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Steam Nozzles and Turbines MCQ

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

Blading efficiency

Gross or stage efficiency

Mechanical efficiency

Nozzle efficiency

Answer

Correct Answer: Blading efficiency

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

Agree

Disagree

Answer

Correct Answer: Agree

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Thermal equilibrium means that the flow of steam is

Hyperbolic

Isothermal

Polytropic

Isentropic

Answer

Correct Answer: Isentropic

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

Vacuum efficiency

Nozzle efficiency

Condenser efficiency

Boiler efficiency

Answer

Correct Answer: Nozzle efficiency

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The critical pressure ratio for initially wet steam is

0.577

0.582

0.601

0.546

Answer

Correct Answer: 0.582

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The discharge is __________ at critical pressure.

Maximum

Zero

Minimum

Answer

Correct Answer: Maximum

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The flow through a nozzle is regarded as

Isothermal flow

Isentropic flow

Constant pressure flow

Constant volume flow

Answer

Correct Answer: Isentropic flow

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The action of steam in a steam turbine is

Dynamic

Neither static nor dynamic

Static

Static and Dynamic

Answer

Correct Answer: Dynamic

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The variation of steam pressure in the nozzle depends upon

Velocity of steam

Specific volume of steam

All of these

Dryness fraction of steam

Answer

Correct Answer: All of these

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In a De-Laval nozzle expanding superheated steam from 10 bar to 0.1 bar, the pressure at the minimum cross-section (i. e. pressure at throat, p2) will be

3.3 bar

9.9 bar

8.2 bar

5.46 bar

Answer

Correct Answer: 5.46 bar

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The pressure at which the steam leaves the nozzle is known as back pressure.

Incorrect

Correct

Answer

Correct Answer: Correct

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The flow of steam is super-sonic

At the entrance to the nozzle

In the convergent portion of the nozzle

At the throat of the nozzle

In the divergent portion of the nozzle

Answer

Correct Answer: In the divergent portion of the nozzle

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

Remains constant

Increases

Decreases

Answer

Correct Answer: Remains constant

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Which of the following statement is correct?

The pressure of steam at throat is called critical pressure.

The expansion of steam in a nozzle follows Rankine cycle.

The friction in the nozzle increases the dryness fraction of steam.

All of these

Answer

Correct Answer: All of these

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

True

False

Answer

Correct Answer: True

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For maximum efficiency of an impulse turbine, the steam should leave the blades at right angles to their motion.

Correct

Incorrect

Answer

Correct Answer: Correct

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

Remains same

Increases

Decreases

Answer

Correct Answer: Increases

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Rateau turbine is

Pressure compounded turbine

Simple reaction turbine

Pressure-velocity compounded turbine

Velocity compounded turbine

Answer

Correct Answer: Pressure compounded turbine

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

Yes

Answer

Correct Answer: No

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De-Laval turbine is a

None of these

Simple impulse turbine

Simple reaction turbine

Impulse-reaction turbine

Answer

Correct Answer: Simple impulse turbine

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