|Thermodynamics and Propulsion|
On a molar basis, the ratio of fuel to air is .
To find the ratio on a mass flow basis, which is the way in which the aeroengine industry discusses it, we need to ``weight'' the molar proportions by the molecular weight of the components. The fuel molecular weight is , the oxygen molecular weight is and the nitrogen molecular weight is (approximately) . The fuel/air ratio on a mass flow basis is thus
If we used the actual constituents of air we would get 0.0667, a value about 0.5% different.
Do we always assume 100% complete combustion? How good an approximation is this? (MP 15.3)