Compressors, Gas Turbines and Jet Engines - Set 12 - ObjectiveBooks

# Practice Test: Question Set - 12

1. 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

2. The thermal efficiency of a gas turbine as compared to a diesel plant is
(A) Same
(B) More
(C) Less
(D) Depends on other factors

3. A large clearance volume in a reciprocating compressor results in
(A) Reduced volume flow rate
(B) Increased volume flow rate
(C) Lower suction pressure
(D) Lower delivery pressure

4. The air-fuel ratio in gas turbines is of the order of
(A) 7: 1
(B) 15: 1
(C) 30: 1
(D) 50: 1.

5. Inter-cooling in multistage compressors is done
(A) To cool the air during compression
(B) To cool the air at delivery
(C) To enable compression in two stages
(D) To minimize the work of compression

6. The pressure ratio in gas turbines is of the order of
(A) 2: 1
(B) 4:1
(C) 61: 1
(D) 9: 1

7. An after-cooler is used to
(A) Remove impurities from air
(B) Reduce volume of air
(C) Cause moisture and oil vapour to drop out
(D) Cool the air

8. The output of a gas turbine is 300 KW and its efficiency is 20 percent, the heat supplied is
(A) 6000 KW
(B) 15 KW
(C) 600 KW
(D) 150 KW

9. 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
(D) None of these

10. The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
(A) Heated
(B) Compressed air before entering the combustion chamber is heated
(C) Bled gas from turbine is heated and readmitted for complete expansion
(D) Exhaust gases drive the compressor

11. Gas turbine blades are given a rake
(A) Equal to zero
(B) In the direction of motion of blades
(C) Opposite to the direction of motion of blades
(D) Depending on the velocity

12. The inlet pressure is always ________ the discharge pressure.
(A) Equal to
(B) Less than
(C) More than
(D) None of these

13. Efficiency of gas turbine is increased by
(A) Reheating
(B) Inter cooling
(D) All of the above

14. Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is
(A) Higher
(B) Lower
(C) Equal
(D) Can’t be compared

15. The volume of air delivered by the compressor is called
(A) Free air delivery
(B) Compressor capacity
(C) Swept volume
(D) None of these

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