Practice Compressors, Gas Turbines And Jet Engines Multiple Choice Questions Quiz-6 - MCQGeeks.com

Q.1

Turbofan engine employs

One air stream
Two or more air streams
No air stream
Solid fuel firing

Q.2

Gas turbines for power generation are normally used

To supply base load requirements
To supply peak load requirements
To enable start thermal power plant
In emergency

Q.3

The criterion of the thermodynamic efficiency for rotary compressor is

Isentropic compression
Isothermal compression
Polytropic compression
None of the above

Q.4

Producer gas is produced by

Carbonisation of coal
Passing steam over incandescent coke
Passing air and a large amount of steam over waste coal at about 65°C
Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast

Q.5

Water gas is produced by

Carbonisation of coal
Passing steam over incandescent coke
Passing air and a large amount of steam over waste coal at about 65°C
Partial combustion of coal, eke, anthracite coal or charcoal in a mixed air steam blast

Q.6

Pick up the false statement

Gas turbine is a self starting unit
Gas turbine does not require huge quantity of water like steam plant
Exhaust losses in gas turbine are high due to large mass flow rate
Overall efficiency of gas turbine plant is lower than that of a reciprocating engine

Q.7

The closed cycle in gas turbines

Provides greater flexibility
Provides lesser flexibility
In never used
Is used when gas is to be burnt

Q.8

Efficiency of gas turbine is increased by

Reheating
Inter cooling
Adding a regenerator
All of the above

Q.9

The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is

Low
High
Same
Low/high depending on make and type

Q.10

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.11

Work ratio of a gas turbine may be improved by

Decreasing the compression work
Increasing the compression work
Increasing the turbine work
Both (A) and (C) above

Q.12

Air-fuel ratio in a jet engine will be of the order of

10: 1
15: 1
20: 1
60: 1

Q.13

The gas in cooling chamber of a closed cycle gas turbine is cooled at

Constant volume
Constant temperature
Constant pressure
None of these

Q.14

In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in

Exit nozzle, which is a constant volume process
Exit nozzle, which is essentially an isentropic process
Turbine blades, which is a constant volume process
Turbine blades, which is essentially an isentropic process

Q.15

Gas turbine as compared to internal combustion engine

Can be driven at a very high speed
Produces uniform torque
Has more efficiency
All of these

Q.16

Adiabatic compression is one in which

Temperature during compression remains constant
No heat leaves or enters the compressor cylinder during compression
Temperature rise follows a linear relationship
Work done is maximum

Q.17

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

Q.18

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

Q.19

The efficiency of roots blower ________ with the increase in pressure ratio.

Decreases
Increases
Does not change
None of these

Q.20

During peak load periods, the best method of controlling compressors is

Start-stop motor
Constant speed unloader
Relief valve
Variable speed

Q.21

Which of the following fuels can be used in turbojet engines?

Liquid hydrogen
High speed diesel oil
Kerosene
Methyl alcohol

Q.22

Ram compression in turbojet involves

Reduction of speed of incoming air and conversion of part of it into pressure energy
Compression of inlet air
Increasing speed of incoming air
Lost work

Q.23

Standard air is the air at ________ and relative humidity of 36 percent.

0.1 bar and 20°C
1 bar and 20°C
0.1 bar and 40°C
1 bar and 40°C

Q.24

Which of the following statement is correct as regard to centrifugal compressors?

The flow of air is parallel to the axis of the compressor
The static pressure of air in the impeller increases in order to provide centripetal force on the air
The impeller rotates at high speeds
The maximum efficiency is higher than multistage axial flow compressors

Q.25

To avoid moisture troubles, the branch connections from compressed air lines should be taken from

Top side of main
Bottom side of main
Left side of main
Right side of main

Q.26

Stalling of blades in axial flow compressor is the phenomenon of

Air stream blocking the passage
Motion of air at sonic velocity
Unsteady periodic and reversed flow
Air stream not able to follow the blade contour

Q.27

A rocket engine uses __________ for the combustion of its fuel.

Surrounding air
Compressed atmospheric air
Its own oxygen
None of these

Q.28

Separators in compressor installations are located

Before inter-cooler
After inter-cooler
After receiver
Between after-cooler and air receiver

Q.29

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

Higher
Lower
Same
None of the above

Q.30

An ideal air compressor cycle without 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 volumes

0 h : 0 m : 1 s