Compressors, Gas Turbines and Jet Engines MCQ Practice Test – Set 9 :: Mechanical Engineering

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Q1. 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

Answer: (C) Less

Q2. The material commonly used for air craft gas turbine is

(A) Stainless steel
(B) High alloy steel
(C) Duralumin
(D) Timken, Haste alloys

Answer: (D) Timken, Haste alloys

Q3. The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is

(A) Less
(B) More
(C) Same
(D) May be less or more depending on ambient conditions

Answer: (A) Less

Q4. The working fluid in a turbine is

(A) In two phases
(B) In three phases
(C) In a single phase
(D) In the form of air and water mixture

Answer: (C) In a single phase

Q5. Pick up the correct statement

(A) Closed cycle gas turbine is an I.C engine
(B) Gas turbine uses same working fluid over and over again
(C) Ideal efficiency of closed cycle gas turbine plant is more than Carnot cycle efficiency
(D) Thrust in turbojet is produced by nozzle exit gases

Answer: (D) Thrust in turbojet is produced by nozzle exit gases

Q6. In a four stage compressor, if the pressure at the first and third stage is 1 bar and 16 bar, then the delivery pressure at the fourth stage will be

(A) 1 bar
(B) 16 bar
(C) 64 bar
(D) 256 bar

Answer: (C) 64 bar

Q7. In a jet propulsion

(A) The propulsive matter is ejected from within the propelled body
(B) The propulsive matter is caused to flow around the propelled body
(C) Its functioning does not depend upon presence of air
(D) None of the above

Answer:(B) The propulsive matter is caused to flow around the propelled body

Q8. A closed cycle gas turbine works on

(A) Carnot cycle
(B) Rankine cycle
(C) Ericsson cycle
(D) Joule cycle

Answer: (D) Joule cycle

Q9. The effective power of gas turbines is increased by adding the following in compressor

(A) Ammonia and water vapour
(B) Carbon dioxide
(C) Nitrogen
(D) Hydrogen

Answer: (A) Ammonia and water vapour

Q10. The compression ratio for the compressor is always _ unity.

(A) Equal to
(B) Less than
(C) More than
(D) None of these

Answer: (C) More than

Q11. 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

Answer:(A) Reduced volume flow rate

Q12. In open cycle turbojet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the

(A) Thrust and range of aircraft
(B) Efficiency of the engine
(C) Both (A) and (B)
(D) None of these

Answer:(A) Thrust and range of aircraft

Q13. A closed gas turbine in which fuel is burnt directly in the air is not possible because of

(A) Paucity of O2
(B) Increasing gas temperature
(C) High specific volume
(D) High friction losses

Answer: (A) Paucity of O2

Q14. Gas turbine cycle with regenerator

(A) Increases thermal efficiency
(B) Allows high compression ratio
(C) Decreases heat loss is exhaust
(D) Allows operation at very high altitudes

Answer: (A) Increases thermal efficiency

Q15. The ratio of the discharge pressure to the inlet pressure of air is called

(A) Compression ratio
(B) Expansion ratio
(C) Compressor efficiency
(D) Volumetric efficiency

Answer: (A) Compression ratio

Q16. 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) Results in saving of power in compressing a given volume to given pressure

Q17. The ratio of isentropic work to Euler work is known as

(A) Pressure coefficient
(B) Work coefficient
(C) Polytropic reaction
(D) Slip factor

Answer:(A) Pressure coefficient

Q18. Mechanical efficiency of gas turbines as compared to I.C engines is

(A) Higher
(B) Lower
(C) Same
(D) None of the above

Answer: (A) Higher

Q19. High air-fuel ratio is used in gas turbines

(A) To increase the output
(B) To increase the efficiency
(C) To save fuel
(D) To reduce the exit temperature

Answer: (D) To reduce the exit temperature

Q20. The work ratio of a gas turbine plant is defined as the ratio of

(A) Net work output and heat supplied
(B) Net work output and work done by turbine
(C) Actual heat drop and isentropic heat drop
(D) Net work output and isentropic heat drop

Answer: (B) Net work output and work done by turbine

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