Investigation of Fuel Additive Effects on Sooting Flames.
Abstract
Measurements were limited to well-defined hydrocarbon/air gaseous- and prevaporized liquid-fueled diffusion flames. Emphasis was given to alkaline-earth salt additives in an ethylene/air flame, as well as to ferrocene in a flame fueled by a prevaporized toluene/iso-octane mixture. Nonperturbing laser/optical diagnostic techniques were used to measure flame temperature, as well as to relate changes in soot particulate size, number density, and volume fraction to additive type and concentration. For the ethylene flame, additive effectiveness was shown to vary from point-to-point in the flame and to maximize in the direction of increasing flame temperature. From the latter, and measured concentrations of metal combustion species, MOH+ (M = Ba, Sr, etc.) were concluded to be the particular species critical to soot suppression. The data indicate additive intervention at both early and late stages of soot formation, but it was not possible to conclude early intervention firmly. For the alkaline-earths, an experiment complementary to the foregoing was conducted to test an often quoted hypothesis of soot suppression in which metal-induced increases in OH concentration are presumed to enhance soot oxidation and removal. This was found, however, not to be valid. The effect of the alkaline-earths on OH was to decrease the concentration of the latter radical at all points in the ethylene/air flame, which fundamentally is not supportive of the preceding hypothesis. For the toluene flame, ferrocene was observed to suppress a visible soot plume completely. Mie scattering measurements at a late combustion stage demonstrated that suppression results almost entirely from particular number density reduction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 31, 1986
- Accession Number
- ADA172522
Entities
People
- Paul A. Bonczyk
Organizations
- United Technologies Corporation