Visualization study on fluid distribution and end effects in core flow experiments with low-field mri method

Core flow experiment is an important means of simulation experiments to evaluate the effect of displacing agent, but conventionally the internal characteristics in the core cannot be intuitively observed, and then some important information can not be directly acquired by experiments. In this paper, a visualization method was used to detect the water-flooding process by using an improved low field nuclear magnetic resonance imaging（MRI） device, and the images describing the distribution of oil and water were collected. The experimental results show that the distribution of oil and water can be visually detected in an appropriate range of core porosity, and the end effect in many mechanics experiments is found to exist also in natural core flow test, and the influence range is about 0.004 m from the end of a 0.05752 m length natural core. The results also indicate that MRI is an effective tool to study the real time fluid distribution in natural core.

Mechanism and numerical analysis of heat transfer enhancement in the core flow along a tube

The present study introduces the principles of enhanced heat transfer in the core flow to form an equivalent thermal boundary layer in the fully developed laminar tube flow, which consequently enlarges the temperature gradient of the fluid near the tube wall, and thereby enhances the heat transfer between the fluid and the tube wall. At the same time, the increase of flow resistance in the tube is not so obvious. Mechanism analysis and numerical calculation based on air and water have been carried out to verify the principle and method presented in this paper, which may bring positive effects to the design of heat exchanger with high heat transfer efficiency and low flow resistance.

The axisymmetric long-wave interfacial stability of core-annular flow of power-law fluid with surfactant

The long wave stability of core-annular flow of power-law fluids with an axial pressure gradient is investigated at low Reynolds number. The interface between the two fluids is populated with an insoluble surfactant. The analytic solution for the growth rate of perturbation is obtained with long wave approximation. We are mainly concerned with the effects of shear-thinning/thickening property and interfacial surfactant on the flow stability. The results show that the influence of shear-thinning/thickening property accounts to the change of the capillary number. For a clean interface, the shear-thinning property enhances the capillary instability when the interface is close to the pipe wall. The converse is true when the interface is close to the pipe centerline. For shear-thickening fluids, the situation is reversed. When the interface is close to the pipe centerline, the capillary instability can be restrained due to the influence of surfactant. A parameter set can be found under which the flow is linearly stable.

Influence of core sand properties on flow dynamics of core shooting process based on experiment and multiphase simulation

The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant turbulence, the flow pattern of sand particles in the shooting head and core box was reproduced with colored core sands. By incorporating the kinetic theory of granular flow(KTGF), kinetic-frictional constitutive correlation and turbulence model, a two-fluid model(TFM) was established to study the flow dynamics of the core shooting process. Two-fluid model(TFM) simulations were then performed and a areasonable agreement was achieved between the simulation and experimental results. Based on the experimental and simulation results, the effects of turbulence, sand density, sand diameter and binder ratio were analyzed in terms of filling process, sand volume fraction(αs) and sand velocity(Vs).

Isothermal Transport (Core-Flow Type) of Heavy and Ultraviscous Oil in Curved Pipes: A Transient Study by CFD

In the scenery of the oil industry, the remaining resources associated with light oils have an increasingly smaller share in the natural energy resources available to man, and in return the importance of resources associated with heavy oils has increased significantly. One of the drawbacks of this type of oil is associated with its low mobility due to the high viscosity in reservoir conditions, making the transport in pipelines very difficult, especially through pumping methods that require high powers. Thus, the development of new techniques and optimization of some existing technologies, aiming at the commercial use of heavy oil accumulations plays an important role. A viable technique that has been used is the core annular flow, in which small amounts of water are injected close to the pipe wall, lubricating the oil core, reducing friction and decreasing the pressure drop during the flow. In this sense, this work aims to perform, numerically, an energetic and hydrodynamic analysis of a heavy oil-water two-phase flow, using the core-flow technique, in curved pipes, in the Ansys CFX software. Results of the velocity, pressure, and volume fraction distribution of the involved phases are presented and analyzed. It was observed that the proposed mathematical model was able to accurately represent the analyzed phenomena and that a reduction factor in the pressure drop of 28.4 was obtained as compared to the heavy oil single-phase flow.

Sufficiently Elevated Core Body Temperature May Be Necessary to Maintain Cerebral Blood Flow Response throughout the Morning

In comparison to a carbohydrate-rich breakfast, a nutritionally balanced breakfast reportedly leads to a higher core body temperature because of diet-induced thermogenesis (DIT) and also results in higher task performance. This study aimed to examine the relationships among the core body temperature, blood glucose level, cerebral blood flow, and cognitive performance when the core body temperature is raised to a similar extent as in DIT in the morning. This crossover study included 18 male participants who performed four sets of cognitive tests in the morning with four different foot baths and glucose intake conditions. In elevated body temperature (EBT) conditions, the core body temperature was increased by a foot bath at 42˚C or 39˚C, while in low body temperature (LBT) conditions, it was maintained at 35˚C by a foot bath;the participants received no glucose or two intakes of 20-g glucose for each thermal condition. In addition to the core body temperature measurement, the cerebral blood flow in the dorsolateral prefrontal cortex (DLPFC) was measured using near-infrared spectroscopy. Three blood collections were performed to measure the changes in blood glucose levels. The results revealed that in the EBT conditions, the core body temperature remained 0.3˚C - 0.5˚C higher than that at wake-up time, while the glucose intake conditions increased blood glucose levels which remained higher than those during fasting. No significant between-treatment difference was observed in the results of cognitive tests. However, the blood flow in the DLPFC increased during the second test period in the EBT/glucose and LBT/glucose conditions, whereas during the fourth test period, it increased solely in the EBT/glucose condition. Thus, in addition to the blood glucose level, an elevated core body temperature within the physiological range may be needed for long-term maintenance of the cerebral blood flow response.

基于GO-FLOW法的失水事故中紧急堆芯冷却系统可靠性分析

应用GO-FLOW法分析在失水事故过程中紧急堆芯冷却系统的可靠性。根据紧急堆芯冷却系统的原理图建立GO-FLOW图,并计算出系统在各个时间点上的成功概率。结果表明:在发生失水事故下紧急堆芯冷却系统的可靠性随系统的响应动作变化很大,而GO-FLOW法可计算系统的故障概率随时间的变化趋势,是分析多时序、多状态系统可靠性的一种有效方法。

基于SCORE结构的QoS模型实现算法

根据在核心路由器不保留每一个流的状态的SCORE(可扩展核心式)网络结构的特点,在文中,提出了两个分布式算法来实现QoS列表和接纳控制。它显著地提高了在数据平面和控制平面的可扩展性,在灵活性、利用率和服务保证的水平方面提供了可保证的服务,接近提供每一个流的状态的保证型服务。

From molecular dynamics to lattice Boltzmann:a new approach for pore-scale modeling of multi-phase flow

Most current lattice Boltzmann （LBM） models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular dynamics （MD） simulation and LBM to avoid such defect. The basic idea is to first construct a molecular model based on the actual components of the rock-fluid system, then to compute the interaction force between the rock and the fluid of different densities through the MD simulation. This calculated rock-fluid interaction force, combined with the fluid-fluid force determined from the equation of state, is then used in LBM modeling. Without parameter fitting, this study presents a new systematic approach for pore-scale modeling of multi-phase flow. We have validated this ap- proach by simulating a two-phase separation process and gas-liquid-solid three-phase contact angle. Based on an actual X-ray CT image of a reservoir core, we applied our workflow to calculate the absolute permeability of the core, vapor-liquid H20 relative permeability, and capillary pressure curves.

Core concepts of landscape ecology

People from different backgrounds may have various opinions and methods dealing with landscape ecology. As a basic ecology theory for decision making in land use planning and resource management, it should provide sound scientific principles, which means some core concepts for landscape ecology need to be established. This paper attempts to introduce some core concepts for landscape ecology, with brief analysis, including: the integrity of landscape system and the heterogeneity of landscape elements; scale in landscape ecology; mosaics of landscape structure; spatial aggregation and spread of ecological flow; physical cultural nature of landscape; the irreversible and human dominated landscape evolution; the multi value of landscape.

Effect on the Flow Behaviors by Adding Internals in a Riser Reactor

Riser reactor is a key unit in the Fluid Catalytic Cracking (FCC), and it has important influences on increasing the yield coefficient of gas and oil. In this paper, the behaviors of gas-solid two-phase flow in the traditional y-type riser reactor are investigated by numerical simulation. The calculated particle concentration distribution is in good agreement with the experimental data, which verified the advanced models and calculating methods. The non-uniform distribution, such as core-annulus flow, may result in the unreasonable matching relationship of catalyst-to-oil ratio. An optimized riser with cuneal internals is proposed and the comparison of two different structures of riser reactor is presented. The comparison results show that the cuneal internals in the riser both can block effectively the slip down of the particles near wall region and weaken core-annulus flow structure due to the redistribution of particles. The results also prove that the particle concentration distribution becomes uniform along the axial and radial direction in the optimized riser by adding cuneal internals, which would be benefits for the catalytic cracking reactions.

一种剃须刀外壳注塑模具设计

以一种剃须刀外壳的设计为基础,通过分析产品结构特征,设计了一模两腔,动、定模多个斜向复杂抽芯的结构,并运用模流分析软件模拟产品的填充、保压、冷却过程。发现该模具结构设计合理,开合模动作准确可靠,多个斜向抽芯之间无干涉,产品成型表面质量较好,可以达到客户的需求。模具结构新颖,可以为同类设计提供借鉴。

双芯移相变压器在主动配电网电压和潮流调控中的应用分析

双芯移相变压器可以有效控制线路电压和潮流,优化潮流分布,提高电网电能质量。针对分布式电源的高比例接入造成的主动配电网电压波动和偏差问题,以及对潮流大小、方向和均衡度的影响,文章研究了双芯移相变压器的拓扑结构和工作原理;然后分析了串联变压器和励磁变压器的具体结构和作用,梳理了移相变压器分别应用于电压调节和潮流控制时的档位控制策略;最后基于MATLAB/Simulink建立了详细的仿真模型,研究了双芯移相变压器的电压调节效果,并对双线路并联、两路电源并联供电、多路电源并联供电三种应用场景下的潮流控制效果作了比较。仿真结果表明,双芯移相变压器可以在有限的档位内将线路电压控制在允许范围;与双线路并联、多路电源并联供电应用场景相比,两路电源并联供电时的潮流均衡效果最好,潮流偏差最小,本研究为双芯移相变压器的广泛应用提供了参考。

The Impact of Fresh Gas Flow Sevoflurane Anesthesia on Perioperative Hypothermia in Adult Patients Undergoing Elective Open or Laparoscopic Digestive Surgery: A Prospective Randomized Controlled Trial

Background: Because body temperature is such an important indicator and a basic requirement for all kinds of life, even tiny variances might induce undesired changes. This study looked at the influence of FGFs sevoflurane anesthesia on heat preservation in patients undergoing open or laparoscopic digestive surgery. Materials and Methods: Two hundred and forty adult patients (18 - 75 years) with an ASA of I-II were scheduled for open and laparoscopic digestive surgery: open surgery (Group O, n = 120 patients) and laparoscopic surgery (Group L, n = 120 patients). Each group was separated randomly into four subgroups (n = 30 patients) based on FGFs (0.7, 1, 1.5, or 2 L/min). Each patient’s HR, MBP, SpO2, FiO2, fluid infusion amount, urine volume, pre/post-Hb, surgery time, and nasopharyngeal temperatures were investigated and recorded every 15 min from 0 to 120 min. Results: Between groupings, there were no significant changes in demographic features. In 240 patients, the results of various FGFs (0.7, 1, 1.5, and 2 L/min), no statistically significant differences were found in core body temperature over time within each subgroup, with no statistically significant differences between the two (open and laparoscopic) (P > 0.05). Conclusions: The study concluded that FGFs (0.7, 1, 1.5, and 2 L/min) could be utilized safely in adult patients undergoing open or laparoscopic digestive surgery. FGFs (0.7, 1, 1.5, and 2 L/min) provide better body heat preservation during surgical operations.

High-Inclination Coring of Chang-63 of the Yanchang Formation in Huaqing Oilfield, Ordos Basin: Implications for Ancient Flow Direction and Fracture Orientation

A promising method is to use coring of high-inclination well to find ancient flow direction and orient tiny natural fractures in massive sandstone of sandy debris flow. Determination of ancient flow direction can reduce the number of exploration wells, and orientation of natural fractures is of guiding significance to the deployment of water injection development well pattern. In Block X of Huaqing Oilfield, Ordos Basin, the cores of Chang 63 section were obtained from Well Y through 16 coring operations, with a total length of 105 m. Cores is oriented through drilling parameters, the number of cores, the angle between the core edge and horizontal bedding, the coincidence degree of core profile and directional flame structure. Therefore, the micro-fractures on the core are directional. The ancient flow directions of sandy debris flow were restored by load casting, groove casting, groove casting and imbricate structure. Our results show that the ancient flow directions of sandy debris flows were southwest, southeast, northwest, and west from bottom to top. The front of the Wuqi Delta is the main source of blocky sandstone with the best oil-bearing property. Affected by the topography of the lake bottom, the sandy debris flow turned locally in the northeast direction, and the sandy debris flow from this direction was formed. The NEE-SWW-trending fractures formed in the Yanshanian period are most developed in the Huaqing area, which should be considered in deploying the flooding well network. The north-south micro-fractures formed in the Himalayan period can improve the physical properties of tight sandstone, which is of great significance for tight sandstone reservoirs.

汉麻秆芯粉体制备方法的研究进展

由于汉麻本身具有天然的杀菌成分和良好的透湿透气性能,使其在纺织界逐渐受到重视。传统汉麻的外层韧皮纤维利用率较高,但汉麻秆芯则会被当做燃料焚烧或直接作为农业废物填埋掉,这部分大概占汉麻纤维产量的70%~80%。对汉麻秆芯能源的开发利用需要进行粉碎加工处理,以便进一步应用。以汉麻秆芯粉体制备理论、制备方法为研究对象,讨论了锤式粉碎、气流式粉碎、振动式粉碎等工艺技术,为汉麻秆芯粉体的转化利用做好前期处理工序准备。

钠冷快堆小栅板联箱压降对组件流量分配影响研究

钠冷快堆堆芯采用大栅板联箱、小栅板联箱和组件的三级流量分配方式,小栅板联箱的压降影响组件的流量分配,进而影响堆芯的安全,因此进行钠冷快堆小栅板联箱压降对组件流量分配影响研究有重要意义。根据小栅板联箱压降造成组件流量分配偏差的机理,提出了理论计算模型和堆芯组件优化设计的方法,并针对中国实验快堆(CEFR)堆芯进行了组件压降的优化设计,通过优化设计降低了CEFR燃料组件流量分配负偏差。结果表明,在进行钠冷快堆堆芯热工水力设计时,需要结合实际堆芯布置分析组件压降设计值的优化方向,并进行敏感性分析,以确定组件的最优设计压降,将小栅板联箱压降对组件流量分配影响降低到最低程度。本文结果可为钠冷快堆堆芯热工水力设计提供参考。

基于功率恒定的防饱和在线取电方法

基于厄流线圈取电装置提出了一种防止铁磁磁心饱和的方法,该方法使用旁路泄流电路将流入电流互感器过多的电流引入到旁路电路中消耗掉,将输出功率作为反馈值来调节旁路电路中开关管的关断,通过控制输出的功率大小,输电线路在宽范围电流内实现恒功率输出和防止电流互感器磁心到达饱和。根据电流互感器各方面的要求,建立电流互感器3D模型,将3D模型导入到Maxwell中对电流互感器本身进行有限元仿真分析,得到电流互感器内部各项参数,再将经过有限元分析的电流互感器模型导入到ANSYS中与外部电路组成取电电路进行联合仿真,通过仿真结果验证电流互感器的取电能力。再加入本次对电流互感器取电优化部分,通过电流互感器二次侧谐振的方式增加一次侧输电线路的等效阻抗,考虑到电流互感器磁心饱和的问题,采用旁路泄流电路将过多的电流通过旁路绕过电流互感器一次侧回到输电线路当中的方法解决。

气液两相条件下叶片开孔对电潜泵性能和内部流场的影响

为了研究电潜泵内部流动机理,从而改善高含气工况下电潜泵的气液混输性能,文中基于欧拉-欧拉非均相流模型,对不同入口含气率工况下叶片开孔前后的气液两相流动特性进行了数值模拟分析,探究了气液两相流条件下叶片开孔对电潜泵性能和内部流场的影响.结果表明,在纯水工况以及低含气率、小流量工况下,叶片开孔会降低电潜泵性能;但是叶片开孔可以改善电潜泵在大流量下的气液混输性能.叶片开孔后会改变叶轮内部压力分布,使电潜泵叶轮内部平均压力升高,进而改善叶轮内部流态.叶片开孔后会冲散气相聚集,使气体分布更加均匀,叶轮流道内涡核分布明显减少,减少了能量耗散.该研究为改善电潜泵气液混输性能提供了理论依据.

碳酸盐岩储层酸蚀蚓孔物模实验研究进展

酸蚀蚓孔是碳酸盐岩储层基质酸化最典型、最基本的特征,其尺寸和形态对酸化效果有着重要影响,关于酸蚀蚓孔的物模研究对于碳酸盐岩储层基质酸化机理研究及现场施工设计具有重要指导意义。文章分别综述了线性流和径向流两种岩心流动实验研究的重要成果和最新进展,指出酸蚀蚓孔实时表征是线性流岩心流动实验研究的发展方向,针对渗透率、尺寸等岩心参数对酸蚀蚓孔发育的影响,应结合融合电测和示踪剂的蚓孔实时表征方法进行进一步研究。针对酸液突破岩心时孔隙体积倍数(PVBT)与岩心参数之间关系的认识,后续应进一步升级径向流岩心流动实验及表征设备,从而开展不同因素对酸蚀蚓孔发育影响的研究,重点解决酸蚀蚓孔从实验尺度升级到现场尺度问题。建议加强电测法室外模拟实验及现场应用研究,从而实现实验尺度和现场尺度酸蚀蚓孔的实时观测和表征。