Which of the following statement is correct relating to rocket engines?
The combustion chamber in a rocket engine is directly analogous to the reservoir of a supersonic wind tunnel
The stagnation conditions exist at the combustion chamber
The exit velocities of exhaust gases are much higher than those in jet engine
All of the above
Correct Answer :
D. All of the above
Related Questions
The compression ratio for the compressor is always __________ unity.
Equal to
Less than
More than
None of these
For perfect intercooling in a three stage compressor
p₂/p₁ = p₃/p₂ = p₄/p₃
p₃/p₁ = p₄/p₂
p₁ p₂ = p₃ p₄
p₁ p₃ = p₂ p₄
The volumetric efficiency of compressor with increase in compression ratio will
Increase
Decrease
Remain same
May increase or decrease depending on clearance volume
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 ratio of the discharge pressure to the inlet pressure of air is called
Compression ratio
Expansion ratio
Compressor efficiency
Volumetric efficiency
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
Choose the correct statement
Gas turbine requires lot of cooling water
Gas turbine is capable of rapid start up and loading
Gas turbines has flat efficiency at part loads
Gas turbines have high standby losses and require lot of maintenance
A rocket engine uses ________ for the combustion of its fuel.
Surrounding air
Compressed atmospheric air
Its own oxygen
None of these
A compressor mostly used for supercharging of I.C. engines is
Radial flow compressor
Axial flow compressor
Roots blower
Reciprocating compressor
The volume of air sucked by the compressor during its suction stroke is called
Free air delivery
Compressor capacity
Swept volume
None of these
In a closed cycle gas turbine, the air is compressed
Isothermally
Polytropically
Isentropically
None of these
Ratio of compression is the ratio of
Gauge discharge pressure to the gauge intake pressure
Absolute discharge pressure to the absolute intake pressure
Pressures at discharge and suction corresponding to same temperature
Stroke volume and clearance volume
The criterion of the thermodynamic efficiency for rotary compressor is
Isentropic compression
Isothermal compression
Polytropic compression
None of the above
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
Volumetric efficiency of air compressors is of the order of
20 - 30 %
40 - 50 %
60 - 70 %
70 - 90 %
Isothermal compression efficiency can be attained by running the compressor
At very high speed
At very slow speed
At average speed
At zero speed
Surging is the phenomenon of
Air stream blocking the passage
Motion of air at sonic velocity
Unsteady, periodic and reversed flow
Air stream not able to follow the blade contour
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 volumetric efficiency for reciprocating air compressors is about
10 to 40 %
40 to 60 %
60 to 70 %
70 to 90 %
The thermal efficiency of a gas turbine as compared to a diesel plant is
Same
More
Less
Depends on other factors
The maximum temperature in a gas turbine is
200°C
500°C
700°C
1000°C
Ram compression in turbojet involves
Reduction of speed of incoming air and conversion of part of it into pressure energy
Compression of inlet air
Increasing speed of incoming air
Lost work
Work ratio of a gas turbine may be improved by
Decreasing the compression work
Increasing the compression work
Increasing the turbine work
Both (A) and (C) above
Reheating in gas turbine results in
Increase of work ratio
Decrease of thermal efficiency
Decrease of work ratio
Both (A) and (B) above
In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into
Atmosphere
Vacuum
Discharge nozzle
Back to the compressor
Mining industry usually employs following motive power
A.C. electric motor
Compressed air
Petrol engine
Diesel engine
Mechanical efficiency of gas turbines as compared to I.C engines is
Higher
Lower
Same
None of the above
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
The absolute pressure of air at the outlet of a compressor is called
Back pressure
Critical pressure
Discharge pressure
None of these
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