Holographic Measurements of Particle Motion in a Resonant Acoustic Mixer

The mixing process is an important aspect of energetic material and solid composite propellants. The LabRAM I™is a Resonant Acoustic® mixer designed to use oscillating motion to a mix highly solids loading composites (e.g., solid propellant). Understanding particle movement within a mixture under LabRAM I mixing conditions will help improve the mixing process and regulate the combustion results. Digital inline holography (DIH) is used to track particles. Measurements of ammonium perchlorate (AP) particles settling in silicone oil filled cuvette using DIH agree with theory validating the measurement in this setup. Subsequent measurements of particle motion during LabRAM operation at 5 g nominal acceleration quantify the multidimensional motion of the particles. The velocity of the particles in the cuvette reference frame are faster than the settling velocity for cases tested. Particle accelerations are observed to be greater than the nominal LabRAM setting. The uncertainty in the direction of the optical axis is also discussed. This work demonstrates the ability to improve the understanding of propellant mixing.