Fractal scaling of soot packing density across five size decades

ABSTRACT

We experimentally map the scaling laws for packing density (θ_f, solid component volume fraction) of soot aggregates across five orders of magnitude of size (R_g/a, normalized radius of gyration by monomer radius). The θ_f − R_g/a scaling relationship evolves through three successive regimes with distinct power-law exponents of −1.20 ± 0.01, −0.58 ± 0.06, and −1.31 ± 0.14. The first cross-over agrees with the classical aerosol-to-gel transition theory. This agreement, however, breaks down at the second cross-over point, where a late-stage cluster-cluster aggregation of aerosol gels takes over.

© 2017 American Association for Aerosol Research

EDITOR:

• Matti Maricq

Acknowledgments

The authors thank Dr. Christopher M. Sorensen at Kansas State University and Dr. Richard L. Axelbaum at Washington University in St. Louis for valuable discussions on this work. The authors also thank Mike K. Shen and Akshay Gopan for their assistance with flame photographing.

Funding

This work was supported by the US National Science Foundation (NSF) grants AGS-1455215 and CBET-1511964, and the NASA Radiation Sciences Program grant NNX15AI66G.