Ignition of Aluminum Particles

Fabien Halter, Valentin Glasziou, Hugo Keck, Guillaume Legros, Christian Chauveau

► To cite this version:

Fabien Halter, Valentin Glasziou, Hugo Keck, Guillaume Legros, Christian Chauveau. Ignition of Aluminum Particles. 11th European Combustion Meeting, Apr 2023, Rouen, France., 10.13140/RG.2.2.15350.20802. hal-04085367

HAL Id: hal-04085367

https://cnrs.hal.science/hal-04085367

Submitted on 28 Apr 2023

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Distributed under a Creative Commons Attribution 4.0 International License
# Ignition of Aluminum Particles

F. Halter¹,², V. Glasziou¹,²,³, H. Keck¹,², G. Legros¹,², C. Chauveau¹

¹ICARE- CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France

² Université d'Orléans, Château de la Source, 45100 Orléans, France

³ CEA-GRAMAT, D14, 46500 Gramat, France

## Objective:

Characterization of the ignition process of an isolated aluminum particle through visual information and temperature measurement. Results are compared to a simple model.

## Experimental Setup, The Electrodynamic Levitator

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* Levitating **charged particle** in a controlled atmosphere

* Symmetrically heated by a split CO2 laser beam ($\lambda$ = 10.6nm)

* High speed PHANTOM camera combined with long distance microscope QUESTAR QM100 allowing a **1.92 µm/px** magnification

* 39000 fps and 768x768 px resolution

## Two-color ratio pyrometry:

* Photomultipliers equipped with interference filters

* $\lambda_1$ = 720 nm; $\lambda_2$ = 830 nm to avoid emission lines of main gaseous species

* Ratio of radiative intensities at different wavelengths: $\Gamma = \frac{L_{\lambda_1}}{L_{\lambda_2}}$

* Absorption along the line of sight is neglected

* Grey body assumption and Planck's law: $T = f(\Gamma, \lambda_1, \lambda_2)$

* Calibration made with a Quartz Tungsten halogen lamp

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Temporally resolved, integrated temperature of the condensed phase

## High Speed Camera:

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## Model Description:

* **Power source:** single Gaussian laser beam integrated on the projected surface of the particle. Absorption efficiency accounts for the amount of laser energy given to the particle. The remaining energy is scattered.

* **Power losses:** conduction, radiation

* **Convection is neglected** due to the staticity of the particle and the absence of induced flow

* Power used to **heat** and **melt** the particle

* Biot number $Bi \ll 1$: Temperature gradients inside the particle are neglected

* $\eta_{abs}$ linearly varying between 0.018 to 0.08

$$ \eta_{abs} \int_{z_p-r_p}^{z_p+r_p} \int_{-(r_p^2-(z-z_p)^2)^{0.5}}^{-(r_p^2-(z-z_p)^2)^{0.5}} \frac{W}{2\pi\sigma^2} e^{-\frac{y^2}{2\sigma^2}} e^{-\frac{z^2}{2\sigma^2}} dydz = m_p c_p \frac{dT}{dt} + L_{Al} \frac{dm_{Al}^{liq}}{dt} + \lambda_{env} 4\pi r_p (T_p - T_0) + \sigma_{SB} \epsilon_{Al_2O_3} (T^4 - T_0^4) = Q_{heat} + Q_{melt} + Q_{cond} + Q_{rad} $$

## Results:

* 3 phases: heating, melting and heating

* Power from the laser is two order of magnitudes higher than thermal losses: **adiabatic process**

* No experimental data below 1200K due to required exposition time

* Combustion temperature around 3500K

* Good prediction: Almost zero exothermic surface reaction

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