Numerical Simulation Analysis of Main Structural Parameters of Hydrocyclones on Oil-Gas Separation Effect

Gas pollution in marine lubricating oil systems is harmful to the normal operation of a ship, and is one of the main reasons for the decline of the performance of lubricating oil. In this research, a classic 75 mm hydrocyclone was selected as the oil–gas separation device. A hydrocyclone is a device that uses the density difference of the two-phase flow to separate the dispersed phase in the centrifugal force field. Compared with ordinary active oil–gas separators, hydrocyclones do not require additional power devices. After establishing the physical model of the hydrocyclone, the distribution characteristics of the flow field and oil–gas two-phase flow separation performance of the hydrocyclone were studied using computational fluid dynamics (CFD) technology. The influence of vortex finder diameter, vortex finder length, spigot diameter, cylindrical-part length, and cone angle on the oil–gas separation performance of the hydrocyclone were investigated. It was found that the vortex finder diameter and the spigot diameter have a significant influence on the oil–gas separation performance, whereas the vortex finder length, the cylindrical-part length, and the cone angle have little influence on its performance. Increasing the vortex finder diameter and reducing the spigot diameter can improve the gas separation efficiency. However, the liquid outflow from the vortex finder increases, which causes the liquid loss rate to increase. The presented research could lay a foundation for the optimal design of a hydrocyclone used for oil–gas separation of a marine lubricating oil system.