Experimental Investigation On Drag Reduction Of Surfactant,Polymer And Their Composite In A Rotating Disk Apparatus

It is of great significance to reduce the consumption and energy saving of internal and external flow equipment to deeply study the turbulence drag reduction characteristics and mechanism of surfactant,polymer and its composite solution.However,there are few researches on composite drag reduction,and the mechanism of drag reduction is still unclear.Therefore,in this paper,the effects of concentration,temperature and Reynolds number on the drag reduction law and rheological properties of surfactant,polymer and their composite aqueous solution outflow turbulence were studied by using rotating disc device and rotating rheometer,respectively.The experimental results were analyzed in detail and the possible microstructure and mechanism of drag reduction were deduced.The conclusions are listed as follows.(1)In the concentration range of CTAC/ NaSaL aqueous solution,As the concentration of the solution increases,the maximum drag reduction rate increases and the critical temperature of effective drag reduction increases.The effect of concentration,temperature and Reynolds number on the drag reduction rate of the solution is not linear.At a lower concentration,the drag reduction rate decreases with the increase of Reynolds number,and is not resistant to high temperature(such as 50 ppm of drag reduction solution at40? deactivation);(2)In the range of temperature and concentration of PEO aqueous solution,the optimal drag reduction temperature of PEO is approximately20?.At different temperature and Reynolds number combination,the solution concentration to achieve the highest drag reduction rate is also different.When the temperature and Reynolds number are low,the 50 ppm solution can achieve the highest drag reduction rate.When the temperature is low and Reynolds number is high,the maximum drag reduction rate can be obtained by 75 ppm solution.When the temperature is high and Reynolds number is low,100 ppm solution can achieve the highest drag reduction rate.When the temperature and Reynolds number are both high,the 150 ppm solution achieves the highest drag reduction rate.Compared with CTAC/NaSal drag-reducing aqueous solutions,PEO does not have critical Reynolds number and critical temperature,and the drag-reducing rate can reach 9% at high temperature or high Reynolds number.(3)The mixed solutions of PEO and CTAC/NaSal combined the advantages of high resistance of CTAC with the high temperature and shear resistance of PEO,and the higher resistance of PEO at high temperature and/or high Reynolds number,with enhanced resistance.Under the condition of high temperature and/or high Reynolds number,the drag reduction rate is higher and the drag reduction is enhanced.The effect of CTAC/NaSal(or PEO)concentration on the drag reduction rate of the mixed solution is smaller at low Reynolds number than at high Reynolds number,and the effect of PEO concentration on the drag reduction rate of the mixed solution is smaller than that of the CTAC/NaSal(or PEO)concentration.For CTAC/NaSal aqueous solutions,the range of drag reduction temperature and Reynolds number is obviously wider with the addition of PEO.For all mixed drag reduction solutions,the optimum temperature for drag reduction is about 30?,and the drag reduction enhancement is most obvious at 40?.The increase of the drag reduction rate of CTAC/NaSal aqueous solution with the addition of PEO is greater than that PEO aqueous solution with the addition of CTAC/NaSal at low temperature and medium Reynolds number,but the latter is greater than the former at high temperature and high Reynolds number(4)The The results of rheological experiments show that under different temperature and concentration,The CTAC/NaSal aqueous solutions only show one shear thickening at low shear rate.The shear thickening of PEO aqueous solution occurs only once at a higher shear rate.However,The results show that the composite solution with some concentration has shear thickening phenomenon at lower shear rate and higher shear rate.This indicates that the composite solution combines the advantages of high drag reduction rate of CTAC at lower shear rate and high shear resistance of PEO,which leads to enhanced drag reduction effect and wider the range of drag reduction Reynolds number and temperature.