Fuel molar ratio is the moles of fuel divided by the total moles of fuel, oxidizer and propellant. Fuel molar ratio will increases as the number of reducing electrons in the fuel decreases.

Fuel molar ratios can be calculated easily for stoichiometric mixtures. Hydrogen with two reducing electrons mixes stoichiometrically with oxygen with four oxidizing electrons for a fuel molar ratio of four to six ( two plus four ), dividing by their greatest common denominator, a ratio of two to three. Methane with eight reducing electrons mixes stoichiometrically with oxygen with four oxidizing electrons for a fuel molar ratio of four to twelve ( eight plus four ), dividing by their greatest common denominator, a ratio of one to three. Quadricyclene with thirty six reducing electrons mixes stoichiometrically with oxygen with four oxidizing electrons for a fuel molar ratio of four to forty ( thirty six plus four ), dividing by their greatest common denominator, a ratio of one to ten. Given the combustion efficiency, fuel molar, mixture, mixture oxidizer mix and mixture oxidizer mix the fuel molar ratio can be calculated.

relative fuel = 1.0 - mixture
mixture oxidizer mix = 1.0 + mixture

unreacted fuel = 0.0
if ( relative fuel > mixture oxidizer mix ) {
    unreacted fuel = relative fuel - mixture oxidizer mix
}

If the combustion isn't ideal:

if ( combustion efficiency < 1.0 ) {

Then the quadratic equation is used to determine the part of each reactant that combines chemically:

    ratio = 9999999.9
    if ( relative fuel != 0.0 ) {
    ratio = mixture oxidizer mix / relative fuel
    }
    unreactability = 1.0 / ( 1.0 - combustion efficiency )
    a = 2 * unreactability * unreactability
    b = a * ( ratio - 1.0 )
    c = ratio + 1.0
    unreacted = 0.5 / a * ( sqrt( b * b + 4.0 * a * c ) - b )
    unreacted fuel = relative fuel * unreacted
}

relative fuel *= fuel molar
mixture oxidizer mix *= oxidizer mix molar
mixture molar = relative fuel + mixture oxidizer mix

fuel molar ratio = relative fuel / mixture molar
 
 

This is used in bipropellant rocket, tripropellant rocket, pumped rocket and rocket cost.
 
 

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