Experiment and study on wall slip of lubricating grease flowing in tube

Based on the theory of boundary layer,two basic formulas for studying flowing in tubes were established according to Mooney method.One is that wall slip speed is determined by roughness and material of tube wall,and it does not change with the tube diameter.And the other is that real rheological model deducted wall slip is independent of the tube diameter.The effects of many factors on the rheological property were studied,such as viscoelasticity,thixotropic property and wall slip of lubricating grease.High accurate tube rheometer was developed for the study on wall slip.Reasonable experimental steps and testing measures were adopted in order to remove the effects of other factors and to separate the wall slip flowing.The two basic formulas were validated through rheological experiments in steel tube with three different diameters.A flowing resistance formula suitable for any tube diameter was developed to calculate the pressure decrease of all sorts of pipelines.It was proved that the smaller the tube diameter was,the better the effect of drag reduction would be.However,tube diameter should be properly chosen for small tube diameter may cause larger flowing resistance.At the same time,the effect of drag reduction was directly proportional to the wall slip speed.New study on the relationship between tube wall and wall slip speed was put forward.The paper established theoretical and experimental foundation for pipeline transport property of centralized grease lubrication systems.