表面活性剂湍流减阻研究进展

表面活性剂较高分子聚合物在流体管道输运中具有可逆机械降解特性的优点,更适用于存在高剪切的场合以及封闭的循环回路进行减阻,但存在对其复杂流变特性及减阻机理认识不完善的问题,使得其在减阻领域的应用受到了限制。本文回顾了作者近年来在表面活性剂溶液微观结构、复杂流变学特性、湍流结构以及其与减阻和传热性能之间的内在联系方面的研究进展;介绍了表面活性剂减阻和壁面微沟槽协同作用减阻的研究成果;指出通过拉伸流的方式能够在压损较小的情况下更有效地提高表面活性剂溶液的传热性能。针对表面活性剂现有研究的不足,本文提出4条建议作为表面活性剂的未来研究方向,分别为开发环境友好型高效表面活性减阻剂、强化换热装置的优化设计及优化布置、表面活性剂与其他减阻方式耦合特性的深入研究以及表面活性剂在尺度放大、防腐和减阻持久性方面的实际工业应用研究。     

提高表面活性剂减阻溶液传热研究进展

分析总结了表面活性剂减阻溶液的传热特性和提高传热特性的方法,介绍了各种方法提高传热的机理。对各种方法取得最佳效果作了比较,分析了各种方法的影响因素及优缺点。分析表明,表面活性剂溶液与水的温度分布不同,存在双热边界层,热阻不在近壁层,是在10<y⁺<100的过渡层;提高传热的方法可概括为破坏胶束结构、制造湍流和强化传热的过程。同时,对今后改善传热提出了自己的看法。     

减阻表面活性剂的研究进展

介绍了表面活性剂减阻的机理。探讨了影响表面活性剂减阻效果的各种因素,包括:表面活性剂与补偿离子的结构及其浓度、管路系统的直径、流体的温度和速度以及环境中的金属离子。论述了表面活性剂的减阻与传热效率之间的关系;并且讨论了在使用减阻表面活性剂的循环系统中提高传热效率的方法。总结了减阻表面活性剂的一般特点。预测了减阻表面活性剂的发展趋势。引用文献35篇。     

壁面微沟槽与表面活性剂耦合对管道中湍流减阻特性的影响

通过矩形管道压降实验研究了壁面微沟槽和表面活性剂的减阻性能及联合减阻的增益效果,用粒子成像测速仪分析了流场特性。实验所用的微沟槽为3种不同结构的顺流向V形沟槽,表面活性剂为十六烷基三甲基氯化胺(CTAC),水杨酸钠(NaSal)作为补偿离子。结果表明,壁面微沟槽和表面活性剂溶液均有减阻效果,二者耦合后减阻率进一步提升,最高减阻率为48.26%。微沟槽的减阻性能主要作用在近壁区,通过影响边界层平均流速、速度脉动强度和涡结构,减少表面活性剂的湍动能损耗。当超过表面活性剂的临界雷诺数后,沟槽尖端的高剪切力会加剧胶束结构分解。表面活性剂能抑制湍流涡的演变,扩大微沟槽有效减阻的雷诺数范围。     

一种新型两性界面活性剂的减阻特性

对一种新合成的两性界面活性剂N,N,N-三甲胺-N′-油酸酰亚胺在二维通道内的减阻特性进行了实验研究.为了能进行低温测试,以20%的甘醇不冻液为溶剂.溶液质量浓度范围为（5×10^-5）～（1×10^-3）,测试温度为-5℃和25℃.用粒子成像测速仪对减阻流动的湍流特性进行了测量.实验表明,这种新型界面活性剂溶液呈现明显减阻特性,且减阻特性与浓度和温度均有很大的关系,最大减阻值可高达83%.该界面活性剂中加入NaNO₂,在低温和低浓度条件下能有效改善减阻效果,而在常温和高浓度条件下反而降低减阻效果.添加界面活性剂抑制了湍流速度脉动和湍流涡脉动,使雷诺剪切应力完全消失.     

湍流边界层内表面活性剂减阻特性研究

湍流主要通过边界层流体与壁面的摩擦引起的,因此,研究表面活性剂的流向上边界层内湍流减阻性非常有意义,通过压降和粒子图像测速法分别研究了质量分数为10×10~(-6),50×10~(-6)和100×10~(-6)下的表面活性剂溶液与水的压降、范宁系数、减阻率、平均速度、速度分布云图、雷诺应力、涡量和涡量分布云图,实验发现:在表面活性剂的壁面范宁系数要比水时壁面的范宁系数要小,在质量分数为50×10~(-6)时减阻效果最好,最大减阻率为20%。得出结论:表面活性剂的加入使湍流边界层的厚度增加,雷诺切应力减小,在靠近管道的中心处的涡量最小,随着远离管道的中心,涡量缓慢地增大,近壁区的涡量降低,表面活性剂的减阻溶液的涡量比水的涡量稍微大一点,说明主要抑制管道中心区域的湍流强度来降低阻力,从而达到减阻效果。     

表面活性剂溶液与壁面纵向微沟槽协同减阻研究

采用直接数值模拟方法对表面活性剂溶液在不同尺寸宽肋矩形微沟槽通道内的湍流流动进行了数值模拟研究。结果表明表面活性剂溶液的减阻性能在合适尺寸的微沟槽通道内能进一步得到强化,同时微沟槽的最优减阻尺寸在表面活性剂溶液中也可以得到放大;表面活性剂溶液在微沟槽通道内的协同减阻强化效果是由微沟槽的“约束作用”和“尖峰作用”这两个主要因素相互博弈的结果。微沟槽尖峰处具有较高的剪切应力,槽谷内部剪切应力很小。当微沟槽能有效防止近壁湍流涡侵入槽谷内部,且又能对部分流向涡的展向运动起到较好的约束作用时,微沟槽将表现出减阻强化性能,反之则会出现增阻性能。微沟槽在槽谷内诱导的数量多、尺寸小且旋转强度弱的二次流向涡是其在表面活性剂溶液中能增大“约束作用”和发挥减阻强化性能的本质因素。     

表面活性剂溶液与壁面纵向微沟槽协同减阻研究

采用直接数值模拟方法对表面活性剂溶液在不同尺寸宽肋矩形微沟槽通道内的湍流流动进行了数值模拟研究。结果表明表面活性剂溶液的减阻性能在合适尺寸的微沟槽通道内能进一步得到强化,同时微沟槽的最优减阻尺寸在表面活性剂溶液中也可以得到放大;表面活性剂溶液在微沟槽通道内的协同减阻强化效果是由微沟槽的"约束作用"和"尖峰作用"这两个主要因素相互博弈的结果。微沟槽尖峰处具有较高的剪切应力,槽谷内部剪切应力很小。当微沟槽能有效防止近壁湍流涡侵入槽谷内部,且又能对部分流向涡的展向运动起到较好的约束作用时,微沟槽将表现出减阻强化性能,反之则会出现增阻性能。微沟槽在槽谷内诱导的数量多、尺寸小且旋转强度弱的二次流向涡是其在表面活性剂溶液中能增大"约束作用"和发挥减阻强化性能的本质因素。     

湍流减阻型聚/表复配体系分子自组装结构及机理的介观分子动力学模拟

采用粗粒化分子动力学模拟方法研究了聚合物/表面活性剂复配减阻添加剂的减阻微观结构及机理,并从分子动力学角度对聚集体的形成过程及其剪切稳定性和在剪切作用下的解体过程进行分析。结果表明：聚合物与表面活性剂(下文简称聚/表)分子间自组装聚集体随浓度升高呈现类“珍珠项链”—“桶珠项链”—“钢筋混凝土”结构的变化规律;复配体系内聚/表分子间的自组装是造成复配溶液减阻性能优于聚合物或表面活性剂单一体系的根本原因。因此,对于湍流减阻型聚/表复配体系的选取,应更侧重于选择聚/表分子间相互连接和组装能力强的体系。     

消防用PEO/OTAC/NaSal减阻体系的介观分子动力学分析

在全球能源紧张的背景下,“过程节能”手段的探索具有重要意义。消防工作在国民经济和社会发展中占据重要地位,将添加剂湍流减阻技术引进到消防系统,能提高消防水的射出速度和射程,在提高灭火效率的同时节省水泵功耗。根据消防水流特点,初步选定聚氧化乙烯/十八烷基三甲基氯化铵的聚合物/表面活性剂复配体系作为研究对象,借助介观分子动力学模拟手段,计算了此体系的抗剪切能力及表面张力。发现此体系的抗剪切能力较聚合物、表面活性剂单一体系有明显提升,且体系的表面张力较纯表面活性剂溶液有所提高,初步证明此体系适用于消防减阻。同时从分子动力学角度深入分析了复配体系内聚合物、表面活性剂分子之间的作用机制,可为进一步寻找适用于消防减阻的聚合物/表面活性剂复配添加剂体系提供理论指导。     

Research progress of physical properties of surfactant solutions

认知表面活性剂溶液物理特性是揭示表面活性剂强化沸腾换热机理的基础。本文以表面活性剂强化沸腾换热为背景,阐述了与沸腾换热密切相关的表面活性剂溶液相关物理特性的研究进展,包括表面活性剂溶液的静态表面张力、动态表面张力、黏度、润湿性能和溶解度等物理特性。最后,指出了目前表面活性剂溶液物理特性的研究不足,并对表面活性剂溶液物理特性的研究方法和研究内容进行了展望。     

THE EFFECT OF HETEROGENEOUS DRAG REDUCING SURFACTANT IN DRAG AND HEAT TRANSFER REDUCTION IN CRUDE OIL SYSTEMS

Pilot scale experiments have been performed to study the effect of a heterogeneous surfactant into the drag and heat transfer coefficient in crude oil pipelines. The effects of surfactant concentration, pipe diameter, Reynolds number and temperature were studied in this research program.

An extensive set of data was obtained for heat transfer and friction coefficients for a heterogeneous surfactant known as MDR-2000. A wide range of Reynolds numbers were covered and experiments were conducted for many different Prandtl numbers. All drag and heat transfer reduction experiments were performed in the same installation using the same measurement techniques which facilitates the assessment of the trends caused by the various parameters studied.

Typical results showed that the friction coefficient was reduced by half at the optimum concentration. While, the heat transfer coefficient was reduced even more dramatically.     

表面活性剂添加对歧管式微通道阻力特性的影响

歧管式微通道（MMC）热沉具有热阻小、结构紧凑、冷却液流量小、流速低、沿着流动方向温度分布均匀等优点,但其小尺寸所产生的较大压降却增加了泵功的损耗.本文研究了表面活性剂添加对其阻力特性的影响,实验选用了纯度为95%的阴离子表面活性剂十二烷基硫酸钠（SDS）和纯度为98%的新型绿色非离子表面活性剂烷基多糖苷（APG）作为减阻添加剂,浓度分别为100和300 mg·kg^-1,结果表明阻力减小率与流速和温度有关.在层流区内减阻效果不是特别明显;但是当流体进入紊流区后阻力减小率开始明显增大,尤其是进入充分发展的紊流区后减阻效果大大加强.此外,温度的提升也可增加阻力减小率,但添加SDS后减阻效果的改善却不及APG.通过对两种不同类型表面活性剂的实验比较,发现温度较高时APG比SDS具有更佳的减阻效果.     

SOME MOLECULAR EFFECTS IN DRAG REDUCTION: A SUMMARY†

Dilute solutions of high molecular weight polymers have drawn a great deal of interest in recent years because of their drag reducing characteristics. It is well-known now that a substantial reduction in turbulent frictional drag can be achieved with a very small amount of polymeric additives, usually only a few parts per million by weight (ppmw) in concentration. This unique phenomenon has offered a new dimension in the design development of new marine systems for higher speed, longer range, larger payload as well as possibly quieter machinery. Although the discovery of this turbulent drag reduction phenomenon may be traced back to Toms¹ and Mysels² in the 1940's, the U.S. Navy's exploration of the turbulent drag reduction effect did not begin until the pioneering effort of Hoyt and Fabula in the 1960's. ³ During a period of several years in the early 19707apos;s, an interdisciplinary group at the Naval Research Laboratory undertook an intensive basic research effort to study the effects of polymer molecular structure on turbulent drag reduction. Model compounds were synthesized in the laboratory, and their drag reducing properties characterized. Polymers including polyacrylamide and its derivatives, polyacrylic acid, poiyphosphate and association colloids have been investigated. In this report, an attempt is made to highlight some of the results from that program in a brief summary form.     

SYNERGISTIC EFFECTS OF ANIONIC SURFACTANT AND NONIONIC POLYMER ADDITIVES ON DRAG REDUCTION

Turbulent drag reduction (DR) behavior of mixed nonionic polymer and anionic surfactant solutions in water was studied in a pipeline set up to explore the synergic effects of mixed additives on DR. The concentration of polymer polyethylene oxide (PEO) was varied from 0 to 2000 ppm and the concentration of surfactant sodium dodecyl sulfate (SDS) was varied from 0 to 5000 ppm. The critical aggregation concentration (CAC), where the interaction between the polymer and the surfactant begins, and the polymer saturation point (PSP), where the polymer molecules become saturated with the surfactant, were determined using electrical conductivity and surface tension measurements. As the polymer concentration was increased the CAC decreased but the PSP increased. The relative viscosity showed a remarkable increase upon the addition of surfactant to the polymer solution due to extension of polymer chains caused by the formation of micelles on the backbone of the polymer molecules. The data exhibited a considerable increase in DR in the case of mixed polymer/surfactant systems. The percent reduction in friction factor was as high as 79 when 3000 ppm or more surfactant was added to the 500 ppm polymer solution. Furthermore, the drag reduction behavior of the polymer solution changed from so-called Type A to Type B. In Type A drag reduction, a transition from laminar to turbulent regime is observed with a clear-cut onset point. In Type B drag reduction, no transition or onset point is observed; the data fall on a gradual extension of the laminar line.     

SOME MOLECULAR EFFECTS IN DRAG REDUCTION: A SUMMARY†

Dilute solutions of high molecular weight polymers have drawn a great deal of interest in recent years because of their drag reducing characteristics. It is well-known now that a substantial reduction in turbulent frictional drag can be achieved with a very small amount of polymeric additives, usually only a few parts per million by weight (ppmw) in concentration. This unique phenomenon has offered a new dimension in the design development of new marine systems for higher speed, longer range, larger payload as well as possibly quieter machinery. Although the discovery of this turbulent drag reduction phenomenon may be traced back to Toms¹ and Mysels² in the 1940's, the U.S. Navy's exploration of the turbulent drag reduction effect did not begin until the pioneering effort of Hoyt and Fabula in the 1960's. ³ During a period of several years in the early 19707apos;s, an interdisciplinary group at the Naval Research Laboratory undertook an intensive basic research effort to study the effects of polymer molecular structure on turbulent drag reduction. Model compounds were synthesized in the laboratory, and their drag reducing properties characterized. Polymers including polyacrylamide and its derivatives, polyacrylic acid, poiyphosphate and association colloids have been investigated. In this report, an attempt is made to highlight some of the results from that program in a brief summary form.