GATE AE 2008 • Q57 MCQ • 2 Marks

Propulsion

Inlets, Combustors & Nozzles

Subtopic: Combustor Design & Flame Stabilization

Question Statement:

Pxy® 4c* 3 Рху 4c where P is a constant. x L The above stress function pertains to a

Options:

  • (A) simply supported beam carrying a point load P at mid span
  • (B) simply supported beam carrying a uniform distributed load of intensity P per unit length
  • (C) cantilever beam clamped at end x = L and carrying a shear load P at x = 0
  • (D) cantilever beam clamped at end x = 0 and carrying a shear load P at x = L

Official Answer Key:

C

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE AE 2008 Q.57)** **1. Governing Concept & Theory**: Governed by principles of **Inlets, Combustors & Nozzles** (Aerospace Propulsion, 2 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 **C**. **3. Official Answer Verification**: - **Official Result**: **C** - **Evaluation Status**: Matches official GATE 2008 master key with 100% accuracy. - **Selected Option**: **(C)** — *"cantilever beam clamped at end x = L and carrying a shear load P at x = 0"*

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