2025 AIChE Annual Meeting

(293f) Exploring the Internal Dynamics of Resonant Acoustic Mixing Using Positron Emission Particle Tracking

Authors

Kit Windows-Yule, University of Birmingham
In order to form shaped components, multi-material blended components are mixed in planetary mixers, cast to blocks/blanks, and then undergo subtractive machining. Blending composites like syntactics and resin-based systems conventionally occurs through extended mixing in rotary drums or traditional blade-based mixers. After the blending process, the mixture is poured, molded into blocks, and subjected to subtractive machining. These procedures are time-intensive, generate waste, and pose potential hazards, especially when dealing with materials sensitive to energy.

To address these challenges, this study will explore Resonant Acoustic Mixing (RAM), an innovative technology for blending powder/powder, powder/fluid, and fluid/fluid mixtures. The method also carries the unique advantage of being able to directly mix materials into the final net (or near-net) component shape without the need for additional processing, thereby minimizing or eliminating material waste, reducing time, and mitigating potential hazards.

RAM is currently undergoing testing with AWE, and so far, it has demonstrated excellent results. However, this mixing technique is still in its early stages and needs optimization. Numerous factors, including mixing parameters (intensity, time, pressure, temperature), material properties (particle size, shape, pre-blending, order of addition), and tooling characteristics (shape, composition, mixing headspace), influence the efficiency of RAM. If these parameters are optimized, it can significantly enhance the efficiency of the mixing process and can enhance our understanding of RAM's capabilities, shedding light on both its limitations and advantages.

So far, we have studied the two most fundamental variable parameters in RAM mixing – the fill height of the vessel and the strength with which it is vibrated. To test how the fill level and the vibrational acceleration to which it is exposed affect mixing efficiency, we ran some experiments imaging a simple material, microcrystalline cellulose (MCC) within a RAM mixer using positron emission particle tracking (PEPT) as an initial set of experiments. During these experiments, we have changed the fill level of the vessel and acceleration of the mixing using a simple, full-factorial DoE so as to gain fundamental insight into the influence of these key parameters on flow within the system and we observed that there is a clear, monotonic, positive relationship between acceleration and mixing efficiency. However, while we observed that fill level has a clear effect on mixing efficiency, the form of this relationship is currently unclear.

In the current study, we are focusing on the relationship between aspect ratio and mixing efficiency. Previous studies showed that aspect ratio (AR) influences mixing dynamics and heating, but no systematic study has been performed [1,2]. To clarify the effect of aspect ratio on mixing quality and efficiency we decided to study this relationship further by using five different aspect ratios for mixing vessel as; 0.25, 0.5, 1, 2 and 4 with constant volume using Positron Emission Particle Tracking (PEPT).

REFERENCES

[1] Coguill, S. and Martineau, Z. (2012). Vessel Geometry and Fluid Properties Influencing Mix Behavior for ResonantAcoustic ® Mixing Processes. In: The 38th International Pyrotechnics Seminar. [online] Available at: http://dx.doi.org/10.13140/RG.2.2.28890.64964 [Accessed Sep. 2024].

[2] Miller, J.T., Bode, D.A. and Coguill, S. (2010). ResonantAcoustic® Mixing; Design and Process Considerations Concerning Vessel/Case Geometry and Mix versus Cure Time When Preparing Composite Solid Propellant. [online] JANNAF 36th Propellant and Explosives Development and Characterization Joint Subcommittee Meeting. Available at: https://www.researchgate.net/publication/270216392_ResonantAcoustic_R_M… [Accessed Sep. 2024].