Topology Chemical Process Research on the Condensing and Growing Phase Multi Micro Oil Droplets Based on Hydrodynamics

The hydrodynamic research about the droplet condensing of the multi phase liquid state on the surface of the coal glass and water discusses the deepening process of convex shape curve and the formation of S shape, and puts emphasis on describing the diagram formation method of the later. In the induction period the active diagram of the micro droplet is decided by pH value forming as convex shape diagram or S shape diagram. When pH value is above 4.0, the damage of convex shape diagram cannot be recovered, in that case produce S shape activity diagram. When pH value is equal to or above 12.0, the hard surface with alkali liquid state loses adhesion, so that the micro droplet condensing of the multi phase liquid state stops completely. The research result shows that the water cleaning conditions of getting rid of the oil micro droplets can be decided by the pH value.

Adhesion forces for water/oil droplet and bubble on coking coal surfaces with different roughness

Surface roughness plays a significant role in floatability of coal.In the present paper,coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements.The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness.The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning.Maximum adhesion forces between water and surfaces were 111.70,125.48,and 136.42μN when the roughness was 0.23,0.98,and 2.79 μm,respectively.In contrast,under a liquid environment,the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water.Maximum adhesion forces of increasing roughness were 97.14,42.76,and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48,145.84,and 121.02 lN between oil droplet and surfaces,respectively.Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.

An experimental study on oil droplet size distribution in subsurface oil releases

Oil droplet size distribution （ODSD） plays a critical role in the rising velocity and transport of oil droplets in subsurface oil releases. In this paper, subsurface oil release experiments were conducted to study ODSD under different experimental conditions in a laboratory water tank observed by two high-speed cameras in March and April 2017. The correlation formulas Oh=lO.2Re-~ and Oh=39.2Re-1 （Re represents Reynolds number and Oh represents Ohnesorge number） were established to distinguish the boundaries of the three instability regimes in dimensionless space based on the experimental results. The oil droplet sizes from the experimental data showed an excellent match to the Rosin-Rammler distribution function with determination coefficients ranging from 0.86 to 1.00 for Lvda 10-1 oil. This paper also explored the influence factors on and change rules ofoil droplet size. The volume median diameter d50 decreased steadily with increasing jet velocity, and a sharp decrease occurred in the laminar-breakup regime. At Weber numbers （We） 〈100, the orifice diameter and oil viscosity appeared to have a large influence on the mean droplet diameter. At 100〈We〈1 000, the oil viscosity appeared to have a larger influence on the relative mean droplet diameter.

Effect of Sealing Air on Oil Droplet and Oil Film Motions in Bearing Chamber

Beating chamber is one of important components that support aero-engine rotors and research on oil droplet and oil film motions is an important part of bearing chamber lubrication and heat transfer design. Consid- ering the pressure of sealing air is an important operating condition that affects the oil droplet and oil film mo- tions, the effect of sealing air pressure on airflow in bearing chamber is investigated in this paper firstly ; and then based on the air velocity and air/wall shear force, the oil droplet moving in core air, deposition of oil droplet im- pact on wall as well as velocity and thickness of oil film are analyzed secondly; the effect of sealing air pressure on oil droplet velocity and trajectory, deposition mass and momentum, as well as oil film velocity and thickness is discussed. The work presented in this paper is conducive to expose the oil/air two phase lubrication mechanism and has certain reference value to guide design of secondary air/oil system.

Behaviors of a micro oil droplet in an EHL contact

Oil-air lubrication supplies lubricants in the form of droplets to elastohydrodynamic lubrication (EHL)contacts,such as those in high-speed spindle bearings.However,there is a paucity of information related to understanding the lubrication behaviors of oil droplets within EHL contacts.In this study,behaviors of lubricant droplets,in terms of spreading around a static contact as well as passing through a roiling contact,were studied with an optical ball-on-disk EHL test rig.Influences of oil droplet size,viscosity,and surface tension on droplet spreading were examined.Lubricating film formation was also investigated when droplets traveled through the EHL contact region.The results indicated that droplet size and running speed significantly influenced film profiles.With increasing entrainment speeds,a small droplet passed through the contact without spreading and generated films with a significant depression in the central contact region.

混沌脉冲组电场作用下油中液滴的聚结特性

混沌脉冲组(CPG)电场可用于乳化液破乳,但是乳化液滴在油中的聚结特性尚不清楚。通过数值方法研究了油中液滴在混沌脉冲组电场中的聚结特性以及电场参数对液滴聚结过程的影响。结果表明:CPG电场作用下液滴聚结过程可分为6个阶段,各阶段的呈现与电场作用时间和电场休止时间相关,其中第Ⅲ阶段的持续时间对聚结时间影响较大;占空比影响液滴聚结过程的状态以及聚结时间;电场强度的增加对液滴聚结状态无显著影响,但明显缩短聚结时间,当电场强度从500 kV/m增加到700 kV/m,液滴聚结时间从0.400 s减小到0.152 s。研究液滴在CPG电场中的聚结特性能够为CPG电场在工业中的应用提供理论依据。

麻疯树油液滴微爆和蒸发特性试验

利用悬挂式液滴蒸发试验装置,结合高速背光成像技术,研究了麻疯树油液滴在高温环境(673、773、873、973和1073 K)下的微爆和蒸发特性,并对麻疯树油中的3种主要组分液滴的蒸发特性进行了分析.结果表明:麻疯树油液滴的微爆是由于内部组分的热解导致的,并且随环境温度的升高,其微爆强度增大.麻疯树油液滴在环境温度为673 K时,液滴稳定蒸发,蒸发过程包括初始膨胀阶段、平衡蒸发阶段和残留物蒸发阶段;在环境温度为773~1073 K时,液滴发生微爆,包含初始膨胀阶段、平衡蒸发阶段、微爆蒸发阶段和残留物蒸发阶段;当环境温度高于873 K时,首次观测到“蒸气羽流”和“蒸气云”现象,液滴蒸发速率大幅提高.

油水膜分离中高黏度油滴行为研究和影响因素分析

膜法分离油田采出废水中的重油组分是膜污染的重要影响因素,且不同膜分离条件下膜面附近的复杂油滴行为直接影响膜分离效果,所以研究膜面附近的高黏度油滴行为十分必要。基于实际油田采出废水物性数据的实验测定结果,采用耗散粒子动力学(DPD)方法结合高黏度油滴轨迹和油滴间相互作用能结果对油滴行为进行细化分析。结果表明,双油滴呈现掠过和聚并两大类行为,又可各分为三个行为阶段:油滴间排液、油滴接触和油滴复稳;双油滴间距和油滴与膜面间距的减小有助于油滴聚并,从而有利于油水分离,且油滴与膜面间距的减小会导致油滴碰撞后的位置更远离膜面;表面活性剂的存在阻碍油滴聚并,不利于油水分离,且离子型表面活性剂因其亲水头间的强排斥力而阻碍作用更强;第3油滴的存在会促进双油滴聚并,有利于油水分离,其促聚并程度受油滴碰撞角的影响。研究结果可为后续的油滴与分离膜相互作用及油水分离效果的研究提供依据,也可为油水膜分离条件的设置和技术优化提供理论支持。

驱油剂对无碱三元复合驱采出液乳化稳定性影响

为探究无碱三元驱油剂对于采出液乳化稳定的机理,为采出液处理提供依据。对游离水中含油量、油水动态界面张力、液滴界面寿命与油滴粒径分布状态及粒径随驱油剂含量的变化进行了研究。加入低浓度表面活性剂(100 mg/L)时,动态界面张力、界面寿命、油滴粒径均显著降低,水中含油量显著增加,随着表面活性剂浓度增加,动态界面张力、界面寿命、粒径、含油量变化均不明显;随着NaCl浓度上升,动态界面张力与界面寿命变化不明显,油滴粒径变大,水中含油量增加;随着聚合物浓度增加,动态界面张力与界面寿命变化不明显,对于油滴粒径与含油量出现双重作用。这表明表面活性剂与NaCl有利于乳化稳定,但表面活性剂作用远大于NaCl;低浓度聚合物不利于乳化稳定,随着浓度增加,有利于乳化稳定。

利用AFM探究聚合物和表面活性剂对油滴间稳定性的影响

采用原子力显微镜(AFM)探究水中油滴之间的相互作用,并考察了聚合物聚(4-苯乙烯磺酸钠)(PSS)和阴离子表面活性剂十二烷基硫酸钠(SDS)对油滴稳定性的影响。采用分子动力学模拟软件模拟了PSS和SDS在水中的相互作用。结果表明:在不含聚合物和表面活性剂的盐溶液中油滴容易聚并;当水溶液中加入100 mg/L的PSS会使油滴稳定,这主要是由于PSS吸附层提供了空间位阻,有效阻止了油滴之间的聚并作用;然而,100 mg/L PSS和0.1 mM/L SDS共存时会导致油滴再次聚并,这是因为PSS和SDS同时存在时,两者易形成团簇,只有少部分PSS吸附到界面,此时PSS无法形成有效的空间位阻,导致油滴在相互靠近时发生聚并,从而影响了水包油体系的稳定性。

重力场中油滴运动速度及聚合规律研究

由于油井中后期产量下降,注水开发技术得到广泛应用。为优化注入水水质、净化地层,需提高采出水中的油水分离效率。油水分离效率的高低取决于对油水两相运动规律的掌握及分离方法的正确应用。该研究在油滴运动理论的基础上,借助Fluent有限元模拟软件,对油滴在流场中的变形和聚并动态进行精细描述。通过实验测试重力场中黏度为5.7 mPa·s和54 mPa·s、直径为3.0~8.5 mm的油滴上升速度及其变形规律。研究结果表明:直径较大的油滴具有较大的加速度,并提前达到最大速度,其上浮过程中的变形系数随着油相黏度的增加逐渐增加。多个油滴的聚合及其速度主要受连续相的黏度变化影响。在原有油滴速度计算模型的基础上考虑了表面张力对油滴变形的影响,得到的新模型对油滴的速度计算误差为±7%,显著提高了油滴速度的计算精度。

油滴与高温固体壁面碰撞的流动与传热及飞溅特性

考虑油滴(油膜)/固体壁面接触角动态变化和油液热力学特征参数受温度影响,基于流体体积法建立了油滴与高温固体壁面碰撞的三维流动与传热数值计算模型,通过试验验证了数值计算模型的正确性。基于数值计算模型,分析了油滴碰撞高温固体壁面后的流动与传热及飞溅特性,以试验和数值计算结果为基础,建立了描述油膜铺展/飞溅临界判据。结果表明:油滴碰撞高温固体壁面后的状态与碰撞条件有关,破碎、飞溅有利于油膜的铺展流动;二次油滴是油膜边缘破碎产生的油带断裂而成,大直径二次油滴分裂为小直径油滴;随油膜铺展进程,壁面平均热流密度增大,而油膜的径向热流密度则逐渐减小;增大碰撞速度、油滴直径和润滑油温度,有利于油膜的破碎与飞溅,二次油滴数量和下飞溅角均随之增大。

温度和乙醇对麻风树油甲酯蒸发特性的影响

为了探究温度和乙醇对麻风树油甲酯(JME)液滴蒸发特性的影响,采用挂滴式实验方法,在973和1073 K的温度下,研究不同乙醇添加量(0%,10%,50%)的JME液滴(JME,JME-E10和JME-E50)的蒸发过程,分析了温度与乙醇含量对燃油单液滴蒸发归一化直径平方的影响。结果显示:973 K时的燃油液滴的蒸发特性与1073 K时的燃油液滴的蒸发特性有明显差异,蒸发特性曲线不能简单地分为瞬态加热阶段、波动蒸发阶段和平衡蒸发阶段这3个阶段。环境温度和乙醇添加量都会在一定程度上影响麻风树油甲酯生物油的蒸发。在高温条件下,液滴中含有的易挥发成分形成气泡使得液滴膨胀发生微爆,并且单液滴的环境温度越高,蒸发时间越短,这是因为在骤变之前液滴的膨胀速率大于蒸发速率。液滴内存在气泡,且不断变大,这是因为气泡因内部压力大于环境压力而向液滴表面移动,气泡达到最大时,发生微爆。在973和1073 K时,JME有一段时间处于平衡蒸发,符合D^(2)定律,而JME-E10和JME-E50则不同,其在蒸发阶段液滴直径波动很大且蒸发过程中还发生了聚合反应。液滴随着温度增加平均蒸发速率变大,JME-E50在1073 K时,蒸发速率最大。3种燃油在不同温度下蒸发,最终都有少许残渣,这是因为不饱和组分发生聚合反应生成了高分子聚合物。

楔形功能图案诱导油滴自发迁移及其减摩研究

为了缓解因润滑剂供给不充分而导致的严重乏油现象,采用化学气相沉积和局部紫外光刻楔形图案相结合的方法,制备了可实现油滴自发迁移的功能表面,研究了油滴体积、楔形角度和楔形长度对油滴迁移特性的影响.结果表明,随着油滴体积增大,油滴的迁移距离和迁移速度先增大后减小,临界值为5μL;楔形角度的增大使油滴迁移距离和迁移速度持续减小;而楔形长度对油滴迁移速度无明显影响.利用该功能表面对润滑剂的诱导迁移作用,将其制备于接触副运行轨道两侧,发现可使接触副摩擦系数显著降低,维持在0.05以下,证实了楔形功能图案表面对润滑剂的自发回流和减摩效果的有效性.

NDM/Cu(OH)2油水分离膜的制备及分离效果分析

为提高Cu(OH)2泡沫铜的油水分离能力,将泡沫铜浸入正十二烷基硫醇(NDM)制得NDM/Cu(OH)2油水分离膜,经过NDM修饰后的泡沫铜实现了连续高效捕获微米级油滴的目的。研究结果表明:油水分离膜具有大约150μm孔径的Cu(OH)2孔状结构;相比未修饰油水分离膜,NDM修饰的油水分离膜的分离效果明显增加,均达95%以上。该研究有助于提高油水分离效果,为后续的应用测试奠定一定的理论基础。

液滴撞击深池上覆油膜的空腔演化特性

为探究液滴撞击深池上覆油膜特性,通过实验和理论方法研究撞击过程中的空腔演化动力特性,构建了多界面模型。结果表明:液滴-油膜-液池的不相溶特性导致更复杂的空腔演化过程,对于较小的弗劳德数Fr条件下,子液滴的产生原因是向下射流发生Rayleigh-Plateau不稳定性。对于大Fr条件下,撞击后形变液滴收缩导致的Rayleigh-Plateau不稳定性是导致子液滴形成的主要原因;由于不相溶界面上的切应力影响,空腔初始扩展速度随着形变界面数量增加而减小;对于薄液膜,由于未考虑油膜-深池界面形变的界面能,其无量纲空腔深度d'与Fr之间关系不满足经典关系d′-F_(r)^(1/4)。而对于厚液膜,其撞击过程可被视为水滴撞击油池,实验观测满足经典关系;采用多界面模型求解获得的有效空腔深度d'_(e)与Fr之间关系满足d′_(e)~F_(r)^(1/4)。

大载荷油动植保无人机喷雾参数对棕榈树冠层雾滴沉积分布的影响

对使用大载荷油动植保无人机对棕榈树进行喷施作业的效果进行了评价,探讨了植保无人机喷洒参数对棕榈树上雾滴沉积的影响。以大载荷油动植保无人机为研究对象,进行了正交试验,考察了3个因素:飞行高度、飞行速度和喷头流量。经过试验比较,当喷头流量为3.4 L/min、作业高度为3 m、作业速度为3 m/s时,雾滴沉积密度和均匀性最佳。其中,喷头流量对雾滴沉积密度的影响最大,其次是作业高度和作业速度;在穿透性方面,喷头流量为3.4 L/min、作业高度为4 m、作业速度为4 m/s和喷头流量为4.2 L/min、作业高度为4 m、作业速度为3 m/s,其雾滴的穿透性较强,分别为15.83%和30.01%。影响雾滴沉积穿透性的因素依次为喷头流量、作业高度和作业速度。本试验对大载荷油动植保无人机在棕榈树合理喷施和提高喷施效果方面具有参考价值。

Design Optimization of an Oil-Air Catch Can Separation System

The Positive Crankcase Ventilation (PCV) system in a car engine is designed to lower the pressure in the crankcase, which otherwise could lead to oil leaks and seal damage. The rotation of crankshaft in the crankcase causes the churn up of oil which conducts to occurrence of oil droplets which in turn may end in the PCV exhaust air intended to be re-injected in the engine admission. The oil catch can (OCC) is a device designed to trap these oil droplets, allowing the air to escape from the crankcase with the lowest content of oil as possible and thus, reducing the generation and emission of extra pollutants during the combustion of the air-fuel mixture. The main purpose of this paper is to optimize the design of a typical OCC used in many commercial cars by varying the length of its inner tube and the relative position of the outlet from radial to tangential fitting to the can body. For this purpose, CFD parametric analysis is performed to compute a one-way coupled Lagrangian-Eulerian two-phase flow simulation of the engine oil droplets driven by the air flow stream running through the device. The study was performed using the finite volume method with second-order spatial discretization scheme on governing equations in the Solid Works-EFD CFD platform. The turbulence was modelled using the k-? model with wall functions. Numerical results have proved that maximum efficiency is obtained for the longest inner tube and the tangential position of the outlet;however, it is recommended further investigation to assess the potential erosion on the bottom of the can under such a design configuration.

一种耐温抗盐的油基超分子体系的驱油性能研究

聚合物微球具备注入爬升压力低、深部运移效果好、耐温耐盐及成本较低等特点,作为一项新型纳米调驱技术,在石油三采领域有广阔的应用前景。聚丙烯酰胺微球乳液作为常用的驱油剂,在温度和矿化度较高的条件下无法在该类油藏条件下取得较好的驱油效果,因此,对非聚丙烯酰胺类新型油基超分子体系的研究十分有必要。选用油田常用的50、100 nm聚丙烯酰胺微球,以及油基超分子微球进行对比研究,在分析和观察其粒径、团聚行为、黏度以及毛细管内油水传质行为和降低界面张力作用的基础上,通过微观可视油滴剥离实验,研究了温度、表面活性剂对聚合物微球原油油滴剥离作用的影响。通过标定不同微球在原油油滴剥离过程中产生的外接触线的移动速度,定量分析了不同种类微球剥离油滴的微观作用效果。结果显示,聚合物微球与表面活性剂有协同作用,可大大提高剥离油滴的速度。在这3种微球中,油基超分子微球体系具有较好的耐温抗盐性能,剥离油滴的效果最好,50 nm微球次之,100 nm微球的剥离效果最差。因此,油基超分子体系是一种具有良好发展前景的新型驱油体系。

茶多酚-淀粉纳米颗粒稳定Pickering乳液的特性

在蜡质玉米淀粉糊化过程中添加茶多酚(tea polyphenols,TP),并采用乙醇沉淀法制备纳米颗粒用于稳定食品级Pickering乳液。通过考察添加TP后淀粉纳米颗粒(starch nanoparticles,SNP)的结构性质、颗粒性质和乳化特性,探究其对Pickering乳液物理稳定性和氧化稳定性的影响。结果表明,TP与淀粉的羟基通过氢键发生相互作用;添加TP导致SNP的粒径由187.00 nm增加至233.80 nm,接触角由53.41°增加至80.60°,Zeta电位绝对值由|-17.20|mV增加至|-22.10|mV;利用TP-SNP稳定的Pickering乳液形成了大量的小乳滴;通过激光共聚焦扫描显微镜观察发现,TP-SNP能吸附在油水界面,形成一层物理屏障,抑制油滴聚结;通过检测Pickering乳液在15 d贮藏期油脂氧化产物的生成量,发现TP-SNP具有延缓乳液油脂氧化的作用,说明TP-SNP可以作为一种具有抗氧化功能的食品级颗粒乳化剂稳定Pickering乳液。