低Weissenberg数黏弹性流体中单气泡上浮运动特性研究

使用VOF法数值研究了气泡在黏弹性流体中的上浮运动,黏弹性模型选用Oldroyd-B模型.在低Weissenberg数(Wi)下,研究了黏性力、松弛时间、表面张力和黏度比对气泡上浮运动的影响.结果表明,当黏性力和弹性力较大(如Ga=2,Wi≥0.5和β=0.2)时,气泡尾部会出现“尾缘尖”现象,“尾缘尖”现象随着弹性的增强和表面张力的减小变得明显;当弹性较弱(如Wi=0.1)时,“尾缘尖”现象消失,气泡呈为帽形;当表面张力较大(如Eo=1)时,气泡呈现为纵向拉长的椭圆形,尾部特征不明显;在黏弹性流体中,表面张力对气泡的影响与在黏性流体中的相似;气泡在上浮过程中,随形状的变化,表现出“持续加速到稳定”和“加速-减速-再加速到稳定”两种上浮形式,在黏弹性流体中,气泡的上浮速度高于在纯黏性流体中的上浮速度;气泡周围的弹性应力与流体的黏度和松弛时间有关,随着黏度的减小和松弛时间的增大,弹性应力作用范围变宽.

三氯化铁分解重铬酸钾滴定法测金属化球中金属铁和氧化亚铁的含量

针对目前金属铁各种测定方法存在的缺陷,建立了用三氯化铁分解重铬酸钾滴定法测定金属化球中金属铁和氧化亚铁的技术方法。通过对试样预处理条件的确定、滴定酸度控制、重铬酸钾标准溶液浓度的选择等方面进行分析,确定了最佳实验条件:样品重量0.1000 g,样品粒径<0.125 mm,搅拌时间40 min,氯化铁溶液浓度和用量分别为100 g/L和40 mL。对样品进行精密度考察和回收率实验,采用MSA法对方法进行评价,说明该方法快速简便,适用于日常检测。

Geochemical identification of coal-sourced oils and inter-bedded shale-sourced oils as revealed by compound specific carbon isotopic analysis

To date, questions remain as to how to differentiate between coal- and interbedded shale-sourced oils in coal measures. Based on the hypothesis that δ13C value of sedimentary organic matter is controlled by the depositional environment and productivities of biota grown in such depositional setting, this note examines compound specific carbon isotopic profiles from coal and interbedded shale extracts using the gas chromatography-isotope ratio mass spec-trometry technique (GC/IRMS). The results show that compound specific carbon isotope values from coal extracts are enriched in 13C relative to that of interbedded shale extracts, and provide useful information in characterizing coal- and interbedded shale-sourced oils in coal measures. An example for its successful application from the Turpan Basin, Northwestern China is presented.