Modeling Study to Evaluate the Ionic Mechanism of Soot Formation in Flames

摘要

A study is underway to evaluate the proposed ionic mechanism of soot formation bydeveloping a computer model and comparing it with experimental results and with equivalent models based on neutral species. During the present report period both the thermodynamic and reaction kinetic dat base for ion-molecule reactions have been updated and expanded. The CHEMKIN-II flame code, revised last report period, to handle ions is now operating routinely and has bee used to calculate ion profiles for the standard acetylene/oxygen flame. The results are generally in good agreement with experiment, except for the benzotropylium ion, for which the calculated value is about three orders of magnitude less than the experimental value. Poor thermodynamics are suspected. A comparison of data in the literature on the effect of equivalence ratio on acetylene and soot yield with values calculated by thermodynamic equilibrium for a number of fuels show that in general measured acetylene and soot concentrations are far in excess of equilibrium, especially below the threshold soot index. The standard acetylene/oxygen flame seems to be an exception. The results continue to support an ionization mechanism of soot formation.... Soot Formation, Ionic Mechanism, Thermodynamics, Ion-Molecule Reactions, Computer Modeling.