管内流动剪切对非牛顿原油作用规律及机理研究

发布时间：2018-01-23 15:01

本文关键词： 含蜡原油流动剪切紊流层流微观特性　出处：《中国石油大学(华东)》2015年硕士论文　论文类型：学位论文

【摘要】：本文利用自主搭建的带浮顶搅拌槽剪切系统和旋转流变仪分别模拟紊流剪切和层流剪切,并通过数码显微成像系统观测了剪切后原油蜡晶微观结构,旨在揭示相同能量耗散率作用下,不同流场结构的流动剪切对含蜡原油低温流变性影响规律的差异,希望对建立更科学的室内模拟热油管道剪切历史方法起到一定的指导作用。基于流场结构相似的特点,采用搅拌槽模拟管道内紊流流动,并设计了浮顶结构,有效地减少了剪切过程中原油轻组分的挥发,讨论了能量耗散率、剪切处理温度、剪切时间等三个影响因素对胶凝原油屈服值和动平衡应力的影响规律;计算了搅拌槽内流体的当量剪切速率,并在同轴圆筒流变仪中设定相同的实验步骤以及剪切速率,以剪切处理温度和能量耗散率为变量,对比两种流态预剪切后的原油在低温下触变特性和胶凝特性差异规律,发现层流剪切后的油样胶凝结构更强,触变特性较差。采用显微镜成像系统和图形处理软件分析了不同流态预剪切作用对含蜡原油蜡晶颗粒大小、形状、分布等结构特征的影响差异和微观变化,综合等积圆直径、圆度、分析维数、特征空隙长度、颗粒总数等五个微观参数解释了不同流态预剪切对原油微观蜡晶结构的作用机理,以及造成原油宏观低温流变性差异的原因。从本文实验结果看,单纯以能量耗散率或当量剪切速率为模拟量,不同脉动强度的紊流掺混剪切效果存在较大的差异(认为层流是脉动强度为零的紊流),因此有必要从其对流体内部分散相结构的研究入手,在搅拌槽实验装置的基础上,可以考虑引入紊流的涡旋尺度作为管流剪切历史评价标准的补充,从而更科学合理地模拟管道剪切历史。
[Abstract]:In this paper, turbulent shear and laminar shear were simulated by using the shear system of mixing tank with floating roof and rotary rheometer, respectively, and the microstructure of wax crystal after shearing was observed by digital microscopic imaging system. The purpose of this paper is to reveal the difference of the effect of flow shear of different flow field structures on the rheological properties of waxy crude oil at low temperature under the same energy dissipation rate. Based on the characteristics of similar flow field the turbulent flow in the pipe was simulated by mixing tank and the floating roof structure was designed. The volatilization of light components of crude oil in shear process is effectively reduced. The influence of three factors, such as energy dissipation rate, shear treatment temperature and shear time, on the yield value and dynamic equilibrium stress of cementitious crude oil are discussed. The equivalent shear rate of the fluid in the stirred tank is calculated, and the same experimental steps and shear rate are set in the coaxial cylinder rheometer. The shear treatment temperature and energy dissipation rate are taken as variables. Comparing the thixotropic characteristics and the gelling characteristics of the two kinds of pre-shearing crude oil at low temperature, it is found that the laminar flow shear oil sample has stronger cementing structure. Using microscope imaging system and graphic processing software, the influence of different flow state preshear on the size, shape and distribution of waxy crude wax grains was analyzed. Five microcosmic parameters, such as the diameter of equal product circle, roundness, analytical dimension, length of characteristic void and the total number of particles, are used to explain the mechanism of the effect of different flow state preshear on the microcrystalline structure of crude oil. According to the experimental results, the energy dissipation rate or equivalent shear rate is used as the simulation quantity. The shear effect of turbulent mixing with different pulsating intensity is quite different (it is considered that laminar flow is turbulent with zero pulsating intensity, so it is necessary to start with the study of the dispersed phase structure inside the fluid. On the basis of the experimental equipment of stirred tank, the vortex scale of turbulent flow can be considered as a supplement to the evaluation standard of shear history of pipe flow, so as to simulate the shear history of pipeline more scientifically and reasonably.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE832

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