Laminar lifted flame speed measurements for aerosols of metals and mechanical alloys

This research develops and validates a novel experimental methodology for measurements of laminar flame speed of metal-air aerosols. The methodology is based on a recently developed laminar, lifted flame aerosol burner (LLFAB) using electrostatic fluidization to produce metal aerosol between the electrodes of a plate capacitor. An aerosol jet directed vertically up, and decelerating in a stagnant gas environment is produced. The jet is ignited, and the position of the propagating downward flame is stabilized at a location where the flame speed becomes equal to the jet velocity with the opposite sign. Therefore, the flame speed determines the vertical location of the lifted flame. Aerosol flame speed measurements using LLFAB are compared vs earlier measurements using Bunsen burner and flame tube in microgravity. The developed technique was used to compare the flame speed for pure aluminum and magnesium powders vs flame speed for a set of aluminum-based mechanical alloys using Mg, Ti, Zr, Li, MgH ₂, or C as alloying elements. It was observed that the flame speeds for all of the tested alloys, except the one with carbon, are higher than that of the pure aluminum aerosol.