The maximum compression ratio in an actual single stage axial flow compressor is of the order of
1 : 1.2
1 : 2
1 : 5
1 : 10
Correct Answer :
A. 1 : 1.2
Related Questions
Which of the following fuels can be used in turbojet engines?
Liquid hydrogen
High speed diesel oil
Kerosene
Methyl alcohol
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
In a single stage, single acting reciprocating air compressor, without clearance, the workdone on the air during isentropic compression is ________ the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.
Equal to
Less than
Greater than
None of these
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
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
The maximum temperature in a gas turbine is
200°C
500°C
700°C
1000°C
The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is
Less
More
Same
More/less depending on compressor capacity
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
The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the
Adiabatic temperature drop in the stage
Total temperature drop
Total temperature drop in the stage
Total adiabatic temperature drop
The overall efficiency of the compressed air system is the
Ratio of shaft output of the air motor to the shaft input to the compressor
Ratio of shaft input to the compressor to the shaft output of air motor
Product of shaft output of air motor and shaft input to the compressor
None of the above
Gas turbines use following type of air compressor
Centrifugal type
Reciprocating type
Lobe type
Axial flow type
The thrust on the rotor in a centrifugal compressor is produced by
Radial component
Axial component
Tangential component
None of the above
A centrifugal compressor works on the principle of
Conversion of pressure energy into kinetic energy
Conversion of kinetic energy into pressure energy
Centripetal action
Generating pressure directly
The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio
Increases
Decreases
First increases and then decreases
First decreases and then increases
An aftercooler is used to
Remove impurities from air
Reduce volume of air
Cause moisture and oil vapour to drop out
Cool the air
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
The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called
Compressor efficiency
Volumetric efficiency
Isothermal efficiency
Mechanical efficiency
Gas turbine works on
Brayton or Atkinson cycle
Carnot cycle
Rankine cycle
Erricson cycle
Standard air is the air at
Atmospheric conditions at any specific location
20°C and 1 kg/cm² and relative humidity 36%
0°C and standard atmospheric conditions
15°C and 1 kg/cm²
The absolute pressure of air at the outlet of a compressor is called
Back pressure
Critical pressure
Discharge pressure
None of these
The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature
0.1 %
0.5 %
1 %
5 %
The pressure ratio of an ideal vaned compressor with increase in mass flow rate
Increases
Decreases
Remain constant
First decreases and then increases
The degree of reaction is usually kept ________ for all types of axial flow compressors.
0.2
0.3
0.4
0.5
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
The inlet pressure is always ________ the discharge pressure.
Equal to
Less than
More than
None of these
Rotary compressors are suitable for
Large discharge at high pressure
Low discharge at high pressure
Large discharge at low pressure
Low discharge at low pressure
The air power of the compressor is also known as
Indicated power
Brake power
Frictional power
None of these
A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine.
Same
Lower
Higher
None of these
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
In a single stage, single acting reciprocating air compressor without clearance volume, the workdone is maximum during
Isothermal compression
Isentropic compression
Polytropic compression
None of these