Study On Influence Of Diameter And Insertion Depth Of Vortex Finder On Cyclone Separation Performance

Energy-saving and emission reduction put forward higher performance requirements for cyclone separators,improving efficiency and reducing resistance has become an urgent problem to be solved in cyclone separators today.In this paper,the effects diameter and insertion depth of vortex finder on the separation performance of PV-type cyclone separator and spiral top cyclone separator were studied by means of experimental and numerical simulation,and the influencing mechanism was analyzed.The thesis draws the following conclusions:（1）When the insertion depth of the vortex finder is lower than the height of the inlet of the cyclone,excessive short-circuit flow will make a large number of dusty gas directly escape from the vortex finder,resulting in low-pressure drop and separation efficiency.When the insertion depth S/inlet height a of the vortex finder increases from 1 to the interface of cyclinder and cone,the pressure drop of the two separators is basically unchanged,and the separation efficiency increases first and then decreases,indicating the optimal insertion depth.The maximum efficiency depth and synergistic range of the two kinds of separator are related to the diameter of the vortex finder,and both of them decrease with the diameter of the vortex finder.According to the fitting results of the test,the relationship between insertion depth at maximum separation efficiency and diameter of straight vortex finder was obtained,PV-type separator was S/a_MSE=（5.15507-28.87786Der）/（1.89954-14.50354Der）,and spiral top separator was S/a_MSE=（9.83471Der-0.04982）/（0.56124+4.54242Der）.（2）Numerical simulation results show that the maximum efficiency of the vortex finder is mainly related to the short-circuit flow and the height of the separation space.Moderately increasing insertion depth can increase the separation capacity of annular space and reduce the proportion of particles near the end of the vortex finder,so as to prevent the particles entailed by short-circuit flow from escaping,and increase the particles entering the separation space and increase the separation efficiency.However,increasing the penetration depth too much and lacking sufficient separation space to separate the particles entrainment by internal and external cyclones,thus reducing the separation efficiency.When the diameter of the vortex finder is small,the short-circuiting flow is low,and the effect of increasing the insertion depth on inhibiting the entrainment of particles of short-circuit flow is no longer significant.Therefore,it is better to reduce the insertion depth appropriately to ensure enough separation space to separate particles.Therefore,the smaller the diameter of the vortex finder is,the smaller the optimal insertion depth and the improvement range are.In addition,the short-circuiting flow of spiral top inlet structure is lower than that of PV-type,and the effect of insertion depth on short-circuit flow suppression is not as good as that of PV-type,so the improvement range of optimal insertion depth of spiral top separator is also lower than that of PV-type.（3）The comparison between the separation performance of the optimal insertion depth of the spiral top and the reference insertion depth of the PV-type shows that the separation efficiency of the spiral top separator is higher than that of the PV-type separator at the same pressure drop under the condition of Der>0.27 and V_i>15m/s.The larger the diameter of the vortex finder is,the more significant the effect of the spiral top separator on prolonging the residence time of the gas is,so the improvement of the separation efficiency is higher.When Der=0.5 and V_i=25m/s,the optimum insertion depth of spiral top can achieve an efficiency improvement of 2.06%under the condition of reducing pressure drop by 50.6%.