Question

A fuel at 25 \(^{\circ} \mathrm{C}\) is burned in a well-insulated steady-flow combustion chamber with air that is also at \(25^{\circ} \mathrm{C}\). Under what conditions will the adiabatic flame temperature of the combustion process be a maximum?

Short answer

Answer: To achieve the maximum adiabatic flame temperature in a combustion process, the following conditions must be satisfied: 1. Both fuel and air should enter the combustion chamber at 25 °C. 2. The combustion process should be complete. 3. The ratio of fuel and air entering the combustion chamber should be stoichiometric, ensuring complete combustion without any excess air or fuel that could remove heat from the combustion zone.

Step-by-step solution

Identify the factors influencing adiabatic flame temperature

The adiabatic flame temperature depends on multiple factors such as the composition of the fuel and air, their initial temperatures, and the ratio of fuel and air entering the combustion chamber.

Understand fuel and air ratio

The ratio of fuel and air entering the combustion chamber is a key factor that affects the flame temperature. The stoichiometric ratio is the ideal ratio where fuel combines completely with oxygen in air, producing the maximum possible heat release. This ratio is critical for our analysis.

Identifying conditions

To maximize the adiabatic flame temperature: 1. Both fuel and air should be at 25 \(^{\circ} \mathrm{C}\). (As given in the problem statement) 2. The combustion should be complete so that the maximum possible chemical energy is released as heat. 3. The fuel and air mixture should be stoichiometric so that there is no leftover oxygen or fuel that could carry away heat with their exit from the combustion chamber. This means that there should be just enough air to completely burn all the fuel without any excess.

Conclusion

The maximum adiabatic flame temperature in the combustion process will be achieved under the following conditions: 1. Both fuel and air should enter the combustion chamber at 25 \(^{\circ} \mathrm{C}\). 2. The combustion process should be complete. 3. The ratio of fuel and air entering the combustion chamber should be stoichiometric, ensuring complete combustion without any excess air or fuel that could remove heat from the combustion zone.