Compressors, Gas Turbines and Jet Engines Objective Questions with Answers - Set 17

Practice Test: Question Set - 17


1. 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

2. 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

3. 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

4. The stagnation pressure rise in a centrifugal compressor takes place
    (A) In the diffuser only
    (B) In the impeller only
    (C) In the diffuser and impeller
    (D) In the inlet guide vanes only

5. What will be the volume of air at 327°C if its volume at 27°C is 1.5 m³/ mt?
    (A) 3 m³/ mt.
    (B) 1.5 m³/ mt.
    (C) 18 m³/ mt.
    (D) 6 m³/ mt.

6. A 3 m³/min compressor means that it
    (A) Compresses 3 m³/min of standard air
    (B) Compresses 3 m³/ min of free air
    (C) Delivers 3 m³/ min of compressed air
    (D) Delivers 3 m³/ min of compressed air at delivery pressure

7. Euler's equation is applicable for
    (A) Centrifugal compressor
    (B) Axial compressor
    (C) Pumps
    (D) All of the above

8. 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

9. Which is false statement about air receivers?
    (A) These are used to dampen pulsations
    (B) These act as reservoir to take care of sudden demands
    (C) These increase compressor efficiency
    (D) These knock out some oil and moisture

10. 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

11. The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation
    (A) 0.1%
    (B) 0.5%
    (C) 1.0%
    (D) 5%

12. 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
    (A) p₂ = (p₁ + p₃)/2
    (B) p₂ = p₁. p₃
    (C) P₂ = Pa × p₃/p₁
    (D) p₂ = Pa p₃/p₁

13. For slow speed large capacity compressor, following type of valve will be best suited
    (A) Poppet valve
    (B) Mechanical valve of the Corliss, sleeve, rotary or semi rotary type
    (C) Disc or feather type
    (D) Any of the above

14. The type of rotary compressor used in gas turbines, is of
    (A) Centrifugal type
    (B) Axial flow type
    (C) Radial flow type
    (D) None of these

15. During base load operation, the best method of controlling compressor is
    (A) Start-stop motor
    (B) Constant speed unloader
    (C) Relief valve
    (D) Variable speed

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