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
Correct Answer :
D. Increase in flow and decrease in efficiency
Related Questions
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 volume of air delivered by the compressor is called
Free air delivery
Compressor capacity
Swept volume
None of these
In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of
Vacuum
Atmospheric air
Compressed air
Oxygen alone
In jet engines the products of combustion after passing through the gas turbine are discharged into
Atmosphere
Back to the compressor
Discharge nozzle
Vacuum
Separators are generally used in air compressor installations
Before the intercooler
After the intercooler
Between the aftercooler and receiver
Before first stage suction
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
Ratio of indicated H.P. and brake H.P. is known as
Mechanical efficiency
Volumetric efficiency
Isothermal efficiency
Adiabatic efficiency
The effective power of gas turbines is increased by adding the following in compressor
Ammonia and water vapour
Carbon dioxide
Nitrogen
Hydrogen
For maximum work, the reheating should be done to an intermediate pressure of (Where p₁ = Maximum pressure, and p₂ = Minimum pressure)
(p₁ - p₂)/2
(p₁ + p₂)/2
p₁/p₂
p₁ p₂
Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is
Higher
Lower
Equal
Cant be compared
Inter-cooling in gas turbine results in
Increase in net output but decrease in thermal efficiency
Increase in thermal efficiency but decrease in net output
Increase in both thermal efficiency and net output
Decrease in both thermal efficiency and net output
A jet engine works on the principle of conservation of
Mass
Energy
Flow
Linear momentum
A compressor at high altitudes will require ________ power.
Same
Less
More
None of these
Axial flow compressor resembles
Centrifugal pump
Reciprocating pump
Turbine
Sliding vane compressor
With the decrease in compression ratio, the volumetric efficiency
Does not change
Increases
Decreases
First decrease and then increase
Axial flow compressor has the following advantage over centrifugal compressor
Larger air handling ability per unit frontal area
Higher pressure ratio per stage
Aerofoil blades are used
Higher average velocities
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
The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.
Equal to
Less than
More than
None of these
The axial flow compressor is preferred in aircraft gas turbines because of
Low frontal area
Higher thrust
High pressure rise
None of these
The ratio of the net work obtained from the gas turbine plant to the turbine work is known as
Compression ratio
Work ratio
Pressure ratio
None of these
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
Reheating in gas turbine results in
Increase of work ratio
Decrease of thermal efficiency
Decrease of work ratio
Both (A) and (B) above
Fighter bombers use following type of engine
Turbojet
Turbo-propeller
Rocket
Ramjet
Maximum work is done in compressing air when the compression is
Isothermal
Adiabatic
Polytropic
None of the above
Gas turbine as compared to steam turbine
Requires less space for installation
Has compressor and combustion chamber
Has less efficiency
All of these
Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be
1.03 kg/cm²
1.06 kg/cm²
1.00 kg/cm²
0.53 kg/cm²
As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio
Increases
Decreases
Remain same
First increases and then decreases
Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on
Mass flow rate
Pressure ratio
Change in load
Stagnation pressure at the outlet
The main purpose of reheating in gas turbine is to
Increase temperature
Reduce turbine size
Increase power output
Increase speed
In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as
Work factor
Slip factor
Degree of reaction
Pressure coefficient