Compressors, Gas Turbines & Jet Engines 1000+ MCQ with answer for RRB ALP

1. For an irreversible gas turbine cycle, the efficiency and work ratio both depend on
A. Pressure ratio alone
B. Maximum cycle temperature alone
C. Minimum cycle temperature alone
D. Both pressure ratio and maximum cycle temperature
Answer : D

2. Isothermal compression efficiency, even when running at high speed, can be approached by using
A. Multistage compression
B. Cold water spray
C. Both (A) and (B) above
D. Fully insulating the cylinder
Answer : C

3. In a single stage, single acting reciprocating air compressor, without clearance, the workdone on the air during isentropic compression is ________ the heat required to raise the temperature of air from T? to T? at a constant pressure.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : A

4. Which of the following statement is correct relating to rocket engines?
A. The combustion chamber in a rocket engine is directly analogous to the reservoir of a supersonic wind tunnel
B. The stagnation conditions exist at the combustion chamber
C. The exit velocities of exhaust gases are much higher than those in jet engine
D. All of the above
Answer : D

5. The ratio of isentropic work to Eulers work is known as
A. Compressor efficiency
B. Isentropic efficiency
C. Euler's efficiency
D. Pressure coefficient
Answer : D

6. The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the
A. Rotor to static enthalpy rise in the stator
B. Stator to static enthalpy rise in the rotor
C. Rotor to static enthalpy rise in the stage
D. Stator to static enthalpy rise in the stage
Answer : C

7. For minimum work required to compress and deliver a quantity of air by multistage compression
A. The compression ratio in each stage should be same
B. The intercooling should be perfect
C. The workdone in each stage should be same
D. All of the above
Answer : D

8. Volumetric efficiency of a compressor with clearance volume
A. Increases with increase in compression ratio
B. Decreases with increase in compression ratio
C. In not dependent upon compression ratio
D. May increase/decrease depending on compressor capacity
Answer : B

9. Inter cooling in compressors
A. Cools the delivered air
B. Results in saving of power in compressing a given volume to given pressure
C. Is the standard practice for big compressors
D. Enables compression in two stages
Answer : B

10. Pick up the wrong statement
A. Centrifugal compressors deliver practically constant pressure over a considerable range of capacities
B. Axial flow compressors have a substantially constant delivery at variable pressures
C. Centrifugal compressors have a wider stable operating range than axial flow compressors
D. Axial flow compressors are bigger in diameter compared to centrifugal type
Answer : D

11. For a two stage reciprocating compressor, compression from p? to p? 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 p? is given by
A. p? = (p? + p?)/2
B. p? = p?. p?
C. P? = Pa × p?/p?
D. p? = Pa p?/p?
Answer : B

12. For perfect intercooling in a three stage compressor
A. p?/p? = p?/p? = p?/p?
B. p?/p? = p?/p?
C. p? p? = p? p?
D. p? p? = p? p?
Answer : A

13. The clearance volume of the air compressor is kept minimum because
A. It allows maximum compression to be achieved
B. It greatly affects volumetric efficiency
C. It results in minimum work
D. It permits isothermal compression
Answer : B

14. In a jet propulsion unit, the products of combustion after passing through the gas turbine are discharged into
A. Atmosphere
B. Vacuum
C. Discharge nozzle
D. Back to the compressor
Answer : C

15. The temperature of air at the beginning of the compression stroke is ________ the atmospheric temperature.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : C

16. When the temperature of air leaving the intercooler, in a two stage compression with intercooler, is ________ the original atmospheric air temperature, then the intercooling is known as perfect or complete intercooling.
A. Equal to
B. Less than
C. More than
D. None of these
Answer : A

17. An air compressor may be controlled by
A. Throttle control
B. Clearance control
C. Blow off control
D. Any one of the above
Answer : D

18. A rocket engine uses ________ for the combustion of its fuel.
A. Surrounding air
B. Compressed atmospheric air
C. Its own oxygen
D. None of these
Answer : C

19. When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be
A. Forward curved B. Backward curved
C. Radial
D. None of these
Answer : A