Oil - water dispersed flow is one of the liquid - liquid two - phase main flow patterns encountered in pipeline operations, in which phase inversion will occur. The flow characteristics of the dispersion and pressure drop change abruptly and significantly at or near the phase inversion point, which will exert dramatically adverse influence on pipeline operations. In this paper three oil samples of different viscosities were used as test fluids. Data analysis showed that pressure gradient of three kinds of oil samples behaved differently in the phase inversion process, mainly reflected in the "climbing stage" and "leaping stage", at the phase inversion point under two different experiments (starting from water dominated mixtures gradually to oil dominated mixtures or reverse) and the O/W or W/O dispersions forming process. However, when far away from phase inversion point, pressure gradient exhibited slight difference. The effect of mixture flow rate on the ambivalent range depends on the viscosity of oil. At the same mixture flow rate, the ambivalent range decreased with viscosity increasing. Droplets changed their shapes after phase inversion and double dispersed system appeared in the water to oil dominated mixtures experiment.%油水分散流是液液两相流中的基本流型之一,在流动过程中会有反相现象发生.油水管道在反相点及其附近运行时,流动特性会发生改变,压降急剧增大,对管道的运行产生极不利影响.对三种不同粘度的油品的反相特性进行了研究.研究结果表明:不同粘度的油品反相时其压降特性不同,主要表现在“爬坡”和“跳跃”特性不同、在水到油与油到水实验反相时的压降梯度特性不同,形成油包水分散体时与水包油分散体时的压降梯度不同,而远离反相点处的压降梯度相差不大;混合流量对两相共存区的宽度的影响与油品的粘度有关；相同流量下,两相共存区的宽度随着粘度的增加而减小；反相前后液滴粒径形状不同,水到油实验中出现二次分散体.
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