Calculator Inputs
Formula Used
For a fuel written as CxHyOzNaSb, complete combustion requires oxygen. The calculator uses O₂ = x + y/4 + b − z/2. Fuel nitrogen is reported as nitrogen gas.
The stoichiometric oxidizer amount equals required oxygen divided by oxidizer oxygen fraction. Actual oxidizer then follows the selected lambda value. Lambda above one represents lean combustion.
Wet flue gas includes water vapor from combustion, humidity, and fuel moisture. Dry flue gas excludes all water vapor. Mole percentages use the corresponding wet or dry total.
How to Use This Calculator
Select a fuel preset or enter a valid custom formula. Choose the fuel amount and its unit. Gas volumes use entered temperature and pressure.
Enable the second fuel when modeling a blend. Enter its mole share and heating values. The primary fuel receives the remaining share.
Choose an oxidizer preset, air-supply method, and reaction model. Add humidity, incomplete products, efficiency, or EGR when needed. Then press the calculation button.
Understanding the Results
The balanced equation gives ideal complete-combustion coefficients. Stoichiometric oxygen represents the exact ideal requirement. Actual oxygen changes with lambda or equivalence ratio.
Product tables show moles, masses, and gas composition. Wet values include water. Dry values help compare measured combustion-analyzer readings.
Energy outputs depend on entered HHV or LHV data. Flame temperature uses constant average heat capacity. It is an estimate, not equilibrium software.
Worked Example
One mole of propane needs five moles of oxygen. Dry air therefore supplies about 23.87 moles. Products ideally contain three moles of carbon dioxide.
The same reaction produces four moles of water vapor. Excess air leaves unused oxygen in exhaust. Nitrogen and inert gases pass through mostly unchanged.
| Fuel | Formula | Stoichiometric O₂ | Ideal CO₂ | Ideal H₂O |
|---|---|---|---|---|
| Methane | CH₄ | 2 mol/mol | 1 mol/mol | 2 mol/mol |
| Propane | C₃H₈ | 5 mol/mol | 3 mol/mol | 4 mol/mol |
| Ethanol | C₂H₆O | 3 mol/mol | 2 mol/mol | 3 mol/mol |
| Hydrogen | H₂ | 0.5 mol/mol | 0 mol/mol | 1 mol/mol |
Limitations and Safety
This calculator handles CHONS fuels without parentheses or ionic charges. Incomplete combustion uses assigned percentages. It does not solve chemical equilibrium or dissociation.
Heating values vary with composition and measurement basis. Gas properties also vary with temperature. Confirm critical designs using approved engineering methods.
Never use estimated outputs as direct operating limits. Combustion systems can create fire, explosion, and toxic-gas hazards. Qualified professionals should review final decisions.
Frequently Asked Questions
What fuel formulas are supported?
Plain formulas containing carbon, hydrogen, oxygen, nitrogen, and sulfur are supported. Parentheses and charged species are not supported.
What does lambda mean?
Lambda is actual oxygen divided by stoichiometric oxygen. A value above one is lean, while a value below one is rich.
What is the equivalence ratio?
The equivalence ratio is the inverse of lambda. Values above one represent richer mixtures.
Why can oxygen shortage appear?
The entered product assumptions may consume more oxygen than supplied. The calculator flags this inconsistency instead of silently hiding it.
Does the calculator predict NOx?
No. Thermal, prompt, and fuel NOx require temperature history, residence time, and detailed chemistry.
Are gasoline and diesel exact formulas?
No. They use representative surrogate formulas. Real commercial fuels contain many compounds and can vary significantly.
What is the difference between wet and dry flue gas?
Wet composition includes water vapor. Dry composition removes water before calculating percentages.
How is humidity included?
Relative humidity and saturation pressure estimate water entering with the oxidizer. That water appears in wet exhaust.
Is flame temperature exact?
No. It uses a constant average heat capacity and ignores equilibrium dissociation. Use specialist software for design-grade values.
Can I calculate continuous fuel flow?
Yes. Select continuous mode. Entered fuel quantity then represents an hourly flow basis.
Can results be exported?
Yes. Use CSV for tables, copy for text, or printing to save a PDF.