Study On Flow Field Of Polymer Drag Reduction In Stirring System

Polymer drag reduction has important engineering applications in petrochemical,urban heating and other fields.Among these applications,study of polymer drag reduction flow in pipe has attracted attention of scholars at home and abroad.Small flow test and small stirring torque test are often used to measure and evaluate effect of polymer drag reduction,in which pressure drop gradient,torque and other parameters are taken as the main indexes of drag reduction evaluation.At the same time,flow field characteristics,as important parameters in the evaluation of polymer drag reduction flow,can reflect the influence law of polymer on flow from the microscopic level when drag reduction effect is exerted,which has attracted extensive attention.In this paper,flow field evaluation of water-soluble and oil-soluble polymer drag reducer in stirring system is carried out by using a small stirring experimental device combined with PIV measurement method,mainly focusing on three aspects.(1)Two kinds of stirring systems,Rushton and Pitch blade,are selected.Radial/Axial velocity and turbulence degree,turbulent energy dissipation rate and turbulent kinetic energy in the two stirring systems are compared and analyzed.Rushton stirring system is used to analyze polymer drag reduction flow field.Phase angle(0 °,15 °,30 °,45 °,60 °)of flow field analysis in stirring system is determined.(2)Four kinds of water-soluble polymer,namely polyacrylamide(PAM),polyethylene oxide(PEO),xanthan gum(XG)and guar gum(GR),are selected to carry out comparative analysis on flow field.When concentration is lower than 100 ppm,these four kinds of polymer have no significant inhibitory effect on axial turbulence degree;PAM and PEO have a small inhibitory effect on radial turbulence degree in region near impeller;XG and GR have no inhibitory effect on radial turbulence degree.Under the concentration of 250 ppm,PAM has better inhibition effect on radial turbulence degree.Evaluation results in this small stirring system are consistent with flow drag reduction evaluation results of these four kinds of polymer in loop flow in the literature,which further confirms the feasibility of polymer drag reduction evaluation in small stirring system.(3)Simulated oil is used as experimental medium,influence of oil-soluble polymer drag reducer(1#,2#)on the stirring flow field is analyzed emphatically.When concentration is 50 ppm,these two kinds of polymer drag reducer has the effect of inhibiting turbulent kinetic energy and energy dissipation rate.It is further found that 1# polymer can effectively inhibit radial turbulence degree in stirring paddle region.