Experimental Study On Turbulent Drag Reduction And Shearing Characteristics Of The Mixed Solution Of Xanthan Gum And Polyacrylamide

Polymer drag reduction is an important energy-saving way,which is widely used in petroleum exploitation and transportation,HVAC and medical engineering because of its remarkable drag reduction effect and environmental friendliness.At present,the research on drag reduction and shear characteristics of single polymer solution has been widespread and thorough,but the research on drag reduction of two or more polymer mixed solutions is rarely reported.It is of great theoretical and practical value to systematically study the influence of concentration and Reynolds number factors of polymer mixed solution on turbulent drag reduction for further understanding the mechanism of turbulence drag reduction and expanding the application occasion of drag reduction.Xanthan gum(XG)has large relative molecular weight,long straight chain,good temperature resistance and salt resistance,which make it a good drag reducer.Polyacrylamide(PAM)has become a widely used drag reducer due to its low cost,fast dissolution and good drag reduction effect.In this paper,through upgrading and optimizing the experimental equipment for polymer turbulent drag reduction,the drag reduction and shear resistance characteristics of XG/PAM aqueous solution and salt solution under different concentrations and Reynolds numbers were studied and analyzed.The main conclusions are as follows:Drag reduction of the mixed solution of xanthan gum and polyacrylamide:(1)When the Reynolds number is less than 3?10~4?3.5?10~4,the drag reduction efficiency of XG/PAM solution increases with increasing Reynolds number,and reaches the best drag reduction effect.When the Reynolds number exceeds the critical Reynolds number,the drag reduction efficiency does not change with Reynolds number.(2)The drag reduction effect of XG/PAM solution is enhanced with increasing XG concentration.When XG concentration greater than saturation concentration(500 ppm XG),the drag reduction effect of mixed solutions is not improved with increasing XG concentration significantly.(3)XG/PAM solutions has the same transformation characteristics as XG solutions from type A drag reduction at low Reynolds number to type B drag reduction at high Reynolds number.(4)The influence of temperature on drag reduction effect of XG/PAM solutions is mainly reflected in the low Reynolds number range,which makes drag reduction onset appear earlier when the temperature rises.Drag reduction of the mixed solution of xanthan gum,polyacrylamide and Na Cl(XG/PAM/Na Cl):(1)Adding Na Cl makes XG/PAM solutions drag reduction onset earlier.(2)Na Cl had a promoting effect on XG/PAM solutions drag reduction at low Reynolds number(1.5?10~4?2.3?10~4),but a inhibiting effect at high Reynolds number.(3)The addition of Na Cl resulted in XG/PAM solutions drag reduction decrease at a higher concentration(200-600 ppm XG),but a slight increase at a lower concentration(100 ppm XG).(4)Na Cl does not change the nature of polymer solution turbulent flow in the tube,and XG/PAM/Na Cl solution also has drag reduction type conversion.The shear properties of xanthan gum/polyacrylamide(XG/PAM)and xanthan gum/polyacrylamide/Na Cl(XG/PAM/Na Cl)solutions:(1)In the shearing process,the shear stability of XG/PAM solution increases with the increase of XG concentration.(2)Adding Na Cl can enhance the shear stability of XG/PAM solution.(3)The greater PAM concentration in mixed solution with the same concentration,the worse the shear stability of the solution.(4)After a long time of shearing,the drag reduction effect of XG/PAM and XG/PAM/Na Cl solution gradually decreased,but still maintained a high drag reduction rate,which indicated that XG/PAM and XG/PAM/Na Cl solution had good shear resistance,and the polymer used in the circulation system could still maintain a good drag reduction effect.