Effect Of Steadys Flow Internals On Flow Field And Performance Of Cyclone Separator

Cyclone is a device that uses the centrifugal force generated by rotation to achieve gas-solid separation.In the flow field of the cyclone,in addition to the double-vortex main flow composed of quasi-free vortex and quasi-forced vortex,there are also secondary flows such as short-circuit flow,vertical vortex,bottom entrainment,and back-mixing.These secondary flows have a negative impact on the performance of cyclones.At present,conventional cyclone still cannot meet the requirements for separation efficiency of micron-sized and submicron particles(the diameter smaller than 5 ?m).The installation of steady flow inner parts can effectively suppress the secondary flows and improve the performance of cyclone.In this paper,the Reynolds stress model(RSM)and discrete phase model(DPM)in FLUENT software were used to investigate the flow field and performance of a Stairmand cyclone with a cylinder vortex stabilizer and an inner cylinder.ICEM CFD software was employed for modeling and meshing.The predicted results were compared with the experimental results of PIV system to ensure the correctness of model selection.The main research work of this paper was as follows:(1)The effects of different size cylinder vortex stabilizer on the flow field and performance of the cyclone were investigated.The results show that the installation of the stabilizer has little effect on the tangential and axial velocity values in the separation area.The maximum tangential velocity is only increased by a maximum of3.29%,but it greatly enhances the axial symmetry of the velocity distribution and the stability of the flow field.The existence of stabilizer can weaken the influence of radial gradient force on particles,suppress the phenomena of back-mixing and precessing vortex core(PVC),reduce the scope of impact of the secondary flows andthe synergy between different secondary flows.The stabilizer has the most significant effect on the lower end of the cone and the ash hopper.This improves the bottom entrainment and tail swing of vortex end,making the particles easily accumulate in the ash hopper.The cyclone with stabilizer can improve the separation efficiency of fine particles whose diameters are smaller than 3 ?m by up to 5.52%.However,the existence of the stabilizer can also cause particles to accumulate near the wall of the stabilizer.Larger or smaller stabilizers have certain negative impact on separation efficiency.The stabilizer brings additional energy loss to the cyclone,but the pressure drop indicates that the energy loss is not large,and the pressure drop is increased by a maximum of 3.61%.When DO/D=0.1,cyclone has the best separation performance.(2)The flow field and performance of the circumfluent cyclone with an inner cylinder were investigated.The results show that installation of the inner cylinder changes the conventional flow path of the fluid,making the airflow more regular,avoiding the collision of upflow and downflow,and eliminating the short-circuit flow and the vertical vortex.Most of the cleaned gas in the circumfluent cyclone is directly discharged,which accelerates the gas-solid separation process,so that the velocity component values in all directions are relatively smaller.At the same time,the energy loss is also greatly reduced(when the inlet velocity is 15 m/s,the pressure drop is reduced by 66.67%),and the impact of bottom entrainment is weakened.The special flow path design of the circumfluent cyclone makes the maximum tangential velocity at the cylinder occurs near the wall of the inner cylinder,resulting in a blurred interface between the quasi-free vortex and quasi-forced vortex.The movement path of particles in the circumfluent cyclone is long,which is conducive to the separation of particles.For particles whose diameters are smaller than 3 ?m,the separation efficiency is improved by 11.27%.