粘弹性聚合物溶液搅拌流场数值模拟研究

发布时间：2018-03-29 00:00

本文选题：部分水解聚丙烯酰胺(HPAM)　切入点：KBKZ本构方程　出处：《沈阳理工大学》2015年硕士论文

【摘要】：部分水解聚丙烯酰胺(HPAM)是广泛应用于油田开采的工业产品之一,HPAM溶解过程是聚合物驱油工艺中的熟化环节,由于现在油田多采用高分子量的HPAM溶液,原有的配置单元对其溶解过程产生不适用性,导致溶解熟化时间长、搅拌效率低,在搅拌槽底部容易结块,直接影响HPAM溶液的输入质量和聚合物驱的宏观经济效益。因此,对于研究HPAM溶液的流变性质,给出适合描述HPAM溶液流变性的本构方程及流动控制方程,建立合理的搅拌流场数学模型,开发新型搅拌装置以及研究其搅拌流场的流型特点,对改善聚合物驱技术和提高原油采收率具有重要理论意义。根据HPAM溶液的粘弹实验数据,采用平均标准偏差作为目标函数,结合KBKZ本构方程,拟合出不同分子量下不同浓度的松弛时间谱。在松弛时间呈10-2-103s之间的规整梯度下,找出对应的松弛模量的变化规律;在准确可靠表征HPAM溶液粘弹性的前提下,将松弛时间谱的个数减少为三个,降低了工程计算的难度。为改进HPAM溶液熟化配置单元,设计出一种螺旋翅片式节能桨,该搅拌桨主体支架为锚形,主体桨叶底部横梁为圆柱形,在搅拌桨两端桨叶紧贴圆管外壁增装螺旋翅片,螺旋翅片逆时针自两端圆管的底端旋转到达圆管的上端。螺旋翅片的这种空间旋转结构有利于流体的轴向流动,并且使待混合流体的轴向速度沿轴线分布均匀,实现了流体在整个搅拌槽内流场分布的优化,同时该搅拌桨降低了其在搅拌过程中的功率消耗,节约能源。采用数值模拟的方法研究了锚式桨和螺旋翅片式节能桨在牛顿流体以及其它不同流变指数的假塑性流体中的三维流场混合性能并进行分析对比,包括两种搅拌桨在不同高度处、不同雷诺数下、不同流变指数流体中的流场特性。对不同螺旋翅片间距以及搅拌桨直径d和搅拌槽直径D比值情况下的流场进行分析,计算获得锚式桨和不同几何尺寸螺旋翅片式节能桨的功率消耗曲线以及Metzner常数。结果表明,螺旋翅片式节能桨与锚式桨相比,促进了搅拌槽内流体的轴向和径向流动,减小了功率消耗,提高了全槽平均剪切速率。随着螺旋翅片间距的增大和d/D比值的减小,搅拌桨功率消耗降低,同时全槽平均剪切速率略有下降。
[Abstract]:Partially hydrolyzed polyacrylamide (HPAM) is one of the industrial products widely used in oilfield production. The dissolution process of HPAM is a maturation link in polymer flooding process. Now, high molecular weight HPAM solution is widely used in oil fields. The original configuration unit is inapplicable to the dissolution process, which leads to long time of dissolution and low agitation efficiency. It is easy to caking at the bottom of stirring tank, which directly affects the input quality of HPAM solution and the macro economic benefit of polymer flooding. In order to study the rheological properties of HPAM solution, the constitutive equations and flow control equations suitable for describing the rheological properties of HPAM solution are given, and a reasonable mathematical model of stirring flow field is established, a new type of mixing device is developed and the characteristics of flow pattern in mixing flow field are studied. It is of great theoretical significance to improve polymer flooding technology and enhance oil recovery. According to the viscoelastic experimental data of HPAM solution, the average standard deviation is used as the objective function and the KBKZ constitutive equation is combined. The relaxation time spectra with different molecular weight and different concentrations were fitted. Under the regular gradient of relaxation time between 10-2-103 s, the corresponding relaxation modulus was found, and the viscoelasticity of HPAM solution was accurately and reliably characterized. The number of relaxation time spectrum is reduced to three, and the difficulty of engineering calculation is reduced. In order to improve the configuration unit of HPAM solution ripening, a kind of helical wing blade type energy-saving propeller is designed, and the main support of the impeller is an anchor. The cross beam at the bottom of the main blade is cylindrical, and the blade at both ends of the agitator is attached to the outer wall of the pipe with spiral fins. The helical fin rotates counterclockwise from the bottom end of the tube to the upper end of the tube. This space rotation structure of the helical fin facilitates the axial flow of the fluid and makes the axial velocity of the fluid to be mixed evenly distributed along the axis. The flow field distribution in the whole tank is optimized and the power consumption of the impeller is reduced. Energy saving. The mixing performance of anchor propeller and helical fin propeller in Newtonian fluid and other pseudoplastic fluid with different rheological index were studied and compared by numerical simulation. The flow field characteristics of two kinds of impellers at different heights, different Reynolds numbers and different rheological exponents are analyzed. The flow field under different pitch of helical fin and the ratio of impeller diameter d to tank diameter D is analyzed. The power consumption curve and Metzner constant of the anchor propeller and the helical fin blade energy-saving propeller with different geometric sizes are obtained. The results show that the helical fin blade energy-saving propeller promotes the axial and radial flow of the fluid in the stirred tank compared with the anchor propeller. With the increase of the helical fin spacing and the decrease of D / D ratio, the power consumption of the impeller decreases, while the average shear rate of the full trough decreases slightly.
【学位授予单位】：沈阳理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.46;O631.4

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