Drag reduction in turbulent pipeline flow of mixed nonionic polymer and cationic surfactant systems

Turbulent drag reduction behaviour of a mixed nonionic polymer/cationic surfactant system was studied in a pipeline flow loop to explore the synergistic effects of polymeric and surfactant drag reducing additives. The nonionic polymer used was polyethylene oxide (PEO) at three different concentrations (500, 1000, and 2000 ppm). The surfactant used was cationic octadecyltrimethylammonium chloride (OTAC) at concentration levels of 1000 and 2500 ppm. Sodium salicylate (NaSal) was used as a counter‐ion for the surfactant at a molar ratio of 2 (MR = Salt/OTAC = 2). Relative viscosity and surface tension were measured for different combinations of PEO and OTAC. While the relative viscosities demonstrated a week interaction between the polymer and the surfactant, the surface tension measurements exhibited negligible interaction. The pipeline results show a considerable synergistic effect, that is, the mixed polymer–surfactant system gives a significantly higher drag reduction (lower friction factors) as compared with pure polymer or pure surfactant. The addition of surfactant to the polymer always enhances drag reduction. However, the synergistic effect in mixed system is stronger at low polymer concentrations and high surfactant concentrations. © 2011 Canadian Society for Chemical Engineering     

Time‐series and extended Karhunen–Loève analysis of turbulent drag reduction in polymer solutions

Direct numerical simulations and statistical analysis techniques are used to study the drag‐reducing effect of polymer additives on turbulent channel flow in minimal domains. Additionally, a new formulation of Karhunen–Loève decomposition for viscoelastic flows is introduced, allowing the dominant features of the polymer stress fields to be characterized. In minimal channels, there are intervals of “active” and “hibernating” turbulence that display very different structural and energetic characteristics; the present work illustrates how the statistics of these intervals evolve over the entire range of drag reduction (DR) levels. The effect of viscoelasticity on minimal channel turbulence is twofold: first, it strongly suppresses the active turbulent dynamics that predominate in Newtonian flow and second, at sufficiently high Weissenberg number it stabilizes the dynamics of hibernating turbulence, allowing it to predominate in the maximum drag reduction regime. In this regime, the stress fluctuations become delocalized from the wall region, encompassing the entire flow domain. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1460–1475, 2014     

阳离子型表面活性剂与聚合物复配体系协同减阻作用

为探究阳离子型表面活性剂和聚合物复配体系的协同减阻作用,以阳离子型表面活性剂十六烷基三甲基氯化铵（CTAC）和聚合物聚丙烯酰胺（PAM）为研究对象,设计搭建多功能湍流减阻实验测试装置,实验分析聚合物离子类型对复配体系协同减阻的影响,优选复配体系,进一步研究复配体系协同减阻作用随表面活性剂浓度、聚合物浓度、温度的变化规律。实验结果表明：CPAM-CTAC/NaSal复配体系协同减阻作用>AmPAM-CTAC/NaSal复配体系协同减阻作用>NPAM-CTAC/NaSal复配体系协同减阻作用>APAM-CTAC/NaSal复配体系协同减阻作用。CPAM-CTAC/NaSal复配体系的协同减阻作用在CTAC/NaSal浓度达到聚合物饱和浓度（PSP）0.3g/L时到达顶峰,平均减阻效率高达69.22%;当CTAC/NaSal浓度增加至0.5g/L后,平均减阻率迅速减小至10.08%,复配体系的临界广义雷诺数亦迅速降至7535.20,抗剪切性减弱。随着CPAM浓度由0.05g/L增加到0.2g/L,减阻破坏区减阻率可由9.08%增加至57.49%,临界广义雷诺数由31272.43增加到45033.36,抗剪切性增强;当CPAM浓度超过第二临界缔合浓度（CAC Ⅱ）0.15g/L后,减阻破坏区减阻率增加趋势及抗剪切性增强趋势均变缓。此外,相较于单一减阻剂,复配体系耐温性显著增强,55℃时最大减阻率增至69.05%。     

Interfacial properties of cationic and anionic Gemini surfactant mixtures

The possibility and the prospect of cationic/anionic (“catanionic”) surfactant mixtures based on sulfonate Gemini surfactant (SGS) and bisquaternary ammonium salt (BQAS) in the field of enhanced oil recovery was investigated. The critical micelle concentration (CMC) of SGS/BQAS surfactant mixtures was 5.0 × 10⁻⁶ mol/L, 1–2 orders of magnitude lower than neat BQAS or SGS. A solution of either neat SGS or BQAS, could not reach an ultra-low interfacial tension (IFT); but 1:1 mol/mol mixtures of SGS/BQAS reduced the IFT to 1.0 × 10⁻³ mN/m at 100 mg/L. For the studied surfactant concentrations, all mixtures exhibited the lowest IFT when the molar fraction of SGS among the surfactant equaled 0.5, indicating optimal conditions for interfacial activity. The IFT between the 1:1 mol/mol SGS/BQAS mixtures and crude oil decreased and then increased with the NaCl and CaCl₂ concentrations. When the total surfactant concentration was above 50 mg/L, the IFT of SGS/BQAS mixtures was below 0.01 mN/m at the studied NaCl concentrations. Adding inorganic salt reduced the charges of hydrophilic head groups, thereby making the interfacial arrangement more compact. At the NaCl concentration was above 40,000 mg/L, surfactant molecules moved from the liquid–liquid interface to the oil phase, thus resulting in low interfacial activity. In addition, inorganic salts decreased the attractive interactions of the SGS/BQAS micelles that form in water, decreasing the apparent hydrodynamic radius (D_{H, app}) of surfactant aggregates. When the total concentration of surfactants was above 50 mg/L, the IFT between the SGS/BQAS mixtures and crude oil decreased first and then increased with time. At different surfactant concentrations, the IFT of the SGS/BQAS mixtures attained the lowest values at different times. A high surfactant concentration helped surfactant molecules diffuse from the water phase to the interfacial layer, rapidly reducing the IFT. In conclusion, the cationic-anionic Gemini surfactant mixtures exhibit superior interfacial activity, which may promote the application of Gemini surfactant.     

Smart anionic polyelectrolytes based on natural polymer for complexation of cationic surfactant

The thermosensitive polyelectrolytes were obtained by grafting 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) onto hydroxypropylcellulose (HPC), a biodegradable polysaccharide. The interactions of the polymers with dodecyltrimethylammonium chloride (DTAC), a model cationic surfactant, were studied. It was found by the measurements of the surface tension and the analysis of fluorescence emission of pyrene used as a fluorescent probe, that the HPC–AMPS graft polymers strongly interact with DTAC with the formation of polymer–surfactant complexes. The critical aggregation concentrations of these polymer–surfactant systems were found to be of the order of 10^?5 mol/dm³. The polymers were found to be potentially useful in the purification of water from cationic surfactants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2401–2407, 2006     

Adsorption of cationic/nonionic surfactant mixtures on polyester

Experiments were performed to characterize the adsorption of the cationic surfactant benzalkonium chloride (BZK) on polyester as well as measure the effect of the cationic surfactant on polyester surface charge. Additional studies were performed to examine the effect of adding nonionic surfactants on surface charge. In studies of adsorption of BZK on polyester, different behaviors were observed at pH values 6 and 10, with adsorption reaching a maximum at pH 10 but not at pH 6. In probing the zeta potential and isoelectric point (IEP) of polyester exposed to solutions composed of BZK (cationic surfactant) and an ethoxylated alcohol (nonionic surfactant), it was seen that the IEP could be shifted to higher pH levels by increasing the mole fraction of nonionic surfactant in a cationic/nonionic surfactant solution. A maximum in the IEP was obtained at a certain mole fraction for most cases. The shift in the IEP was hypothesized to be driven by increased deposition of the cationic, since the nonionic itself did not significantly change the IEP. The cooperative interactions between cationic and nonionic species were theorized to be driven not so much by attractive interactions, but other interactions, such as minimization of cationic charge repulsion.     

添加盐对Gemini阳离子表面活性剂溶液的影响

通过流变学方法研究了水杨酸钠(NaSal)对Gemini阳离子表面活性剂2-羟亚丙基-1,3-双(二甲基十二烷基氯化铵)(以12-3(OH)-12(2Cl)表示)水溶液黏弹性能的影响。结果发现,无机盐诱导12-3(OH)-12(2Cl)产生盐析作用,而NaSal可促使胶束生长;在固定n(NaSal)/n(12-3(OH)-12(2Cl))=0.6,12-3(OH)-12(2Cl)质量摩尔浓度较低时,溶液的黏度很小;随12-3(OH)-12(2Cl)质量摩尔浓度增加,溶液黏度明显增大并显示Maxwell流体行为;溶液的零剪切黏度(η_0)随12-3(OH)-12(2Cl)质量摩尔浓度增加有一个最大值出现,是因为体系中12-3(OH)-12(2Cl)的阳离子和水杨酸根(Sal~-)反离子形成的氢键使棒状胶束之问相互连接,导致网络结构形成;测定的晶体结构验证了分子间氢键的形成。     

Surface remobilization of buoyancy-driven surfactant-laden drops at low reynolds and capillary numbers

It is well known that the terminal velocity of a drop settling in a viscous fluid is impacted by surface tension gradients. These gradients can develop because of nonuniform accumulation of surfactant on the surface as a result of a number of transport mechanisms. Here, a surfactant transport model based on a sorption-limited Frumkin framework is used to describe surfactant transport in the presence of both surface convection and diffusion at low Reynolds and capillary numbers. Constants characterizing surfactant transport in the Frumkin framework are experimentally determined and used to predict aqueous drop velocities with varying surfactant concentrations and volumes. Computation is carried out by satisfying equations governing mass, momentum, and interface species conservation. Experiments demonstrate qualitative and quantitative agreement between predicted and measured drop velocities. It is shown that surface remobilization explains some observed trends in measured velocity as the drop size decreases. © 2018 American Institute of Chemical Engineers AIChE J, 65: 294–304, 2019     

阳离子型Gemini表面活性剂对交联聚合物溶液性质的影响

采用核微孔滤膜过滤实验、落球粘度计及动态光散射法,研究了阳离子型Gemini表面活性剂对交联聚合物溶液(LPS)的封堵性能、粘度及交联聚合物线团(LPC)大小的影响。结果表明,加入50 mg/L和100 mg/L的Gemi-ni表面活性剂后,LPS对核微孔滤膜的封堵性能增加,但是当Gemini表面活性剂质量浓度为200 mg/L时,LPS对孔径为1.2μm的核孔膜的封堵性能变化不大。LPS-Gemini表面活性剂复合体系的粘度低于不加表面活性剂的交联聚合物溶液。动态光散射法测得LPS-Gemini表面活性剂复合体系中LPC的平均流体力学半径为180 nm,比不加表面活性剂的LPS中的LPC的粒径小。     

Effect of a non-ionic surfactant on skin-retention of cationic minoxidil microparticles suspended in an anionic surfactant solution

The effect of Brij 78, a nonionic surfactant, on the interactions between cationic minoxidil (MXD) microparticles and sodium lauryl ether sulfate (SLES) in an aqueous phase was investigated. Cationic MXD microparticles were prepared by high pressure homogenization, where distearyldimethylammonium chloride (DSDMAC) was used as a cationic dispersant. The positive surface charge of MXD microparticles was neutralized at the equimolar ratio of SLES/DSDMAC and became negative in the presence of excess amount of SLES, whether Brij 78 was included in the MXD suspensions or not. On the other hand, when nonionic surfactant was included in the suspension so that the molar ratio of Brij 78/DSDMAC was 0.063: 1, the suspension of the cationic microparticles was stable in terms of turbidity change even in the presence of excess amount of SLES. It means that while electrostatic interactions between DSDMAC and SLES were occurring, the aggregation of cationic MXD microparticles was prevented with the aid of Brij 78. Due to the cationic microparticle-stabilizing effect of Brij 78 in the presence of the anionic surfactant, the substantivity of the cationic MXD microparticles having Brij 78 was about two times higher than that of the microparticles without the nonionic surfactant.     

Characteristic time scales for predicting the scalar flux at a free surface in turbulent open‐channel flows

The purpose of this study is to predict the turbulent scalar flux at a free surface subject to a fully developed turbulent flow based on a hydrodynamic analysis of turbulence in the region close to the free surface. The effect of the Reynolds number on turbulent scalar transfer mechanisms is extensively examined. A direct numerical simulation technique is applied to achieve the purpose. The surface‐renewal approximation is used to correlate the free‐surface hydrodynamics and scalar transport at the free surface. Two types of characteristic time scales have been examined for predicting turbulent scalar flux. One is the time scale derived from the characteristic length and velocity scale at the free surface. The other is the reciprocal of the root‐mean‐square surface divergence. The results of this study show that scalar transport at the free surface can be predicted successfully using these time scales based on the concept of the surface‐renewal approximation. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Dynamic salinity-induced phase-inversion conductivity measurements used to characterize alcohol ethoxylate based surfactant/oil/water systems

Dynamic conductivity measurements proved to be an effective and rapid method to determine the optimal experimental conditions for a salinity-induced phase-inversion from surfactant/oil/water (SOW) systems consisting of nonionic surfactants, more specifically alcohol ethoxylates. This emerging methodology can be used as a rapid screening tool to determine the impact of alcohol ethoxylate surfactants in a SOW solution and was demonstrated to be not only repeatable, but highly comparable to the traditional static method, in which the solutions are added to flat bottom tubes and allowed to equilibrate at a given temperature for extended time periods. Given a set of experimental conditions (oil-type, temperature, etc.), these dynamic salinity-induced phase-inversion (Dy-SPI) conductivity measurements can be used to determine the optimal salinity (S*) for a given surfactant at a set concentration, as well as its characteristic curvature via a series of experiments with varying oil types. Additionally, Dy-SPI was used to confirm the previously observed inverse relationship between the concentration of an alcohol ethoxylate and S* under a given set of conditions. What makes this method so unique is the amount of time (30 min to 1 h) and the simplicity of the equipment needed for these Dy-SPI conductivity measurements, allowing for a rapid screening tool for these SOW parameters.     

工业水处理表面活性剂的减阻性能研究

为了探讨将工业水处理表面活性剂作为循环水管道减阻剂使用的可行性,用旋转黏度计对十二烷基二甲基苄基氯化铵杀菌灭藻剂和椰油酸二乙醇酰胺缓蚀阻垢剂组成的多功能减阻剂配方进行了初步筛选,然后在室内模拟环道评价装置上进一步评价。当循环水中减阻剂质量浓度为1.2g/L和循环水流速为2.55m/s时减阻率为52.3%。     

Influence of polymer on dynamic interfacial tensions of EOR surfactant solutions

The effects of different types of polymers, partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM), on dynamic interfacial tensions (IFTs) of surfactant/model oil systems have been investigated by the spinning drop method in this article. Two anionic surfactants, 1,2‐dihexyl‐4‐propylbenzene sulfonate (366), 1,4‐dibutyl‐2‐nonylbenzene sulfonate (494) and an anionic–nonionic surfactant octyl‐[ω‐alkyloxy‐poly(oxyethylene)]yl‐benzene sulfonates (828) with high purity were selected as model surfactants. The influences of polymer concentration on IFT were expounded. It was found that the addition of polymer mostly results in increasing IFT because the interfacial molecular arrangement is modified owing to the interaction between polymer and surfactants. For HPAM, the polymer chains will enter the surfactant adsorption layer to form mixed‐adsorption layer. Therefore, HPAM shows strong effect on surfactant molecules with large size, such as 366. Conversely, surfactants can interact with the hydrophobic blocks of HMPAM and form mixed micelle‐like associations at interface. As a result, HMPAM shows more impact on IFT of 494 due to small steric hindrance for the formation of interfacial associations. This mechanism has been ensured by 828 molecules with two long alkyl chains. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40562.     

气液界面Marangoni效应对传质系数的影响

在气液相际传质过程中,界面Marangoni湍动会对传质过程产生重要的影响,为此,建立了一套气液接触传质设备,以使得通过N2与异丙醇稀溶液逆流接触将液体中使表面张力降低的溶质解吸出来,从而引发Marangoni湍动,提高传质速率。发生Marangoni对流时,液相的传质系数比只依靠扩散传质而不考虑Marangoni效应时大,因此引出增强因子F这一概念,通过计算F的值即可判断Marangoni效应对传质速率影响的程度。提出了一个包括Marangoni准数的计算传质系数关联式,其计算结果与实验结果相符．     

Physico-chemical concept of drag reduction nature in dilute polymer solutions (the Toms effect)

The physicochemical concept of turbulent drag reduction (the Toms effect) integrates physicochemical characteristics of polymer solutions with hydrodynamic and rheological flow parameters into a generalized equation, where the increment in volumetric flow rate Q_P is a function of the external shear stress τ_w, temperature, volume of macromolecular coils with immobilized solvent V_c and a function of their volume fraction Ψ = C · [η]/(1 + C · [η]). The Q_P depends on the coil intrinsic elasticity [G] = kT/V_c as well. This model allows one: (1) to describe the Toms effect in terms of useful elastic work spent by macromolecular coils with immobilized solvent to overcome the frictional forces (i.e. the forces of intermolecular interactions), (2) to forecast the initial conditions of the Toms effect (τ_* ≈ (RT)/(M · [η])) and (3) to explain the unusual temperature dependence of the polymer solutions flow.     

盐对阴阳离子表面活性剂水溶液相行为的影响

以阴阳离子表面活性剂混合体系为研究对象,通过测定体系在不同种类盐溶液中的三元相行为,探索了盐对体系相行为中的双水相区位置及相区宽度的影响规律.研究发现,阴离子双水相区的位置与宽度主要受盐阳离子的影响,盐阳离子半径越大,极化率越高,阴离子双水相区向阴离子表面活性剂方向移动的趋势越大,相区越宽;而盐的阴离子是影响阳离子双水相区位置与宽度的主要因素.     

Experimental study of the role of the Weber and capillary numbers on Mesler entrainment

Mesler entrainment is the formation of a very large number of very small bubbles by a relatively low velocity drop impacting a liquid surface. The role of the Weber number in Mesler entrainment has received significant attention. However, the effect of the capillary number, which quantifies the relative importance of viscous and surface tension forces, has not been explored. This is due primarily to the fact that virtually all Mesler entrainment research has used a single liquid, water, as the working fluid. This, combined with certain experimental restrictions, makes difficult an independent variation of the Weber and capillary numbers. To address this problem, Mesler entrainment was investigated using two silicone oils, having kinematic viscosities of 0.65 cSt and 10.0 cSt, respectively, revealing the effect of the capillary number on Mesler entrainment, a result which has not been obtained heretofore. The silicone oils give extremely repeatable results when compared to water. © 2012 American Institute of Chemical Engineers AIChE J, 2012