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GATE 2024 AE – Question 19

Propulsion · Gas turbine combustors: types, combustion and stoichiometric fuel-to-air ratio · 1 mark · Multiple choice

In an airbreathing gas turbine engine, the combustor inlet temperature is 600 K. The heating value of the fuel is $43.4 \times 10^6$ J/kg. Assume $C_p$ to be 1100 J/kg K for air and burned gases, and fuel-air ratio $f \ll 1.0$. Neglect kinetic energy at the inlet and exit of the combustor and assume 100% burner efficiency. What is the fuel-air ratio required to achieve 1300 K temperature at the combustor exit?

  1. 0.0177
  2. 0.0215
  3. 0.0127
  4. 0.0277

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Correct answer: (A) 0.0177

Explanation

The energy balance for a burner with $f \ll 1$ is $f\,Q_R = C_p(T_4 - T_3)$. So $f = \frac{1100 \times (1300 - 600)}{43.4 \times 10^6} = 0.0177$.