Effect Of Inlet Structure Andgas Velocity On Transient Properties Of Internal Swirl Flow In Cyclone Separator

With continuous improvement,the modern high-efficiency cyclone separator has been able to basically remove particles with a net particle diameter of more than 10 ?m,but the ability to capture ultra-fine particles below 5 ?m still needs further excavation.Studies have shown that the ability of cyclone separator to trap fine particles is weakened by the presence of some local vortex flows in the separator,and the phenomena of Precessing Vortex Core(PVC)is one of them.The center(vortex core)of air flow rotating in the separator will deviate from the geometric center of the equipment and swing at a certain frequency,which is known as the precession vortex phenomenon.The PVC phenomenon exists in the whole space of the cyclone separator,but the vortex core oscillates at the most violently at the dust outlet.The swirling vortex core will bring some particles which have been captured by the wall surface into the inner swirling flow,resulting in a large number of particles backmix and escape.Therefore,to suppress the effect of the internal swirltransient properties on particle back-mixing and escape,to further increase the efficiency of the cyclone separator,it is necessary to first understand the influencing factors of the PVC and the corresponding change rules.In this paper,the numerical simulation method was used to study the internal swirl transient properties of the cyclone gas and gas-solidphase flow field in cyclone separator.The volute wrapping angle,entrance cut-off,inlet symmetry,and inlet gas velocity of the volute inlet separator were investigated.The effect of the frequency and eccentricity degree of the vortex core and the influence oftransient properties of the vortex core on particle escape were simulated.The main content and results of this paper are as follows:(1)The structure of axial symmetry in the gas-phase flow field,such as the 270° volute wrapping angle and the symmetric double inlet,shows clear unsteady properties in the gas-solid flow field.After the particles are added,the frequency of vortex cores will decrease,and the distance from the vortex core to the geometric center will increase.(2)In the gas and gas-solid phase flow field,the frequency of the vortex core and the distance from the geometric center are consistent with the variation ofthe volute wrapping angle and the inlet cutting schedule.With the increase of the volute wrapping angle,its basically decreased;with the increasing of the inlet cutoff,frequency and eccentricity degree first decreased and then increased.(3)In the gas-solid phase flow field,the frequency and eccentricity of the vortex core in the flow field of the symmetric double inlet structure are both smaller than that of the single inlet,and the efficiency is also better than that of the single inlet.When the inlet gas velocity is 20 m/s,the frequency and eccentricity of the vortex core are the least.The efficiency of the separator is the highest,and the proportion of particle escape caused by PVC to the total escaped volume is also the smallest.(4)By analyzing the attenuation of the mechanical energy from the inlet of the separator to the dust outlet,it was found that the eccentricity degree of vortex core was more strongly related to the energy loss of the downdraft compared with the symmetry of the inlet structure.When the energy loss of the downward airflow was greater,the energy getting from outer vortex to inner vortex zones was higher,and upward flow would suffer greater horizontal disturbances.When the energy of the incoming air flow exceeded a certain threshold value,the vortex core oscillation was induced.