# Gas Power Cycles - Mechanical Engineering (MCQ) questions and answers

1)   For the same maximum pressure and temperature, what is the relation among the efficiencies of the Otto cycle, the Diesel cycle and the Dual cycle?

a. ηDual > ηDiesel > ηOtto
b. ηDiesel > ηDual > ηOtto
c. ηDiesel > ηOtto > ηDual
d. ηOtto > ηDiesel > ηDual
 Answer  Explanation ANSWER: ηDiesel > ηDual > ηOtto Explanation: No explanation is available for this question!

2)   What is the difference between the Brayton cycle and the Rankine cycle?

a. Brayton cycle has two reversible isobars whereas Rankine cycle has two isotherms
b. The working fluid of Brayton cycle always remains in gaseous phase whereas in Rankine cycle the working fluid undergoes phase change
c. Brayton cycle operates between higher pressure ratio than the Rankine cycle for same capacity
d. all of the above
 Answer  Explanation ANSWER: The working fluid of Brayton cycle always remains in gaseous phase whereas in Rankine cycle the working fluid undergoes phase change Explanation: No explanation is available for this question!

3)   What is the effect of increasing bypass ratio of a turbofan engine on its thrust?

a. thrust increases with increase in bypass ratio of turbofan engine
b. thrust decreases with increase in bypass ratio of turbofan engine
c. thrust of the turbofan engine only depends upon the fuel rate, so no change of thrust with increase in bypass ratio
d. cannot say
 Answer  Explanation ANSWER: thrust increases with increase in bypass ratio of turbofan engine Explanation: No explanation is available for this question!

4)   In turbofan engine, the bypass ratio is the ratio of

a. total mass flow rate of exhaust stream to the mass flow rate of stream from turbine exhaust
b. total mass flow rate of exhaust stream to the mass flow rate of stream from fan exhaust
c. the mass flow rate of stream from turbine exhaust to the mass flow rate of stream from fan exhaust
d. the mass flow rate of stream from fan exhaust to the mass flow rate of stream from turbine exhaust
 Answer  Explanation ANSWER: the mass flow rate of stream from fan exhaust to the mass flow rate of stream from turbine exhaust Explanation: No explanation is available for this question!

5)   In turbofan engine, fan is used

a. to compress the inlet air more efficiently
b. to increase the total thrust of the engine
c. both a. and b.
d. none of the above
 Answer  Explanation ANSWER: to increase the total thrust of the engine Explanation: No explanation is available for this question!

6)   The propulsive efficiency is the ratio of

a. the propulsive power to the energy input rate
b. the exit velocity rate of exhaust gases to the energy input rate
c. the work done by the turbine to the energy input rate
d. velocity of aircraft to the energy input rate
 Answer  Explanation ANSWER: the propulsive power to the energy input rate Explanation: No explanation is available for this question!

7)   The propulsive power developed by the thrust of engine is given by

a. mair (Vexit – Vinlet)
b. mair (Vexit – Vinlet) × Vaircraft
c. (Vexit – Vinlet) × Vaircraft
d. none of the above
 Answer  Explanation ANSWER: mair (Vexit – Vinlet) × Vaircraft Explanation: No explanation is available for this question!

8)   Why do the airplanes fly at higher altitude during the long flights?

a. to avoid collisions as they are at very high speed and controlling will be difficult if something (like towers, hills) comes in the way
b. it is easy to communicate with satellites at high altitudes
c. to save the fuel as air at higher altitude exerts smaller drag force on aircraft
d. none of the above
 Answer  Explanation ANSWER: to save the fuel as air at higher altitude exerts smaller drag force on aircraft Explanation: No explanation is available for this question!

9)   In working condition of turbojet engine, velocity of air entering the engine is

a. higher than the velocity of exhaust gases leaving the engine
b. lower than the velocity of exhaust gases leaving the engine
c. equal to the velocity of exhaust gases leaving the engine
d. cannot say
 Answer  Explanation ANSWER: lower than the velocity of exhaust gases leaving the engine Explanation: No explanation is available for this question!

10)   Which among the following engines is NOT the type of aircraft gas turbine which works on jet propulsion cycle?

a. turbojet
b. turbofan
c. turboprop
d. none of the above
 Answer  Explanation ANSWER: none of the above Explanation: No explanation is available for this question!

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