Flame Temperature Calculator

What This Flame Temperature Calculator Estimates

This calculator estimates the theoretical flame temperature for carbon monoxide combustion in air when the fuel mixture also contains inert nitrogen. It uses a simple adiabatic energy balance with constant average heat capacities.

The calculator assumes complete conversion of CO to CO₂ and no heat loss to the surroundings.

Excess Air Meaning

In combustion calculations, 0% excess air means the exact stoichiometric air required for complete combustion. 100% excess air means twice the stoichiometric air.

More excess air usually lowers the flame temperature because extra O₂ and N₂ absorb heat.

Energy Balance Used

The calculator uses the heat released by CO oxidation and divides it by the heat capacity of the product gases.

Product Gas Composition

For the 1 mol dry fuel mixture basis:

• CO produces CO₂.
• Stoichiometric oxygen required is 0.5 mol O₂ per mol CO.
• Excess oxygen leaves in the product gas.
• Nitrogen comes from both the original mixture and the supplied air.

Why This Is Only an Estimate

Real adiabatic flame temperature calculations usually require temperature-dependent heat capacities and chemical equilibrium. At high temperatures, species can dissociate and the product composition can change.

Example: 20% CO and 80% N₂

Suppose the dry fuel mixture contains 20 mol% CO and 80 mol% N₂, with 50% excess air and an initial temperature of 25°C.

Basis: 1 mol fuel mixture

CO = 0.20 mol
N2 in mixture = 0.80 mol

O2 required = 0.5 × 0.20 = 0.10 mol
Air factor = 1 + 50/100 = 1.50
O2 supplied = 0.10 × 1.50 = 0.15 mol
Excess O2 = 0.15 − 0.10 = 0.05 mol

Heat released = 0.20 × 283 = 56.6 kJ

Common Mistakes

• Thinking 100% excess air means stoichiometric air. It actually means double the theoretical air.
• Using percent values that do not sum to 100% for the CO/N₂ fuel mixture.
• Assuming this simplified constant-Cp model equals a real equilibrium flame temperature.
• Ignoring heat losses to walls, burners, exhaust, and surroundings.
• Using the result for safety-critical combustion equipment.

Frequently Asked Questions

What is theoretical flame temperature?

It is the estimated temperature reached by combustion products under ideal adiabatic conditions, meaning no heat is lost to the surroundings.

Why does excess air reduce flame temperature?

Excess air adds extra oxygen and nitrogen that do not release heat but still absorb heat, reducing the final temperature.

Can this calculate methane, propane, or hydrogen flames?

No. This version is specifically for CO mixed with inert N₂. Hydrocarbon flames require different stoichiometry and include H₂O products.

Does this include dissociation?

No. The model assumes fixed products and constant average heat capacities.

Can I use this for burner design?

No. Use professional combustion software, validated data, and qualified engineering review for real combustion equipment.