Reynolds stress model was used to simulate zero axial velocity surface of gas phase flow field in cylindrical cyclone separator.The effects of rotational flow instability

inlet velocity and structural parameters such as inlet area and vortex finder diameter on the distribution of zero axial velocity surfaces were studied.The results show that zero axial velocity boundaries exhibit contorted state in the whole separated space due to the inherent existence of rotational flow instability.In the velocity range studied

the flow field is in mould area and the separator is in kinematic similarity

so the inlet velocity has little effect on zero axial velocity boundaries.Vortex finder diameter and inlet area have significant effects on zero axial velocity boundary around the vortex finder entrance.With the decrease of vortex finder diameter and increase of inlet area

zero axial velocity boundary shrinks gradually.Far away from the vortex finder entrance

the effect of vortex finder diameter and inlet area abates and the width of zero axial velocity boundary increases gradually and trends are similar.The separator with specific vortex finder diameter and inlet area that make the flow field stable can make zero axial velocity boundary of cross section keep preferable circular degree.Simulation results can provide reference on separation mechanism research and structure optimization of separator.