The processing vortex core phenomenon (PVC) diminished the efficiency of a cyclone in capturing fine particles. In this paper

the numerical simulation method was used to study the motion frequency of vortex core and eccentricity degree from vortex core to geometrical center in a gas-flow field with a spiral inlet. Generally

the surface minimum pressure was regarded as the vortex core

and the PVC phenomenon was swung most heavily at the dust outlet section. Therefore

the variation of minimum pressure over time at dust outlet was analyzed by the fast Fourier transform (FFT)

and the location of the vortex core was recorded. The results showed that the frequency and eccentricity degree at the dust outlet were gradually decreased with the increase of volute wrapping angle

and the PVC phenomenon was weakened. While the volute wrapping angle was more than 270°

the PVC phenomenon in the gas-flow field almost disappeared. The influence of the entrance cut-off on the movement characteristics of the vortex core at the dust outlet section would vary depending on the volute wrapping angle. Compared with the symmetry of the inlet structure

the eccentricity degree of vortex core was more strongly related to the energy loss of the down draft. 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. The vortex core rotation frequency was less affected by the energy loss of the downward airflow.