Compressors, Gas Turbines and Jet Engines MCQ Practice Test – Set 15 :: Mechanical Engineering

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Q1. The volume of air delivered by the compressor is called

(A) Free air delivery
(B) Compressor capacity
(C) Swept volume
(D) None of these

Answer: (B) Compressor capacity


Q2. The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the

(A) Adiabatic temperature drop in the stage
(B) Total temperature drop
(C) Total temperature drop in the stage
(D) Total adiabatic temperature drop

Answer: (C) Total temperature drop in the stage


Q3. The weight per horse power ratio for gas in Turbine as compared to I.C. engine and steam turbine is

(A) Same
(B) Higher
(C) Lower
(D) None of these

Answer: (C) Lower


Q4. Which of the following plants is smallest and lightest for generating a given amount of power?

(A) Gas turbine plant
(B) Petrol engine
(C) Diesel engine
(D) Solar plant

Answer: (A) Gas turbine plant


Q5. Standard air is the air at

(A) Atmospheric conditions at any specific location
(B) 20°C and 1 kg/cm² and relative humidity 36%
(C) 0°C and standard atmospheric conditions
(D) 15°C and 1 kg/cm²

Answer: (B) 20°C and 1 kg/cm² and relative humidity 36%


Q6. 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

Answer: (A) Start-stop motor


Q7. Stalling of blades in axial flow compressor is the phenomenon of

(A) Air stream blocking the passage
(B) Motion of air at sonic velocity
(C) Unsteady periodic and reversed flow
(D) Air stream not able to follow the blade contour

Answer: (D) Air stream not able to follow the blade contour


Q8. If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix ‘I’ and ‘o’ stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity

(A) Vi = Vo
(B) Vt > Vo
(C) U < Vo
(D) V = Uo

Answer: (A) Vi = Vo


Q9. The propulsive power of the rocket is (where v₁ = Jet velocity, and v₂ = Aircraft velocity)

(A) (v₁² -v₂²)/2g
(B) (v₁ – v₂)²/2g
(C) (v₁² -v₂²)/g
(D) (v₁ – v₂)²/g

Answer: (A) (v₁² -v₂²)/2g


Q10. Inter-cooling in gas turbine results in

(A) Increase in net output but decrease in thermal efficiency
(B) Increase in thermal efficiency but decrease in net output
(C) Increase in both thermal efficiency and net output
(D) Decrease in both thermal efficiency and net output

Answer:(A) Increase in net output but decrease in thermal efficiency


Q11. The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the

(A) Rotor to static enthalpy rise in the stator
(B) Stator to static enthalpy rise in the rotor
(C) Rotor to static enthalpy rise in the stage
(D) Stator to static enthalpy rise in the stage

Answer:(C) Rotor to static enthalpy rise in the stage


Q12. In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is __ the heat required to raise the temperature of air from T₁ to T₂ at a constant pressure.

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

Answer:(A) Equal to


Q13. 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

Answer: (B) Axial flow type


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