- Author
- Wersborg, B. L. | Howard, J. B. | Williams, G. C.
- Title
- Physical Mechanisms of Carbon Formation in Flames.
- Coporate
- Purdue Univ., West Lafayette, IN
- Sponsor
- Office of Naval Research, Arlington, VA
- Report
- MIT-66-PU, June 1972, 33 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- carbon | kinetics | soot formation | nucleation | coagulation | microscopy | charged particles
- Identifiers
- carbon formation in flames; nucleation kinetics; soot coagulation; kinetics of carbon particle growth; electric charge of carbon particles in flames; electron microscopy of young soot particles
- Abstract
- The size, size distribution, number concentration, and number charged of carbon particles down to about 15 A diameter in a flat acetylene-oxygen flame at 20 mm Hg were measured using a molecular beam sampling system combined with electrical deflection of the beam and electron microscope analysis of bean deposites. Coagulation of carbon particle occurs at all positions sampled in the flame. This process and surface growth form particle clusters that gradually change from roughly spherical at early and intermediate stages of growth to chainlike in the flame tail. The particle size distribuiton changes from Gaussian in the early stages of carbon formation to lognormal in the later stages. Particle number concentration and the rate of nucleation and coagulation each exhibit a maximum soon after the onset of carbon formation, but the rate of surface growth is maximum initially. The number fraction of charged particles is 10 to 40%. The measured coagulation rate constant agrees with the theoretical value if the increase due to Van derWaals and electrical forces is a factor of about 30, which is within the predicted range. Electrostatic forces are responsible for the formation of particle clusters in chains instead of more compact shapes.