Understanding the characteristics and functions of axial velocity fluctuation zone in hydrocyclones part 2 particle classification

Abstract

The axial velocity fluctuation zone (AVFZ) characterizes the fluctuation range of the locus of zero vertical velocity, where the momentum transfer between the medium and solids is critical but has not been well revealed yet. Based on the viscosity-modified mixture and DPM models, this paper numerically investigated particles' motion behaviour, dynamic forces, spatial distribution, and flow characteristics. The results indicate that the particle size mainly influences drag force (FD) and has little effect on pressure gradient (FP) and centrifugal forces (FC), whereas the particle density affects FC/FP without changing FD. Due to the strong turbulence dispersion in the AVFZ, similar magnitudes of FD, FP, and FC cause prolonged residence time, higher accumulation rate, and higher circulation flow rate of near-cut-size particles, resulting in limited separation sharpness. Taking the AVFZ as a ‘bridge’, novel insights in the classification process along with the effects of main structural and operating parameters are provided.