# Characterization of products of non-stoichiometric combustion

To give some background, I'm looking at this from an aerospace standpoint as to the calculation of the efficiency of a propellant reaction at a given oxidizer-fuel ratio. That efficiency is a prerequisite to obtaining other results such as the adiabatic flame temperature, the specific impulse ($I_{sp}$) and other such data.

How is it that the relative abundances of products can be obtained from a non-stoichiometric combustion in an analytic manner (i.e. without needing to obtain empirical data)? This is particularly important because rocket engines rarely run stoichiometric, due to exhaust considerastions.

From the Wikipedia article on combustion, it shows that incomplete combustion results in primarily carbon dioxide, carbon monoxide, water and elemental hydrogen gas. However, it also states that:

For stoichiometric (complete) combustion, $z = x + ¼y$. When $z$ falls below roughly 50% of the stoichiometric value, $\ce{CH4}$ can become an important combustion product; when $z$ falls below roughly 35% of the stoichiometric value, elemental carbon may become stable.

This makes sense, as anyone who has left the barrel of a lit Bunsen burner shut has seen the sooty smoke it produces; but is there a manner in which these products may be analytically identified (and quantified)?

To cover all bases, I've had some experience with the use of NASA's CEA program, and it appears to have some ability to calculate thermodynamic parameters of propellants that aren't given as choices (i.e. RP-1, $\ce{H2}$, etc.). I've read the manual on its theory of operation, but I'd like a more gentle introduction to the underlying behavior, if at all possible.