Multiple Choice Questions and Answers (MCQs) on Compressors, Gas Turbines and Jet Engines
01. If the flow of air through the compressor is perpendicular to its axis, then it is a
(A) Reciprocating compressor
(B) Centrifugal compressor
(C) Axial flow compressor
(D) Turbo compressor
Answer: Option B
02. Gas turbines use following type of air compressor
(A) Centrifugal type
(B) Reciprocating type
(C) Lobe type
(D) Axial flow type
Answer: Option D
03. The gas in cooling chamber of a closed cycle gas turbine is cooled at
(A) Constant volume
(B) Constant temperature
(C) Constant pressure
(D) None of these
Answer: Option C
04. The maximum combustion pressure in gas turbine as compared to I.C. engine is
(A) More
(B) Less
(C) Same
(D) Depends on other factors
Answer: Option B
05. In a closed cycle gas turbine, the air is compressed
(A) Isothermally
(B) Polytropically
(C) Isentropically
(D) None of these
Answer: Option C
06. The closed cycle in gas turbines
(A) Provides greater flexibility
(B) Provides lesser flexibility
(C) In never used
(D) Is used when gas is to be burnt
Answer: Option A
07. The overall thermal efficiency of an ideal gas turbine plant is (where r = Pressure ratio)
(A) r ɣ-1
(B) 1 – r ɣ-1
(C) 1 – (1/r) ɣ-1/ɣ
(D) 1 – (1/r) ɣ/ɣ-1
Answer: Option C
08. Pick up the correct statement
(A) Large gas turbines use radial inflow turbines
(B) Gas turbines have their blades similar to steam turbine
(C) Gas turbine’s blade will appear as impulse section at the hub and as a reaction section at tip
(D) Gas turbines use both air and liquid cooling
Answer: Option C
09. The degree of reaction is usually kept ________ for all types of axial flow compressors.
(A) 0.2
(B) 0.3
(C) 0.4
(D) 0.5
Answer: Option D
10. Ram compression in turbojet involves
(A) Reduction of speed of incoming air and conversion of part of it into pressure energy
(B) Compression of inlet air
(C) Increasing speed of incoming air
(D) Lost work
Answer: Option A
11. A compressor mostly used for supercharging of I.C. engines is
(A) Radial flow compressor
(B) Axial flow compressor
(C) Roots blower
(D) Reciprocating compressor
Answer: Option A
12. In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of
(A) Vacuum
(B) Atmospheric air
(C) Compressed air
(D) Oxygen alone
Answer: Option C
13. The workdone on a compressor will be minimum if air is taken from
(A) The atmosphere
(B) A source at 0°C
(C) A source of low temperature air
(D) A source of high temperature air
Answer: Option C
14. In the aircraft propellers
(A) The propulsive matter is caused to flow around the propelled body
(B) Propulsive matter is ejected from within the propelled body
(C) Its functioning does not depend on presence of air
(D) All of the above
Answer: Option D
15. 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: Option C
16. To avoid moisture troubles, the branch connections from compressed air lines should be taken from
(A) Top side of main
(B) Bottom side of main
(C) Left side of main
(D) Right side of main
Answer: Option A
17. In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as
(A) Work factor
(B) Slip factor
(C) Degree of reaction
(D) Pressure coefficient
Answer: Option C
18. To avoid moisture troubles, the compressed air main line should
(A) Rise gradually towards the point of use
(B) Drop gradually towards the point of use
(C) Be laid vertically
(D) Be laid exactly horizontally
Answer: Option B
19. The volumetric efficiency of a compressor
(A) Increases with decrease in compression ratio
(B) Decreases with decrease in compression ratio
(C) Increases with increase in compression ratio
(D) Decreases with increase in compression ratio
Answer: Option D
20. The efficiency and work ratio of a gas turbine plant can be increased by
(A) Adding heat exchanger
(B) Injecting water in/around combustion chamber
(C) Reheating the air after partial expansion in the turbine
(D) All of the above
Answer: Option D
21. The capacity of compressor will be highest when its intake temperature is
(A) Lowest
(B) Highest
(C) Anything
(D) Atmospheric
Answer: Option D
22. The volume of air sucked by the compressor during its suction stroke is called
(A) Free air delivery
(B) Compressor capacity
(C) Swept volume
(D) None of these
Answer: Option C
23. Which is false statement about multistage compression?
(A) Power consumption per unit of air delivered is low
(B) Volumetric efficiency is high
(C) It is best suited for compression ratios around 7:1
(D) The moisture in air is condensed in the intercooler
Answer: Option B
24. Standard air is the air at ________ and relative humidity of 36 percent.
(A) 0.1 bar and 20°C
(B) 1 bar and 20°C
(C) 0.1 bar and 40°C
(D) 1 bar and 40°C
Answer: Option B
25. Out of the following, from where you will prefer to take intake for air compressor
(A) From an air conditioned room maintained at 20°C
(B) From outside atmosphere at 1°C
(C) From coal yard side
(D) From a side where cooling tower is located nearby
Answer: Option D