The effect of the expansion chamber on the flow pattern and performance of cyclones

Abstract

Abstract. An expansion chamber is an optional structure installed between the cyclone cone and dipleg. Some previous researches have reported that adding an expansion chamber in Stairmand cyclone geometries, the separation efficiency can be significantly improved. In this paper the effects of an expansion chamber on the flow field and performance of a Stairmand high-efficiency cyclone were investigated numerically and experimentally. The numerical simulation adopts the RSM model and the cyclone geometries which are identical to the ones used in experiment. The gas velocity field, pressure field and vortex length in the Stairmand cyclone and with a expansion chamber at two locations in the cyclone geometry were simulated and compared. The experiments were carried out at different inlet veloocities under atmospheric environment. Results show that, with or without an expansion chamber, and with an expansion chamber in the upper or lower elevations, the tangential velocities in the cyclone space do not have much difference. But the axial velocity profiles would be changed obviously. The vortex length is slightly increased with the increase of the cyclone inlet velocity. The expansion chamber could extend the vortex tail to the bottom of the chamber or its underneath. The presence of an expansion chamber generally results in a slight decrease in the cyclone pressure drop. The cyclone separation efficiencies were observed higher when the vortex tail does not go throngh the expansion chamber.