非离子表面活性剂在水流中的减阻机理

Study of drag-reducing mechanism of nonionic surfactant in a water flow

为探讨非离子表面活性剂的减阻机理,在实验确认表面活性剂APG水溶液(Alkyl Polyglucoside)具有湍流减阻功效的基础上,对其剪切粘度、应力松弛特性以及剪切双折射效应,使用锥板流变仪及流动双折射测试仪进行了实验研究。最大减阻率可达70%的APG水溶液,其剪切粘度在低剪切速率区域表现为牛顿流体特性,在大于临界剪切速率区域表现为'SIS'(Shear-Induced Structure),呈现非牛顿流体特性;APG水溶液的剪切应力松弛特性与纯水基本相似,表明'SIS'并不具有粘弹性特性。由剪切双折射效应证实的的棒状胶束聚合结构和具有的较大拉伸粘度可认为是APG水溶液能够实现湍流减阻的主要原因。

To explore the mechanism of turbulent drag-reduction by adding non-ionic surfactants additives into a water flow, the shear viscosity, shear stress relaxation, and flow birefringence effects were experimentally investigated by a cone-plate rheometer and a birefringence de- vice, after experimentally identified the turbulent drag-reducing for APG （Alkyl Polyglucoside） solution in a circle pipe flow. APG solution showing to be drag-reducing up to 70%, has Newtonian shear viscosities at smaller shear-rates, non-Newtonian shear viscosities at larger shear rates, and it also shows SIS （Shear-Induced Structure） at a critical shear rate. The shear stress relaxation behavior is identical to that for water, which implies that APG solution is drag-reducing, but shows SIS rheological characteristics without viscoelastics. The rod-like micelles proved from the birefringent effects, and higher extensional viscosity could be considered to be essential for the drag-reduction.