Ionic Mechanisms of Soot Formation in Flames.
Abstract
The ionic theory of incipient soot formation has been further evaluated. Accurate temperature profiles through a series of low pressure, 2.7 kPa, acetylene-oxygen flames on either side of the threshold soot index were measured using radiation loss compensated electrically heated thermocouples. With these data and Langmuir probe curves determined in these same flames the absolute ion concentrations were obtained. These were in excellent agreement with similar data obtained by others using a molecular beam ion sampling technique. It was thus demonstrated that the ion concentration peak precedes the appearance of soot, the ion concentration is greater than the concentration of soot particles, and ions decay as soot appears. Characteristic times were calculated for a phi = 3 flame which indicates that ion molecule reaction rates are sufficient to account for soot formation; they also indicate the reactions which must be included in any detailed computer model of the process of soot formation--the ultimate goal of this study. Experimental temperature measurements at the soot threshold of flames of varying fuel/oxygen/nitrogen mixtures produced the surprising result that the experimental temperature was a constant for a given fuel although the adiabatic flame temperature varied over a large range.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1986
- Accession Number
- ADA173213
Entities
People
- Douglas B. Olson
- H. F. Calcote