关键词: 进口尺寸, 计算流体力学, 旋转流场结构, 湍流, 分离

Abstract: The design of inlet size for hydrocyclone is an effective method to improve separation accuracy. However, for a long term, the study on hydrocylone inlet size is largely dependent on practical experience. Few studies have been on the influence of inlet size on the hydrocyclone flow field. In this article, the flow field inside a 50 mm hydrocyclone is investigated with CFD method. The pressure profile, three-component velocity distribution and secondary vortex structure are analyzed. The results show that the tangential velocity is the component being affected most since it grows apparently, while the axial and radial velocities vary less, which means that the centrifugal factor increases while the separation structure keeps similar. The swirl velocity of the flow in the far side from the inlet is reinforced. The double-peak phenomenon is found in axial velocity and the reduction of inlet size magnifies this effect. In this sense, the flow field with smaller inlet is prone to better separation. However, smaller inlet size facilitates the formation of secondary vortexes and enhances the entrainment of fluid by the injected flow, which may hamper the separation. Thus, the cut-off size will not always decrease with the reduction of inlet size. Moreover, the increase of energy consumption is mostly attributed to the greater local loss in the connection of inlet and cylinder and the formation of more secondary vortexes.

Key words: inlet size, CFD, hydrocyclone flow structure, turbulent flow, separation