Lower Torque and Higher Efficiency Mixing with Contra-Rotating, Baffle-Free Impellers

This work intends to investigate the intersection of two fields of work: single axis, contra-rotating impellers and buoyancy of solid suspensions. The objectives of this study are to (1) create a working model to quantitatively understand particle mixing, (2) characterize and compare contra-rotating single shaft impellers to single shaft dual impellers, and (3) improve quantification of particle mixing through image processing for both computational and experimental techniques. Twelve cases were studied by changing the direction of impeller rotation, impeller pumping direction, and the presence of baffles. Particles with SG of 0.866 and 1.05 were introduced into the experimental and computational systems in a finite and countable number. The numerical solutions are obtained by using the Lattice Boltzmann Method and the Discrete Particle Method. The evaluation of the input torques, time averaged flow profiles, and particle dispersions versus rotating speeds will be reported. Finally, the comparison of mixing efficiency will be analyzed and concluded. This work will help understand mixing efficiency and provide justification for design decisions to improve industrial processes.