Micro-exploding metal particles and formation of oxide nanoparticles: Development of in situ imaging techniques and advanced morphological image analysis
Final Report Abstract
The combustion of metal powder enables a CO2-free generation of heat and electricity. However, the combusting particles might fragment (also known as micro-explosion), and/or emit metal vapor, gaseous oxides, or oxide nanoparticles. This asymmetric particle combustion contributes significantly to the total heat release. In this work, we investigated the combustion of single aluminum particles, in a single-particle experiment and in a dust flame, as well as single iron particles in an iron dust flame. To study the combustion of single aluminum particles, an aluminum wire was moved above a flat flame. In that flame, the wire locally melts and releases an aluminum droplet into the flame, where it combusts. During the symmetric combustion, the droplet is surrounded by a thin, spherically symmetric, flame sheet of alumina particles as combustion products. The particles partially deposit on the aluminum droplet’s surface where they locally superheat the aluminum, leading to instantaneous vaporization of aluminum. This results in local and strong evaporation associated with the droplet accelerating into the opposite direction, i.e., droplet jetting, leaving behind a condensation trail of alumina particles. This process is the asymmetric combustion phase. In the second part of the project, single combusting aluminum particles were investigated within a dust flame. As in the single-particle experiment, the particles melt, ignite, combust symmetrically, and eventually asymmetrically. Light extinction and scattering were quasi-simultaneously imaged onto a high-speed camera to determine size and volume of alumina nanoparticles in the condensation trails. In the third part of the project, light extinction and laser-induced incandescence were used to visualize iron-oxide nanoparticles.
Publications
-
Ignition, stabilization and particle-particle collision in lifted aluminum particle cloud flames. Proceedings of the Combustion Institute, 40(1-4), 105596.
Ruan, Can; Wu, Zhiyong; Sun, Jinguo; Jüngst, Niklas; Berrocal, Edouard; Aldén, Marcus & Li, Zhongshan
-
Flame structure of single aluminum droplets burning in hot steam-dominated flows. Combustion and Flame, 271, 113838.
Wu, Zhiyong; Ruan, Can; Qiu, Yue; Stiti, Mehdi; Xu, Shijie; Jüngst, Niklas; Berrocal, Edouard; Aldén, Marcus; Bai, Xue-Song & Li, Zhongshan
-
Light extinction and scattering to determine nanoparticle formation rates during droplet jetting in aluminum dust flames. Powder Technology, 453, 120633.
Jüngst, Niklas; Wu, Zhiyong; Ruan, Can; Aldén, Marcus & Li, Zhongshan
-
Visualization of unsteady combustion of single aluminum droplets: coalescence, eruption and fragmentation. Combustion and Flame, 275, 114103.
Wu, Zhiyong; Ruan, Can; Sun, Jinguo; Jüngst, Niklas; Aldén, Marcus & Li, Zhongshan
