Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Atmospheric Chemistry Program Seminar

Soot: So Ubiquitous, So Destructive, So Important, Yet So Elusive: Exploring the Mysteries of Soot Formation

by Prof. Hope Michelsen,
Mechanical Engineering, CU Boulder

"There are substantial gaps in our understanding of the mechanisms controlling soot inception, particle growth, and chemical evolution during combustion. The first steps in soot formation involve the transition of gas-phase hydrocarbon precursors to physically or covalently bound complexes. These complexes are known as “incipient particles”, and the search for their formation and growth mechanisms is a subject of active research [1-3]. These incipient particles undergo further particle growth, generating liquid-like hydrocarbon particles, which eventually reach sizes in the range of 10-50 nm, known as “primary particles” [1-5]. As these particles grow, they also lose hydrogen, solidify, and agglomerate into loosely bound clusters. Under high-temperature conditions, they become graphitic, covalently bound aggregates with a dendritic structure. Soot aggregate sizes, primary-particle sizes, and volume fractions grow as particles age in the flame [4,5]. At high temperatures in the presence of oxygen, the aggregates fragment [6,7], and the primary-particle sizes and volume fractions decrease through oxidation [4,8]. There is a poor understanding of the mechanisms by which particles undergo these transitions and the parameters that influence them. This talk will describe our current understanding of soot formation and the scientific evidence that supports this understanding.

This talk will also cover the gaps in our understanding of soot chemistry, some reasons for these gaps, and what we may need to do in order to bridge these gaps and develop more insight into soot formation and evolution."

[1] H.A. Michelsen, Proc. Combust. Inst. 36, 717 (2017). [2] H. Wang, Proc. Combust. Inst. 33, 41 (2011). [3] K.O. Johansson, M.P. Head-Gordon, P. E. Schrader, K. R. Wilson, H. A. Michelsen, Science 361, 997 (2018). [4] R.A. Dobbins, C.M. Megaridis, Langmuir 3, 254 (1987). [5] R. Puri, T. F. Richardson, R.J. Santoro, R.A. Dobbins, Combust. Flame 92, 320 (1993). [6] K.G. Neoh, J.B. Howard, A.F. Sarofim, Proc. Combust. Inst. 20, 951 (1985). [7] C.A. Echavarria, I.C. Jaramillo, A.F. Sarofim, J.S. Lighty, Proc. Combust. Inst. 33, 659 (2011). [8] K.O. Johansson, F. El Gabaly, P.E. Schrader, M.F. Campbell, H.A. Michelsen, Aerosol Sci. Technol. 51 (12), 1333 (2017).


Monday, December 2, 2019
12:00pm to 1:00pm


Ekeley S274