Granular Dynamics in a Vertical Bladed Mixer: Secondary Flow Patterns.

0497842 - ÚCHP 2020 RIV NL eng J - Journal Article
Havlica, Jaromír - Jirounková, K. - Trávníčková, Tereza - Stanovský, Petr - Petrus, P. - Kohout, M.
Granular Dynamics in a Vertical Bladed Mixer: Secondary Flow Patterns.
Powder Technology. Roč. 344, FEB 15 (2019), s. 79-88. ISSN 0032-5910. E-ISSN 1873-328X
R&D Projects: GA ČR(CZ) GAP105/12/0664; GA ČR(CZ) GA15-05534S
Institutional support: RVO:67985858
Keywords : granular mixing * granular flow * granular dynamics
OECD category: Chemical process engineering
Impact factor: 4.142, year: 2019
Method of publishing: Limited access

This article deals with numerical simulations and experimental measurements of the granular mixing process in a vertical cylindrical mixer with two opposed flat blades with a 45° rake angle. The computer simulations were conducted via discrete element method. The experimental measurements were recorded by a color high-speed camera. Both approaches describe the mixing process in the same way with significant agreement in observations. Even though the geometry and operating conditions are simple, the dynamics of the system is often very complex and a variety of flow structures can be created. For that reason, the behavior of individual flows patterns was analyzed and discussed. The effect of the centrifugal force on deformation of the free level of the granular material and the formation of empty spaces behind the stirrer blades was described. In addition, the behavior of individual particles in specific regions was characterized. At low rotational speed of the blades, particles tend to move close to the bottom of the vessel behind the stirrer blade towards the shaft. At high values, particles are moving in the exact opposite direction. Described movements near the base of the vessel create secondary flow in the form of recirculation zones. Presence of the secondary flow during the mixing process was also confirmed by the experimental measurements. Based on the acquired knowledge, two competing mechanisms of secondary flow formation were presented: (i) the different contact time of the particles with the blade, (ii) the different magnitude of inertial forces acting on the particles around the stirrer blade.
Permanent Link: http://hdl.handle.net/11104/0294052