The GATE Grind

GATE 2019 AE – Question 21

Propulsion · Engine performance: ramjet, turbojet, turbofan, turboprop, turboshaft and after-burners · 1 mark · Multiple choice

At Mach 2 and altitude 11 km, arrange the following engines in increasing order of thrust-specific fuel consumption for the same thrust.

  1. Turbofan, ramjet, turbojet
  2. Turbofan, turbojet, ramjet
  3. Ramjet, turbojet, turbofan
  4. Turbojet, turbofan, ramjet

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Show answer and explanation

Correct answer: (B) Turbofan, turbojet, ramjet

Explanation

For the comparative engine operating conditions intended by this question, the turbofan has the lowest TSFC, followed by the turbojet and then the ramjet: B. The ramjet relies entirely on flight-speed compression and is less favourable at this Mach number than at its higher-speed design regime. This ranking is conditional on the stated comparison, rather than a universal ranking across all engine designs.

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