Q.1

The thrust of a jet propulsion power unit can be increased by

  • injecting water into the compressor
  • burning fuel after gas turbine
  • injecting ammonia into the combustion chamber
  • all of the above
Q.2

The velocity of air entering in a rocket is __________ as compared to an aircraft.

  • zero
  • less
  • more
  • same
Q.3

With the decrease in compression ratio, the volumetric efficiency

  • does not change
  • increases
  • decreases
Q.4

The operation of the reciprocating air motor is similar to reciprocating air compressor.

  • True
  • False
Q.5

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

  • reciprocating compressor
  • centrifugal compressor
  • axial flow compressor
  • turbo-compressor
Q.6

In a centrifugal compressor, the flow of air is __________ to the axis of compressor.

  • parallel
  • perpendicular
  • inclined
  • none of these
Q.7

The operation of the reciprocating air motor is similar to reciprocating air compressor.

  • True
  • False
Q.8

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

  • forward curved
  • backward curved
  • radial
  • none of these
Q.9

Which of the following statement is correct?

  • The reciprocating compressors are best suited for high pressure and low volume capacity
  • The effect of clearance volume on power consumption is negligible for the same volume of discharge
  • both (a) and (b)
  • none of these
Q.10

The volumetric efficiency of the compressor is defined as the ratio of volume of free air delivery per stroke to the swept volume of the piston.

  • Yes
  • No
Q.11

For minimum work required to compress and deliver a quantity of air by multi-stage compression,

  • the compression ratio in each stage should be same
  • the intercooling should be perfect
  • the workdone in each stage should be same
  • all of the above
Q.12

Slip factor in a centrifugal compressor indicates the amount of air leaked from the storage vessel.

  • Yes
  • No
Q.13

A centrifugal compressor is an axial flow compressor.

  • Correct
  • Incorrect
Q.14

The speed of rotary air compressor is __________ as compared to reciprocating air compressor.

  • high
  • low
Q.15

Separators are generally used in air compressor installations

  • before the intercooler
  • after the intercooler
  • between the aftercooler and receiver
  • before first stage suction
Q.16

The multi-stage compression ofair as compared to single stage compression

  • improves volumetric efficiency for the given pressure ratio
  • reduces workdone per kg of air
  • gives more uniform torque
  • all of these
Q.17

The speed of rotary air compressor is __________ as compared to reciprocating air compressor.

  • high
  • low
Q.18

The volume of air sucked by the compressor during its suction stroke is called

  • free air delivery
  • compressor capacity
  • swept volume
  • none of these
Q.19

The ratio of the isentropic work to the Euler's work is known as pressure coefficient.

  • Yes
  • No
Q.20

A compressor must be driven by some prime mover.

  • Agree
  • Disagree
Q.21

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

  • single stage compression
  • multi-stage compression without intercooling
  • multi-stage compression with intercooling
  • none of these
Q.22

If the flow of air through the compressor is perpendicular to its axis, then it is a

  • reciprocating compressor
  • centrifugal compressor
  • axial flow compressor
  • turbo compressor
Q.23

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

  • Backward curved blades has poor efficiency
  • Backward curved blades lead to stable performance
  • Forward curved blades has higher efficiency
  • Forward curved blades produce lower pressure ratio
Q.24

A turbo-prop is preferred to turbo-jet because

  • it has high propulsive efficiency at high speeds
  • it can fly at super sonic speeds
  • it can fly at high elevations
  • it has high power for take off
Q.25

The absolute pressure of air at the outlet of a compressor is called

  • back pressure
  • critical pressure
  • discharge pressure
  • none of these
Q.26

In air compressors, free air delivery means the

  • actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
  • volume of air delivered by the compressor
  • volume of air sucked by the compressor during its suction stroke
  • none of the above
Q.27

In a jet engine, the air-fuel ratio is

  • 30:1
  • 40:1
  • 50:1
  • 60:1
Q.28

The air power of the compressor is also known as

  • indicated power
  • brake power
  • frictional power
  • none of these
Q.29

The efficiency of the vane blower is (where W1 = Workdone due to compression, and W2 = Workdone due to back flow)

Q.30

Volumetric efficiency of a compressor decreases with __________ in compression ratio.

  • decrease
  • increase
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