Oil–water two-phase flow-induced vibration of a cylindrical cyclone with vortex finder

Abstract

Cylindrical cyclones play an important role in oil–water separation and sewage treatment in the petroleum industry. Here, we describe the characteristics of vibration induced by a two-phase rotational flow in a cylindrical cyclone. The cyclone operating parameters together with a dimensional analysis and multiphase flow numerical simulation were used to understand the flow field characteristics. The frequency and amplitude of pressure fluctuation were obtained by measuring pressure changes at points on the axis of the device. It shows that the pressure in a cylindrical cyclone varies periodically during separation and that fluctuation frequency and amplitude are related to the inlet velocity and flow split ratio. The effect of the overflow split ratio on the pressure fluctuation frequency is negligible, but increasing the overflow split ratio will cause greater fluctuation of the flow. For a cylindrical cyclone, the pressure fluctuation frequency can be calculated from the inlet velocity. Adjusting the inlet velocity and the overflow split ratio changes the mechanical response of the structure. The results of a modal analysis show that the structural vibration response is consistent with the response state of the lowest point of the internal central-vortex pressure and that both are in approximate circular motion. Furthermore, the frequency of pressure fluctuation induced by the flow is close to the intrinsic frequency of the structure with a single bottom constraint, which can cause unwanted resonance easily. Therefore, an appropriately added constraint on a cylindrical cyclone should be taken into consideration to avoid the resonance frequency.