A reflection-type oil-film skin-friction meter

Tanner has shown analytically that the slope characteristics of a thin oil-film lying in contact with a surface on which an aerodynamic boundary-layer is developing are explicitly related to the local skin-friction. Unlike many conventional methods of measuring skin-friction, the oil-film method is absolute in nature, requires no calibration and in principle, can be universally applied. In all existing forms of the meter, however, interferometry is used to make measurements of the oil film. In the present contribution, the technique has been simplified by completely eliminating interferometry. This has been achieved by making direct and dynamic measurements of the oil-film slope by directing a reflected beam of light off the top of the oil film to a small position sensing photodiode. The raw data now is very different from that in the interferometric method and consequently, new methods of determining skin-friction from measured oil-film slope histories have been developed. The reflection method has been verified in incompressible flat plate turbulent boundary-layers. The standard of deviation of the measurements is about 10% of the mean. The present version of the meter is compact and simple.     

Application of oil-film interferometry skin-friction measurement to large wind tunnels

The oil-film interferometry skin-friction technique is described and applied to flows in some of the NASA Ames large wind tunnel facilities. Various schemes for applying the technique are discussed. Results are shown for tests in several wind tunnels that illustrate the oil film's ability to measure a variety of flow features such as shock waves, separation, and three-dimensional flow.     

非定常短轴承油膜力公式的变分修正

本文采用了变分方法对非定常短轴承的油膜压力分布公式进行了修正，既保留了短轴承公式的简洁形式，又使其适用于大长径比轴承。得出了具有足够精度、适合轴颈大扰动情况下的有限长圆柱轴承非定常油膜力的解析公式。与差分充零算法相比，短轴承公式的结果在轴承长径比为0．6时，误差已经超过百分之二百，而本方法计算结果的误差小于百分之五。因此采用本方法既提高了短轴承油膜力公式的计算精度，又保持了油膜力公式的简洁形式，不失为进行转子-轴承系统非线性动力分析的一种有效方法。     

用瑞利-李兹法求解瞬时非稳态滑动轴承油膜力的新算法

提出了一个利用瑞利一李兹方法求解Reynolds边界条件下非稳态滑动轴承油膜力的近似算法,充分利用油膜力分布的特性,用双曲余弦函数来表示油膜力的轴向压力分布,而用多项式函数插值法来求解油膜力的周向压力分布,并同时计算出油膜力的破裂边界。算例表明本算法达到了相当高的精度,可用于转子系统的非线性数值分析,能大大降低数值求解瞬态油膜力的计算时间。     

大型轧机油膜轴承锥套损伤问题研究

利用弹塑性接触问题边界元法分析了轧机油膜轴承锥套与轧辊辊颈装配过程中的变形和载荷特性,讨论了接触应力和变形对锥套与辊颈损伤的影响,给出了防止锥套与辊颈装配过程损伤的具体改进措施。最后通过实验验证了理论分析结果和改进方案的正确性。     

Oil recovery in the presence of microbubbles in the filtration flow

This paper presents mathematical models for oil-gas flow taking into account the various processes due to the formation of gas micronuclei (microbubbles) in oil: slip of oil relative to the walls of the pore channels (gas lubrication), changes in oil viscosity, and motion of microbubles with respect to oil. We consider examples of oil flow in the near-wellbore zone for the case where a reduction in pressure to the saturation pressure leads to the formation of gas microbubbles and micronuclei and examples of the action of a water-gas mixture in the case where oil foams in the contact area with the injected gas, i.e., a finely dispersed mixture of oil and microbubbles is formed. The behavior of indicator curves for an oil well with the formation of microbubbles is simulated, and the effect of microbubbles on the oil recovery factor in a water-alternating-gas injection process is studied.     

球盘点接触区外润滑油分布的试验研究

利用激光激发荧光技术对球-盘弹流接触区附近以及自由表面上的润滑油分布进行了试验观察,探究了离心力作用下接触区附近以及自由表面上润滑油分布的变化规律. 结果表明:随着速度增大,内外两侧油池及自由表面上的油量分布均有所减少,其中外侧油池及自由表面上外侧油带的变化较明显;在一定工况条件下,外侧油池的大小存在极限,因此速度较大时外侧油池宽度对供油量变化不显著,而该极限由离心力作用和毛细力作用共同决定;在离心力作用下,自由表面上的油带有向外侧铺展的趋势,而接触区周围的油池分布对自由表面上的油带分布起决定作用.      

含油轴承表面供油行为与自润滑机理分析

含油轴承是一类重要的减摩自润滑零件,轴承基体中油液的渗流特性对表面润滑性能有重要影响. 建立含油轴承孔隙渗流与表面油膜润滑的耦合力学模型,分析含油轴承系统中油液的渗流特性,探讨轴承表面油液的供油行为与自润滑机理. 结果表明:在含油轴承的收敛区内同时存在周向旋转流、径向伸缩流和法向渗析流,油液在各方向上的流动状况由该向流体压力梯度决定;受油膜压力影响,油液在接触区向多孔基体渗入,在接触区入口部位向多孔表面析出,由此构成了油液渗入和析出的闭环速度流线,增强摩擦界面间的泵吸效应. 油液在法向上的渗析速度随中心膜厚增加而减小,随转速升高而增大,渗析速度越大,对泵吸效应的增强作用越显著,接触区入口的油液也更易进入摩擦界面,保障含油轴承的良好自润滑效果. 研究结果对揭示含油轴承的供油自润滑机理具有重要意义.      

气泡夹带对壁面油膜流动特性的影响

油-气润滑系统工作过程中,润滑油膜受微油滴冲击和压缩空气扰动影响易形成气泡夹带现象,气泡夹带行为将对壁面润滑油膜层的形成及流动过程产生重要影响。基于VOF数值模拟方法,对含气泡油膜沿倾斜壁面的流动行为进行研究,考察了气泡的存在对油膜形态和流动速度的影响规律,以及气泡破裂阶段空腔邻域内流体压力变化特性。研究表明,油膜夹带气泡的形变和迁移诱发气泡周围微流场的速度扰动现象,导致气液界面处产生非均匀速度梯度分布,进而引发油膜表面的形态波动。气泡发生破裂时,油膜空穴部位发生明显的正负压力波动现象,气泡附近壁面将承受一定的交变载荷作用。     

基于电容法的温度对舰船汽轮机油分水性影响研究

依据汽轮机油与水的介电常数差值大,其混合相作为电介质,会发生电容值变化显著的原理,采用同轴圆柱形电容作为测试传感器,选取符合世界主流海军舰船汽轮机油产品规范的8个油样,利用电容法对比研究室温(18~24 ℃)和54 ℃对油样的分水性影响规律,选取了分水性变化明显的油样进行分水后油层微观形貌分析. 试验结果表明:在54 ℃条件下,从油水混合到分离结束,电容值-时间曲线重合度更高,油水均匀混合重复性好,表现出了优于室温的重复性和稳定性;分水速率曲线具有良好的重复性,验证了电容法评定汽轮机油分水性的可靠性,在相同温度下分水速率和破乳化时间受水相分布与运动态势影响小;确定用电容法评定汽轮机油分水性时,环境温度选择54 ℃为最佳;作用机理分析说明,温度是影响舰船汽轮机油分水性的关键指标.      

进口润滑条件对活塞环-缸套摩擦副润滑性能的影响

目前内燃机活塞环-缸套摩擦副润滑分析中,活塞环与缸套之间的润滑状态一般假设为充分润滑或固定状况的贫油润滑,不是通过对实际润滑油膜形成情况的分析确定.本文中以一多缸四行程内燃机为研究对象,基于润滑油流量以及控制体体积变化方程,建立活塞环-缸套间润滑油的流动模型,进行了不同进口处润滑油膜供给量对活塞环-缸套摩擦副润滑特性的影响分析.结果表明:活塞环进口处的润滑条件对活塞环-缸套摩擦副的润滑性能有显著影响;进口处润滑油供给量增加,活塞环-缸套摩擦副的最小油膜厚度增加,最大油膜压力、微凸体作用力、摩擦力和功耗均相应减小;进口处供给油膜厚度较小的情况下,增加油膜供给厚度可以明显改善活塞环-缸套摩擦副的润滑性能.     

On the spreading radius of surface tension driven oil on deep water

The spread of a thin oil film by surface tension gradients from an oil source of unlimited mass on deep water is considered. A similarity solution for the velocity fields of the oil and water, the oil thickness and the rate at which each grow is obtained both for axisymmetric and the previously explored planar spreading. The dimensionless size of the spread, which is oil type independent, is shown to be 1.0754 and 1.4150 for axisymmetric and planar spreading respectively. It is further shown that the oil film equation of state, which relates surface tension to oil thickness, is unique to each oil or oil-surfactant mixture.     

The Effect of Reservoir Wettability on the Production Characteristics of the VAPEX Process: An Experimental Study

The impact of fractional wettability on the production characteristics of a VAPEX process at the macroscale was investigated. Conventional VAPEX experiments were conducted in a 220 Darcy random packing of glass beads in a rectangular physical model and n-pentane was used to recover the Cold Lake bitumen from the oil-saturated model in the absence of connate water. The composition of oil-wet beads in the packed bed was altered from completely water-wet beads to completely oil-wet beads at different proportions of oil-wet beads mixed with water-wet beads. A substantial increase (about 40%) in the production rate of live oil was observed during the VAPEX process when the wettability of the porous packing was entirely oil-wet beads. A critical oil-wet fraction of 0.66 was found for the heterogeneous packing of water-wet and oil-wet beads of similar size distribution. Above this critical composition, the live oil production rate was not affected by further increase in the proportion of the oil-wet beads. It is believed that above this critical composition of the oil-wet beads, the crevice flow process is dominated by the continuity of higher conductivity live oil films between particles through the oil-wet regions. Below this critical composition, the live oil production rate increased linearly with the fraction of the oil-wet beads in the packing. The oil-wet regions favor the live oil drainage compared to that of the water-wet regions as they enhance the rate of imbibition of the live oil from the oil-filled pores to the vacated pores near the nominal VAPEX interface. These two factors enhance the live oil production rate during the VAPEX process. The solvent content of the live oil, the solvent-to-oil ratio (SOR), and the residual oil saturation did not correlate strongly with the proportion of the oil-wet beads in the packing. The average solvent content of the live oil and the residual oil saturation were measured to be 48% by weight and 7% by volume respectively.     

Hydrodynamic models of the residual oil distribution in water-flood reservoirs

Models of the residual oil saturation distribution are proposed for linear, axisymmetric, and general flows. The steady displacing fluid flow model makes it possible to find equilibrium residual oil saturation distributions corresponding to given flow regimes by treating the porous medium with capillary-trapped oil as a medium with permeability that depends on the displacement conditions. The dynamics of the mobilized globules of the residual oil are excluded from consideration. The simulation results indicate that the residual oil saturation distribution after stimulation of the wash-out zone by means of enhanced oil recovery techniques is generally essentially nonuniform. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 98–104, May–June, 2000.     

油气条件下供油时间对弹流润滑性能的影响分析

采用油气发生器,通过润滑剂厚度测量试验,建立了表面油层随供油时间变化关系.基于点接触乏油润滑模型和滚道表面油膜衰减模型研究了不同速度、载荷和表面粗糙度条件下自由表面油层厚度对润滑性能的影响.结果表明油气润滑条件下建立充分供油条件所需时间基本不随工况条件而变化,存在最佳供油时间和供油间隔.     

Studies on the viscosity of solid stabilized emulsions

Summary Viscosities have been determined for kerosene/water and olive oil/water emulsions, stabilized by freshly precipitated, finely divided solids, by a Rheo Viscometer with particular reference to the influence on the viscosity of the amount of the emulsifier, concentration of the disperse phase, nature of the oil and homogenization. It has been found that the viscosity for 11 oil/water ratio increases with increase in the concentration of the emulsifier and also increases at 1% solid content with increasing oil/water ratio. Homogenization of the emulsion increases its viscosity as it renders the adsorbed film more resistant. The olive oil emulsions which tend to be more viscous than the analogous kerosene ones are characterized by abrupt changes in the viscosity after a certain concentration of the oil (60–70% oil) when some of them invert to W/O type. Emulsions with a large interfacial area tend to show less decrease of viscosity with time, although exceptions are observed.     

供油量对对数滚子弹流润滑特性的影响研究

针对现有的凸度设计研究没有考虑供油量因素的现状，研究了供油量对对数滚子弹流润滑特性的影响，指出:在轴向中部，对数滚子的乏油润滑特性与无限长线接触弹流的乏油润滑特性相似；在轴向端部，当供油量较小时，膜厚较小且轴向颈缩不明显；随供油量的增加，膜厚沿滚子轴线方向逐渐由中部向端部增大，轴向颈缩逐步建立，直至形成膜厚的端部闭合效应达到充分供油润滑. 在供油量由乏油到充分供油的变化过程中，压力的边缘效应趋于显著. 因此，充分供油条件下的凸度设计结果不能直接用于乏油工况，乏油时需要的凸度量将小于充分供油润滑的凸度量.      

Influence of the Gravity Override on the Optimal Gas Flooding Strategies

Fluid Dynamics - Water-alternating-gas injection into oil reservoirs, i.e., the gas method of enhancd oil recovery that supposes water and carbon dioxide injection in the reservoir with the aim to...