Combustion of aluminum powder with steam entrained in a helium plasma using a 2.45 GHz microwave plasma torch

Abstract

Ignition and combustion of ~20 µm diameter aluminum powder was achieved with a helium–steam-based 2.45 GHz microwave plasma torch as a proof of concept due to interest in utilizing aluminum powder as a fuel source for power generation given the material’s high energy density. Optical emission spectroscopy of the plasma in air, with steam-entrainment, and with aluminum particle injection was obtained in order to observe the radical species present. The combustion products were analyzed with x-ray diffraction (XRD) to determine the post-combustion composition and compared with published XRD data involving aluminum-water combustion. The results revealed that a microwave plasma torch in a steam environment is capable of igniting aluminum particles and sustains combustion between aluminum powder and radicals from water molecules. The torch design results in a mixing delay between the aluminum and steam radical reactants prior to sustained combustion. Enhanced mixing will be pursued with an improved injector design.

Experimental study on microwave ignition of ADN-based liquid propellant droplets doped with alumina nanoparticles

“…Furthermore, the unique dielectric constant shape and surface characteristics of metals and metal oxides facilitate strong coupling with microwaves, promoting localized microwave energy deposition. The directed input of microwave energy contributes to active control for enhancing the release of heat from the flame [20,21]. Barkley et al investigated the effects of NaNO 3 nanoparticles on the combustion of composite propellants by inducing flame-induced deposition of microwave energy at Na atomic formation sites [22].…”