Modeling Study to Evaluate the Ionic Mechanism of Soot Formation.
Abstract
To evaluate the ionic mechanism of soot formation, calculated ion profiles are compared with experimental profiles. The Sandia Flame Code has been modified to accommodate ions. The thermochemical data base on ions has been expanded to accommodate larger ions and additional isomers. Thermochemistry plays a greater role than expected. Good agreement between calculated and experiment is obtained up to ion mass 165, perinaphthalene, by reducing the maximum flame temperature by 10%. However, when the calculations are extended to ion mass 301, coronene, it is necessary to reduce the maximum flame temperature to 1700 K to obtain agreement. This indicates a serious problem. One possibility being tested, previously suggested by S. Stein, is that the flame ions add a hydrogen atom in the sampling cone of the mass spectrometer so that the observed ion is not the ion in the flame. Additional evidence for the ionic mechanism has been developed: (1) the rate of carbon growth is faster for an ionic mechanism than for a free radical mechanism; (2) the thermochemical driving force toward large ions is greater than toward large neutrals; and (3) the only change in flame property at the threshold soot index is a dramatic change in ion concentration and an increase in ion size. jg p.1
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1994
- Accession Number
- ADA299404
Entities
People
- C. H. Berman
- D. G. Keil
- H. F. Calcote
- R. J. Gill