III. Coalescence as a Rate-Controlling Process

Abstract

Oxide and carbon particles in flames are observed to grow by inter-particle Brownian collision and fusion, Previous investigators have tacitly assumed that coalescence is instantaneous and that growth is controlled solely by the collision frequency. Growing particles, however, are often found to be flocculated, suggesting that fusion rather than collision is the rate controlling process. In this study, a growth rate expression is derived which considers both collision and coalescence phenomena. A new parameter is introduced, N_p, the number of primary particles within a Hoc. Predicted values of N_p were compared with those estimated from electron micrographs of silica aggregates. Comparison of predicted with measured values of N_p is inconclusive. Better data, in situ, for aggregates in flames are needed.