# Compressors, Gas Turbines and Jet Engines MCQ Practice Test – Set 11 :: Mechanical Engineering

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## Q1. The maximum compression ratio in an actual single stage axial flow compressor is of the order of

(A) 1 : 1.2
(B) 1 : 2
(C) 1 : 5
(D) 1 : 10

Answer: (A) 1 : 1.2

## Q2. The ideal efficiency of simple gas turbine cycle depends on

(A) Pressure ratio
(B) Maximum cycle temperature
(C) Minimum cycle temperature
(D) All of the above

Answer: (A) Pressure ratio

## Q3. In turbo fan engine, the jet velocity as compared to turbojet engine is

(A) Less
(B) More
(C) Same
(D) May be less or more depending upon speed

Answer: (A) Less

## Q4. The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called

(A) Compressor efficiency
(B) Volumetric efficiency
(C) Isothermal efficiency
(D) Mechanical efficiency

Answer:(D) Mechanical efficiency

## Q5. 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

Answer: (C) Cause moisture and oil vapour to drop out

## Q6. Separators are generally used in air compressor installations

(A) Before the inter-cooler
(B) After the inter-cooler
(C) Between the after-cooler and receiver
(D) Before first stage suction

Answer: (C) Between the after-cooler and receiver

## Q7. Which of the following fuels can be used in turbojet engines?

(A) Liquid hydrogen
(B) High speed diesel oil
(C) Kerosene
(D) Methyl alcohol

Answer: (C) Kerosene

## Q8. Reheating in gas turbine results in

(A) Increase of work ratio
(B) Decrease of thermal efficiency
(C) Decrease of work ratio
(D) Both (A) and (B) above

Answer: (D) Both (A) and (B) above

## Q9. The compressor capacity with decrease in suction temperature

(A) Increases
(B) Decreases
(C) Remain unaffected
(D) May increase or decrease depending on compressor capacity

Answer: (A) Increases

## Q10. Euler’s equation is applicable for

(A) Centrifugal compressor
(B) Axial compressor
(C) Pumps
(D) All of the above

Answer: (D) All of the above

## Q11. Volumetric efficiency of a compressor decreases with __ in compression ratio.

(A) Decrease
(B) Increase
(C) Remain same
(D) Does not change

Answer: (B) Increase

## Q12. The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio

(A) Increases
(B) Decreases
(C) First increases and then decreases
(D) First decreases and then increases

Answer: (A) Increases

## Q13. Turbofan engine employs

(A) One air stream
(B) Two or more air streams
(C) No air stream
(D) Solid fuel firing

Answer: (B) Two or more air streams

## Q14. The work ratio of simple gas turbine cycle depends on

(A) Pressure ratio
(B) Maximum cycle temperature
(C) Minimum cycle temperature
(D) All of the above

Answer: (D) All of the above

## Q15. 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

Answer: (B) 15 KW

## Q16. Producer gas is produced by

(A) Carbonisation of coal
(B) Passing steam over incandescent coke
(C) Passing air and a large amount of steam over waste coal at about 65°C
(D) Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast

Answer: (D) Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast

## Q17. Propulsive efficiency is defined as ratio of

(A) Thrust power and fuel energy
(B) Engine output and propulsive power
(C) Propulsive power and fuel input
(D) Thrust power and propulsive power

Answer: (D) Thrust power and propulsive power

## Q18. Work ratio of a gas turbine plant is ratio of

(A) Net work output and work done by turbine
(B) Net work output and heat supplied
(C) Work done by turbine and heat supplied
(D) Work done by turbine and net work output

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

## Q19. The maximum propulsion efficiency of a turbojet is attained at around following speed

(A) 550 km/hr
(B) 1050 km/hr
(C) 1700 km/hr
(D) 2400 km/hr

Answer: (D) 2400 km/hr

## Q20. In a high pressure compressor, the delivery pressure is

(A) 1 to 5 bar
(B) 5 to 8 bar
(C) 8 to 10 bar
(D) 10 to 15 bar

Answer: (C) 8 to 10 bar

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