Burning characteristics of aluminum-air flames

International audienceMetal particles present an interesting potential as a carbon-free energy carrier. Indeed, they are highly energetic, and its combustion in atmospheric air could provide the specific energy and power density that metal-air batteries are still struggling to achieve. In order to better evaluate this potential, it is necessary to know the metal-air aerosol laminar burning velocity, which is a fundamental property describing the mixture’s reactivity, heat production, and heat transfer. However, experimental data on the burning velocity of metal-air aerosols are still scarce and scattered. Moreover, metal flames are subjected to a series of particular effects such as the presence of a particle size distribution, implying different burning rates for particles of different sizes in the powder, and possibly scale-dependent influence of radiation [1]. These effects raise even the question of whether a non-stretched laminar burning velocity can be properly defined for metal dust clouds [2]. Therefore, in order to reduce such uncertainties on the burning velocity measurements, it is necessary to work under well-controlled conditions. Among the different possible metal choices for an energy carrier, this work focuses on aluminum, since it presents satisfying energy density and specific energy. Furthermore, the development of a laminar dust burner inspired by previous works in the literature [3, 4] is presented. The experimental setup is capable of stabilizing aluminum-air flames through the generation of well-controlled dust aerosols. Various optical diagnostics, such as high-speed tomography, direct visualization of AlO(g) emissions and spectroscopy, were conducted in order to measure the flame properties. The results are then compared with the existing literature, and analyzed in a context of zero-carbon power generation