# 让旋转滴“静止”：为什么“自动锁定与位置控制”是精准测量超低界面张力的关键？ > **Keep the Spinning Drop Still: Why “Automatic Locking and Position Control” Is the Key to Precise Ultra-Low Interfacial Tension Measurement?** > [!question] **[[CNGTX 科学仪器]]** > [!SUMMARY] **编者按 | Editor's Note** > 在三次采油（EOR）和表面活性剂研发领域，将界面张力（IFT）降低至 $10^{-3}$ mN/m 以下是衡量化学驱油剂性能的“金标准”。然而，由于旋转滴界面张力仪（SDT）在高转速下对密度差和水平度极度敏感，液滴在毛细管内的轴向漂移成为了长期困扰实验人员的难题。本文深入解析了 **CNGTX 600/700 系列旋转滴界面张力仪（SDT）** 如何通过——“旋转滴位置进行自动锁定和调整的”发明专利技术，如同为液滴安装了“自动驾驶仪”，解决了旋转滴轴向漂移的问题。通过对比 CNGTX 的上一代经典产品 TX500C，揭示了新一代智能系统如何消除人工操作的误差与局限，确立了超低 IFT 测量的行业新标杆。 > > > In the fields of Enhanced Oil Recovery (EOR) and surfactant R&D, reducing Interfacial Tension (IFT) below $10^{-3}$ mN/m is the "gold standard" for evaluating chemical flooding agents. However, due to the extreme sensitivity of Spinning Drop Tensiometers (SDT) to density differences and levelness at high rotational speeds, the axial drift of droplets within the capillary has long been a vexing problem for researchers. This article provides an in-depth analysis of how the **CNGTX 600/700 Series Spinning Drop Tensiometer (SDT)** utilizes the invention patent technology of "automatic locking and adjustment of spinning drop position" to act like an "autopilot" for the droplet, effectively solving the problem of axial drift. By comparing it with CNGTX's classic previous-generation product, the TX500C, we reveal how this new generation intelligent system eliminates the errors and limitations of manual operation, establishing a new industry benchmark for ultra-low IFT measurement. ![[Image 1]] _The "Twin Pillars" of Accuracy in the CNGTX 600/700 Series_ ### 1. 理论基础：Vonnegut 方程与灵敏度分析 > **1. Theoretical Foundations: The Vonnegut Equation and Sensitivity Analysis** 超低界面张力测量方法基于 Bernard Vonnegut 在 1942 年建立的理论框架。理解 IFT 对实验参数的数学依赖性，**对于理解为什么 CNGTX 600/700 系列 的位置和速度控制不是锦上添花的功能，而是数据有效性的基本前提。** > The ultra-low interfacial tension measurement method is based on the theoretical framework established by Bernard Vonnegut in 1942. Understanding the mathematical dependency of IFT on experimental parameters is crucial **to understanding why the position and velocity control of the CNGTX 600/700 Series are not just icing on the cake, but a fundamental prerequisite for data validity.** #### 1.1 流体动力学平衡 > **1.1 The Hydrodynamic Equilibrium** 考虑一个低密度油滴浸没在水平毛细管中的高密度水性表面活性剂溶液中。当管绕其纵轴以角速度 $\omega$ 旋转时，离心力将密度较大的水相推向管壁，产生径向压力梯度。较轻的油滴被浮力推向中心（旋转轴）。随着 $\omega$ 增加，向心压力梯度挤压液滴，迫使其沿轴向伸长，最终在高速下转变为带有半球形端盖的圆柱体。 > Consider a drop of low-density oil immersed in a higher-density aqueous surfactant solution within a horizontal capillary tube. As the tube rotates about its longitudinal axis with angular velocity $\omega$, centrifugal force drives the denser aqueous phase toward the tube walls, creating a radial pressure gradient. The lighter oil drop is buoyed toward the center (the axis of rotation). As $\omega$ increases, the centripetal pressure gradient squeezes the drop, forcing it to elongate along the axis, finally transforming into a cylinder with hemispherical end-caps at high speeds. #### 1.2 Vonnegut 方程与误差传播矩阵 > **1.2 The Vonnegut Equation and Error Propagation Matrix** 当液滴的长度超过其直径的四倍时，界面张力 $\gamma$ 由 **Vonnegut 方程** 计算： > When the length of the drop is more than four times its diameter, Interfacial Tension $\gamma$ is calculated by the **Vonnegut Equation**: $\gamma = \frac{\Delta \rho \cdot \omega^2 \cdot R_{drop}^3}{4}$ 控制的关键性在对该方程进行灵敏度分析时变得显而易见。让我们对 $\gamma$ 关于可控变量 $\omega$ 和测量变量 $R_{drop}$ 进行微分。IFT 的相对误差 ($\frac{\delta \gamma}{\gamma}$) 大致是各分量相对误差与其指数缩放后的总和： > The criticality of control becomes evident when we perform a sensitivity analysis on this equation. Let us differentiate $\gamma$ with respect to the controllable variables $\omega$ and the measured variable $R_{drop}$. The relative error in IFT ($\frac{\delta \gamma}{\gamma}$) is roughly the sum of the relative errors of the components, scaled by their exponents: $\frac{\delta \gamma}{\gamma} \approx \frac{\delta (\Delta \rho)}{\Delta \rho} + 2 \frac{\delta \omega}{\omega} + 3 \frac{\delta R_{drop}}{R_{drop}}$ 这个方程向实验者揭示了一个可怕的现实： > This equation reveals a terrifying reality for the experimentalist: 1. **对半径的立方依赖 (**$R^3$**)：** 测量液滴半径时仅 1% 的误差就会导致计算出的 IFT 产生 **3% 的误差**。这给成像系统的分辨率和聚焦带来了巨大的负担。 > **Cubic Dependence on Radius (**$R^3$**):** A mere 1% error in measuring the drop's radius results in a **3% error** in the calculated IFT. This places an immense burden on the imaging system's resolution and focus. 2. **对速度的平方依赖 (**$\omega^2$**)：** 电机速度 1% 的波动会导致 IFT 产生 **2% 的误差**。然而，这种相互作用更为阴险。由于半径 $R_{drop}$ 是由 $\omega$ 物理决定的，速度波动会导致液滴“呼吸”（膨胀和收缩）。这种动态不稳定性会模糊图像边缘，同时增加 $\delta R_{drop}$。 > **Squared Dependence on Velocity (**$\omega^2$**):** A 1% fluctuation in motor speed results in a **2% error** in IFT. However, the interaction is more insidious. Since the radius $R_{drop}$ is physically determined by $\omega$, a fluctuation in speed causes the drop to breathe (expand and contract). This dynamic instability blurs the image edges, increasing $\delta R_{drop}$ simultaneously. 因此，旋转速度的不稳定性充当了误差的**双重倍增器**：它直接改变计算结果，_并且_降低了半径的光学测量质量。**CNGTX 600/700 系列** 通过精密的伺服控制消除了这一隐患。 > Thus, instability in rotational velocity acts as a **double multiplier** of error: it directly alters the calculation _and_ degrades the optical measurement of the radius. The **CNGTX 600/700 Series** eliminates this hazard through precise servo control. ![[Image 2]] _The Multiplier Effect of Error_ ### 2. 不稳定性的解剖：液滴为何漂移 > **2. The Anatomy of Instability: Why Drops Drift** 如果说速度控制解决了测量的_热力学_有效性，那么**位置控制**解决的就是_操作可行性_。老一代手动仪器（如早期 TX500 系列）用户最常抱怨的问题是液滴会游走，沿管轴向漂移并移出相机的视野。 > While velocity control addresses the _thermodynamic_ validity of the measurement, **position control** addresses the _operational feasibility_. The most frequent complaint among users of legacy manual instruments (like early TX500 series) is that the drop wanders, drifting axially along the tube and moving out of the camera's field of view. #### 2.1 轴向漂移的物理学 > **2.1 The Physics of Axial Drift** 在理想的宇宙中，水平旋转的完美圆柱形管不会对液滴施加轴向力。但在现实世界中，几个矢量共同作用导致液滴移动： > In an ideal universe, a perfectly cylindrical tube rotating horizontally would exert no axial force on the drop. In the real world, several vectors conspire to move the drop: 1. 重力倾斜（斜面效应）： 如果仪器没有完全水平，旋转管就像一个斜面。较轻的油滴有浮力；它想往“上”走。即使 $0.01^{\circ}$ 的微小错位也会产生平行于管轴的重力分量矢量： $F_{drift} = V_{drop} \cdot \Delta \rho \cdot g \cdot \sin(\theta)$ 考虑到周围水相的低粘度，即使这微小的力也能让液滴缓慢但不可避免地向管的较高一端蠕动。 > Gravitational Tilt (The Inclined Plane Effect): If the instrument is not perfectly leveled, the rotating tube acts as an inclined plane. The lighter oil drop is buoyant; it wants to go "up." Even a misalignment of $0.01^{\circ}$ creates a gravitational component vector parallel to the tube axis: > > $F_{drift} = V_{drop} \cdot \Delta \rho \cdot g \cdot \sin(\theta)$ > > Given the low viscosity of the surrounding water phase, even this minute force allows the drop to creep slowly but inevitably toward the higher end of the tube. 2. **热马兰戈尼对流：** 张力仪通常被加热以模拟油藏条件（$60^{\circ}$C 至 $90^{\circ}$C）。如果加热不完全均匀（例如管安装在轴承处的端部效应），就会产生热梯度。$\frac{dT}{dx}$ 导致密度梯度 ($\frac{d\rho}{dx}$) 和表面张力梯度 ($\frac{d\gamma}{dx}$)。这会引起本体流体流动（对流）和界面流动（马兰戈尼效应），沿轴线拖动液滴。 > **Thermal Marangoni Convection:** Tensiometers are often heated to simulate reservoir conditions ($60^{\circ}$C to $90^{\circ}$C). If the heating is not perfectly uniform (e.g., end effects where the tube mounts to the bearings), thermal gradients arise. $\frac{dT}{dx}$ leads to density gradients ($\frac{d\rho}{dx}$) and surface tension gradients ($\frac{d\gamma}{dx}$). This induces bulk fluid flow (convection) and interfacial flow (Marangoni effect), dragging the drop along the axis. 3. **机械振动：** 轴承永远不会完美。微振动可以整流为净运动，这种现象称为振动流化或漂移。 > **Mechanical Vibration:** Bearings are never perfect. Micro-vibrations can rectify into net motion, a phenomenon known as vibro-fluidization or drift. ![[Image 3]] _The Physics of Drop Drift_ ### 3. 极致稳定：CNGTX 600/700 系列核心专利技术的深度解构 > **3. Unmatched Stability: Deconstructing the Core Patent of the CNGTX 600/700 Series** 为了解决上述物理难题，CNGTX Scientific 开发了**“一种对旋转滴位置进行自动锁定和调整的控制系统及方法”**，并将其作为 CNGTX 600/700 系列 的核心引擎。这项技术并非简单的升级，而是通过**将人工智能检测、智能控制、精密机械设计与制造等跨专业技术进行有机结合**，将仪器从被动观测工具转变为主动控制系统。 > To solve these physical puzzles, CNGTX Scientific developed the **"Automatic locking and position adjustment control system for spinning drop tensiometer,"** implementing it as the core engine of the **CNGTX 600/700 Series**. This technology is not a simple upgrade but an **organic combination of cross-disciplinary technologies such as artificial intelligence detection, intelligent control, and precision mechanical design and manufacturing**, transforming the instrument from a passive observation tool into an active control system. #### 3.1 智能检测：人工智能旋转滴检测技术——眼睛 > **3.1 Intelligent Detection: Artificial Intelligence Spinning Drop Detection Technology — The Eye** 不同于传统的光电传感器，**CNGTX 600/700 系列** 采用先进的**人工智能旋转滴检测算法**。该模型经过大量不同形态（浑浊、乳化、极细长）液滴图像的训练，**具备了智能识别旋转滴的能力**。即使在原油与表面活性剂发生复杂相变、界面变得模糊不清时，AI 仍能精准识别液滴的质心坐标，误差控制在像素级别。这种智能检测手段赋予了仪器一双“慧眼”，能在复杂环境中精准捕捉目标。 > Unlike traditional photoelectric sensors, the **CNGTX 600/700 Series** employs an advanced **Artificial Intelligence Spinning Drop Detection Algorithm**. Trained on a vast number of droplet images of varying morphologies (turbid, emulsified, extremely elongated), this model **possesses the capability of intelligent rotating drop recognition**. Even when complex phase transitions occur between crude oil and surfactants, causing the interface to become blurred, the AI can still precisely identify the droplet's centroid coordinates with pixel-level accuracy. This intelligent detection endows the instrument with a "wise eye" capable of precisely tracking targets in complex environments. #### 3.2 自动锁定：智能控制算法——大脑 > **3.2 Automatic Locking: Intelligent Control Algorithm — The Brain** 系统内置的微控制器运行**智能控制算法**。它实时计算液滴当前位置与屏幕中心点的偏差（误差 $e(t)$），并预测漂移趋势。该算法不仅能纠正当前的偏差，还能通过积分项消除稳态误差，确保调整过程平滑、无震荡，避免因调节过猛导致液滴形态改变。这如同系统的大脑，时刻进行着精密的计算与决策。 > The built-in microcontroller runs an **Intelligent Control Algorithm**. It calculates the deviation (error $e(t)$) between the droplet's current position and the screen center point in real-time and predicts drift trends. This algorithm not only corrects current deviations but also eliminates steady-state errors through the integral term, ensuring a smooth and oscillation-free adjustment process that prevents droplet shape alteration due to aggressive regulation. This acts as the brain of the system, constantly performing precise calculations and decision-making. #### 3.3 位置控制：精密蜗轮蜗杆——肌肉 > **3.3 Position Control: Precision Worm Gear — The Muscle** 执行机构采用了专利设计的**蜗轮蜗杆（Worm Gear and Turbine）**传动结构。由步进电机驱动蜗杆，再带动连接样品管的水平摆动组件。 > The execution mechanism adopts a patented **Worm Gear and Turbine** transmission structure. A stepper motor drives the worm, which in turn moves the horizontal swing component connected to the sample tube. - **自锁特性：** 蜗轮蜗杆具有天然的机械自锁功能，这意味着在电机停止时，角度被绝对锁定，不会因震动而滑移。 > **Self-Locking Feature:** The worm gear has a natural mechanical self-locking function, meaning that when the motor stops, the angle is absolutely locked and will not slip due to vibration. - **高减速比：** 这种结构将电机的旋转转化为极微小的角度倾斜（微弧度级），实现了对液滴位置的微米级精细微调。 > **High Reduction Ratio:** This structure converts the motor's rotation into extremely minute angular tilts (micro-radian level), achieving micron-level fine-tuning of the droplet position. 这种高精度的传动机制与**高精度 CNC 数控转台（5轴加工中心）**中所使用的核心技术如出一辙。正如 CNC 机床需要在巨大的切削力下保持航空涡轮叶片的微米级定位精度一样，**CNGTX 600/700 系列** 利用这一机制在长达数天的实验中，“刚性”地锁死测量管的倾斜角度，彻底消除了由于震动或重力分量引起的任何机械回差与漂移。 > This high-precision transmission mechanism mirrors the core technology used in **High-Precision CNC Rotary Tables (5-Axis Machining Centers)**. Just as a CNC machine must maintain micron-level positioning of aerospace turbine blades under immense cutting forces, the **CNGTX 600/700 Series** utilizes this mechanism to "rigidly" lock the tilt angle of the measurement tube throughout multi-day experiments. This effectively eliminates any mechanical backlash or drift caused by vibration or gravitational components. ![[Image 4]] _The Intelligent Control Loop of the CNGTX 600/700 Series_ ### 4. 技术演进：从经典 TX500C 到新一代 CNGTX 600/700 系列旋转滴界面张力仪 > **4. Technological Evolution: From the Classic TX500C to the Next-Gen CNGTX 600/700 Series Spinning Drop Tensiometer** CNGTX-Scientific 的 **TX500C** 曾是行业内坚固耐用的入门级标杆产品，为无数实验室提供了可靠的数据。然而，随着超低 IFT 研究标准的提高，我们必须正视手动控制的物理局限性。**CNGTX 600/700 系列旋转滴界面张力仪** 的问世，代表了 CNGTX 自身产品线的重大演进，是品牌自我革新的体现。 > CNGTX-Scientific's **TX500C** has been a rugged, entry-level industry benchmark, providing reliable data for countless laboratories. However, as the standards for ultra-low IFT research have risen, we must face the physical limitations of manual control. The introduction of the **CNGTX 600/700 Series Spinning Drop Tensiometer** represents a significant evolution in CNGTX's own product line, embodying the brand's self-innovation. |对比维度 Comparison Dimension|经典款产品 (TX500C) Classic Model (TX500C)|CNGTX 600/700 系列 (智能系统) CNGTX 600/700 Series (Intelligent System)|演进价值 Evolutionary Value| |---|---|---|---| |**液滴跟踪** Drop Tracking|**依赖人眼**：操作员需时刻注视，易产生视觉疲劳。<br><br>**Human Eye**: Requires constant operator attention; prone to fatigue.|**AI 全时监控**：机器视觉 24 小时锁定，无视疲劳。<br><br>**AI Monitoring**: 24/7 locking by machine vision; fatigue-free.|从“人工值守”进化为“无人值守”。<br><br>Evolution from "manned" to "unmanned" operation.| |**位置调整** Position Adjustment|**手动旋钮**：响应滞后，手部微颤可能干扰液滴。<br><br>**Manual Knob**: Laggy response; hand tremors can disturb the drop.|**智能精密电机**：微弧度级响应，丝般顺滑。<br><br>**Intelligent Precision Motor**: Micro-radian response; silky smooth.|消除人为扰动，确保液滴处于热力学稳态。<br><br>Eliminates human disturbance, ensuring thermodynamic steady state.| |**数据完整性** Data Integrity|**断点风险**：夜间无人时液滴可能移出视野。<br><br>**Gap Risk**: Drop may drift out of view at night.|**连续曲线**：无论实验多久，液滴始终在中心。<br><br>**Continuous Curve**: Drop stays centered indefinitely.|能够完整捕捉长周期的吸附动力学过程。<br><br>Captures full long-cycle adsorption kinetics.| |**实验成功率** Success Rate|**受限**：液滴撞壁可能导致实验报废。<br><br>**Limited**: Wall collisions can ruin experiments.|**极高**：主动防撞，保护珍贵样品。<br><br>**Very High**: Active collision prevention protects samples.|极大提升了实验室通量和研发效率。<br><br>Drastically improves lab throughput and R&D efficiency.| ### 5. 技术效益：为超低 IFT 测量保驾护航 > **5. Technical Benefits: Safeguarding Ultra-Low IFT Measurement** 这项专利技术不仅是“方便”，更是“必要”。在 $10^{-5}$ mN/m 的超低张力下，液滴极度敏感，任何人为的粗暴调节都会导致液滴破裂或乳化。**CNGTX 600/700 系列** 通过智能控制解决了这一难题。 > This patented technology is not just "convenient," it is "essential." At ultra-low tensions of $10^{-5}$ mN/m, droplets are extremely sensitive; any rough manual adjustment can cause droplet rupture or emulsification. The **CNGTX 600/700 Series** solves this problem through intelligent control. - 像素级的重复性： CNGTX 600/700 系列 的智能锁定系统消除了操作员个体差异带来的误差。无论谁来操作，液滴都处于相同的光学中心，背景光照和边缘识别条件高度一致，确保了数据的可重复性。 > Pixel-Level Repeatability: The intelligent locking system of the CNGTX 600/700 Series eliminates errors caused by operator variability. No matter who operates it, the droplet is always at the same optical center, with highly consistent background lighting and edge detection conditions, ensuring data reproducibility. - 长效动态监测： 许多 EOR 聚合物体系需要 48-72 小时才能达到吸附平衡。CNGTX 600/700 系列 使得进行长周期的“马拉松式”测试成为可能，而无需担心第二天早上看到空空如也的屏幕。 > Long-Term Dynamic Monitoring: Many EOR polymer systems require 48-72 hours to reach adsorption equilibrium. The CNGTX 600/700 Series makes long-cycle "marathon" testing possible without the fear of waking up to an empty screen the next morning. ### 6. 应用场景：从实验室到油田 > **6. Application Scenarios: From Lab to Oilfield** - 三次采油（EOR）配方筛选： 快速评估成百上千种表面活性剂配方，自动剔除不稳定的体系，利用 CNGTX 600/700 系列 筛选出能稳定维持在 $10^{-3}$ mN/m 以下的“黄金配方”。 > Enhanced Oil Recovery (EOR) Formulation Screening: Rapidly evaluate hundreds of surfactant formulations, automatically weed out unstable systems, and use the CNGTX 600/700 Series to screen for "golden formulations" that can stably remain below $10^{-3}$ mN/m. - 微乳液相行为研究： 在中相微乳液形成过程中，液滴不仅拉长，还会伴随增溶现象导致体积变化。CNGTX 600/700 系列 的智能位置控制系统能适应这种动态变化，始终锁定核心观测区域。 > Microemulsion Phase Behavior Studies: During the formation of middle-phase microemulsions, droplets not only elongate but also change volume due to solubilization. The intelligent position control system of the CNGTX 600/700 Series adapts to these dynamic changes, always locking onto the core observation area. - 化学破乳剂性能测试： 捕捉破乳剂注入瞬间液滴界面的动态响应，记录从球形到扁平再到破裂的毫秒级过程。 > Chemical Demulsifier Performance Testing: Capture the dynamic response of the droplet interface at the moment of demulsifier injection, recording the millisecond-level process from spherical to flattened to rupture. ### 7. 结论：稳如磐石，方能确信真理 > **7. Conclusion: Only with Absolute Stillness Can You Be Certain of the Truth** 在科学仪器领域，真正的创新往往源于对细节的极致追求。**CNGTX 600/700 系列旋转滴界面张力仪** 所搭载的自动锁定和调整控制系统，不仅仅是一次硬件升级，它是对旋转滴测量方法论的一次完善。通过消除**液滴漂移的不确定性**，摒弃**人工干预的干扰**，我们赋予了科学家一种**掌控微观世界的定力**。 > In the field of scientific instrumentation, true innovation often stems from an unrelenting pursuit of detail. The **Automatic Locking and Adjustment Control System** equipped in the **CNGTX 600/700 Series Spinning Drop Tensiometer** is not just a hardware upgrade; it is a refinement of the methodology of spinning drop measurement. By eliminating the **uncertainty of droplet drift** and discarding the **disturbances of manual intervention**, we have endowed scientists with **unwavering control over the microscopic world**. 对于那些在该领域追求极致准确性的实验室而言，选择 **CNGTX 600/700 系列** 不仅仅是选择了一台仪器，更是选择了一种对实验数据负责的态度。因为在超低界面张力的世界里，只有**稳如磐石**，才能确信真理。 > For laboratories pursuing ultimate accuracy in this field, choosing the **CNGTX 600/700 Series** is not just selecting an instrument; it is choosing an attitude of responsibility towards experimental data. Because in the world of ultra-low interfacial tension, only by **achieving absolute stillness** can you be certain of the truth. > [!question] **[[CNGTX 科学仪器]]**