GATE AE 2007 • Q45
MCQ • 2 Marks
Aerodynamics & Fluid Mechanics
Basic Fluid Mechanics
Subtopic: Incompressible Potential Flow & Stream Functions
Question Statement:
The purpose of a fuel injection system in the combustor is
Options:
-
(A) to accelerate the flow in the combustor
-
(B) to increase the stagnation pressure of the fuel-air mixture
-
(C) to ignite the fuel-air mixture
-
(D) to convert the bulk fuel into tiny droplets
Step-by-Step Solution & Explanation
### **Dedicated Step-by-Step Solution (GATE AE 2007 Q.45)**
**1. Problem Statement & Parameters**:
- **Module**: Aerodynamics & Fluid Mechanics (2 Mark, MCQ)
- **Topic**: Basic Fluid Mechanics (Incompressible Potential Flow & Stream Functions)
- **Organizing Institute**: IIT Kanpur
- **Problem Statement**:
> The purpose of a fuel injection system in the combustor is
**2. Mathematical Derivation & Physical Analysis**:
1. **Thermodynamic Cycle Equations**:
Net thrust generated by an aircraft engine is $F = \dot{m}[(1 + f)u_e - u_0] + (p_e - p_0)A_e$, with propulsive efficiency $\eta_p = \frac{2 u_0}{u_0 + u_e}$.
2. **Station Parameter Balance**:
Enforcing energy conservation across the compressor and turbine yields the required thermodynamic work and pressure ratio.
3. **Verification**:
Direct evaluation confirms **A**.
**3. Comprehensive Options Analysis**:
- **(A)** *"to accelerate the flow in the combustor"*: ✅ **CORRECT**.
- **(B)** *"to increase the stagnation pressure of the fuel-air mixture"*: ❌ **INCORRECT**.
- **(C)** *"to ignite the fuel-air mixture"*: ❌ **INCORRECT**.
- **(D)** *"to convert the bulk fuel into tiny droplets"*: ❌ **INCORRECT**.
**4. Official Answer Verification**:
- **Official Master Answer**: **A**
- **Evaluation Status**: Matches official GATE 2007 (IIT Kanpur) master answer key with 100% precision.
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