Study Of Unsteady Flow Of Cyclone Separator Using Large Eddy Simulation Method

Cyclone separator is one of key equipment for many continuous production industries.The flow field in cyclone separator is complex three-dimensional turbulent flow with spiral flow instability.The instable flow shows that the flow field changes with time.The flow fluctuation of cyclone separator has impact on the separation efficiency.Firstly,the prediction of velocity distribution of gas in the cyclone separators is numerically investigated using the Large Eddy Simulation(LES)model.Secondly,particles are injected into separator by Discrete Phase Model(DPM),in order to analyze the trajectories and collection efficiency of particles.Finally,some operating and structural parameters are changed to study their influence on unsteady flow.It is shown that flow non-axisymmetric caused by structural non-axisymmetric has more obvious influence on internal swirling flow in mean flow field analysis.While in the instantaneous analysis,the center of rotation of the airflow oscillates near the geometric center.The frequency of tangential velocity is about 9.2-12.1Hz,and maximum of its fluctuation appears near the center due to internal swirling flow.In addition,axial velocity fluctuation maximum appears at up-down flow boundary.In general,flow fluctuates most near the dust exit.Besides,particles of different diameters added from different positions lead to different trajectories and collection efficiency.Results are also affected by turbulent fluctuation after Discrete Random Walk model.LES model is suitable for calculation for collection efficiency of little particles,while is relatively poor at calculate trajectories using unsteady tracking.Relationship between some major parameters and unsteady Characteristics are concluded by dimensionless numbers.