Q.1

Which of the following statement is correct for steam turbines as compared to reciprocating steam engines?

  • A steam turbine develops higher speeds
  • The efficiency of steam turbine is higher
  • The steam consumption is less
  • all of these
Q.2

A steam nozzle converts

  • heat energy of steam into kinetic energy
  • kinetic energy into heat energy of steam
  • heat energy of steam into potential energy
  • potential energy into heat energy of steam
Q.3

Rateau turbine is

  • simple reaction turbine
  • velocity compounded turbine
  • pressure compounded turbine
  • pressure-velocity compounded turbine
Q.4

A nozzle is said to be a divergent nozzle

  • when the cross-section of the nozzle increases continuously from entrance to exit
  • when the cross-section of the nozzle decreases continuously from entrance to exit
  • when the cross-section of the nozzle first decreases from entrance to throat and then increases from its throat to exit
  • none of the above
Q.5

The friction in the nozzle __________ exit velocity of steam.

  • has no effect on
  • decreases
  • increases
Q.6

The pressure of steam, in reaction turbines, is reduced in the fixed blades as well as in moving blades.

  • Correct
  • Incorrect
Q.7

The effect of friction on the flow of steam through a nozzle is to

  • decrease the mass flow rate and to increase the wetness of steam
  • increase the mass flow rate and to increase the exit temperature
  • decrease the mass flow rate and to decrease the wetness of steam
  • increase the exit temperature without any effect on mass flow rate
Q.8

De-Laval turbines are mostly used

  • where low speeds are required
  • for small power purposes and low speeds
  • for large power purposes
  • for small power purposes and high speeds
Q.9

The density of supersaturated steam is about __________ that of the ordinary saturated vapour at the corresponding pressure.

  • same as
  • 2 times
  • 4 times
  • 8 times
Q.10

The maximum discharge of steam through a convergent-divergent nozzle depends upon

  • area of nozzle at throat
  • initial pressure and volume of steam
  • final pressure ofsteam leaving the nozzle
  • both (a) and (b)
Q.11

The ratio of the work delivered at the turbine shaft to the heat supplied is called overall thermal efficiency of turbine.

  • True
  • False
Q.12

The ratio of the cumulative heat drop to the isentropic heat drop is called reheat factor.

  • Yes
  • No
Q.13

In a reaction turbine

  • the steam is allowed to expand in the nozzle, where it gives a high velocity before it enters the moving blades
  • the expansion of steam takes place partly in the fixed blades and partly in the moving blades
  • the steam is expanded from a high pressure to a condenser pressure in one or more nozzles
  • the pressure and temperature of steam remains constant
Q.14

The compounding of turbines is done in order to

  • reduce speed of rotor
  • improve efficiency
  • reduce exit losses
  • all of these
Q.15

A stage, in reaction turbine, is represented by

  • number of casing
  • number of entries of steam
  • number of exits of steam
  • each row of blades
Q.16

A single stage turbine is not used because it requires large reduction gearing due to very high rotational speed.

  • Agree
  • Disagree
Q.17

In a nozzle, the effect of supersaturation is to

  • decrease dryness fraction of steam
  • decrease specific volume of steam
  • increase the entropy
  • increase the heat drop
Q.18

In pressure compounding of an impulse turbine, the total pressure drop of the steam does not take place in the first nozzle ring, but is divided equally among all the nozzle rings.

  • Agree
  • Disagree
Q.19

The maximum efficiency of a De-Laval turbine is (where α = Nozzle angle)

  • sin2 α
  • cos2 α
  • tan2 α
  • cot2 α
Q.20

In turbines, the fluid undergoes a continuous steady flow process and the speed of flow is

  • low
  • very low
  • high
  • very high
Q.21

Which of the following statement is correct?

  • The efficiency of steam turbines is greater than steam engines.
  • A flywheel is a must for steam turbine.
  • The turbine blades do not change the direction of steam issuing from the nozzle
  • The pressure of steam, in reaction turbines, is increased in fixed blades as well as in moving blades
Q.22

When the cross-section of a nozzle __________ continuously from entrance to exit, it is called a convergent nozzle.

  • increases
  • decreases
Q.23

The pressure compounded impulse turbine as compared to velocity compounded turbine require __________ number of stages.

  • same
  • less
  • more
Q.24

Degree of reaction is defined as the ratio of

  • heat drop in fixed blades to the heat drop in moving blades
  • heat drop in moving blades to the heat drop in fixed blades
  • heat drop in moving blades to the heat drop in fixed blades plus heat drop in moving blades
  • heat drop in fixed blades plus heat drop in moving blades to the heat drop in moving blades
Q.25

The blade friction in the impulse turbine reduces the velocity of steam by __________ while it passes over the blades.

  • 10 to 15%
  • 15 to 20%
  • 20 to 30%
  • 30 to 40%
Q.26

In velocity compounding of an impulse turbine, the expansion of steam takes place in a nozzle or a set of nozzles from the boiler pressure to condenser pressure.

  • True
  • False
Q.27

The efficiency of an impulse turbine is maximum when (where Vb = Blade speed, V = Absolute velocity of steam entering the blade, and α = Nozzle angle)

  • Vb = 0.5 V cos α
  • Vb = V cos α
  • Vb = 0.5 V2 cos α
  • Vb = V2 cosα
Q.28

A nozzle is said to be a convergent-divergent nozzle, when the cross-section of a nozzle first decreases from its entrance to throat and then increases from its throat to exit.

  • True
  • False
Q.29

The pressure velocity compounded impulse turbine allows a bigger pressure drop and hence __________ number of stages are required.

  • more
  • less
Q.30

In an ideal impulse turbine, the

  • absolute velocity at the inlet of moving blade is equal to that at the outlet
  • relative velocity at the inlet of the moving blade is equal to that at the outlet
  • axial velocity at inlet is equal to that at the outlet
  • whirl velocity at inlet is equalto that at the outlet
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