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What is the correct answer?

4

Maximum work is done in compressing air when the compression is

A. Isothermal

B. Adiabatic

C. Polytropic

D. None of the above

Correct Answer :

B. Adiabatic


Related Questions

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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

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

For an irreversible gas turbine cycle, the efficiency and work ratio both depend on

A. Pressure ratio alone

B. Maximum cycle temperature alone

C. Minimum cycle temperature alone

D. Both pressure ratio and maximum cycle temperature

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4

Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on

A. Mass flow rate

B. Pressure ratio

C. Change in load

D. Stagnation pressure at the outlet

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4

Pick up the correct statement

A. Large gas turbines use radial inflow turbines

B. Gas turbines have their blades similar to steam turbine

C. Gas turbine's blade will appear as impulse section at the hub and as a reaction section at tip

D. Gas turbines use both air and liquid cooling

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4

Which is false statement about advantages of multistage compressor in comparison to single stage compressor?

A. Less power requirement

B. Better mechanical balance

C. Less loss of air due to leakage past the cylinder

D. Lower volumetric efficiency

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4

The air entry velocity m a rocket as compared to aircraft is

A. Same

B. More

C. Less

D. Zero

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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

A closed cycle gas turbine consists of a

A. Compressor

B. Heating chamber

C. Cooling chamber

D. All of these

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4

Inter cooling in compressors

A. Cools the delivered air

B. Results in saving of power in compressing a given volume to given pressure

C. Is the standard practice for big compressors

D. Enables compression in two stages

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4

In a single stage, single acting reciprocating air compressor, without clearance, the workdone on the air during isentropic compression is ________ the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.

A. Equal to

B. Less than

C. Greater than

D. None of these

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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

The mass of gas turbine per kW developed is about ________ as that of an I.C. engine.

A. Same

B. One-half

C. One fourth

D. One sixth

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4

The axial flow compressor is preferred in aircraft gas turbines because of

A. Low frontal area

B. Higher thrust

C. High pressure rise

D. None of these

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4

In multistage compressor, the isothermal compression is achieved by

A. Employing intercooler

B. By constantly cooling the cylinder

C. By running compressor at very slow speed

D. By insulating the cylinder

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4

Gas turbine works on

A. Brayton or Atkinson cycle

B. Carnot cycle

C. Rankine cycle

D. Erricson cycle

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4

High air-fuel ratio is used in gas turbines

A. To increase the output

B. To increase the efficiency

C. To save fuel

D. To reduce the exit temperature

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4

The blades of gas turbine are made of

A. High nickel alloy

B. Stainless steel

C. Carbon steel

D. High alloy steel

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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

The workdone on a compressor will be minimum if air is taken from

A. The atmosphere

B. A source at 0°C

C. A source of low temperature air

D. A source of high temperature air

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4

The ratio of isentropic work to Euler work is known as

A. Pressure coefficient

B. Work coefficient

C. Polytropic reaction

D. Slip factor

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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

The thermodynamic efficiency of rotary compressor is based on

A. Isothermal compression

B. Adiabatic compression

C. Isentropic compression

D. Polytropic compression

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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

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

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

More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than

A. 2 kg/cm²

B. 6 kg/cm²

C. 10 kg/cm²

D. 14.7 kg/cm²

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4

The air-fuel ratio in gas turbines is of the order of

A. 7 : 1

B. 15 : 1

C. 30 : 1

D. 50 : 1.

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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

The maximum delivery pressure in a rotary air compressor is

A. 10 bar

B. 20 bar

C. 30 bar

D. 50 bar