Soot Morphology and Nanostructure in Complex Flame Flow Patterns via Secondary Particle Surface Growth

Area of Science:

• Combustion science
• Aerosol science
• Fluid dynamics

Background:

• Most soot formation studies use simplified 1D flames.
• Real-world flames exhibit complex flow patterns (turbulence, recirculation, buoyancy).
• The impact of complex flows on soot properties is not well understood.

Purpose of the Study:

• To investigate soot growth differences between 1D laminar and recirculating flames.
• To understand the influence of complex flow dynamics on soot physicochemical properties.
• To model soot formation in large-scale turbulent flames.

Main Methods:

• Utilized an inverted gravity flame reactor (IGFR).
• Employed computational fluid dynamics (CFD) and experimental observations.
• Analyzed soot particle morphology using transmission electron microscopy (TEM).

Main Results:

• Observed particle oscillations between fuel-rich growth and high-temperature oxidation zones.
• Recirculating flames produced larger primary soot particles (25-75 nm) than 1D flames (10-25 nm).
• Larger particles from recirculating flames exhibited single and multiple cores.

Conclusions:

• Complex flow, particularly recirculation, promotes larger soot particle formation.
• Soot growth in recirculating flames is attributed to PAH condensation and carbonization.
• The IGFR provides a model for studying soot in large-scale, complex flames like forest fires.