A qualitative study on the pulsatile flow phenomenon in a dense fly ash pneumatic conveyor

Understanding of the dynamic particulate flow structures within a dense gas-fly ash pneumatic conveyor must be improved in order to better aid its design guidance. The complex pulsatile movement of the gas-fly ash mixture dominates the flow performance within the pipeline, and historically, non-invasive measurement devices such as the electrical capacitance tomography (ECT) were often used to sufficiently capture the flow dynamics. However, inadequate studies have been conducted on the pulsatile flow phenomenon, which directly relate to the gas-fly ash two-phase flow performance. This paper aims to investigate the pulsatile flows using an ET device. Initially, pulsatile flow patterns under various experimental conditions were obtained through ECT. Pulses within a flow were then characterised into pulse growth and decay segments, which represent the superficial fluidisation and deaeration processes during conveying. Subsequently, structural and statistical analyses were performed on the pulse growth and decay segments. Results suggested that the increasing air mass flow rate led to the decrease of the superficial fluidisation/deaeration magnitude, however, the increase of the superficial fluidisation/deaeration durations. Also, the air mass flow rate was indicated as the dominant factor in determining the pulsing statistical parameters. This research provides fundamental insights for further modelling the dense fly ash pneumatic flows. (C) 2014 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.