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4

An ideal air compressor cycle with 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

Correct Answer :

B. Two adiabatic and two isobaric


Related Questions

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There is a certain pressure ratio (optimum) for a gas turbine at which its thermal efficiency is maximum. With increase in turbine temperature, the value of pressure ratio for the peak efficiency would

A. Remain same

B. Decrease

C. Increase

D. None of the above

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4

Pick up the correct statement

A. Closed cycle gas turbine is an I.C engine

B. Gas turbine uses same working fluid over and over again

C. Ideal efficiency of closed cycle gas turbine plant is more than Carnot cycle efficiency

D. Thrust in turbojet is produced by nozzle exit gases.

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Open cycle gas turbine works on

A. Brayton or Atkinson cycle

B. Rankine cycle

C. Carnot cycle

D. Erricson cycle

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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

Ratio of indicated H.P. and brake H.P. is known as

A. Mechanical efficiency

B. Volumetric efficiency

C. Isothermal efficiency

D. Adiabatic efficiency

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4

When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be

A. Forward curved

B. Backward curved

C. Radial

D. None of these

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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

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

Fighter bombers use following type of engine

A. Turbojet

B. Turbo-propeller

C. Rocket

D. Ramjet

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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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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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If the flow of air through the compressor is parallel to its axis, then the compressor is

A. Reciprocating compressor

B. Centrifugal compressor

C. Axial flow compressor

D. Turbo compressor

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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 stagnation pressure rise in a centrifugal compressor takes place

A. In the diffuser only

B. In the impeller only

C. In the diffuser and impeller

D. In the inlet guide vanes only

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Propulsive efficiency is defined as ratio of

A. Thrust power and fuel energy

B. Engine output and propulsive power

C. Propulsive power and fuel input

D. Thrust power and propulsive power

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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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The clearance volume of the air compressor is kept minimum because

A. It allows maximum compression to be achieved

B. It greatly affects volumetric efficiency

C. It results in minimum work

D. It permits isothermal compression

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Separators in compressor installations are located

A. Before intercooler

B. After intercooler

C. After receiver

D. Between after-cooler and air receiver

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The volumetric efficiency of compressor with increase in compression ratio will

A. Increase

B. Decrease

C. Remain same

D. May increase or decrease depending on clearance volume

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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

The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called

A. Pressure ratio

B. Pressure coefficient

C. Degree of reaction

D. Slip factor

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4

The assumption made in two stage compression with intercooler is that

A. There is no pressure drop in the intercooler

B. The compression in both the cylinders is polytropic

C. The suction and delivery of air takes place at constant pressure

D. All of the above

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4

In axial flow compressor, exit flow angle deviation from the blade angle is a function of

A. Blade camber

B. Blade camber and incidence angle

C. Spacechord ratio

D. Blade camber and spacechord ratio

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The work done per unit mass of air in compression will be least when n is equal to

A. 1

B. 1.2

C. 1.3

D. 1.4

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The compressor performance at higher altitude compared to sea level will be

A. Same

B. Higher

C. Lower

D. Dependent on other factors

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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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Adiabatic compression is one in which

A. Temperature during compression remains constant

B. No heat leaves or enters the compressor cylinder during compression

C. Temperature rise follows a linear relationship

D. Work done is maximum

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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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For minimum work in multistage compression, assuming same index of compression in all stages

A. Work done in first stage should be more

B. Work done in subsequent stages should increase

C. Work done in subsequent stages should decrease

D. Work done in all stages should be equal

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4

Mechanical efficiency of gas turbines as compared to I.C engines is

A. Higher

B. Lower

C. Same

D. None of the above