Visualization Studies of Three Dimensional Flow and Solid Motion in a Rotary Kiln

Abstract

Results of flow visualization studies in a transparent cylindrical chamber are presented to advance the knowledge of three-dimensional flow structure and mixing behavior in rotary kiln incinerators. Reynolds number based on inlet air velocity and diameter of inlet port ranges from 1,700 to 13,700 and covers the laminar, transitional, and turbulent flow regimes. Results show that there are recirculation zones near the inlet corners due to sudden expansion of the chamber. A potential-like core exists in the central and entrance region of the chamber and separates viscous layers near side walls. When Reynolds number exceeds certain critical value, flow instability in the form of large eddies would be generated. These large eddies would break up to smaller eddies in the downstream, and flow becomes turbulent at higher Reynolds number. Small-scale eddies and turbulent motion appear more vigorous when chamber is partly loaded with a bed of solid materials. Effects of size and shape on the movement of single solid material in the rotary kiln are also examined.