截面积突然扩大的胶束减阻流的紊流基本特性

Fundamental Characteristics of Drag-reducing Micelle Solution Turbulent Flow Across Abrupt Expansion Pipe

为揭示胶束减阻水溶液突扩流的紊流基本特性,对质量分数分别为1×10^(-4)、4×10^(-4)的季铵盐CTAB稀薄水溶液通过一个横截面积比为1∶4的突扩管的流动局部阻力、阻力发展及压力分布特性进行了试验研究。结果显示,胶束减阻突扩流在紊流基本特性上与高分子减阻剂完全不同。当突扩进口流的雷诺数小于1.2倍的临界值时,突扩局部阻力损失系数以小于10%的量级小于纯水,压力恢复最大值大于纯水;当突扩来流大于1.2倍的临界值雷诺数时,突扩局部阻力损失略大于纯水,而压力恢复最大值与纯水基本相同。突扩进口为具有一定减阻效果的胶束减阻流,在突扩下游再次形成充分发展流所需要的压力恢复长度远大于纯水。突扩进口为暂时失去减阻效果的1×10^(-4)稀液流,于下游粗管内再次恢复稳定的减阻能力需要110倍下游管径。胶束稀液突扩流的上述紊流基本特性与胶束聚合结构的形成特性有关。

To reveal the fundamental characteristics of a drag-reducing micelle solution flowing turbulently in a suddenly expended pipe,the expansion loss coefficients,drag development and pressure distributions have been investigated experimentally in an expansion pipe with an area ratio of 1 : 4,using two weight concentrations of 1×10-4 and 4×10-4 of hexadecyl trimethyl ammonium bromide solutions. The drag-reducing micelle solutions in abruptly expanded pipes are different from drag-reducing polymer solutions in turbulent fundamental characteristics. At inlet Reynolds numbers of less than 1.2 times of the critical value,the pressure recovery maximum is greater than that for water,and the expansion loss coefficient is order of 90% of that for water,while at inlet Reynolds numbers greater than 1.2 times of the critical value,it is almost the same as for water,and the expansion loss coefficient is slightly above that for .*water Furthermore,the pressure recovery length required to regain a fully developed flow in the expansion pipe is well above that for water. For the 1×10-4 concentration of micelle solutions lost its drag-reducing ability in the upstream,110 times of the downstream pipe diameter is necessary for recovering a fully developed drag-reducing flow. It can be concluded that these characteristics are associated with the reforming time characteristics of the micelle shear-induced structure.