Development Of The New Diffused Cyclone Based On Full Diversion

Existing studies have shown that the presence of secondary vortices of the clone can cause disturbances in internal and external vortex flow,which causing violent turbulence in the flow field and resulting in phenomena such as “gray ash ring”,“short-circuit current”,“secondary dust”,and “granule entrainment”,which affects the separation of ultrafine particles.In this paper,three-dimensional modeling of the cyclone separator was carried out by using the modeling software Gambit.The flow field inside the cyclone separator was numerically simulated using the flow field simulation software Fluent to study the flow field characteristics and particle motion trajectory in the separator.In views of the instability of the secondary vortex in the flow field of the cyclone,the structure of the cyclone is improved by using a deflector,a steady flow column and numerical simulation and flow field analysis are performed.The total separation efficiency,particle size separation efficiency and pressure drop of the cyclone were measured by experiment.Specific tasks include:(1)The effects of structures of the Stairmand cyclone,the diffuser cyclone,and the circulation cyclone on secondary vorticity at different locations were investigated.The simulation results show that the internal flow guide of the cyclone remover effectively reduces the “gray ash ring” and "short-circuit flow".And the velocity,turbulence intensity,and eddy current scale of the secondary vortex near the upper part of the cylinder and the exhaust pipe are all reduced.The deflectors of the diffused cyclone separator have a significant effect on reducing the "secondary dust" and "grain entrainment",and the secondary vortex velocity,turbulence intensity,and eddy current scale near the dust ejection opening are all reduced.The reasonable addition of internal components in the cyclone separator weakens the influence of the secondary vortex to a certain extent,makes the flow field more stable,and effectively alleviates the problem of the "upper grey ring","short-circuit current","secondary dust" and "granule entrainment" that existing in the conventional cyclone.(2)The influence of structural improvement on the flow field of a diffusedcyclone dust collector was investigated.The simulation results show that the baffle avoids the generation of longitudinal vortexes at the top of the cylinder and eliminates the upper ash ring in the barrel.Compared with the diffused cyclone,turbulent intensity of new structure reduced from 1.85% to 1.42%.The steady flow column weakens the problems of high energy consumption,disturbance of the inner swirl flow,back mixing of the ash bucket in the cone.The symmetry of the tangential velocity is better,and the maximum turbulence intensity of the new structure is reduced by 38%compared to the diffused cyclone.The static pressure drop and turbulence intensity at different sections in the new structure are significantly reduced.Compared with the diffused cyclone,the static pressure of the new structure is reduced by 27%,the maximum turbulence intensity is reduced by 43%.The impact of the distance between the reflecting screen and the inner tube on the dust collector was investigated.The tangential velocity,pressure drop and turbulence intensity of different models were analyzed and it was found that the performance of the cyclone is optimal when the distance between the reflective screen and the inner cylinder is 0.75 D.(3)By using the discrete DPM model,the movement behavior of solid particles in the diffused cyclone and the new diffused cyclone was investigated.The simulation results show that the ultrafine particles are subjected to a small centrifugal force and the motion trajectory has a strong randomness.The baffles prevent the solid particles from rotating near the top cover,eliminating the formation of the upper grey ring.At the cone,the number of rotations of the solid particles under the steady flow column is significantly increased,and the residence time of the solid particles in the cyclone is prolonged.(4)The performance of the new diffusion cyclone dust collector was examined through experiments.The results showed that the total separation efficiency of the new structure has a good stability over a wide speed range,and the separation efficiency gradually increases with the increase of the inlet gas velocity..The new structure has an efficiency of 85% for particles with the particle size of 2?m and an efficiency of more than 90% for particles with the particle size of 5?m with an inlet gas velocity of18 m/s.