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
Correct Answer :
C. Three times
Related Questions
The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature
0.1 %
0.5 %
1 %
5 %
Separators are generally used in air compressor installations
Before the intercooler
After the intercooler
Between the aftercooler and receiver
Before first stage suction
In a single acting reciprocating air compressor, without clearance, the compression of air may be
Isothermal
Polytropic
Isentropic
Any one 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
The maximum temperature in a gas turbine is
200°C
500°C
700°C
1000°C
The process, which causes the air to enter the impeller blades of a centrifugal compressor at ________ velocity (without effecting the mass of air to flow and velocity of flow) is known as prewhirl.
Reduced
Increased
Zero
None of these
Out of the following, from where you will prefer to take intake for air compressor
From an air conditioned room maintained at 20°C
From outside atmosphere at 1°C
From coal yard side
From a side where cooling tower is located nearby
Volumetric efficiency of air compressors is of the order of
20 - 30 %
40 - 50 %
60 - 70 %
70 - 90 %
The air-fuel ratio in gas turbines is of the order of
7 : 1
15 : 1
30 : 1
50 : 1.
When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be
Forward curved
Backward curved
Radial
None of these
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.
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
In a four stage compressor, if the pressure at the first and third stage is 1 bar and 16 bar, then the delivery pressure at the fourth stage will be
1 bar
16 bar
64 bar
256 bar
For minimum work in multistage compression, assuming same index of compression in all stages
Work done in first stage should be more
Work done in subsequent stages should increase
Work done in subsequent stages should decrease
Work done in all stages should be equal
The velocity of air entering in a rocket is ________ as compared to an aircraft.
Zero
Less
More
Same
In a centrifugal compressor, the highest Mach number leading to shock wave in the fluid flow occurs at
Diffuser inlet radius
Diffuser outlet radius
Impeller inlet radius
Impeller outlet radius
Which is false statement about air receivers?
These are used to dampen pulsations
These act as reservoir to take care of sudden demands
These increase compressor efficiency
These knock out some oil and moisture
A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine.
Same
Lower
Higher
None of these
The net work input required for compressor with increase in clearance volume
Increases
Decreases
Remains same
Increases/decreases depending on compressor capacity
Volumetric efficiency is
The ratio of stroke volume to clearance volume
The ratio of the air actually delivered to the amount of piston displacement
Reciprocal of compression ratio
Index of compressor performance
Work ratio of a gas turbine plant is ratio of
Net work output and work done by turbine
Net work output and heat supplied
Work done by turbine and heat supplied
Work done by turbine and net work output
The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is
Less
More
Same
May be less or more depending on ambient conditions
Ratio of indicated h.p. to shaft h.p. in known as
Compressor efficiency
Isothermal efficiency
Volumetric efficiency
Mechanical efficiency
The capacity of compressor will be highest when its intake temperature is
Lowest
Highest
Anything
Atmospheric
In the axial flow gas turbine, the work ratio is the ratio of
Compressor work and turbine work
Output and input
Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet
Actual compressor work and theoretical compressor work
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
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
Reheating in gas turbine results in
Increase of work ratio
Decrease of thermal efficiency
Decrease of work ratio
Both (A) and (B) above
Free air is the air at
Atmospheric conditions at any specific location
20°C and 1 kg/cm² and relative humidity of 36%
0°C and standard atmospheric conditions
15°C and 1 kg/cm²
Reciprocating air compressor is best suited for
Large quantity of air at high pressure
Small quantity of air at high pressure
Small quantity of air at low pressure
Large quantity of air at low pressure