Numerical investigation of the effects of the central channel on the flow field in an oil–gas cyclone separator

•Flow fields of separators with different central channel parameters were obtained.•Effects of the central channel diameters and heights on the flow field were analysed.•The position of the maximum tangential velocity was decided by the outlet diameter.•The effects of the central channel in the top annular space were examined.

The Reynolds stress turbulence model (RSM) was used in this study to numerically investigate the effects of the central channel parameters on the flow field in five cylinder-shaped oil–gas cyclone separators that are commonly used in compressor systems. Based on real working conditions, a wide range of central channel dimensions and pressure-out boundary conditions were employed. The results indicated that the central channel diameter and height has an insignificant effect on the flow field in the separator chamber and the effects of decreasing and increasing the central channel diameter and height were analysed. The tangential velocity near the wall was about 0.8–1.0 times that of the inlet velocity, and the maximum tangential velocity was about 1.8–2.0 times that of the inlet velocity. Particularly, the radial position of the maximum tangential velocity was determined by the outlet diameter, not the central channel diameter. In addition, the effects of the central channel in the top annular space were also examined.