Characteristics and mechanisms of particle adhesion patterns in an aerodynamic cyclone

Characteristics of particle adhesion (deposition) patterns in an aerodynamic cyclone were studied by both experimental methods and computational fluid dynamic (CFD) simulation methods. The cyclone used in the experiment was made of acrylonitrile butadiene styrene (ABS). The particles were a plaster material, with an average size of 1.13 μm and a density of 2300 kg/m3. Four levels of particle load rates were examined, ranging from 0.28 g/m3 to 0.96 g/m3 at a fixed mass flow rate of 2.1 g/s. Experimental results showed three key features of particle adhesion patterns. They are large-scale spiral patterns (SPs), small-scale wave patterns (WPs), and thick adhesion layer (TAL) at the cyclone tip region. It was observed that the SPs had five turns and the WPs were periodic discrete patterns that crept slowly against the flow direction. The formation of WPs was explained based on the Barchan sand dune mechanism. Under zero particle load rate, six different mass flow rates ranging from 1.24 g/s to 3.16 g/s were simulated using CFD. It was found that the precessional bent vortex end (PBVE), precessing along the circumference of the cyclone tip, occurred close to the cyclone tip. The PBVE was believed to be the cause of the TAL, because there was a weak wall shear stress region below the PBVE. In addition, particle trajectories were simulated at a mass flow rate of 2.26 g/s. Simulation results showed that particles had spiral trajectories that were supposed to be linked with the SPs.