AFR and excess-air factor λ from measured fuel and air flows. Diesel engines typically λ = 2.0–3.5 at full load.
Formula
$$ AFR = \frac{\dot m_\text{air}}{\dot m_\text{fuel}}, \quad \lambda = \frac{AFR}{AFR_\text{stoich}} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\dot m_\text{air}$ | Air mass flow | kg/h | charge-air meter |
| $\dot m_\text{fuel}$ | Fuel mass flow | kg/h | fuel-flow meter |
| $AFR_\text{stoich}$ | Stoichiometric AFR for the fuel | - | combustion chemistry |
| $λ$ | Excess-air factor | - | result |
Sources
- Heywood - Internal Combustion Engine Fundamentals.