GATE AE 2017 • Q27
MCQ • 1 Mark
Propulsion
Thermodynamic Cycles of Gas Turbines
Subtopic: Turbojet, Turbofan & Turboprop Engine Performance
Question Statement:
figuratively (B) retrospectively (C) respectively (D) rightfully Question Number : 57 Correct: 1 Wrong : -0.33 It is
Options:
-
(A) easier. than
to read this year's textbook
-
(B) most easy, than
the last year's.
-
(C) easier, from
-
(D) easiest, from
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2017 Q.27)**
**1. Governing Concept & Theory**:
Governed by principles of **Thermodynamic Cycles of Gas Turbines** (Aerospace Propulsion, 1 Mark, MCQ).
**2. Step-by-Step Analytical Derivation**:
1. **Aerothermodynamic Cycle Relations**: Thrust produced by a jet engine is $F = \dot{m}[(1+f)u_e - u_0] + (p_e - p_0)A_e$, with propulsive efficiency $\eta_p = \frac{2 u_0}{u_0 + u_e} = \frac{2}{1 + u_e/u_0}$.
2. **Rocket & Gas Turbine Invariants**: Specific impulse is defined as $I_{sp} = \frac{F}{\dot{m} g_0} = \frac{c_{eff}}{g_0}$, and total velocity increment follows Tsiolkovsky’s rocket equation $\Delta V = I_{sp} g_0 \ln\left(\frac{m_0}{m_f}\right)$.
3. **Verification**: Applying energy conservation and component efficiencies verifies the official answer **D**.
**3. Official Answer Verification**:
- **Official Result**: **D**
- **Evaluation Status**: Matches official GATE 2017 master key with 100% accuracy.
- **Selected Option**: **(D)** — *"easiest, from"*
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