The Numerical Simulation Research Of The Viscoelastic Polymer Solution Mixing Flow Field

Partially hydrolyzed polyacrylamide(HPAM) is used widely in oil recovery, which is one kind of the industrial products. The hydrolysis process of HPAM solution is the slaking link of the polymer oil displacement process. Because the high molecular weight of HPAM solution is used more in oilfield, the original configuration unit is not suitable for its hydrolysis process. So the length of slaking time is long, the efficiency of the mixing process is low, the agglomerate is easy to produce in the bottom of the stirred tank. The quality of the input of HPAM solution and macro economic benefit of polymer flooding are affected directly by the length of slaking time and the efficiency of the mixing process. Therefore, to study the rheological properties of HPAM solution, the constitutive equation and the flow control equations of HPAM solution are given, which is suitable to describe the rheological property of HPAM solution. The reasonable mathematical models for mixing flow field are established. One kind of new mixing plant are developed and the characteristics of mixing flow field are studied. These studies have great significance to improve the technology of polymer flooding and enhance the oil collection rate.Based on the viscoelasticity experimental data of HPAM solution, the average standard deviation was used as objective function. Combined with KBKZ constitutive equation, the relaxation time spectrum of different concentration under different molecular weight was fit out. Under the uniform gradient of relaxation time and the interval of which is 10-2-103 s. The changing rule of the corresponding relaxation modulus is found out. Under the premise of accurate characterization of HPAM solution viscoelasticity, the number of relaxation time spectrum is reduced to three, so the difficulty of the engineering calculation is reduced.For improving the HPAM solution slaking configuration unit, one kind of spiral finned energy-saving impeller is designed. The anchoring stent is used as the body stent of the impeller. The bottom beam of the impeller is cylindrical shape. On both ends of impeller, spiral fins are equipped along the outer wall of the circular pipes, spiral finned counterclockwise rotates from both bottom of the pipe to the top of it. The rotational structure of the spiral fin is advantageous to the axial flow of fluid, and it makes the axial velocity of mixed fluid distributed evenly along the axis. The flow field distribution of the fluid in the stirred tank is optimized. At the same time, the power consumption of the impeller in the mixing process is reduced and the energy is saved.Based on the numerical simulation method, the three dimensional flow field mixing performance of anchor impeller and spiral finned energy-saving impeller in the Newtonian fluid and different rheological index of pseudoplastic fluid were studied and analyzed. The flow field characteristics under different high place, different Reynolds number and different rheological index fluid were included. The flow field of the impeller under different spiral fin spacing and impeller diameter d and agitation tank diameter D ratio was analyzed. The power consumption curve and Metzner constant of anchor impeller and spiral finned energy-saving impeller are obtained by calculation. The results show that, spiral finned energy-saving impeller compared with anchor impeller, the axial and radial velocity of the mixing fluid are promoted. Power consumption is reduced and the average shear rate of the tank is improved. Along with the increase of spiral fin spacing and the decrease of d/D ratio, the power consumption is reduced and the average shear rate of the tank is reduced slightly.