.12638888888888888
B : 0.37777777777777777
C : 0.16874999999999998
D : 0.12569444444444444

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0.37777777777777777

Q. 60. Water Jet 0.0015 Sq. meter area issues from a nozzle with 15m/s velocity. It is made to
impinge perpendicular onto a plate that moves away with the velocity of 5 m/s. The force on the
plate due to this impact is

A : 150 N
B : 1470 N
C : 340 N
D : 900 N

150 N

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