Combustion/Fuel Calculator

Computes theoretical fuel-air stoichiometry and energy release. Input the fuel formula or select from common fuels.

Chemical Formula (e.g. CH₄, C₆H₁₄): Enter the molecular formula of your fuel (C, H, O, N, S elements supported)

Carbon (C) %:

Hydrogen (H) %:

Oxygen (O) %:

Nitrogen (N) %:

Sulfur (S) %:

Moisture %:

Ash %:

Enter elemental composition by weight percentage (must sum to 100%)

Select Fuel:

Air Temperature (°C):

Fuel Temperature (°C):

Excess Air (%):

Results

Stoichiometric Air-Fuel Ratio (mass): – kg air/kg fuel

Actual Air-Fuel Ratio (mass): – kg air/kg fuel

Higher Heating Value (HHV): – MJ/kg

Lower Heating Value (LHV): – MJ/kg

Adiabatic Flame Temperature: – °C

CO₂ Emissions: – kg CO₂/kg fuel

H₂O Produced: – kg H₂O/kg fuel

Molar Results (per kg fuel)

O₂ Required: – kmol

N₂ Required: – kmol

CO₂ Produced: – kmol

H₂O Produced: – kmol

SO₂ Produced: – kmol

Total Flue Gas: – kmol

Combustion Theory

Combustion is a chemical reaction between a fuel and oxygen that releases energy in the form of heat and light. Complete combustion occurs when all the carbon in the fuel burns to CO₂, all hydrogen burns to H₂O, and all sulfur burns to SO₂.

The stoichiometric air-fuel ratio is the exact amount of air needed for complete combustion. In practice, excess air is supplied to ensure complete combustion and account for imperfect mixing.

The Higher Heating Value (HHV) includes the heat released from condensing water vapor in the combustion products, while the Lower Heating Value (LHV) excludes this heat since water vapor typically remains as vapor in exhaust gases.

Calculation Assumptions

Air composition: 21% O₂, 79% N₂ by volume (neglecting argon and other trace gases)
Complete combustion (no CO or unburned hydrocarbons in products)
Ideal gas behavior for all components
Adiabatic flame temperature assumes no heat loss to surroundings
Specific heats of gases are temperature-averaged values
Heating values are calculated from standard formation enthalpies

Practical Applications

Boiler and furnace design and efficiency calculations
Fuel consumption estimation for engines and power plants
Emissions calculations and environmental impact assessments
Process heating requirements in industrial applications
Comparison of different fuel types and their energy content
Safety calculations for flammable mixtures