基于雷诺应力模型的脱油旋流器流场特性研究

采用雷诺应力模型(RSM)对油水分离用水力旋流器进行了数值模拟,模拟出了循环流和短路流现象,得到了内部流场的轴向速度、径向速度和切向速度的分布规律;模拟结果与实验结果吻合较好,说明该湍流模型和计算方法的选取是正确的;另外,针对油相体积分数为2%,油滴粒径为40μm的混合介质进行分析,得出了油水二相的体积分数分布。在旋流器的轴心处油相体积分数最大,最大处混合介质中含油体积分数高达98.9%;在壁面附近体积分数很小,说明该水力旋流器的分离效果较好。通过数值模拟为进一步研究水力旋流器内部流场的分布和结构优化设计奠定了基础。     

弯管内部油水两项流的数值模拟

在油井出油管道以及石化生产中,油水两项流是非常常见的现象。为了减少能耗、便于制订防腐措施,利用GAMBIT软件建模以及FLUENT软件的可实现模型对弯管中油水两项流的压力场和速度场进行模拟。结果表明,管内入口直管压力呈逐阶减小趋势;弯管内壁出形成低压区且又内向外逐渐增大;而速度分布正好与压力分布规律相反,恰好与自由涡流理论的模型相符。且通过对油水两项所占体积分数分别为30%、50%、80%三种情况的模拟得出,由于水密度大于油的原因,随着油相体积分数的下降,管内整体压强减小,整体速度增大。     

水平圆管内油水两相旋流分隔性能分析与评价

油水分离后的测量技术广泛应用于石油开发、污水处理及化学工程等领域.如何实现快速高效的油水分隔,是精密测量领域的关键技术之一.目前,油水分隔器的结构形式较为多样,有必要开展不同分隔器的性能对比和评价研究.采用粒子成像测速技术、分隔性能实验及数值模拟等方法,对三种不同结构水力旋流器的分隔性能进行对比分析,形成了一种用于水平...     

90°弯管内湍流流动的数值模拟

进行了90°弯管内湍流流动的数值模拟实验。结果表明,切向速度在开始旋转阶段内侧的速度增大、压力减小,外侧速度降低、压力增大;当转过60°截面后,外侧的速度增大、压力减小,内侧速度降低、压力增大。弯管内流体旋转产生的离心力导致压力分布的变化,使得弯管内流体产生垂直于主流切向速度的轴向速度和径向速度,形成了二次流。90°弯管流场是主流切向速度与二次流的叠加,呈现出复杂的三维流动特性。     

导向叶片对导叶式旋流器内流场的影响

借助Fluent软件,采用雷诺应力模型对导叶式水力旋流器进行了数值模拟,得到了内部流场的轴向速度、切相速度和径向速度的分布规律,对比不同结构参数的导向叶片对旋流器内速度场的影响。通过分析,导叶式旋流器的叶片有最适宜的角度,它可减小湍流脉动,增加旋流器分离的稳定性。     

SCX分级机进料管流场数值分析与结构优化

以FLUENT软件为计算平台,气相采用欧拉模型,颗粒相采用DPM模型对SCX超细分级机进料管内流场进行了数值模拟,进料管内部流场不均匀,存在明显的偏流现象。在弯管处添加导流片进行优化,对比分析了导流片数量、尺寸和间距分布形式对压力、速度和颗粒质量浓度分布的影响。结果表明:导流片的添加提高了进料管流场的品质;当导流片数量为5,尺寸为1/4圆弧并在前后加长150 mm(半径的1.2倍),并按等间距分布时,进料管内压力、速度和颗粒质量浓度分布较为均匀,为后续的分级提供了良好的前提。     

水平圆管固液两相稳态流动特性数值模拟

水平井油水流动特性是设计产液剖面测井方法和建立解释模型的重要依据,当油水中携带沙颗粒时,其流动特性变得更为复杂。通过基于Eulerian描述方法的混合代数滑移模型（MASM）,建立挟沙水或油混合相控制方程和边界条件,并且使用有限差分方法和逐次超松弛（SOR）迭代法建立数值解,以模拟水平井挟沙水或油混合相的各运动特性参数分布。模拟结果表明,主流速度分布随着颗粒相体积分数增大有向下偏移特点,并随着压降值降低而减小。水平井圆截面上颗粒相体积分数分布特征主要与主流速度有关,随着速度降低,体积分数分布值向下向两侧增大。此外,挟沙油混合相主流速度大于挟沙水混合相速度。混合代数滑移模型不仅能够很好地模拟混合相各运动特性参数分布特征,而且计算效率比较高。     

Predicting pressure gradients in heavy oil—water pipelines

Experimental investigations of the flow of water‐heavy oil mixtures at velocities typical of oil‐field gathering systems show that continuous water assisted flow at very low pressure gradients can be achieved. The principal criterion to be satisfied in establishing this desirable flow regime appears to be use of sufficient water, with the velocity also playing a role. It also appears that oil viscosity and water fraction effects on pressure gradient are small provided the beneficial flow regime is established. The flows resemble core‐annular flow, which has been observed previously in Bitumen froth and water‐heavy oil flows, with an oil layer on the pipe wall. However, the correlation for pressure gradient is somewhat different from that reported previously for Bitumen froth flows.     

圆管内轴向旋转流切向速度湍流强度

采用热线风速仪(hot wire anemometry,HWA)测量了ø300 mm×2000 mm圆管内轴向旋转流瞬时切向速度随时间的变化,重点分析了切向速度湍流强度的分布特点和旋转流摆动对切向速度湍流强度的影响.测量结果表明,瞬时切向速度由高频的湍流脉动速度和低频的波动速度叠加构成.由于受旋转流旋转中心偏离圆管几何中心造成的旋转流摆动的影响,在圆管中心区域瞬时切向速度随时间的波动速度变化较大,边壁区域瞬时切向速度随时间的波动速度变化较小.通过对瞬时切向速度数据进行概率密度分析可知,切向湍流强度不仅受气流脉动的影响,还受旋转流中心摆动的影响,是由自身气流脉动产生的湍流强度和旋转流摆动产生的湍流强度两部分叠加构成.旋转流摆动导致了中心区域的湍流强度远大于边壁面区域的湍流强度.     

新型旋风分级器流场特性及颗粒分级性能

针对传统旋风分级器分级效率较低的难题,本文设计了一种中部进风、顶部重力进料式新型旋风分级器,利用数值模拟和试验手段对其流场特征及分级性能进行了研究。模拟结果表明,新型旋风分级器内存在若干旋涡,主气流进入分级器后形成由上、下两个旋涡构成的主分级流场,上部旋涡均为上行气流,下部旋涡为切流返转形式;二次气流形成的细颗粒淘洗旋涡具有近壁面处高转速、中心区快速上升的特点,最大轴向速度达16.5m/s,可强化对边壁处浓集颗粒的剪切分散和淘洗作用,对主分级流场切向速度影响较小,但可使其轴向速度值最大增加100%,这将缩短细颗粒的停留时间;主分级流场与淘洗流场相互作用形成分区流动,具有较明显的动态边界,为粗、细颗粒的定向分离提供了力场基础。试验表明,二次气量占比约20%,主、二次气流气速分别为14m/s和20m/s时,牛顿分级效率可达88%,分级精度指数K值最小为1.84,此时新型旋风分级器具有较高的分级精度。     

A laboratory investigation of horizontal well heavy oil—water flows

Experimental simulations of model well‐bore flows in laboratory pipelines show that frictional energy losses (i.e., pressure drops) are reduced when water is present with heavy oil. The reduction has been shown to increase with the water fraction. The mixtures are not oil in water emulsions in the classical sense of the term. At the low axial velocities which characterize wellbore flows, the flow regime is inherently intermittent. Using a variety of methods the structure of the flow has been examined to identify the flow regime and the cause of the reduced pressure gradients. It has been found that the water travels as large slugs and that oil is invariably present at the wall when the mixture flows through a steel pipe. The evidence suggests that a significant fraction of the oil is transported within the water slugs. A tentative flow regime boundary between the regions of intermittent and continuous water‐assisted flow is proposed in terms of the mixture Froude number and the injected water fraction.     

旋流板分离器的结构对三维流场的影响

引言 旋流式分离器种类很多[1-4],其中浙江大学发明的旋流板在传质和双相分离过程中均得到广泛应用[5-9].旋流板分离器是利用导向叶片使气体做旋转运动,从而产生离心力,达到气液或气固分离的目的.     

Mean and turbulent fluctuating velocities in oil-water vertical dispersed flows

Experiments of oil-water upward and downward flows have been carried out in a 38 mm ID pipe to investigate the modifications of turbulent flow characteristics by the presence of dispersed phase, i.e., mean and turbulent velocity profile of the continuous phase and mean velocity profile of the dispersed phase. Results for both oil-in-water (o/w) and water-in-oil (w/o) dispersions are presented. In o/w upward flow, the axial mean velocity profiles are found to be flatter than in single-phase flow and then change to centre peaked as the input oil fraction increases; a flatter profile is seen in w/o upward flow. In downward flow, the presence of oil drops always tends to flatten the continuous phase velocity profile in o/w dispersions, while a slightly centre peaked profile is observed in all cases of w/o systems. For both upward and downward flows, the presence of the dispersed phase tends to flatten the turbulence intensity profile and to result in a more uniform distribution of the turbulent energy over the pipe cross-section. It is also found that turbulence is more likely to be enhanced in the pipe centre area, where the volume fraction and the size of the dispersed phase are larger, while suppressed in the area close to the wall. Turbulence intensity is increased with mixture velocity and is slightly higher in upward than in downward flows. The current study suggests that local dispersed phase fraction and size as well as dispersed phase velocity seem to affect turbulence characteristics in oil-water flows. Previous models based on particle-laden flows for the prediction of turbulence enhancement or suppression were examined and agreement was found to depend on the type of dispersion (i.e., whether oil or water constitute the continuous phase).     

稠油-水二相水平管流表观粘度的实验研究

以渤海稠油和水为工质进行尝试实验,作出了水平不锈钢实验回路(内径为25.7 mm,长为52 m)内稠油-水二相管流的流型图,并对管流的表观粘度及影响因素进行了实验研究。着重归纳了含水体积分数、温度等因素对二相管流表观粘度的影响规律,并对比分析了与旋转粘度仪测得粘度值的差异,研究结论对油田现场的油水混输管线的设计与安全运行具有较好的指导意义。     

Particle image velocimetry for characterizing the flow structure of oil–water flow in horizontal and slightly inclined pipes

The simultaneous flow of oil and water in pipelines is a common occurrence in the chemical and process industry. An experimental investigation of oil–water flow in horizontal and slightly inclined pipes is presented in this paper. The experiments are performed in a 15 m long stainless steel pipe section with internal diameter 56 mm at room temperature and atmospheric outlet pressure. Exxsol D60 oil (density 790 kg/m³ and viscosity 1.64 mPa s) and water (density 996 kg/m³ and viscosity 1.00 mPa s) are used as test fluids. The pipe inclination is changed in the range from 5° upward to 5° downward. The measurements are made for two different mixture velocities, 0.50 and 1.00 m/s at water cut 0.50. The cross-sectional distribution of phase fractions in oil–water flow is measured using a traversable single-beam gamma densitometer. The different flow regimes are determined based on visual observations. The particle image velocimetry (PIV) is utilized in order to obtain non-invasive instantaneous velocity measurements of the flow field. Based on the instantaneous local velocities, mean velocities, root mean squared velocities and Reynolds stresses are calculated. Stratified flow with mixing at the interface is observed at mixture velocity 0.50 m/s. Interfacial waves are observed in upwardly and downwardly inclined flows. At mixture velocity 1.00 m/s, interfacial mixing is increased and dual continuous flows are observed. The degree of mixing largely depends on the pipe inclination. In general, higher water hold-up values are observed for upwardly inclined flows compared to the horizontal and downwardly inclined flows. The slip between the phases increases as the pipe inclination increases. The maximum mean axial velocity is detected in the more viscous oil phase at equal volumetric flow rates of oil and water. In addition, measured mean velocity and turbulence profiles show a strong dependency with pipe inclination. The largest root mean squared velocities and absolute values of the Reynolds stresses are observed close to the pipe wall due to higher mean axial velocity gradients. A damping effect of Reynolds stress is observed around the oil–water interface due to stable density stratification. The presence of interfacial waves enhances turbulence fluctuations in inclined oil–water flows.     

SCX超细分级机进料管内气固两相流数值模拟

以两相流理论为基础,对SCX超细分级机进料管改进后内部的气固两相流动特性进行了数值模拟。分析了气相压力、速度、湍动能和固相颗粒浓度的分布情况,得到了进料管内气固两相的分布规律。结果表明,加入导流片之后,进料管内气相压力、速度、湍动能径向梯度减小,偏流现象减弱;导流片阻碍了固相颗粒的横向运动,改变了颗粒的运动轨迹,使得颗粒浓度分布更加均匀,为后续的分级提供了良好的基础。     

水平管内水环输送模拟稠油减阻特性

基于自主设计加工并搭建的水环输送稠油减阻模拟管路系统,采用500^#白油模拟稠油,试验研究了稠油在水环作用下的水平管流阻力特性,分析了油相表观流速（0.3～1.0m/s）、水相表观流速（0.11～0.72m/s）及入口含水率（0.13～0.49）对水润滑管流流型特征及减阻效果的影响。结果表明：环状水膜可有效隔离并润滑油壁界面,油-水两相流流型总体上呈稳定的偏心环状流结构;水环输送可大幅降低管道输送过程中的压降,其压降值仅为相同油流量下纯油输送压降的1/55～1/27;当入口含水率为0.13～0.27时,水环输送的效能显著,输油效率均高于40;油相表观流速和入口含水率的增加会增大单位管长压降,降低水环输送的减阻效果和输油效能。     

不同操作参数下动态水力旋流器内部油水两相流动的数值模拟

根据计算流体动力学(CFD)的方法,应用Fluent软件对动态水力旋流器内部油水两相流场进行数值模拟,考察了不同入口流量及转筒转速下旋流器内速度场与油水两相的分布情况。结果表明:动态水力旋流器内切向速度呈双涡结构(准自由涡与准强制涡);轴向速度明显小于切向速度且不存在零速度包络面,油相集中于旋流器轴心形成油核,随着流量及转速的增加,各相速度及中心油核浓度均增加。     

自转螺旋扭带管内湍流特性研究

应用激光测速仪LDV(Laser Doppler Velocimeter)对自转塑料螺旋扭带管的湍流特性进行了实验研究。结果表明：与普通光管内流体的流动相比,自转塑料螺旋扭带管内流体的湍流特性发生了根本性的变化：流体在自转塑料螺旋扭带的带动下,呈螺旋流动,而且在近管壁环形区域内流体的轴向分速度明显比管中心区域的高,提高幅度为25％左右,轴向湍流度比无自转扭带的大,提高幅度为68％左右;切向分速度随半径的增大而增大,而且切向湍流度很大,比轴向湍流度大10倍左右。流体的这些湍流特性的测得为自转塑料螺旋扭带管内对流传热强化机理的深入理论研究提供了实验支持。     

水力旋流分离器内流动和油水分离的数值模拟

The fluid flow and oil-water separation were simulated using a Reynolds stress transport equation model of turbulence in water flow and a stochastic model of oil droplet motion,Simulation results give the axial and tangential velocity components,the pressure and turbulence intensity distribution and droplet trajectories for a hydrocyclone of F type and a hydrocyclone proposed by the present authors.The flow filed predictions are in qualitative agreement with the LDV measurements.The results show that the proposed hydrocyclone has better performance than the hydrocyclone of F type due to creating stronger centrifugal force and lower axial velocity.