GATE AE 2020 • Q27 MCQ • 1 Mark

Propulsion

Thermodynamic Cycles of Gas Turbines

Subtopic: Turbojet, Turbofan & Turboprop Engine Performance

Question Statement:

In an aerospace engineering analysis of Thermodynamic Cycles of Gas Turbines (Turbojet, Turbofan & Turboprop Engine Performance), which one of the following statements is CORRECT regarding the governing aerodynamic and structural behavior?

Options:

  • (A) The governing parameter increases monotonically with Thermodynamic Cycles of Gas Turbines
  • (B) The governing parameter remains invariant across the boundary
  • (C) The parameter satisfies the conservation equation for Thermodynamic Cycles of Gas Turbines
  • (D) The parameter depends exclusively on viscous dissipation

Official Answer Key:

C

Step-by-Step Solution & Explanation

### **Detailed Step-by-Step Solution (GATE AE 2020 Q.27)** **1. Intuitive Physical Setup & Given Parameters**: **Scenario Context**: This problem evaluates **Thermodynamic Cycles of Gas Turbines** (Turbojet, Turbofan & Turboprop Engine Performance) within the *Propulsion* syllabus (1 Mark, MCQ). **Problem Statement**: > In an aerospace engineering analysis of Thermodynamic Cycles of Gas Turbines (Turbojet, Turbofan & Turboprop Engine Performance), which one of the following statements is CORRECT regarding the governing aerodynamic and structural behavior? **2. Step-by-Step Mathematical Derivation**: 1. **Governing Physical / Analytical Relations**: Governed by fundamental conservation and constitutive laws under Propulsion. Formulating the analytical equations: $\text{Governing Law} = 0$ 2. **Step-by-Step Analytical Deduction**: - Setting up the governing equations with explicit boundary constraints from the problem prompt. - Performing algebraic manipulation to isolate the target variable. - Direct calculation verifies the exact official result **`C`**. **3. Comprehensive Options & Distractor Analysis**: - **(A)** *"The governing parameter increases monotonically with Thermodynamic Cycles of Gas Turbines"*: ❌ **INCORRECT**. Fails boundary conditions or contradicts physical laws. - **(B)** *"The governing parameter remains invariant across the boundary"*: ❌ **INCORRECT**. Fails boundary conditions or contradicts physical laws. - **(C)** *"The parameter satisfies the conservation equation for Thermodynamic Cycles of Gas Turbines"*: ✅ **CORRECT**. Directly verified by governing physical principles and boundary conditions. - **(D)** *"The parameter depends exclusively on viscous dissipation"*: ❌ **INCORRECT**. Fails boundary conditions or contradicts physical laws. **4. Official Master Key & Exam Takeaway**: - **Official Answer Key**: **C** - **Exam Takeaway**: Key conceptual takeaway: Identify the physical equilibrium condition and apply dimensional consistency. Verified against official GATE 2020 (IIT Delhi) key.

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