Turbofan engine uses a large fan at inlet to _____

A)
increase wing tip lift
B)
increase tailplane lift
C)
increase flow velocity
D)
increase efficiency of the engine

Correct Answer :   increase efficiency of the engine

Explanation : To Increase efficiency, more specifically propulsive efficiency of the engine a turbofan engine uses a fan. Some air is bypassed around the engine and not being used for combustion. This helps to increase efficiency.

Recently Updated in Aircraft Design Questions
Determine the propeller efficiency if propeller velocity is 300ft/s and thrust of 1320 lb. Given bhp is 800.
A)
0.03%
B)
0.09%
C)
0.895%
D)
90%

Correct Answer : Option (D) :   90%

Explanation : Propeller efficiency = (thrust*velocity) / (bhp*550) = 1320*300/ (550*800) = 0.9 = 0.9*100 % = 90%.

Determine the required thrust coefficient to produce thrust of 1000N. Given diameter is 1.2m and n=22 rps.
A)
0.1
B)
0.32
C)
0.489
D)
0.813

Correct Answer : Option (D) :   0.813

Explanation : Thrust coefficient = Thrust / (density*diameter4*rps2) = 1000 / (1.225*1.24*222) = 0.813.

If a propeller has bhp of 700 and diameter as 1.2 ft. and rotating with 20 rps then, determine power coefficient. Consider sea level density.
A)
1.8
B)
15.8
C)
30.2
D)
40

Correct Answer : Option (B) :   15.8

Explanation : Power coefficient = 550*bhp / (density*diameter5*rps3)
= 550*700 / (1.225*1.25*203) = 15.8.

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