ThermoFluidCalc Report

Combustion & AFT β€” 2026-09-15 13:29:05
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πŸ”₯ Adiabatic Flame Temperature

Calculate flame temperatures for fuel combustion under constant pressure or constant volume conditions.

⚑ Fortran 90 Engine Double Precision (IEEE 754) βœ“ ISO / ASME Validated
Adiabatic Flame Temperature Thermodynamics
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⚑ Solves 191
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πŸ“… Released Jun 2026
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πŸ“ Configuration

β›½ Fuel Selection
πŸ§ͺ Custom Fuel Formula (Cβ‚“HᡧOα΅€)
🌑️ Operating Conditions
0% = stoichiometric, 50% = 50% more air than needed
Key Equations:

Cβ‚“HᡧOα΅€ + a(Oβ‚‚ + 3.76Nβ‚‚) β†’ xCOβ‚‚ + y/2 Hβ‚‚O + 3.76a Nβ‚‚
a = x + y/4 βˆ’ z/2
AFR = (a/0.21) Γ— 28.97 / M_fuel
T_ad from Ξ£H_react = Ξ£H_prod(T_ad)
Ο† (equivalence ratio) = AFR_stoich / AFR_actual

πŸ“Š Results

Configure inputs and click Analyze to view results.

πŸ“˜ Methodology

Stoichiometry

Complete combustion of a hydrocarbon fuel Cβ‚“HᡧOα΅€ with air yields COβ‚‚, Hβ‚‚O, and Nβ‚‚. The stoichiometric Oβ‚‚ requirement is a = x + y/4 βˆ’ z/2 moles per mole of fuel. Excess air ensures complete combustion in practice.

Adiabatic Flame Temperature

T_ad is the maximum flame temperature assuming no heat loss. It is found by equating reactant and product enthalpies: Ξ£H_react(T_inlet) = Ξ£H_prod(T_ad). The calculation uses constant average c_p values for each species.

Flue Gas & Dew Point

The flue gas composition depends on fuel type and excess air. The dew point is the temperature at which water vapor in flue gas begins to condense, determined by the partial pressure of Hβ‚‚O. Operating below dew point causes corrosion.

πŸ“˜ Calculation Methodology: Adiabatic Flame Temperature & Dissociation

Mathematical Model & Theory

The adiabatic flame temperature $T_{ad}$ is the maximum temperature reached by combustion products when all heat of reaction is retained without external heat loss or work output:

$$H_{reactants}(T_{in}) = H_{products}(T_{ad}) \implies \sum_{R} n_i \left( \Delta h^\circ_{f,i} + \Delta h_i \right) = \sum_{P} n_j \left( \Delta h^\circ_{f,j} + \Delta h_j(T_{ad}) \right)$$
$$\Delta h(T) = \int_{298}^{T} c_p(T') dT'$$

Assumptions

  • Complete adiabatic stoichiometric combustion.
  • Ideal gas mixture with temperature-dependent NASA polynomial specific heats.

Academic References

  1. Turns, S. R.: An Introduction to Combustion, McGraw-Hill, 3rd Edition.
  2. Glassman, I., & Yetter, R. A.: Combustion, Academic Press.

Worked Engineering Example

Problem Statement:
Methane ($CH_4$) burns stoichiometrically in pure oxygen initially at $298\text{ K}$. Estimate the constant-pressure adiabatic flame temperature.

Step-by-step Solution:
1. Reaction: $CH_4 + 2O_2 \to CO_2 + 2H_2O$.
2. Lower Heating Value: $LHV = 802.3\text{ kJ/mol}$.
3. Equating product enthalpy yields $T_{ad} \approx 3050\text{ K}$ with dissociation ($CO, H_2, OH$).
Final Result:
Adiabatic flame temperature is $\mathbf{3050\text{ K}}$ ($2777^\circ\text{C}$).