渐扩管内气液环状流附壁特性研究

Research on Coanda Effect Appeared in Oil-air Annular Flow Through the Conical Diffuser

利用Fluent软件模拟了油气两相流在渐扩管内的液相的附壁情况,得到了渐扩管扩张段的速度场和压力的分布规律,并分析了改变渐扩管的扩张角对扩张段环状流液膜附壁的影响。结果表明,渐扩管扩张段的锥角对环状流液膜的附壁有很大的影响,扩张段横截面的速度差值和压降随扩张角增大而增大,但是轴向梯度力却随之减小。这些结论对油气润滑系统中的输运有指导意义。

In this paper,physical model and numerical simulation model for oil-air annular flow through conical diffusers are built by the Fluent software,and Coanda Effect which is a commonly phenomenon appeared in this kind of oil-air annular flow field is studied,especially influences of Coanda Effect on the attachment of the liquid phase of annular flow trended to the curved wall are analyzed in detail by changing expansion angles to calculate the radial pressure distribution and pressure drop.The simulation results show that the expansion angle has a great influence on the attachment of liquid phase in annular flow to the curved wall,the radial pressure gradient is an important factor of the Coanda Effect which could make the liquid phase of annular flow convey near the wall,and the radial pressure gradient will decrease but the velocity difference of the section and the pressure drop increase when the expansion angle becomes larger. These conclusions will provide useful reference in designing pipelines conveying the two-phase annular flow in oil-air lubrication system.