Theory

At $\lambda = 1$ all the oxygen is consumed; the exhaust consists of CO₂, H₂O and the nitrogen and argon of the air. Above 1 the surplus air passes through unchanged, so the exhaust tends towards air as $\lambda$ grows: less CO₂ and H₂O, and a molar mass and heat capacity closer to those of air. The other products are given in Fuel.

Typical values:

diesel: 1.3-2 (about 1.3-1.5 at full load);
gasoline engine with a three-way catalyst: 1.0;
natural gas: 1.0 stoichiometric, or 1.6-2 lean-burn.

Equations

n_{\mathrm{O_2}} = (\lambda - 1)\left(1 + \frac{y}{4}\right), \qquad a = \lambda\left(1 + \frac{y}{4}\right)

(1)

where	meaning	unit
$\lambda$	Excess-air ratio (this setting)	-
$y$	H/C atom ratio of the fuel	-
$n_{\mathrm{O_2}}$	Moles of unused O₂ per mole of carbon	mol
$a$	Moles of O₂ supplied per mole of carbon	mol/mol

Default and rule

Default: 1.5
Rule: 1.5.
Source: Stoichiometry of complete combustion, equation (1). The typical values given under Theory are the program's guidance; they are not taken from a cited source.

Valid range 1 to 20

Values

1 to 20.

Lean only

Values below 1 (rich mixtures) are refused: they form CO and H₂, which the composition model does not include.

Theory

Equations

Default and rule

Valid range 1 to 20

Related 3