润滑油水污染对齿轮热弹流润滑特性的影响研究

以渐开线直齿圆柱齿轮为研究对象,考虑热效应和时变效应,建立油水两相流模型和齿轮的热弹流润滑模型,探究了润滑油中含水率对油水两相流体的黏度及齿面润滑特性的影响.研究结果表明,润滑油中混入冷却水后,当含水率不超过5％时,随着含水率的增加,油水两相流体的黏度不断增大;含水率为5％时,油水两相流体的黏度达到其峰值,之后随着含水率的增加,油水两相流体的黏度不断减小.适当增加含水率可改善齿面的润滑特性,但考虑油膜温升及对设备的腐蚀磨损,应将含水率控制在5％以内.     

润滑油水污染对齿轮热弹流润滑特性的影响研究

以渐开线直齿圆柱齿轮为研究对象,考虑热效应和时变效应,建立油水两相流模型和齿轮的热弹流润滑模型,探究润滑油中含水率对油水两相流体的黏度及齿面润滑特性的影响。研究结果表明:润滑油中混入冷却水后,当含水率不超过5%时,随着含水率的增加,油水两相流体的黏度不断增大;含水率为5%时,油水两相流体的黏度达到其峰值,之后随着含水率的增加,油水两相流体的黏度不断减小。适当增加含水率可改善齿面的润滑特性,但考虑油膜温升及对设备的腐蚀磨损,应将含水率控制在5%以内。     

基于相位法在线实时油井含水率仪研究

目前油田中使用的流体取样式电容法产出剖面测井仪不能满足测量高含水油田含水率的高精度和实时在线性测量要求。文中根据油井产出液不同含水率下介电特性不同的这一特性,以油水混合介质作为电磁波的传播载体,通过测量电磁波在不同含水率的油水混合介质传播时产生不同的相位偏系数,研制了以相位法测量油井含水率的新型含水率测量仪。该仪器能够实现井下含水率的实时高精度连续测量,室内试验和先导现场测试证明该方法能够实现油田高含水开发后期油井层段含水率的准确测量,为地质分析提供有效数据支撑。     

油水两相流中2种含水率计算模型比较

油水两相流广泛存在于石油开采、储运、化工、能源等工业领域。含水率是油水两相流系统的重要参数之一,含水率的准确测量不仅与采用的测量方法有关,而且还与计算模型有很大关系。结合电导式测量方法建立了电阻-电容并联网络含水率计算模型,并在3种流型下与Maxwell含水率模型进行了仿真和实验对比。结果表明,建立的并联电阻-电容网络含水率模型,在泡状流下与Maxwell含水率计算模型的误差基本相同,而在环状流、分层流下,测试误差均小于Maxwell含水率计算模型的误差,具有更高的测试精度,可适用于环状流、分层流、泡状流等流型。     

AD7745在油井含水率检测电路中的应用

油田开发处于高含水期时,准确、可靠地测量油井两相流的含水率具有重要意义。油水混合物中,不同含水率引起的介电常数差异很大,根据这一理论,文章设计了过流式的电容传感器,采用高精度的电容数字转换芯片AD7745,解决了从电容到数字直接转换的复杂且困难的信号处理难题。实验结果表明,该系统性能好、成本低,具有较好的应用价值。     

AICD智能控水装置实验研究

介绍一种解决油井高含水问题的AICD智能控水装置。通过地面实验,以清水和不同粘度原油、不同含水率的油水混合液为样品模拟井下生产状况,对比研究了AICD智能控水装置对不同粘度流体的过流性能。实验结果表明AICD智能控水装置具有很好的控水、增油作用。     

新型油井含水率测量仪的研制

由于水、油介电特性差异较大，导致电磁波在不同含水率的油水混合介质中传播时的相位系数有很大不同。新型含水率测量仪器是利用同轴线作传感器，油水混合介质在同轴线内流过，并构成传播电磁波的载体，通过测量同轴线两端电磁波在同轴线内油水混合介质中传播的相位系数，来得到油水混合介质的含水率。该仪器能够实现油井含水率的连续测量，室内试验和初步现场试验证明该方法能够解决高含水油田油井含水率很难测准这一难题。     

基于嵌入式系统的油水液位检测系统的设计

针对传统油水分离技术存在检测精度低、过程繁琐等问题,设计了一种基于新型电容传感器的油水液面检测系统。该系统以STM32和CPLD为开发平台,硬件部分设计了激励信号源电路、微小电容检测电路、相敏解调电路等。通过利用新型分段式电容传感器检测油水界面时传感器中电容的变化量来拟定油水液位高度和电压的线性曲线,最后计算出油水液位的高度。实际实验结果表明,该系统具有测量精度高,误差小于3 mm,稳定性好等优点。     

含水率对油水乳化液传输频率特性影响分析

为了掌握油水乳化液中含水率对其动态特性的影响,建立含水率与乳化液传输的频率特性之间的非线性关系。首先,推导了油水乳化液在管体中压力波传播速度公式,分析了含水率对乳化液传输速度的影响规律;然后,利用分布参数理论以及传递矩阵法建立了油水乳化液的传输频率模型,表明在PVC透明钢丝软管中考虑流固耦合作用时含水率增加,其传播速度呈降低趋势;反之,钢管内乳化液的传输速度随着含水率的增加而呈递增趋势;含水率对系统的谐振频率影响也较为明显,乳化液中含水率越大,系统的同阶谐振频率越低,且随着含水率的增加,谐振频率的阶次越大,同阶次的谐振频率之间的差值也相应变大。实验验证所建模型是有效的,为有效检测油中含水率以及保障系统安全运行提供一定的理论基础。     

油品含水率在线检测仪的研制

介绍油品含水率检测原理、电容／电压转换方法以及系统设计。实验结果表明，该仪器能够准确、快速地检测出油品的含水率．从而避免了润滑失效所带来的潜在危害。     

A theoretical model for a capacitance tool and its application to production logging

A new theoretical model for a capacitance sensor used for measuring water holdup in production logging is proposed in this paper. The model realizes that the capacitance sensor is sensitive to oil droplets that collide against the sensor's inner electrode coated with an insulator when the water is electrically conductive and is the continuous phase in an oil/water bubbly flow. The sensor still has the ability to distinguish between oil and water in this case, its sensitivity decreasing with fluid velocity. The experiments were performed in a multiphase flow loop, and the results strongly confirm the theory. On the basis of the model, the measuring principle of the sampling-type capacitance tool is discussed, and an attempt to evaluate average oil droplet size with the capacitance sensor in the case of oil in water is also made.     

Experimental Support for the Dynamic Concentration Theory of Forming an Oil Reservoir at the Inlet of the Roll Bite by Measuring the Onset Speed of Starvation as a Function of Oil Concentration and Droplet Size

The dynamic concentration theory describes a mechanism of how an oil reservoir forms at the inlet of the roll bite when an emulsion is used as the lubricant. This theory assumes that oil droplets larger than the thickness of the lubricant film in the deformation zone become trapped when they come into contact by both the surface of the sheet and the surface of the work roll. As the droplets move toward the deformation zone, water is left behind or squeezed out by the flattening of the oil droplets. At some point, the surfaces of the trapped oil droplets come into contact with each other, resulting in an inversion where oil becomes the continuous phase. The dynamic concentration theory predicts that the height of the meniscus where this inversion occurs is a function of the percent oil concentration and the diameter of the oil droplets. To test the dynamic concentration theory, the onset speed of starvation on a laboratory rolling mill was determined by measuring the speed in which load increases relative to the load measured for the same process but where the lubricant film is fully flooded. Both the concentration of oil and the size of the monodisperse oil droplets were varied to change the height of the meniscus and consequently the onset speed of starvation. Solid support for the dynamic concentration theory was obtained when starvation occurred at the same speed for emulsions with different oil droplet sizes in which their concentrations were specifically adjusted so that their meniscus heights theoretically were the same. Finally, an unexpected consequence of the dynamic concentration theory was that the thickness of a starved lubricant film is independent of rolling speed, but this is only true at high speeds.     

表面织构对角接触球轴承润滑性能的影响

为研究油气润滑状态下表面织构对角接触球轴承润滑性能的影响,在角接触球轴承的内圈滚道上设计表面织构,基于气液两相流理论,采用多重参考坐标系(MRF)模型和流体体积(VOF)法,对高速角接触球轴承腔内润滑油流动特性进行数值分析,对比分析长沟槽、短沟槽、矩形、圆柱形4种表面织构对角接触球轴承润滑性能的影响,发现长沟槽形的表面织构对改善角接触球轴承的润滑性能效果最为显著,并进一步分析长沟槽形表面织构结构参数对轴承润滑性能的影响。结果表明：轴承腔内油相体积分数随着沟槽深度和面积率的增大先增大后减小,随着沟槽宽度的增加逐渐增大,存在最佳织构参数使得轴承腔内油相体积分数最大。因此,合理地设计织构参数能有效提高角接触球轴承润滑性能,该研究结果对角接触球轴承表面织构设计具有一定的参考价值。     

Friction and wear characteristics of steel on rock under water and oil based lubricated sliding conditions

Abstract

In recent years, drilling extended reach wells have become more and more common in the petroleum industry to optimise the oil and gas production. Extended reach wells are defined as wells that have two times more horizontal step out than true vertical depth. High friction (frictional torque) and drag are two of the mechanical limiting factors while drilling longer horizontal wellbores. There are numerous methods and tools developed to lower the drillstring friction. Drilling non-circular wellbores is a new concept with potential to minimise the mechanical friction by reducing drillstring and sidewalls contact area. However, this will cause an increase of contact pressure owing to the reduced contact area between drillstring and the formation. This article presents results obtained from an experimental study pertaining to the friction behaviour using a pin on disc set-up with steel pin and granite disc in the presence of water and oil based lubricants. These tests have been designed to represent frictional contact conditions between a rotating steel drillstring and the wellbore wall at different contact pressures. Test results show that the friction coefficient decreases with an increase of contact pressure in wet condition for both water and oil based lubricants. It is also observed that the friction factor increased by adding sand and phyllite particles to the water based lubricant. Considering the wear scars, the friction coefficient shows reduction with increased contact pressure in all tests with and without particles for both water and oil based lubricants.     

超疏水表面液滴的冷凝成长特性研究

利用聚二甲基硅氧烷(PDMS)为基底采用光刻技术制备了微方柱状超疏水表面,分析了冷凝条件下超疏水表面液滴的冷凝生长特征,发现液滴的生长过程可分为微液滴成核冷凝独立生长、冷凝微液滴合并生长以及大液滴生长3个阶段。超疏水表面初始合并的液滴呈Wenzel-Cassie状态和Wenzel状态,随着冷凝液滴的成长,液滴的液-固接触面积与粗糙结构表面的表观面积之比f随着冷凝液滴尺寸的增大而增大,Wenzel-Cassie状态向完全Wenzel状态转变。最后分析了超疏水性破坏的原因。     

A study on the contact angles of a water droplet on smooth and rough solid surfaces

We investigated the wetting characteristics such as contact angle, wetting radius and topography of water droplets on smooth and random solid surfaces. Molecular dynamic simulation is employed to analyze the wetting behavior of water droplets on smooth and rough surfaces by considering different potential energy models of bond, angle, Lennard-Jones and Coulomb to calculate the interacting forces between water molecules. The Lennard-Jones potential energy model is adopted as an interaction model between water molecules and solid surface atoms. The randomly rough surface is generated by changing the standard deviation of roughness height from 1 Å to 3 Å with the fixed autocorrelation length. The size of water droplet considered is in the range from 2,000 to 5,000 molecules. The contact angles increase generally with increasing number of water molecules. For a hydrophobic surface whose characteristic energy is 0.1 kcal/mol, the contact angles depend rarely on the standard deviation of the roughness height. However, when the surface energy is 0.5 and 1.0 kcal/mol, the contact angles depend on both the roughness height of surfaces and droplet size.     

微量供油条件下润滑油液滴的生长与脱附

润滑油液滴的生长与脱附性能对于微量供油过程和微量润滑效果有重要影响。采用试验和数值仿真相结合的方法,研究微量供油条件下、在重力环境中的润滑油液滴在毛细管出口端的生长与脱附行为,考察毛细管管径和表面润湿特性变化对润滑油液滴脱附性能的影响。结果表明,润滑油液滴的生长与脱附是毛细力、黏性力、表面张力和重力等共同作用的结果;减小毛细管管径或增大润滑油液滴在毛细管表面的接触角,均可有效减弱毛细效应,降低润滑油液的爬移高度和脱附粒径,改善液滴脱附性能;毛细管管径由1.2 mm减小至0.7 mm过程中,液滴脱附粒径减小了4.5%;接触角由5°逐渐增加至90°的过程中,液滴脱附粒径减小了9.3%;通过选用低表面能材料制作微量供油的毛细管可以显著增大接触角。     

Numerical simulation of droplet formation in a micro-channel using the lattice Boltzmann method

This study investigates droplet formation in a micro-channel using the lattice Boltzmann (LB) method. A cross-junction micro-channel and two immiscible, water and oil phase fluids, were used to form the micro-droplets. Droplets are formed by the hydrodynamic instability on the interface between two immiscible fluids when two immiscible fluids are imported simultaneously in a cross-junction micro-channel. The Shan & Chen model, which is a lattice Boltzmann model of two-phase flows, is used to treat the interaction between immiscible fluids. The detailed process of the droplet formation in the cross-junction micro-channel was illustrated. The results of the droplet formation by the LBM predicted well the experimental data by PIV (particle image velocimetry). The effect of the surface tension and the flow rate of water phase fluid on the droplet length and the interval between droplets was also investigated. As the surface tension increased, the droplet length and the interval between droplets were increased. On the other hand, when we increased the flow rate of the water phase fluid under the condition of the fixed oil-phase fluid flow rate, the droplet size was increased while the interval between droplets was decreased.     

Elastohydrodynamic Lubrication with Oil Droplets

In oil–air lubrication, lubricants are supplied in the form of oil droplets to tribo-pairs. Numerical work has been carried out to investigate transient EHL characteristics when a series of oil droplets are entrained along the center line of the contact zone. Results show that the spacing distance between oil droplets is an important parameter for continuous EHL film formation. For oil droplets with the same volume, the effective lubrication time increases first and then decreases as the droplet distance increases. An optimum droplet distance can be found for the maximum effective lubrication time with continuous EHL films. Moreover, entrainment speed, lubricant viscosity and oil/solid interface can also affect the effective lubrication time significantly and change the optimum droplet distance accordingly. Numerical results showed a close correlation to the experiments. This study is useful to basic understanding of lubrication by limited lubricant supply.     

超亲水-水下疏油铜网润湿性及油水分离研究

为研究铜网表面润湿性对油水分离性能影响,以金属氧化法处理后的超亲水-水下疏油铜网为油水分离介质,讨论处理前后空气中水、水下油接触角变化情况。分析不同油样、不同含油体积分数、不同滤网目数对油水分离性能影响。利用Cell Registers功能进行数值模拟,分析空气中水滴铺展和水下油滴聚集状态。结果表明:处理后的铜网表面形成的Cu(OH)2微结构在空气中呈超亲水性,随着铜网目数增加,水下疏油性增强;油水两相密度差越大、黏度差越大以及含油体积分数越大、铜网数目越大,均能得到较高的油水分离效率;亲水表面的水滴铺展系数随时间增加而逐渐增大,水下疏油表面的油滴铺展系数先缓慢增大后稳定不变。超亲水-水下疏油铜网的应用对提高和强化油水分离性能具有较好的发展前景。