Gas turbines use following type of air compressor
Centrifugal type
Reciprocating type
Lobe type
Axial flow type
Correct Answer :
D. Axial flow type
Related Questions
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
The mass of gas turbine per kW developed is about ________ as that of an I.C. engine.
Same
One-half
One fourth
One sixth
The stagnation pressure rise in a centrifugal compressor takes place
In the diffuser only
In the impeller only
In the diffuser and impeller
In the inlet guide vanes only
An air compressor may be controlled by
Throttle control
Clearance control
Blow off control
Any one of the above
The air-fuel ratio in gas turbines is of the order of
7 : 1
15 : 1
30 : 1
50 : 1.
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
In a single acting reciprocating air compressor, without clearance, the compression of air may be
Isothermal
Polytropic
Isentropic
Any one 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
Ratio of indicated H.P. and brake H.P. is known as
Mechanical efficiency
Volumetric efficiency
Isothermal efficiency
Adiabatic efficiency
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 ratio of workdone per cycle to the stroke volume of the compressor is known as
Compressor capacity
Compression ratio
Compressor efficiency
Mean effective pressure
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
The workdone on a compressor will be minimum if air is taken from
The atmosphere
A source at 0°C
A source of low temperature air
A source of high temperature air
If p₁ is the pressure of air entering the L.P, cylinder and p₃ is the pressure of air leaving the H.P. cylinder, then the ratio of cylinder diameters for a single acting, two stage reciprocating compressor with complete intercooling is given by
D₁/D₂ = (p₁ p₃)1/2
D₁/D₂ = (p₁/p₃)1/4
D₁/D₂ = (p₁ p₃)1/4
D₁/D₂ = (p₃/p₁)1/4
The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turbine and fixed higher and lower temperature) with increase in pressure ratio will
Increase first at fast rate and then slow
Increase first at slow rate and then fast
Decrease continuously
First increase, reach maximum and then decrease
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
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
What will be the volume of air at 327°C if its volume at 27°C is 1.5 m³/ mt?
3 m³/ mt.
1.5 m³/ mt.
18 m³/ mt.
6 m³/ mt.
The efficiency of the vane blower is (where W₁ = Workdone due to compression, and W₂ = Workdone due to back flow)
W₁/(W₁ + W₂)
W₂/(W₁ + W₂)
(W₁ + W₂)/W₁
(W₁ + W₂)/W₂
A closed gas turbine in which fuel is burnt directly in the air is not possible because of
Paucity of O2
Increasing gas temperature
High specific volume
High friction losses
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
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
The volumetric efficiency for reciprocating air compressors is about
10 to 40 %
40 to 60 %
60 to 70 %
70 to 90 %
The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called
Slip factor
Velocity factor
Velocity coefficient
None of the above
Turbofan engine employs
One air stream
Two or more air streams
No air stream
Solid fuel firing
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
The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of
75 %
85 %
90 %
99 %
The efficiency of jet engine is
Lower at low speed
Higher at high altitudes
Same at all altitudes
Higher at high speed
The thrust of a jet propulsion power unit can be increased by
Injecting water into the compressor
Burning fuel after gas turbine
Injecting ammonia into the combustion chamber
All of the above
The volumetric efficiency of a compressor
Increases with decrease in compression ratio
Decreases with decrease in compression ratio
Increases with increase in compression ratio
Decreases with increase in compression ratio