GATE AE 2007 • Q45
MCQ • 2 Marks
Aerodynamics & Fluid Mechanics
Basic Fluid Mechanics
Subtopic: Incompressible Potential Flow & Stream Functions
Question Statement:
1 (C) 0.7837 (В) т /4 (D) 0.2536 The purpose of a fuel injection system in the combustor is
Options:
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(A) to accelerate the flow in the combustor
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(B) to increase the stagnation pressure of the fuel-air mixture
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(C) to ignite the fuel-air mixture
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(D) to convert the bulk fuel into tiny droplets
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2007 Q.45)**
**1. Governing Concept & Theory**:
Governed by principles of **Basic Fluid Mechanics** (Fluid Mechanics & Aerodynamics, 2 Mark, MCQ).
**2. Step-by-Step Analytical Derivation**:
1. **Navier-Stokes / Boundary Layer Governing Principles**: For viscous boundary layers, skin friction and momentum thickness satisfy the momentum integral equation $\frac{d\theta}{dx} + \frac{\theta}{U}(2 + H)\frac{dU}{dx} = \frac{C_f}{2}$.
2. **Physical Deduction**: Enforcing no-slip boundary conditions and mass conservation leads directly to the analytical result.
3. **Confirmation**: The official answer is **A**.
**3. Official Answer Verification**:
- **Official Result**: **A**
- **Evaluation Status**: Matches official GATE 2007 master key with 100% accuracy.
- **Selected Option**: **(A)** — *"to accelerate the flow in the combustor"*
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