Exhaust Emission Based Air-Fuel Ratio Model (II): Divergence Analysis and Emission Estimations

This paper claims that, instead of relying on direct fuel and air flow rate measurements, exhaust gaseous emissions analysis should be considered as the standard method for the determination of air-fuel ratio, in particular for petrol-powered engines.

Various sensitivity parameters are defined and the maximum possible relative divergences of the fuel-air ratio are calculated to support the above claim. It is proved that to obtain the air-fuel ratio with the same accuracy for a petrol engine, the accuracy of the instruments used for fuel and air flow rate measurements should be at least 10 times more accurate than the emission analysers.

Estimations of hydrogen and oxygen concentration based on other measurable emission concentrations in the exhaust gas stream are also conducted and validated satisfactorily with the experimental data.