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4

When air is to be compressed at a high pressure, then it is advantageous to use

A. Single stage compression

B. Multistage compression without intercooling

C. Multistage compression with intercooling

D. None of these

Correct Answer :

C. Multistage compression with intercooling


Related Questions

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4

Work ratio of a gas turbine may be improved by

A. Decreasing the compression work

B. Increasing the compression work

C. Increasing the turbine work

D. Both (A) and (C) above

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4

In a centrifugal compressor, the highest Mach number leading to shock wave in the fluid flow occurs at

A. Diffuser inlet radius

B. Diffuser outlet radius

C. Impeller inlet radius

D. Impeller outlet radius

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4

The type of rotary compressor used in aeroplanes, is of

A. Centrifugal type

B. Axial flow type

C. Radial flow type

D. None of these

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4

The efficiency and work ratio of a gas turbine plant can be increased by

A. Adding heat exchanger

B. Injecting water in/around combustion chamber

C. Reheating the air after partial expansion in the turbine

D. All of the above

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4

Isothermal compression though most efficient, but is not practicable because

A. It requires very big cylinder

B. It does not increase pressure much

C. It is impossible in practice

D. Compressor has to run at very slow speed to achieve it

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4

Standard air is the air at ________ and relative humidity of 36 percent.

A. 0.1 bar and 20°C

B. 1 bar and 20°C

C. 0.1 bar and 40°C

D. 1 bar and 40°C

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4

It is not possible to use closed gas turbine cycle in aeronautical engines because

A. It is inefficient

B. It is bulky

C. It requires cooling water for its operation

D. None of the above

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4

A compressor mostly used for supercharging of I.C. engines is

A. Radial flow compressor

B. Axial flow compressor

C. Roots blower

D. Reciprocating compressor

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4

Which one of the following is the effect of blade shape on performance of a centrifugal compressor?

A. Backward curved blades has poor efficiency

B. Backward curved blades lead to stable performance

C. Forward curved blades has higher efficiency

D. Forward curved blades produce lower pressure ratio

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4

If the clearance ratio for a reciprocating air compressor is 'K', then its volumetric efficiency is given by

A. 1 - k + k (p₁/p₂)1/n

B. 1 + k - k (p₂/p₁)1/n

C. 1 - k + k (p₁/p₂) n- 1/n

D. 1 + k - k (p₂/p₁) n-1/n

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4

The closed cycle in gas turbines

A. Provides greater flexibility

B. Provides lesser flexibility

C. In never used

D. Is used when gas is to be burnt

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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

Which of the following plants is smallest and lightest for generating a given amount of power?

A. Gas turbine plant

B. Petrol engine

C. Diesel engine

D. Solar plant

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4

In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into

A. Atmosphere

B. Vacuum

C. Discharge nozzle

D. Back to the compressor

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4

The thermal efficiency of a gas turbine as compared to a diesel plant is

A. Same

B. More

C. Less

D. Depends on other factors

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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

For perfect intercooling in a two stage compressor

A. p₂/p₁ = p₃/p₂

B. p₁/p₃ = p₂/p₁

C. p₁ = p₃

D. p₁ = p₂ p₃

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4

Standard air is the air at

A. Atmospheric conditions at any specific location

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

C. 0°C and standard atmospheric conditions

D. 15°C and 1 kg/cm²

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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

In jet engines, paraffin is usually used as the fuel because of its

A. High calorific value

B. Ease of atomisation

C. Low freezing point

D. Both (A) and (C) above

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4

Which of the following statement is correct as regard to centrifugal compressors?

A. The flow of air is parallel to the axis of the compressor

B. The static pressure of air in the impeller increases in order to provide centripetal force on the air

C. The impeller rotates at high speeds

D. The maximum efficiency is higher than multistage axial flow compressors

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4

Reheating in a gas turbine

A. Increases the thermal efficiency

B. Increases the compressor work

C. Increases the turbine work

D. Decreases the thermal efficiency

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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

Inter-cooling in multistage compressors is done

A. To cool the air during compression

B. To cool the air at delivery

C. To enable compression in two stages

D. To minimise the work of compression

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4

The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.

A. Equal to

B. Less than

C. More than

D. None of these

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4

Volumetric efficiency of air compressors is of the order of

A. 20 - 30 %

B. 40 - 50 %

C. 60 - 70 %

D. 70 - 90 %

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4

In jet engines the products of combustion after passing through the gas turbine are discharged into

A. Atmosphere

B. Back to the compressor

C. Discharge nozzle

D. Vacuum

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4

Fighter bombers use following type of engine

A. Turbojet

B. Turbo-propeller

C. Rocket

D. Ramjet

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4

A jet engine has

A. No propeller

B. Propeller in front

C. Propeller at back

D. Propeller on the top

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4

A turboprop is preferred to turbojet because

A. It has high propulsive efficiency at high speeds

B. It can fly at supersonic speeds

C. It can fly at high elevations

D. It has high power for take off