Air Compressors Set 1 MCQs

Q1 | An ideal air compressor cycle with clearance on p-v diagram can be represented by following processes

one adiabatic, two isobaric, and one constant volume

two adiabatic and two isobaric

two adiabatic, one isobaric and one constant volume,

one adiabatic, one isobaric and two constant volume

Q2 | The work done per unit mass of air in compression will be least when n is equal to

1

1.2

1.3

1.4

Q3 | Isothermal compression though most efficient, but is not -practicable because

it requires very big cylinder

it does not increase pressure much

it is impossible in practice

compressor has to run at very slow speed to achieve it

Q4 | Ratio of indicated H.P. and brake H.P. is known as

mechanical efficiency

volumetric efficiency

isothermal efficiency

adiabatic efficiency

Q5 | The ratio of work doen per cycle to the swept volume in case of compressor is called

compression index

compression ratio

compressor efficiency

mean effective pressure

Q6 | Cylinder clearance in a compressor should be

as large as possible

as small as possible

about 50% of swept volume

about 100% of swept volume

Q7 | Ratio of compression is the ratio of

gauge discharge pressure to the gauge intake pressure

absolute discharge pressure to the absolute intake pressure

pressures at discharge and suction corresponding to same temperature

stroke volume and clearance volume

Q8 | Clearance volume in actual reciprocating compressors is essential

to accommodate Valves in the cylinder head

to provide cushioning effect

to attain high volumetric efficiency

to provide cushioning effect and also to avoid mechanical bang of piston with cylinder head.

Q9 | The net work input required for compressor with increase in clearance volume

increases

decreases

remains same

increases/decreases depending on compressor capacity

Q10 | Ratio of indicated h.p. to shaft h.p. is known as

compressor efficiency

isothermal efficiency

volumetric efficiency

mechanical efficiency

Q11 | Volumetric efficiency is

the ratio of stroke volume to clearance volume

the ratio of the air actually delivered to the amount of piston displacement

reciprocal of compression ratio

index of compressor performance

Q12 | Volumetric efficiency of a compressor with clearance volume

increases with increase in compression ratio

decreases with increase in compression ratio

is not dependent upon compression ratio

may increase/decrease depending on compressor capacity

Q13 | Volumetric efficiency of a compressor without clearance volume

increases with increase in compression ratio

decreases with increase in compression ratio

is not dependent upon compression ratio

may increase/decrease depending on compressor capacity

Q14 | The clearance volume of the air compressor is kept minimum because

it allows maximum compression to be achieved

it greatly affects volumetric efficiency

it results in minimum work

it permits isothermal compression

Q15 | Which is false statement about multistage compression.

Power consumption per unit of air delivered is low

Volumetric efficiency is high

It is best suited for compression ratios around 7:1

The moisture in air is condensed in the intercooler

Q16 | Reciprocating air compressor is best suited for

large quantity of air at high pressure

small quantity of air at high pressure

small quantity of air at low pressure

large quantity of air at low pressure

Q17 | Rotary compressor is best suited for

large quantity of air at high pressure

small quantity of air at high pressure

small quantity of air at low pressure

large quantity of air at low pressure

Q18 | After-cooler is used to

cool the air

decrease the delivery temperature for ease in handling

cause moisture and oil vapour to drop out

reduce volume

Q19 | The compressor performance at higher altitude compared to sea level will be

same

higher

lower

dependent on other factors

Q20 | Pick up the wrong statement about advantages of multistage compression

better lubrication is possible advantages of multistage

more loss of air due to leakage past the cylinder

mechanical balance is better

air can be cooled perfectly in between

Q21 | Losses in a centrifugal compressor are due to

inlet losses

impeller channel losses

diffuser losses

all of the above

Q22 | For supplying intermittent small quantity of air at high pressure, following compressor is best suited

centrifugal

reciprocating

axial

screw

Q23 | For minimum work in multistage compression, assuming same index of compression in all stages

work done in first stage should be more

work done in subsequent stages should increase

work done in subsequent stages should decrease

work done in all stages should be equal

Q24 | Diffuser in a compressor is used to

increase velocity

make the flow stream-line

convert pressure energy into kinetic energy

convert kinetic energy into pressure energy

Q25 | Phenomenon of choking in compressor means

no flow of air

fixed mass flow rate regardless of pressure ratio

reducing mass flow rate with increase in pressure ratio

increased inclination of chord with air steam