The effects of molecular structures and reactant temperatures on soot formation in a coflow laminar flame

The objective of the present study is to explore the effects of aromatic hydrocarbons and reactant temperatures on soot formation in a coflow diffusion flame. The study is motivated by the observation that soot formation is influenced by the flame boundary and ambient conditions, i.e. fuel species, pressure, temperature, etc. The effects of aromatic hydrocarbons and reactant temperatures have not been widely covered by current fundamental studies. With the help of experimental and numerical tools, the present study will extend our understanding of soot formation under various conditions. The effects of molecular structures of alkylbenzenes on soot formation in a coflow laminar flame are presented in Chapters 3, 4, and 5 of Part I. It is shown that 1,2,4-trimethylbenzene has a greater sooting tendency than n-propylbenzene because the former forms polycyclic aromatic hydrocarbons (PAHs) through efficient radical recombination whereas the latter forms PAHs via the sequential Hydrogen-Abstraction-C2H2-Addition (HACA) mechanism. The importance of both mechanisms was highlighted by assessing the effect of naphthalene addition to both 1,2,4-trimethylbenzene and n-propylbenzene. It is found that naphthalene addition affects n-propylbenzene more than 1,2,4-trimethylbenzene, suggesting that the effect is fuel-type dependent. Furthermore, the role of alkylbenzenes in a jet fuel surrogate on soot formation was also assessed and it is found that their roles are moderate. The effects of elevated reactant temperatures on soot formation in a coflow laminar flame are presented in Chapters 6, 7, and 8 of Part II. Experimental studies show increasing the reactant temperature promotes soot aggregation and soot surface growth. It also yields curved nanostructures that decelerate soot surface growth. In addition, the modeling study shows the promotion of soot formation is likely due to early fuel pyrolysis that promotes PAH formation. The increase in PAH production also signifies the importance of the PAH adsorption mechanism. Finally, the temperature dependence of alkylbenzenes was explored. It is found that alkylbenzenes are less sensitive to the change in reactant temperature than alkanes and alkenes. This may be attributed to differences in their pathways for PAH formation.

Department dc:contributor.department

Mechanical and Industrial Engineering

Year dc:date.issued

2021

Author dc:creator

• Chu, Carson

Advisor dc:contributor.advisor

• Thomson, Murray J

• Alkylbenzenes
• Combustion
• Emission
• High temperature
• laser-induced incandescence
• Soot formation

Statement dc:rights

• Attribution-NonCommercial 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc/4.0/

Handle dc:identifier.uri

http://hdl.handle.net/1807/109287

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/109287