共查询到19条相似文献,搜索用时 171 毫秒
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对磁性液滴在不互溶液体中的运动和接触传热特性进行了实验研究和理论分析,建立了磁性液滴在不互溶液体中运动的数学模型和传热关联式。实验结果表明,外加磁场对磁性液滴的流动和传热具有显著的强化作用。 相似文献
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本文对固着纯组分液滴的蒸发研究现状进行了综合评述。介绍了固着液滴蒸发的恒接触半径模式、恒接触角模式及混合模式,分析了完全润湿和部分润湿两种固着液滴的蒸发过程及其特点,系统讨论固着液滴的蒸发动力学理论规律,并对固着液滴蒸发的实验研究进行了简要介绍。 相似文献
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针对传统流动共聚焦法两相流注入结构复杂,外部封装体积大的问题,本文开展了毛细管中微液滴生成的相关技术研究,借助商品化T形管,提出了一种基于T形共流聚焦结构的液滴生成方法。该方法不但简化了两相流的注入结构,较好地解决了封装难的问题,而且便于对液滴生成的相关参数开展进一步研究。对于液滴生成的相关参数,本文深入研究了液滴生成中液滴尺寸、流速比和生成频率之间的关系;通过正交试验深入研究了流速比、出口锥角角度和出口管径对液滴均一性的影响,其影响的主次顺序为:锥角角度>流速比>出口管径,在最优参数锥角角度为4°,流速比190∶1,出口管径72μm的条件下,所生成液滴平均体积为8.3nL,生成频率0.7Hz,均一性0.011。 相似文献
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液滴生成的动力学过程和机理,对溶剂萃取、喷墨打印机设计、飞行器保护等有重要意义。虽然已有很多相关的实验、理论和计算研究,但对涉及拓扑变形界面的该问题研究仍富有挑战性,常用的有限元等模拟方法还有待改进。1988年提出的水平集(Level set)方法,可以比较简方便地模拟多相变形界面问题,已成功用于多相流、结晶、浇铸、模式识别等过程的计算。作者在对水平集方法进行改进并用于相间传质模拟的基础上,本文数值模拟了单个液滴在毛细管口的生长和脱离过程。假设流体均为不可压缩液体或气体作层流流动,采用二维轴对称欧拉坐标和交错网格,利用控制容积法和SIMPLE算法离散求解藕合水平集函数的运动方程组。水平集函数的发展方程和重新初始化方程的空间与时间离散格式,分别采用5阶WENO(Weighted essentially nonoscillatory)和3阶TVD(Total variation diminishing)Runge-Kutta格式。初步计算了不同参数的单液滴在气体或另一不互溶液体中的生成过程,液滴的拓扑形状、两相流场和液滴大小与实验或文献报道的模拟结果基本吻合,为今后拓展模拟三维空间的不稳定运动液滴或气泡生成过程的流动和传递奠定了基础。 相似文献
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研究了同轴微通道内水-硅油体系的液滴生成过程。在不同的连续毛细数Cac和分散相Weber数Wed下,观察到滴出流和喷射流两种不同的流型。实验考察了两相流量、黏度和内管结构对液滴尺寸和液滴生成频率的影响。结果表明液滴尺寸随着分散相流量增加而增大,而随着连续相流量和黏度的增加而降低。此外,随着Wed的增加,流型会从滴出流过渡到喷射流,而更大尺寸的内管会更早过渡到喷射流,从而得到更大的液滴尺寸。对于液滴生成频率,其随Cac和Wed的增加均呈现先快速增加后变缓的趋势。当内管通道尺寸基本相同时,不同结构的内管通道在固定Cac时其液滴生成频率相差不大,且随着通道尺寸的减小,液滴生成频率逐渐增加。基于实验结果,建立了液滴尺寸预测模型,预测值与实验值吻合较好。 相似文献
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双重液滴在化学、医学、食品科学、生命科学中有广泛应用.与传统方法相比,微流控芯片在生成双重液滴上具有较大优越性,因此应用前景极为广泛.本文对微流控芯片上形成双重液滴的方法进行了总结,比较了各种方法的优缺点. 相似文献
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高强电场中液滴的破碎 总被引:5,自引:1,他引:5
徐国华 《高校化学工程学报》1994,8(3):221-229
对高强电场中液滴的破碎进行了研究。提出了置于电介质连续相中的导电液滴在静电场中的受力模型,并通过实验对高强交变电场中影响液滴破碎的诸因素进行了研究。获得了诸因素在一定范围内对液滴破碎影响的规律,同时证明了静电场中液滴受力模型的合理性。 相似文献
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A numerical investigation of the unsteady motion of a deformed drop released freely in another quiescent liquid contaminated by surfactant is presented in this paper. The finite difference method was used to solve numerically the coupled time-dependent Navier-Stokes and convective-diffusion equations in a body-fitted orthogonal coordinate system. Numerical simulation was conducted on the experimental cases, in which MIBK drops with the size ranging from 1.24 mm to 1.97 mm rose and accelerated freely in pure water and in dilute sodium dodecyl sulphate (SDS) aqueous solution. The applicability of the numerical scheme was validated by the agreement between the simulation results and the experimental data. Both the numerical and experimental results showed that the velocitytime profile exhibited a maximum rising velocity for drops in SDS solutions, which was close to the terminal velocity in pure water, before it dropped down to a steady-state value. The effect of the sorption kinetics of surfactant on the accelerating motion was also evaluated. It is also suggested that introduction of virtual mass force into the formulation improved obviously the precision of numerical simulation of transient drop motion. 相似文献
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Magnetic ionic liquid‐water Janus droplets: Preparation,structure and morphology adjustment and magnetic manipulation 下载免费PDF全文
Peng Guo Changfeng Zeng Chongqing Wang Lixiong Zhang 《American Institute of Chemical Engineers》2017,63(9):4115-4123
Surfactant‐free magnetic ionic liquid (MIL)‐water Janus microdroplets with adjustable structures and morphologies are prepared in capillary‐based microfluidic devices. Their morphologies (e.g., sizes, curvatures of the interfaces, and structures from Janus to core/shell) can be adjusted in a wide range by changing the flow rate ratio of water to MIL, adding different mass fractions of polyethylene glycol in water, and using soybean oil rather than liquid paraffin as the continuous phase. MIL‐water‐MIL ternary Janus magnetic microdroplets with adjustable symmetric and asymmetric structures are also prepared. These Janus microdroplets can be manipulated by magnetic attraction, leading to easy formation of water‐MIL‐water, MIL‐water‐oil, necklace‐structured MIL‐water alternative Janus droplets as well as more complex Janus droplets, such as MIL‐CO2‐in‐water and MIL‐water‐water droplets. Such preparation strategy is simple and can be applied in fields like pharmaceuticals, multi‐drug chemotherapies, and catalysis with expensive materials. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4115–4123, 2017 相似文献
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Julia Schuler Laura Maria Neuendorf Kai Petersen Norbert Kockmann 《American Institute of Chemical Engineers》2021,67(2):e17111
Droplet generation in microfluidic devices has emerged as a promising approach for the design of highly controllable processes in the chemical and pharmaceutical industry. However, droplet generation is still not fully understood due to the complexity of the underlying physics. In this work, micro-computed tomography is applied to investigate droplet formation in a circular channel in a co-flow configuration at different flow conditions (Ca < 0.001). The application of an in-house developed scanning protocol assisted by comprehensive image processing allows for the time-resolved investigation of droplet formation. By tracking different droplet parameters (length, radii, volume, surface, Laplace pressure) the effect of flow conditions on droplet progression is determined. As characteristic for the squeezing regime, final droplet size was nearly independent of Ca for higher Ca tested. For lower Ca, the final droplet size increased with decreasing Ca, which points to the leaking regime that was recently introduced in the literature. 相似文献
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Shenglin Yan Yan Zhang Chong Peng Xiaoyong Yang Yuan Huang Zhishan Bai Xiao Xu 《中国化学工程学报》2022,45(5):229-237
Flotation is an efficient pre-treatment technology for oily water. In this work, the interaction process between the moving oil droplet and the gas bubble was studied by high-speed camera and Bassset-Boussinesq-Oseen (BBO) theoretical model, and the experimental and simulation results of the oil droplet trajectory were compared. Moreover, the micro-particle image velocimetry system was utilized to observe the flow inside and outside of the moving oil droplet. The results show that the BBO model with the mobile bubble’s surface can reflect the velocity change trend of the oil droplet during the interaction process between the moving oil droplet and the gas bubble, but there are some significant differences between the experimental and simulation results. While the oil droplet is moving on the bubble’s surface, the velocity of the area near the contact point of oil droplet–gas bubble is less than that of the other areas inside the oil droplet. Meanwhile, the flow of water above the oil drop is more biased towards the gas bubble. 相似文献
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采用VOF方法模拟了液滴以相同速度撞击到接触角分别为63°、90°、118°和160°的固体壁面上的形态演变过程。结果表明:固壁的亲憎水性对液滴撞击表面后形态的演化有较大影响,亲水壁面有利于液滴的铺展,在接触角为90°的壁面上液滴部分反弹,而当接触角为160°时,液滴完全反弹;当三相接触线开始回缩时,中心液体的表层部分在惯性力的作用下继续向铺展的液滴边缘聚集,导致近中心处液膜逐渐减薄至断裂,最终形成边缘较厚的液环;同时,液滴最大铺展系数随壁面接触角的增大而减小,达到最大铺展系数的时间也相应缩短。 相似文献
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利用高速摄像机研究了不对称T型微通道内液滴的无阻塞破裂过程。以甘油-水溶液为分散相,含4%(质量分数)表面活性剂Span-20的矿物油为连续相。液滴的无阻塞破裂过程可分为三个阶段:进入阶段、形变阶段和破裂阶段。其中破裂阶段又可分为快速破裂阶段和细丝破裂阶段两个子阶段。考察了表观流速、无量纲液滴长度和两相黏度比对破裂阶段的影响。结果表明:快速破裂阶段是一个自相似过程,无量纲颈部最小宽度与无量纲剩余时间呈幂律关系,幂律指数约为1.35。细丝破裂阶段无量纲最小颈部宽度与无量纲剩余时间呈线性关系。斜率随着表观速度和无量纲液滴长度的增大而增大,随两相黏度比的增大而减小。 相似文献
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利用高速摄像仪研究了截面为400 μm×400 μm Y聚焦型微通道内磁流体液滴在矿物油中的生成过程。以水基磁流体EMG 807为分散相,含4%表面活性剂Span-20的矿物油为连续相。实验观察到了3种流型:弹状流、滴状流和喷射流。分别考察了两相流量、连续相毛细数及磁感应强度对液滴尺寸及生成过程的影响。结果表明:可通过改变两相流量及磁场调控液滴尺寸。当分散相流量不变时,液滴尺寸随着两相流量比的增加而减小。液滴尺寸随着连续相毛细数及磁感应强度的增加而减小,随着分散相流量的增加而增加。以两相流量比、连续相毛细数和磁Bond数为参数提出了一个液滴尺寸的关联式,预测值与实验值吻合良好。 相似文献
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Hao Zhou Shan Jing Qi Fang Shaowei Li Wenjie Lan 《American Institute of Chemical Engineers》2017,63(9):4188-4200
The lack of experimental data for the droplet breakup has been one of the limitations for the application of population balance model (PBM). In this work, a high‐speed camera was used to directly measure the droplet breakup frequency and daughter size distribution in a pulsed disc and doughnut column. It was found from the captured video that multiple breakup events were more frequently observed than binary breakup. The multiple breakup was treated as an original breakup and several intermediate breakups to characterize the process quantitatively. The effects of pulsation intensity, dispersed phase flow rates, and the spatial locations were investigated in detail. Empirical correlations were finally established for both the breakup frequency function and the daughter droplet size distribution function and fitted well with the experimental data. The correlation equations were then used in a simplified PBM to calculate the droplet number density, which further proved the feasibility of the correlations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4188–4200, 2017 相似文献
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Size distribution of droplets above a rotating stream tray and model of droplet motion therein 总被引:1,自引:0,他引:1
Droplet size distributions have been investigated with a two-probe system above a rotatingstream tray of 300 mm diameter.The measured distributions are found to follow the upper limitedlognormal distribution with three parameters dependent primarily on gas hole F-factor.A probabilitymethod is used to describe the initial state of the droplet population above the tray,and a model fordroplet motion is presented.The results computed with model agree well with experimental data. 相似文献