Time-resolved LII signals from aggregates of soot particles levitated in room temperature air

TL;DR

This study investigates time-resolved laser-induced incandescence signals from soot aggregates levitated in air, revealing how aggregation and disintegration influence LII signals and enabling improved monitoring of soot formation.

Contribution

It provides the first detailed analysis of how soot aggregate structure affects LII signals under different laser fluences, combining experimental measurements with modeling.

Findings

Aggregation reduces conductive cooling at low fluences.

Disintegration occurs at moderate fluences, diminishing aggregation effects.

Results enable better soot and nanoparticle monitoring using LII.

Abstract

We observed and modeled time-resolved laser-induced incandescence (LII) signals from soot aggregates. Time-resolved LII signals were observed from research-grade soot particles, levitated in room temperature air. We were able to measure sizes and structural properties of our soot particles ex situ, and use those measurements as input parameters when modeling the observed LII signals. We showed that at low laser fluences, aggregation significantly influences LII signals by reducing conductive cooling to the ambient air. At moderate laser fluences, laser-induced disintegration of aggregates occurs, so the effects of aggregation on LII signals are negligible. These results can be applied to extend LII for monitoring formation of soot and nanoparticle aggregates.