In aircraft gas turbine combustor design, the combustor loading parameter ($\text{CLP}$) scales as $\frac{\dot{m}}{p^n V_{\text{comb}} T^m}$. Combustion blowout stability limits under high-altitude relight conditions are primarily dictated by:

(A) Low combustor operating pressure and temperature which increase chemical reaction times relative to flow residence time

(B) Excessive aerodynamic flame holding drag

(C) Turbine blade centrifugal stress limits

(D) Nozzle choking at low flight Mach numbers

Answer Key:

Verified in official key

### 1. Strategy & Theoretical Principles Combustor stability depends on the Damköhler number ($Da$): $$Da = \frac{\tau_{\text{residence}}}{\tau_{\text{chemical}}}$$ - Chemical reaction time scales as $\tau_{\text{chem}} \propto p^{-n} \exp(E / RT)$. - At high altitudes, ambient air density and pressure drop drastically, lowering compressor delivery pressure $p_{03}$ and temperature $T_{03}$. - This vastly inflates chemical reaction times $\tau_{\text{chem}}$ until $\tau_{\text{chem}} > \tau_{\text{residence}}$, extinguishing the flame (blowout). ### 2. Distractor Forensics - **Option A:** Correct chemical kinetics explanation. ### 3. Exam Trap & Standard Reference - **Trap Alert:** Altitude relight is limited by chemical kinetics at low pressures and temperatures. - **Standard Reference:** Mattingly, J.D., *Elements of Propulsion*, Chapter 7.

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