Chaotic Characteristics of Cocurrent Upflow and Downflow Gas/Solids Systems in Fully Developed Regime of Vertical Pipes

摘要

This paper studies the transient characteristics in the fully developed cocurrent upflow and downflow gas/solids systems of vertical pipes using deterministic chaos theory. Fluctuation signals which reflect the density pulsation in systems were obtained by an optical density probe. The results show the local chaos parameters (correlation dimension, D_(ml) and Kolmogorov entropy, K_(ml)) are in the same range of value for both the riser and the downer and are strongly related with the local solids fraction. D_(ml) and K_(ml) decrease sharply with increasing solids fraction at solids fraction below 0.01 and almost keep constant when the solids fraction is above 0.01, which implies that the solids fraction is a key factor of influencing the turbulent structure in two-phase flow systems and must be considered carefully in modeling the riser and downer.