The Transport and Growth of Soot Particles in Laminar Diffusion Flames

TLDR

Soot formation, growth, and burnout in ethene/air laminar diffusion flames are investigated. The study tracks soot growth along individual particle paths using detailed particle, temperature, and velocity field measurements, examining residence time, flame geometry, growth rates, soot volume fraction in annular and center‑line regions, and particle size and number density. In the annular region, longer residence time at higher fuel flow rates drives increased soot formation while rates remain similar across flow rates; on the center line, soot formation is governed by a minimum temperature (~1300 K), indicating that annular‑region processes control the nonsmoking‑to‑smoking transition.

Abstract

Abstract The Transport and Growth of Soot Particles in Laminar Diffusion Flames Abstract-The formation, growth and burnout of soot particles is examined in a series of ethene/air laminar diffusion flames. Detailed particle, temperature and velocity field measurements are utilized to investigate soot growth along individual particle paths. The importance of changes in the particle residence time, flame geometry and growth rates are evaluated as a function of fuel flow rate. Emphasis is given to the soot volume fraction measurements in two characteristic regions of the flame: the annular region near the flame front where soot is first observed to form, and the center line of the flame. In the annular region, increases in the residence time with increasing fuel flow rate are found to be the major reason for increased soot formation. The rates of soot formation are found to be similar in this region for the range of flow rates investigated. Along the center line, the soot formation processes are observed to be very similar for different flow rates if differences in the temperature-time history are taken into account by introducing a minimum temperature at which soot formation is observed. In the present work, this temperature was found to be near 1300 K. From these result s. it is concluded that processes occurring in the annular region are controlling the transition from a nonsmoking to a smoking flame. Detailed particle size and number den sity measurements obtained in these flames are also discussed.