Q.1

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

  • decrease
  • increase
Q.2

The degree of reaction is usually kept __________ for all types of axial flow compressors.

  • 0.2
  • 0.3
  • 0.4
  • 0.5
Q.3

Which of the following bladings will give maximum pressure rise in a centrifugal compressor, assuming the same overall dimensions, blade inlet angle and rotational speeds ?

  • Forward curved blades
  • Backward curved blades
  • Radial blades
  • all of these
Q.4

The volumetric efficiency of a compressor

  • constant with decrease in compression ratio
  • decreases with decrease in compression ratio
  • increases with increase in compression ratio
  • decreases with increase in compression ratio
Q.5

The volumetric efficiency of a compressor

  • constant with decrease in compression ratio
  • decreases with decrease in compression ratio
  • increases with increase in compression ratio
  • decreases with increase in compression ratio
Q.6

In an axial flow compressor, the ratio of pressure in theTOtor blades to the pressure rise in the compressor in one stage is known as

  • work factor
  • slip factor
  • degree of reaction
  • pressure coefficient
Q.7

Reheating in a multi-stage expansion gas turbine __________ compressor work.

  • has no effect on
  • decreases
  • increases
Q.8

The propulsive power of the rocket is (where v1 = Jet velocity, and v2 = Air-craft velocity)

Q.9

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

  • blade camber
  • blade camber and incidence angle
  • space-chord ratio
  • blade camber and space-chord ratio
Q.10

The actual volume of air delivered by a compressor, When reduced to the normal temperature and pressure conditions is called compressor capacity.

  • Yes
  • No
Q.11

An aftercooler is used to

  • remove impurities from air
  • reduce volume of air
  • cause moisture and oil vapour to drop out
  • cool the air
Q.12

Which of the following statement is correct?

  • The ratio of the discharge pressure to the inlet pressure of air is called compressor efficiency.
  • The compression ratio for the compressor is always greater than unity.
  • The compressor capacity is the ratio of workdone per cycle to the stroke volume.
  • During isothermal compression of air, the workdone in a compressor is maximum.
Q.13

Which of the following statement is wrong?

  • In a two stage reciprocating air compressor with complete intercooling, maximum work is saved.
  • The minimum work required for a two stage reciprocating air compressor is double the work required for each stage.
  • The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency.
  • none of the above
Q.14

Rotary compressors are used for delivering

  • small quantities of air at high pressures
  • large quantities of air at high pressures
  • small quantities of air at low pressures
  • large quantities of air at low pressures
Q.15

The compression ratio in a gas turbine is

  • 4
  • 1
  • 9
  • 12
Q.16

High air-fuel ratio in gas turbines

  • increases power output
  • improves thermal efficiency
  • reduces exhaust temperature
  • do not damage turbine blades
Q.17

In the aircraft propellers

  • the propulsive matter is ejected from within the propelled body
  • the propulsive matter is caused to flow around the propelled body
  • its functioning does not depend upon the presence of air
  • none of the above
Q.18

In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in __________ of the piston.

  • three strokes
  • one stroke
  • two strokes
  • four strokes
Q.19

Workdone by a two-stage reciprocating air compressor per cycle is equal to the workdone in LP. cylinder and H.P. cylinder.

  • True
  • False
Q.20

Intercooling in compressors results in saving of power in compressing given volume of air to a given pressure.

  • Correct
  • Incorrect
Q.21

The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as

  • compressor efficiency
  • volumetric efficiency
  • isothermal efficiency
  • mechanical efficiency
Q.22

The type of rotary compressor used in gas turbines, is of

  • centrifugal type
  • axial flow type
  • radial flow type
  • none of these
Q.23

The increase in pressure in a vane blower takes place first due to compression and then due to back flow of air.

  • Correct
  • Incorrect
Q.24

A rotary compressor is driven by an

  • electric motor
  • engine
  • either (a) or (b)
  • none of these
Q.25

Only rocket engines can be propelled to space because

  • they can generate very high thrust
  • they have high propulsion efficiency
  • these engines can work on several fuels
  • they are not air-breathing engines
Q.26

If p1, is the pressure of air entering the L.P. cylinder and p2 is the pressure of air leaving the L.P. cylinder (or intercooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D1 = Dia. of L.P. cylinder, and D2 = Dia. of H.P. cylinder)

  • D1/D2 = p1p2
  • D1/D2 = p1/p2
  • D1/D2 = p2/p1
  • none of these
Q.27

The volume of air delivered by the compressor is called

  • free air delivery
  • compressor capacity
  • swept volume
  • none of these
Q.28

The maximum delivery pressure in a rotary air compressor is

  • 10 bar
  • 20 bar
  • 30 bar
  • 50 bar
Q.29

In a centrifugal compressor, an increase in speed at a given pressure ratio causes

  • increase in flow
  • decrease in flow
  • increase in efficiency
  • increase in flow and decrease in efficiency
Q.30

The maximum combustion pressure in gas turbine is __________ as compared to I.C. engine.

  • more
  • less
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