The figure below shows the blading of the rotors of two different axial
turbomachines under their typical operating conditions, labelled as Configuration I
and Configuration II. Which of the following statements is/are TRUE?
Options:
(A) Configuration I corresponds to the rotor of a compressor and Configuration II
corresponds to the rotor of a turbine
(B) Configuration I corresponds to the rotor of a turbine and Configuration II
corresponds to the rotor of a compressor
(C) The rotor blades of the turbomachine in Configuration I move along the +𝜃
direction
(D) The rotor blades of the turbomachine in Configuration II move along the +𝜃
direction
Official Answer Key:
A, D
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2026 Q.27)**
**1. Governing Concept & Theory**:
Governed by principles of **Thermodynamic Cycles of Gas Turbines** (Aerospace Propulsion, 1 Mark, MSQ).
**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 **A, D**.
**3. Official Answer Verification**:
- **Official Result**: **A, D**
- **Evaluation Status**: Matches official GATE 2026 master key with 100% accuracy.
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