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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

Correct Answer :

B. Volumetric efficiency is high


Related Questions

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A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine.

A. Same

B. Lower

C. Higher

D. None of these

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4

In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to

A. N.T.P. conditions

B. Intake temperature and pressure conditions

C. 0°C and 1 kg/cm²

D. 20°C and 1 kg/cm²

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4

A rotary compressor is driven by an

A. Electric motor

B. Engine

C. Either (A) or (B)

D. None of these

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4

Pick up the wrong statement

A. Large gas turbines employ axial flow compressors

B. Axial flow compressors are more stable than centrifugal type compressors but not as efficient

C. Axial flow compressors have high capacity and efficiency

D. Axial flow compressors have instability region of operation

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4

Losses in a centrifugal compressor are due to

A. Inlet losses

B. Impeller channel losses

C. Diffuser losses

D. All of the above

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4

Out of the following, from where you will prefer to take intake for air compressor

A. From an air conditioned room maintained at 20°C

B. From outside atmosphere at 1°C

C. From coal yard side

D. From a side where cooling tower is located nearby

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4

For slow speed large capacity compressor, following type of valve will be best suited

A. Poppet valve

B. Mechanical valve of the Corliss, sleeve, rotary or semi rotary type

C. Disc or feather type

D. Any 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

Isothermal compression efficiency, even when running at high speed, can be approached by using

A. Multistage compression

B. Cold water spray

C. Both (A) and (B) above

D. Fully insulating the cylinder

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4

In turbo fan engine, the jet velocity as compared to turbojet engine is

A. Less

B. More

C. Same

D. May be less or more depending upon speed

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4

In n₁ and n₂ are the indices of compression for the first and second stage of compression, then the ratio of workdone on the first and second stages (W₁/W₂) with perfect intercooling is given by

A. W₁/W₂ = n₂(n₁ - 1)/n₁(n₂ - 1)

B. W₁/W₂ = n₁(n₂ - 1)/n₂(n₁ - 1)

C. W₁/W₂ = n₁/n₂

D. W₁/W₂ = n₂/n₁

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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

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

A simple turbojet engine is basically

A. A propeller system

B. Gas turbine engine equipped with a propulsive nozzle and diffuse

C. Chemical rocket engine

D. Ramjet engine

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4

For speed above 3000 km/hour, it is more advantageous to use

A. Turbojet engine

B. Ramjet engine

C. Propellers

D. Rockets

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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

Surging is the phenomenon of

A. Air stream blocking the passage

B. Motion of air at sonic velocity

C. Unsteady, periodic and reversed flow

D. Air stream not able to follow the blade contour

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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

What will be the volume of air at 327°C if its volume at 27°C is 1.5 m³/ mt?

A. 3 m³/ mt.

B. 1.5 m³/ mt.

C. 18 m³/ mt.

D. 6 m³/ mt.

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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

Rotary compressors are used for delivering

A. Small quantities of air at high pressures

B. Large quantities of air at high pressures

C. Small quantities of air at low pressures

D. Large quantities of air at low pressures

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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

The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called

A. Compressor efficiency

B. Volumetric efficiency

C. Isothermal efficiency

D. Mechanical efficiency

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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

Maximum delivery pressure is a rotary air compressor is of the order of

A. 6 kg/cm²

B. 10 kg/cm²

C. 16 kg/cm²

D. 25 kg/cm²

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4

The working fluid in a turbine is

A. In two phases

B. In three phases

C. In a single phase

D. In the form of air and water mixture

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4

Propulsion efficiency of the following order is obtained in practice

A. 34 %

B. 50 %

C. 60 %

D. 72 %

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4

In a single stage, single acting reciprocating air compressor, without clearance volume, the workdone is minimum during

A. Isothermal compression

B. Isentropic compression

C. Polytropic compression

D. None of these

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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