Ning, Daoguan ; Li, Tao ; Mich, Johannes ; Scholtissek, Arne ; Böhm, Benjamin ; Dreizler, Andreas (2023)
Multi-stage oxidation of iron particles in a flame-generated hot laminar flow.
In: Combustion and Flame, 256
doi: 10.1016/j.combustflame.2023.112950
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

The paper presents multi-parameter high-speed optical diagnostics of single iron particle oxidation in a hot laminar flow consisting of O, HO, CO, and N. Prior to luminous combustion, micron-sized particles are visualized using diffuse-backlight-illumination with high temporal and spatial resolutions, enabling in situ particle sizing. The incandescent burning particles are then monitored by direct high-speed imaging. This approach allows for a successful determination of the multiple oxidation stages of individual iron particles, including the solid phase, melting, and liquid phase. Two characteristic timescales are quantified as a function of the resolved particle diameter at various O volume fractions, namely the solid-phase oxidation time (SOT, defined as the time between the onset of rapid particle heating and melting) and the liquid-phase combustion time (LCT, defined as the duration between melting initiation and peak luminosity). SOT shows a linear dependence on the inverse O mass fractions at relatively high O levels but it tends to plateau when the O content is below . LCT is inversely proportional to the O mass fraction, suggesting that liquid-phase oxidation of iron particles is limited by external oxygen diffusion. The experimental LCT quantitatively agrees with a theoretical mode developed for nonvolatile particle combustion in the diffusion-limited regime, considering O as the only oxidant. This also implies that at the presence of O, the oxidizing effect of HO and CO on diffusion-limited iron particle combustion is negligible.

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