Practice Compressors, Gas Turbines And Jet Engines Multiple Choice Questions Quiz-5 - MCQGeeks.com

Q.1

In jet engines, paraffin is usually used as the fuel because of its

High calorific value
Ease of atomisation
Low freezing point
Both (A) and (C) above

Q.2

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.3

Pick up the wrong statement

Centrifugal compressors deliver practically constant pressure over a considerable range of capacities
Axial flow compressors have a substantially constant delivery at variable pressures
Centrifugal compressors have a wider stable operating range than axial flow compressors
Axial flow compressors are bigger in diameter compared to centrifugal type

Q.4

Pick up the wrong statement

Large gas turbines employ axial flow compressors
Axial flow compressors are more stable than centrifugal type compressors but not as efficient
Axial flow compressors have high capacity and efficiency
Axial flow compressors have instability region of operation

Q.5

The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation

0.1%
0.5%
1.0%
5%

Q.6

In open cycle turbojet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the

Thrust and range of aircraft
Efficiency of the engine
Both (A) and (B)
None of these

Q.7

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

W₁/(W₁ + W₂)
W₂/(W₁ + W₂)
(W₁ + W₂)/W₁
(W₁ + W₂)/W₂

Q.8

A compressor at high altitudes will require ________ power.

Same
Less
More
None of these

Q.9

In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into

Atmosphere
Vacuum
Discharge nozzle
Back to the compressor

Q.10

In jet engines the products of combustion after passing through the gas turbine are discharged into

Atmosphere
Back to the compressor
Discharge nozzle
Vacuum

Q.11

The minimum work required for a three stage reciprocating air compressor is ________ the work required for each stage.

Equal to
Double
Three times
Six times

Q.12

The working fluid in a turbine is

In two phases
In three phases
In a single phase
In the form of air and water mixture

Q.13

High air-fuel ratio is used in gas turbines

To increase the output
To increase the efficiency
To save fuel
To reduce the exit temperature

Q.14

An air receiver is to be placed outside. Should it be placed in

Sun
Shade
Rain
Enclosed room

Q.15

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

Zero
Less
More
Same

Q.16

The compressed air may be used

In gas turbine plants
For operating pneumatic drills
In starting and supercharging of I.C. engines
All of the above

Q.17

The overall isothermal efficiency of the compressor is defined as the ratio of

Work required to compress the air isothermally to the actual work required to compress the air for the same pressure ratio
Isothermal power to the shaft power or B.P. of the motor or engine required to drive the compressor
Volume of free air delivery per stroke to the swept volume of the piston
Isentropic power to the power required to drive the compressor

Q.18

The overall isothermal efficiency of compressor is defined as the ratio of

Isothermal h.p. to the BHP of motor
Isothermal h.p. to adiabatic h.p.
Power to drive compressor to isothermal h.p.
Work to compress air isothermally to work for actual compression

Q.19

The work ratio of a gas turbine plant is defined as the ratio of

Net work output and heat supplied
Net work output and work done by turbine
Actual heat drop and isentropic heat drop
Net work output and isentropic heat drop

Q.20

The maximum propulsion efficiency of a turbojet is attained at around following speed

550 km/hr
1050 km/hr
1700 km/hr
2400 km/hr

Q.21

Pick up the correct statement

Large gas turbines use radial inflow turbines
Gas turbines have their blades similar to steam turbine
Gas turbine's blade will appear as impulse section at the hub and as a reaction section at tip
Gas turbines use both air and liquid cooling

Q.22

Pick up the correct statement

Gas turbine uses low air-fuel ratio to economise on fuel
Gas turbine uses high air-fuel ratio to reduce outgoing temperature
Gas turbine uses low air-fuel ratio to develop the high thrust required
All of the above

Q.23

A gas turbine used in air craft should have

High h.p. and low weight
Low weight and small frontal area
Small frontal area and high h.p.
High speed and high h.p.

Q.24

The compressor capacity with decrease in suction temperature

Increases
Decreases
Remain unaffected
May increase or decrease depending on compressor capacity

Q.25

The mean effective pressure of the compressor is 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.26

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

Q.27

In gas turbines, high thermal efficiency is obtained in

Closed cycle
Open cycle
Both of the above
Closed/open depending on other considerations

Q.28

An after-cooler is used to

Remove impurities from air
Reduce volume of air
Cause moisture and oil vapour to drop out
Cool the air

Q.29

Pick up the correct statement

Closed cycle gas turbine is an I.C engine
Gas turbine uses same working fluid over and over again
Ideal efficiency of closed cycle gas turbine plant is more than Carnot cycle efficiency
Thrust in turbojet is produced by nozzle exit gases

Q.30

Choose the correct statement

Gas turbine requires lot of cooling water
Gas turbine is capable of rapid start up and loading
Gas turbines has flat efficiency at part loads
Gas turbines have high standby losses and require lot of maintenance

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