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4

In a closed cycle gas turbine, the air is compressed

A. Isothermally

B. Polytropically

C. Isentropically

D. None of these

Correct Answer :

C. Isentropically


Related Questions

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4

Free air is the air at

A. Atmospheric conditions at any specific location

B. 20°C and 1 kg/cm² and relative humidity of 36%

C. 0°C and standard atmospheric conditions

D. 15°C and 1 kg/cm²

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4

An ideal air compressor cycle without clearance on PV diagram can be represented by following processes

A. One adiabatic, two isobaric, and one constant volume

B. Two adiabatic and two isobaric

C. Two adiabatic, one isobaric and one constant volume

D. One adiabatic, one isobaric and two constant volumes

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4

Volumetric efficiency is

A. The ratio of stroke volume to clearance volume

B. The ratio of the air actually delivered to the amount of piston displacement

C. Reciprocal of compression ratio

D. Index of compressor performance

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4

Ramjet engine

A. Is self operating at zero flight speed

B. Is not self operating at zero flight speed

C. Requires no air for its operation

D. Produces a jet consisting of plasma

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4

Pick up the correct statement

A. Gas turbine uses low air-fuel ratio to economise on fuel

B. Gas turbine uses high air-fuel ratio to reduce outgoing temperature

C. Gas turbine uses low air-fuel ratio to develop the high thrust required

D. All of the above

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4

For a two stage compressor, if index of compression for higher stage is greater than index of compression for lower stage, then the optimum pressure as compared to ideal case will

A. Increase

B. Decrease

C. Remain unaffected

D. Other factors control it

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4

The ratio of workdone per cycle to the stroke volume of the compressor is known as

A. Compressor capacity

B. Compression ratio

C. Compressor efficiency

D. Mean effective pressure

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4

A closed gas turbine in which fuel is burnt directly in the air is not possible because of

A. Paucity of O2

B. Increasing gas temperature

C. High specific volume

D. High friction losses

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4

The absolute pressure of air at the outlet of a compressor is called

A. Back pressure

B. Critical pressure

C. Discharge pressure

D. None of these

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4

In which case the air-fuel ratio is likely to be maximum?

A. Gas turbine

B. 4-stroke petrol engine

C. 4-stroke diesel engine

D. Multi cylinder engine

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4

The maximum combustion pressure in gas turbine as compared to I.C. engine is

A. More

B. Less

C. Same

D. Depends on other factors

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4

Ram compression in turbojet involves

A. Reduction of speed of incoming air and conversion of part of it into pressure energy

B. Compression of inlet air

C. Increasing speed of incoming air

D. Lost work

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4

The compressor efficiency is the

A. Isothermal H.P/indicated H.R

B. Isothermal H.P./shaft H.R

C. Total output/air input

D. Compression work/motor input

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4

Maximum temperature in a gas turbine is of the order of

A. 700°C

B. 2000°C

C. 1500°C

D. 1000°C

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4

For perfect intercooling in a three stage compressor

A. p₂/p₁ = p₃/p₂ = p₄/p₃

B. p₃/p₁ = p₄/p₂

C. p₁ p₂ = p₃ p₄

D. p₁ p₃ = p₂ p₄

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4

Turbofan engine employs

A. One air stream

B. Two or more air streams

C. No air stream

D. Solid fuel firing

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4

Isothermal compression efficiency can be attained by running the compressor

A. At very high speed

B. At very slow speed

C. At average speed

D. At zero speed

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4

The indicated work per unit mass of air delivered is

A. Directly proportional to clearance volume

B. Greatly affected by clearance volume

C. Not affected by clearance volume

D. Inversely proportional to clearance volume

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4

The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation

A. 0.1 %

B. 0.5 %

C. 1.0 %

D. 5 %

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4

Pressure ratio in gas turbines is the ratio of

A. Compressor pressure ratio

B. Highest pressure to exhaust pressure

C. Inlet pressure to exhaust pressure

D. Pressures across the turbine

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4

The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as

A. Compressor efficiency

B. Volumetric efficiency

C. Isothermal efficiency

D. Mechanical efficiency

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4

After-cooler is used to

A. Cool the air

B. Decrease the delivery temperature for ease in handling

C. Cause moisture and oil vapour to drop out

D. Reduce volume

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4

Only rocket engines can be propelled to space because

A. They can generate very high thrust

B. They have high propulsion efficiency

C. These engines can work on several fuels

D. They are not air breathing engines

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4

Euler's equation is applicable for

A. Centrifugal compressor

B. Axial compressor

C. Pumps

D. All of the above

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4

The pressure ratio of an ideal vaned compressor with increase in mass flow rate

A. Increases

B. Decreases

C. Remain constant

D. First decreases and then increases

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4

The ideal efficiency of simple gas turbine cycle depends on

A. Pressure ratio

B. Maximum cycle temperature

C. Minimum cycle temperature

D. All of the above

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4

Diffuser in a compressor is used to

A. Increase velocity

B. Make the flow streamline

C. Convert pressure energy into kinetic energy

D. Convert kinetic energy into pressure energy

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4

The ratio of work done per cycle to the swept volume in case of compressor is called

A. Compression index

B. Compression ratio

C. Compressor efficiency

D. Mean effective pressure

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4

For minimum work required to compress and deliver a quantity of air by multistage compression

A. The compression ratio in each stage should be same

B. The intercooling should be perfect

C. The workdone in each stage should be same

D. All of the above

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4

Which is false statement about multistage compression?

A. Power consumption per unit of air delivered is low

B. Volumetric efficiency is high

C. It is best suited for compression ratios around 7:1

D. The moisture in air is condensed in the intercooler