Effect Mechanism of Air/Fuel Ratio on Ion Current Signal

Abstract:

The effect of air/fuel ratio on ion current signal was studied with methane as the fuel in a highpressure constant combustion vessel. The results show that the peak value of ion current signal is the highest and the peak timing is also the most advanced when the excess air ratio is 0.90. The ion formation process, concentration, and distribution were numerically simulated with the established methane ionization mechanism model. The simulation results show that chemical ionization occurs in the flame front and the main ion product is H3O+ while thermal ionization occurs in the high temperature postflame area. The main ion product is NO+. Chemical reaction path analysis results indicate that when the excess air ratio is 0.90, and the neat production rate and concentration of H3O+ and NO+ are the highest, which results in the highest value of chemical ionization peak and thermal ionization peak.

Key words:air/fuel ratio; ion current signal; reaction mechanism; numerical simulation