Evolution of Turbulent Swirling Flow in a Small-Scale Cyclone with Increasing Flow Rate: A LES Study

The flow field, vortex behaviour and pressure losses in a small-scale cyclone have been studied at a wide range of flow rate 0.23–39.7 NLPM (measured at 1 atm and 20∘C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$20\,^\circ \hbox {C}$$\end{document}) using the LES simulations that have been validated based on experimental measurements of the cyclone pressure drop. The following flow characteristics such as (1) the radial distribution of the tangential velocity; (2) the maximum tangential velocity and axial downward flow rate; (3) natural vortex length and rotation frequency of the vortex end; and (4) pressure losses in the cyclone have been analysed as a function of Reynolds number. The radial distribution of the tangential velocity inside the cyclone has been described by a proposed equation for adapted Burger’s vortex. The position of the lower end of the vortex (natural vortex length) as well as its rotational frequency have been investigated with the pressure sensing method. A unique vortex behaviour such as “vortex end jump” was revealed at some Reynolds numbers. Additionally, a deep analysis of the pressure losses in the cyclone has been performed which showed that the main pressure losses (up to 48%) occur in the vortex finder. Four flow regimes were revealed and a one-term power series model has been proposed to describe the effects of the Reynolds number on the Euler number (dimensionless pressure losses).