Q.1

In an impulse turbine, steam expands

  • wholly in blades
  • wholly in nozzle
  • partly in the nozzle and partly in blades
  • none of these
Q.2

In a nozzle, the effect of supersaturation is to increase the dryness fraction of steam.

  • Yes
  • No
Q.3

The isentropic enthalpy drop in moving blade is two-third of the isentropic enthalpy drop in fixed blades of a turbine. The degree of reaction will be

  • 0.4
  • 0.56
  • 0.67
  • 1.67
Q.4

The stage efficiency (ηS) is given by (where ηB = Blading efficiency, and ηN = Nozzle efficiency)

  • ηS = ηB x ηN
  • ηS = ηBN
  • ηS = ηNB
  • none of these
Q.5

The discharge of steam in a convergent-divergent nozzle __________ after the throat (i.e. in the divergent portion of the nozzle)

  • remains constant
  • decreases
  • increases
Q.6

The impulse reaction turbine has its driving force

  • as an impulsive force
  • as a reaction force
  • partly as an impulsive force and partly as a reaction force
  • none of the above
Q.7

The critical pressure ratio for initially dry saturated steam is more as compared to initially wet steam.

  • Yes
  • No
Q.8

The difference of supersaturated temperature and saturation temperature at that pressure is called

  • degree of supersaturation
  • degree of superheat
  • degree of undercooling
  • none of these
Q.9

When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be

  • choked
  • underdamping
  • overdamping
  • none of these
Q.10

The variation of steam pressure in the nozzle depends upon

  • velocity of steam
  • specific volume of steam
  • dryness fraction of steam
  • all of these
Q.11

The critical pressure gives the velocity of steam at the throat

  • equal to the velocity of sound
  • less than the velocity of sound
  • more than the velocity of sound
  • none of these
Q.12

The rate of discharge through the nozzle __________ when the exit pressure is gradually reduced.

  • remains same
  • decreases
  • increases
Q.13

The efficiency of reaction turbine is maximum when (where α = Angle made by the absolute velocity (V) at inlet)

  • Vb = 0.5 V cos α
  • Vb = V cos α
  • Vb = 0.5 V2 cos α
  • Vb = V2 cos α
Q.14

In a convergent divergent nozzle, the discharge depends upon the initial conditions of steam and the area of nozzle at throat.

  • Correct
  • Incorrect
Q.15

In reaction turbines, the axial thrust is due to

  • pressure drop across the rotor
  • change in axial velocity
  • both (a) and (b)
  • none of these
Q.16

The turbine, in which the general direction of the steam flow is parallel to the turbine axis, is called axial flow turbines

  • True
  • False
Q.17

The ratio of the workdone on the blades to the energy supplied to the blades, is called

  • blading efficiency
  • nozzle efficiency
  • gross or stage efficiency
  • mechanical efficiency
Q.18

Steam turbines are used for

  • large marine propulsion
  • electric power generation
  • direct drive of fans, compressors, pumps
  • all of these
Q.19

The Parsons' reaction turbine has

  • only moving blades
  • only fixed blades
  • identical fixed and moving blades
  • fixed and moving blades of different shape
Q.20

In reaction turbines, the axial thrust is due to

  • pressure drop across the rotor
  • change in axial velocity
  • both (a) and (b)
  • none of these
Q.21

The velocity of steam leaving the nozzle (V) is given by (where K = Nozzle coefficient or nozzle efficiency, and hd = Enthalpy or heat drop during expansion of steam in a nozzle)

  • V = 44.72 hd K
  • V = 44.72 K hd
  • V = 44.72 K hd
  • V = 44.72 K hd
Q.22

A regenerative steam cycle renders

  • increased work output per unit mass of steam
  • decreased work output per unit mass of steam
  • increased thermal efficiency
  • decreased work output per unit mass of steam as well as increased thermal efficiency
Q.23

Parson's reaction turbine is a __________ reaction turbine.

  • 40 percent
  • 50 percent
  • 60 percent
  • 70 percent
Q.24

The ratio of the useful heat drop to the isentropic heat drop is called

  • condenser efficiency
  • nozzle efficiency
  • boiler efficiency
  • vacuum efficiency
Q.25

Which of the following statement is correct?

  • The expansion of steam in a nozzle follows Rankine cycle.
  • The friction in the nozzle increases the dryness fraction of steam.
  • The pressure of steam at throat is called critical pressure.
  • all of the above
Q.26

The critical pressure gives the velocity of steam at the throat equal to the velocity of sound.

  • Agree
  • Disagree
Q.27

The discharge is __________ at critical pressure.

  • zero
  • minimum
  • maximum
Q.28

The ratio of the useful heat drop to the isentropic heat drop is called

  • condenser efficiency
  • nozzle efficiency
  • boiler efficiency
  • vacuum efficiency
Q.29

Parson's turbine is a

  • simple impulse turbine
  • simple reaction turbine
  • impulse-reaction turbine
  • none of these
Q.30

The action of steam in a steam turbine is

  • static
  • dynamic
  • static and dynamic
  • neither static nor dynamic
0 h : 0 m : 1 s