Experimental and numerical investigations of a dynamic cyclone

Abstract

Cyclones are well known for their simple structure and stable performance. However, cyclones’ separation efficiency is not high enough, especially for particles smaller than 10 µm. The conventional cyclone is improved by adding rotor blades to the cyclone; this new configuration is known as a dynamic cyclone. To explore dynamic cyclone further, the separation efficiency and flow field in this dynamic cyclone were experimentally and numerically investigated. A homogeneous computational fluid dynamics (CFD) model, which included a turbulence model based on the RNG k–ɛ model and the Reynolds stress model (RSM), was developed to analyse the flow field in the cyclone. Then, the discrete phase model (DPM) based on the Eulerian–Lagrangian method was used to predict the separation efficiencies and particle trajectories. The performance of the cyclone was numerically investigated in detail in terms of the tangential velocity, separation efficiency and total pressure. The effects of the inlet velocity, rotational speeds and the configuration of the blades on the dynamic cyclone were also analysed. The model was verified through experimentation, and the data were obtained from an electrical low pressure impactor (ELPI), digital microtonometer and Pitot tube. The results indicate that the separation efficiency and total pressure drop of dynamic cyclones increase significantly as the rotational speed and inlet gas velocity increase. The number of blades and the inclination angle of the blades have strong impacts on the separation efficiency and total pressure drop of the apparatus. In addition, the simulation predictions demonstrate that the tangential velocity distributions are dominated by the rotational speeds of the blades and inlet velocities of the gas. The simulation of the tangential velocity distributions can more clearly explain the increase in the separation efficiency.