Study On The Mechanism And Properties Of The Influence Of Pipe Flow Shear On Non-Newtonian Crude Oil

In this paper,in order to simulate turbulent shear and laminar shear respectively,original stirred tank shear system with floating roof and rotary Rheometer are used,through the digital microscopic imaging system,micro-crystal structure of crude oil wax were observed after pre-sheared.Based on the same energy dissipation rate,to reveal that pre-shear of different structure flow have different effect on low-temperature rheology of crude oil.I hope it's helpful to establish a more scientific laboratory method of simulating shear history of crude oil pipeline.Because of structural similarity of flow field,using stirred tank to simulate turbulent flow in pipeline,and the floating roof will effectively reduce the volatilization of light components of oil,and three factors such as energy dissipation,shear time and shear temperature influences on the yield stress and balanced stress of gelled crude oil flow are discussed;the equivalent shear rate of fluid in the stirred tank were calculated,and set the same experimental procedure and shear rate on the Rheometer,based on experimental conditions of temperature and the energy dissipation rate,comparing the difference of thixotropic characteristics and gelling characteristic of crude oil after by the two kinds of fluidized pre-sheared,it turned out that the gelled oil laminar-pre-sheared got stronger structure and worse thixotropic characteristic.Effects and microscopic changes on particle size,shape and distribution of structure characteristics of wax crystal under the different pre-shear flow by microscopy imaging system and image processing software were analyzed,five micro-parameters such as the equal area circle diameter,roundness,dimension analysis,the length of the gap,the total number of particles were used to described the effects from different flow pre-shear,and interpreted the causes of differences on low-temperature rheological properties of waxy crude oil.Due to the experimental results,we could know that simply consider the energy dissipation rate or equivalent shear rate as the only analog quantity,different fluctuation intensity of turbulent flows would cause different effects on wax crystal(laminar flow could be considered as zero fluctuation intensity),which will lead to that the experimental results will be relatively deviation somehow,so it's necessary to study on the fluid from the internal structure of the dispersed phase.On the basis of experimental device of stirred tank,consider add vortex scale into evaluation standard of turbulent pipe flow shear history,which would be more scientific and reasonable for simulation of pipeline shear history.