Research On The Application Of Coanda Effect For Structure Design Of Oil-air Lubricating Pipeline

Coanda Effect refers to the fluid tend to along its figure of the curved surface. Coanda Effect has wide industrial applications in fluid transport projects, and Coanda Effect plays an important role in the mixture, distribution and transmission of media in oil-air lubricating pipeline. So the research on the application of Coanda Effect for structure design of oil-air lubricating pipeline is very significant.Based on the oil-air two phase flow theory, jet theory and Coanda Effect theory, Coanda Effect in the application of oil and air pipeline structure design is studied by theoretical and numerical analysis method, and main research work and conclusions are as follows,(1) Using mathematical model of Coanda Effect, the liquid Coanda phenomenon of oil-air two-phase lubrication flow in free and limited space is simulated. The results show that the free space curved wall is against liquid to attach to the curved wall, but the limited space curved surface is just the opposite.(2) The related influence parameters of Coanda Effect in gas-liquid two phase flow about oil-air lubrication is studied, and then Coanda Effect on the impact of distribution characteristics of oil-air annular flow in T-junction is studied, and finally the numerical simulation is carried out. The results show that the more different the T-junction curvature is, the greater the different pressure gradient of the level branch pipe is, therefore, uneven distribution of oil-air annular flow will be formed. The existing of the Coanda Effect is the main cause of the different pressure distribution of T-junction.(3) The simulation analysis for internal flow field of the circular arc junction and T-junction is done and gas-liquid distribution coefficients of oil-air annular flow in these junctions are calculated. Results show that the gas-liquid distribution coefficients of circular arc junction are more stable, and close to the ideal value. The oil distribution of circular arc junction is more homogeneous and stable than T-junction. Taking the circular arc junction as an oil and air distributor is a good choice. And the fundamental reason is that the structure of circular arc junction overcomes Coanda Effect influence on the oil-air distribution of T-junction.(4) The characteristics of the oil-air annular flow through conical diffuser are studied. The pressure losses of two kinds of conical diffusers, one is the same expansion angle but different variable diameter ratio, another is the same expansion ratio but different expansion angle, are calculated under the same annular flow condition. The influence of the expansion angle and variable diameter ratio on local pressure loss is analyzed when annular flow through conical diffuser.(5) Coanda Effect existed in the annular flow in horizontal pipeline through the conical diffuser is simulated. Results show that expansion angle and variable diameter ratio have a great influence on attachment of the liquid phase of annular flow to the curved wall. Liquid phase of the oil-air annular flow is attached easily to the curved wall when the fluid expansion angle is greater than the cone angle of conical diffuser.All of the above conclusions can be taken as important reference values for the structure design of oil-air lubricating pipeline in oil-air lubrication system.