Experimental study on a compact axial separator with conical tube for liquid-liquid separation

•A compact axial separator with conical tube was studied.•The droplet trajectory comparison in the conical tube and equal-diameter tube was observed.•The effect of inlet oil fraction and liquid flow on separation efficiency was investigated.•The split ratio has considerable effect on separation performance. Centrifugal technology for two-phase flow separation is widely used in industrial fields. However, the liquid-liquid separation is more difficult than solid-liquid and gas-liquid separation due to its relative small density difference and emulsion caused by droplets breakup. And the current hydrocyclones for liquid-liquid separation have some shortcomings limiting further improvement of separation efficiency. Axial separators with static swirler emerged as an effective alternative method. In this paper, a compact axial separator with conical tube was introduced and investigated experimentally using oil as the dispersed phase and tap water as the continuous phase. A high-speed camera was used to verify the advantages of conical tube compared to a cylindric tube by oil droplets trajectories. Additionally, the separation performance and pressure drop on different inlet flow rate and oil fraction was studied. In the experiment, the split ratio was changed by controlling the valve in HPO pipe, and the results show that separation efficiency can be improved by increasing the split ratio to ensure the drain of oil core.