Mechanical Engineering-Hydraulic Machines Important MCQ PDF

1. Reciprocating pumps are no
more to be seen in industrial applications (in comparison to centrifugal pumps)
because of
(a) high initial and maintenance cost
(b) lower discharge
(c) lower speed of operation
(d) necessity of air vessel
(e) all of the above.
Ans: a

2. In a centrifugal pump casing, the flow of
water leaving the impeller, is
(a) rectilinear flow
(b) radial flow    
(c) free vortex motion
(d) forced vortex
(e) none of the above.
Ans: c

3. Head developed by a centrifugal pump
depends on
(a) impeller diameter
(b) speed
(c) fluid density
(d) type of casing
(e) (a) and (b) above.
Ans: e

4. For starting an axial flow pump, its
delivery valve should be
(a) closed
(b) open
(c) depends on starting condition and flow
desired
(d) could be either open or closed
(e) partly open and partly closed.
Ans: b

5. The efficiency of a centrifugal pump is
maximum when its blades are
(a) straight
(b) bent forward
(c) bent backward
(d) bent forward first and then backward
(e) bent backward first and then forward.
Ans: c

6. In a centrifugal pump casing, the flow of
water leaving the
(a) radial
(b) radial
(c) centrifugal    
(d) rectilinear
(e) vortex.
Ans: e

7. Centrifugal pump is started with its
delivery valve
(a) kept fully closed
(b) kept fully open
(c) irrespective of any position
(d) kept 50% open
(e) none of the above.
Ans: a

8. Axial flow pump is started with its
delivery valve
(a) kept fully closed
(b) kept fully open
(c) irrespective of any position
(d) kept 50% open
(e) none of the above.
Ans: b

9. When a piping system is made up primarily of vertical lift and very little
pipe friction, the pump characteristics should be
(a) horizontal
(b) nearly horizontal
(c) steep
(d) first rise and then fall
(e) none of the above.
Ans: c

10. One horsepower is equal to
(a) 102 watts
(b) 75 watts
(c) 550 watts
(d) 735 watts
(e) 33000 watts.
Ans: d

11. Multistage centrifugal pumps are used to
obtain
(a) high discharge
(b) high head
(c) pumping of viscous fluids
(d) high head and high discharge
(e) high efficiency.
Ans: b

12. When a piping system is made up primarily
of friction head and very little of vertical lift, then pump characteristics
should be
(a) horizontal    
(b) nearly horizontal
(c) steep
(d) first rise and then fall
(e) none of the above.
Ans: b

13. In a single casing, multistage pump
running at constant speed, the capacity rating is to be slightly lowered. It
can be done by
(a) designing new impeller
(b) trimming the impeller size to the
required size by machining
(c) not possible
(d) some other alterations in the impeller
(e) none of the above.
Ans: b

14. If a pump is handling water and is
discharging a certain flow Q at a constant total dynamic head requiring a
definite B.H.P., the same pump when handling a liquid of specific gravity 0.75
and viscosity nearly same as of water would discharge
(a) same quantity of liquid
(b) 0.75 Q
(c) Q/0.75
(d) 1.5 Q
(e) none of the above.
Ans: a

15. The horse power required in above case
will be
(a) same
(b) 0.75 B.H.P.
(c) B.H.P./0.75    
(d) 1.5 B.H.P.
(e) none of the above.
Ans: b

16. Low specific speed of a pump implies it
is
(a) centrifugal pump
(b) mixed flow pump
(c) axial flow pump
(d) any one of the above
(e) none of the above.
Ans: a

17. The optimum value of vane exit angle for
a centrifugal pump impeller is
(a) 10-15°
(b) 20-25°
(c) 30-40°
(d) 50-60°
(e) 80-90°.
Ans: b

18. In a centrifugal pump, the liquid enters
the pump
(a) at the top
(b) at the bottom
(c) at the center  
(d) from sides
(e) none of the above.
Ans: c

19. For small discharge at high pressure,
following pump is preferred
(a) centrifugal    
(b) axial flow
(c) mixed flow    
(d) propeller
(e) reciprocating.
Ans: e

20. In centrifugal pumps, maximum efficiency
is obtained when the blades are
(a) straight
(b) bent forward
(c) bent backward
(d) radial
(e) given aerofoil section.
Ans: c

21. Motion of a liquid in a volute casing of
a centrifugal pump is an example of
(a) rotational flow
(b) radial
(c) forced spiral vortex flow
(d) forced cylindrical vortex flow
(e) spiral vortex flow.
Ans: e

22. For very high discharge at low pressure
such as for flood control and irrigation applications, following type of pump
is preferred
(a) centrifugal    
(b) axial flow
(c) reciprocating  
(d) mixed flow
(e) none of the above.
Ans: b

23. Medium specific speed of a pump implies
it is
(a) centrifugal pump
(b) mixed flow pump
(c) axial flow pump
(d) any one of the above
(e) none of the above.
Ans: b

24. High specific speed of a pump implies it
is
(a) centrifugal pump
(b) mixed flow pump
(c) axial flow pump
(d) any one of the above
(e) none of the above.
Ans: c

25. Indicator diagram of a reciprocating pump
is a graph between
(a) flow vs swept volume
(b) pressure in cylinder vs swept volume
(c) flow vs speed
(d) pressure vs speed
(e) swept volume vs speed.
Ans: b

26. Low specific speed of turbine implies it
is
(a) propeller turbine
(b) Francis turbine
(c) impulse turbine
(d) any one of the above
(e) none of the above.
Ans: c

27. Any change in load is adjusted by
adjusting following parameter on turbine
(a) net head
(b) absolute velocity
(c) blade velocity
(d) flow
(e) relative velocity of flow at inlet.
Ans: d

28. Runaway speed of a hydraulic turbine is
(a) full load speed
(b) the speed at which turbine runner will be
damaged
(c) the speed if the turbine runner is
allowed to revolve freely without load and with the wicket gates wide open
(d) the speed corresponding to maximum
overload permissible
(e) none of the above.
Ans: c

29. The maximum number of jets generally
employed in impulse turbine without jet interference is
(a) 4
(b) 6
(c) 8
(d) 12
(e) 16.
Ans: b

30. Medium specific speea of turbine implies
it is
(a) propeller turbine
(b) Francis turbine
(c) impulse turbine
(d) any one of the above
(e) none of the above.
Ans: b

31. High specific speed of turbine implies it
is
(a) propeller turbine
(b) Francis turbine
(c) impulse turbine
(d) any one of the above
(e) none of the above.
Ans: a

32. The specific speed of turbine is defined
as the speed of a unit
(a) of such a size that it delivers unit
dis-charge at unit head
(b) of such a size that it delivers unit
dis-charge at unit power
(c) of such a size that it requires unit
power per unit head
(d) of such a size that it produces unit
horse power with unit head
(e) none of the above.
Ans: d

33. Puck up the wrong statement about centrifugal
pump
(a) discharge a diameter
(b) head a speed2
(c) head a diameter
(d) Power a speed3
(e) none of the above is wrong.
Ans: a

34. A turbine pump is basically a centrifugal
pump equipped additionally with
(a) adjustable blades
(b) backward curved blades
(c) vaned diffusion casing
(d) inlet guide blades
(e) totally submerged operation facility.
Ans: c

35. Casting of a centrifugal pump is designed
so as to minimize
(a) friction loss    
(b) cavitation
(c) static head
(d) loss of kinetic energy
(e) starting time.
Ans: d

36. In reaction turbine, draft tube is used
(a) to transport water downstream without
eddies
(b) to convert the kinetic energy to flow
energy by a gradual expansion of the flow cross-section
(c) for safety of turbine
(d) to increase flow rate
(e) none of the above.
Ans: b

37. Guide angle as per the aerofoil theory of
Kaplan turbine blade design is defined as the angle between
(a) lift and resultant force
(b) drag and resultant force
(c) lift and tangential force
(d) lift and drag
(e) resultant force and tangential force.
Ans: a

38. Francis turbine is best suited for
(a) medium head application from 24 to 180 m
(b) low head installation up to 30 m
(c) high head installation above 180 m
(d) all types of heads
(e) none of the above.
Ans: a

39. The flow rate in gear pump
(a) increases with increase in pressure
(b) decreases with increase in pressure
(c) more or less remains constant with
in-crease in pressure
(d) unpredictable
(e) none of the above.
Ans: c

40. 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
cavitation
(e) about 2.5 m below the tail race to avoid
cavitation.
Ans: b

41. Francis, Kaplan and propeller turbines
fall under the category of
(a) Impulse turbines
(b) Reaction turbines
(c) Axial flow turbines
(d) Mixed flow turbines
(e) Reaction-cum-impulse turbines.
Ans: b

42. Reaction turbines are used for
(a) low head
(b) high head
(c) high head and low discharge
(d) high head and high discharge
(e) low head and high discharge.
Ans: e

43. The discharge through a reaction turbine
with increase in unit speed
(a) increases
(b) decreases
(c) remains unaffected
(d) first increases and then decreases
(e) first decreases and then increases.
Ans: b

44. The angle of taper on draft tube is
(a) greater than 15°
(b) greater than 8°
(c) greater than 5°
(d) less than 8°
(e) less than 3°.
Ans: d

45. Specific speed for reaction turbines
ranges from
(a) 0 to 4.5
(b) 10 to 100
(c) 80 to 200
(d) 250 to 300
(e) none of the above.
Ans: b

46. In axial flow fans and turbines, fluid
enters and leaves as follows
(a) radially, axially
(b) axially, radially
(c) axially, axially
(d) radially, radially
(e) combination of axial and radial.
Ans: c

47. Which place in hydraulic turbine is most
susceptible for cavitation
(a) inlet of draft rube
(b) blade inlet      
(c) guide blade
(d) penstock
(e) draft tube exit.
Ans: a

48. Air vessels in reciprocating pump are
used to
(a) smoothen flow
(b) reduce acceleration to minimum
(c) increase pump efficiency
(d) save pump from cavitation
(e) increase pump head.
Ans: b

49. Saving of work done and power by fitting
an air vessel to single acting reciprocating pump is of the order of
(a) 39.2%
(b) 49.2%
(c) 68.8%
(d) 84.8%
(e) 91.6%.
Ans: d

50. Saving of work done and power by fitting
an air vessel to double acting reciprocating pump is of the order of
(a) 39.2%
(b) 49.2%
(c) 68.8%
(d) 84.8%
(e) 91.6%.
Ans: a

51. According to fan laws, for fans having
constant wheel diameter, the air or gas capacity varies
(a) directly as fan speed
(b) square of fan speed
(c) cube of fan speed
(d) square root of fan speed
(e) none of the above.
Ans: a

52. According to fan laws, for fans having
constant wheel diameter, the pressure varies
(a) directly as fan speed
(b) square of fan speed
(c) cube of fan speed
(d) square root of fan speed
(e) none of the above.
Ans: b

53. According to fan laws, for the fans
having constant wheel diameters, the power demand varies
(a) directly as fan speed
(b) square of fan speed
(c) cube of fan speed
(d) square root of fan speed
(e) none of the above.
Ans: c

54. According to fan laws, at constant speed
and capacity, the pressure and power vary
(a) directly as the air or gas density
(b) inversely as square root of density
(c) inversely as density
(d) as square of density
(e) as square root of density.
Ans: a

55. According to fan laws, at constant
pressure, the speed capacity and power vary
(a) directly as the air or gas density
(b) inversely as square root of density
(c) inversely as density
(d) as square of density
(e) as square root of density.
Ans: b

56. According to fan laws, at constant weight
of air or gas, the speed, capacity and pressure vary
(a) directly as the air or gas density
(b) inversely as square root of density
(c) inversely as density
(d) as square of density
(e) as square root of density.
Ans: c

57. Pressure intensifier increases the
pressure in proportion to
(a) ratio of diameters
(b) square of ratio of diameters
(c) inverse ratio of diameters
(d) square of inverse ratio of diameters
(e) fourth power of ratio of diameters.
Ans: b

58. A hydraulic accumulator normally consists
of
(a) two cylinders, two rams and a storage
device
(b) a cylinder and a ram
(c) two co-axial rams and two cylinders
(d) a cylinder, a piston, storage tank and
control valve
(e) special type of pump with storage device
and a pressure regulator.
Ans: b

59. A hydraulic intensifier normally consists
of
(a) two cylinders, two rams and a storage
device
(b) a cylinder and a ram
(c) two co-axial rams and two cylinders
(d) a cylinder, a piston, storage tank and
control valve
(e) special type of pump with storage device
and a pressure regulator.
Ans: c

60. Hydraulic accumulator is used for
(a) accumulating oil
(b) supplying large quantities of oil for
very short duration
(c) generally high pressures to operate
hydraulic machines
(d) supplying energy when main supply fails
(e) accumulating hydraulic energy.
Ans: d

61. Maximum impulse will be developed in
hydraulic ram when
(a) waste valve closes suddenly
(b) supply pipe is long
(c) supply pipe is short
(d) ram chamber is large
(e) supply pipe has critical diameter,
Ans: a

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