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
Correct Answer :
B. Isentropic compression
Related Questions
When air is to be compressed at a high pressure, then it is advantageous to use
Single stage compression
Multistage compression without intercooling
Multistage compression with intercooling
None of these
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 ratio of isentropic work to Eulers work is known as
Compressor efficiency
Isentropic efficiency
Euler's efficiency
Pressure coefficient
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
Diffuser in a compressor is used to
Increase velocity
Make the flow streamline
Convert pressure energy into kinetic energy
Convert kinetic energy into pressure energy
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
A turboprop is preferred to turbojet because
It has high propulsive efficiency at high speeds
It can fly at supersonic speeds
It can fly at high elevations
It has high power for take off
More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than
2 kg/cm²
6 kg/cm²
10 kg/cm²
14.7 kg/cm²
The performance of air compressor at high altitudes will be ________ as compared to that at sea level.
Same
Lower
Higher
None of these
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
In jet engines the products of combustion after passing through the gas turbine are discharged into
Atmosphere
Back to the compressor
Discharge nozzle
Vacuum
For perfect intercooling in a two stage compressor
p₂/p₁ = p₃/p₂
p₁/p₃ = p₂/p₁
p₁ = p₃
p₁ = p₂ p₃
Losses in a centrifugal compressor are due to
Inlet losses
Impeller channel losses
Diffuser losses
All of the above
The following property is most important for material used for gas turbine blade
Toughness
Fatigue
Creep
Corrosion resistance
Open cycle gas turbine works on
Brayton or Atkinson cycle
Rankine cycle
Carnot cycle
Erricson cycle
Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is
Higher
Lower
Equal
Cant be compared
Reheating in a multistage expansion gas turbine __________ compressor work.
Has no effect on
Decreases
Increases
None of these
The assumption made in two stage compression with intercooler is that
There is no pressure drop in the intercooler
The compression in both the cylinders is polytropic
The suction and delivery of air takes place at constant pressure
All of the above
In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in ________ of the piston.
One stroke
Two strokes
Three strokes
Four strokes
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
A closed cycle gas turbine works on
Carnot cycle
Rankine cycle
Ericsson cycle
Joule cycle
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
For a two stage reciprocating compressor, compression from p₁ to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by
p₂ = (p₁ + p₃)/2
p₂ = p₁. p₃
P₂ = Pa × p₃/p₁
p₂ = Pa p₃/p₁
During base load operation, the best method of controlling compressor is
Start-stop motor
Constant speed unloader
Relief valve
Variable speed
The thermal efficiency of a gas turbine as compared to a diesel plant is
Same
More
Less
Depends on other factors
For an irreversible gas turbine cycle, the efficiency and work ratio both depend on
Pressure ratio alone
Maximum cycle temperature alone
Minimum cycle temperature alone
Both pressure ratio and maximum cycle temperature
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
Inter-cooling in multistage compressors is done
To cool the air during compression
To cool the air at delivery
To enable compression in two stages
To minimise the work of compression
Volumetric efficiency of a compressor with clearance volume
Increases with increase in compression ratio
Decreases with increase in compression ratio
In not dependent upon compression ratio
May increase/decrease depending on compressor capacity
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