Distribution of void fraction for gas-liquid slug flow in aninclined pipe

In order to investigate the effect of inclination angle on the spatial distribution of phases, experiments on gas-liquid two-phase slug flow in an inclined pipe were carried out by using the optical probe and an EKTAPRO 1000 high speed motion analyzer. It has been demonstrated that the inclination angle and the mixture velocity are important parameters to influence the distribution of void fraction for upward slug flow in the inclined pipe. At high mixture velocity, the gas phase profile is axial symmetry in the cross-section of the pipe. This is similar to that for vertical slug flow. In contrast, most of the gas phase is located near the upper pipe wall at low mixture velocity. By measuring the axial variation of void fraction along the liquid slug, it can be concluded that there is a high void fraction wake region with length of 3～4D in the front of liquid slug. In the fully developed zone of liquid slug, the peak value of the void fraction is near the upper wall.

Computational fluid dynamic simulations on liquid film behaviors at flooding in an inclined pipe

The complex liquid film behaviors at flooding in an inclined pipe were investigated with computational fluid dynamic(CFD) approaches. The liquid film behaviors included the dynamic wave characteristics before flooding and the transition of flow pattern when flooding happened. The influences of the surface tension and liquid viscosity were specially analyzed. Comparisons of the calculated velocity at the onset of flooding with the available experimental results showed a good agreement. The calculations verify that the fluctuation frequency and the liquid film thickness are almost unaffected by the superficial gas velocity until the flooding is triggered due to the Kelvin–Helmholtz instability. When flooding triggered at the superficial liquid velocity larger than0.15 m·s-1, the interfacial wave developed to slug flow, while it developed to entrainment flow when it was smaller than 0.08 m·s-1. The interfacial waves were more easily torn into tiny droplets with smaller surface tension, eventually evolving into the mist flow. When the liquid viscosity increases, the liquid film has a thicker holdup with more intensive fluctuations, and more likely developed to the slug flow.

Axial power flow distributions of ultrasonic guided waves in viscous liquid-filled pipes

The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the (pipe’s) wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.

K-ε-T MODEL OF DENSE LIQUID-SOLID TWO-PHASE TURBULENT FLOW AND ITS APPLICATION TO THE PIPE FLOW

To predict the characteristics of dense liquid-solid two-phase flow, K-Ε-T model is established, in which the turbulent flow of fluid phase was described with fluid turbulent kinetic energy Kf and its dissipation rate Εf, and the particles random motion was described with particle turbulent energy Kp and its dissipation rate Εp and pseudothermal temperature Tp. The governing equations were also derived. With K-Ε-T model, numerical study of dense liquid-solid two-phase turbulent up-flow in a pipe is performed. The calculated results are in good agreement with experimental data of Alajbegovic et al. (1994), and some flow features are captured.

Microscale Infrared Observation of Liquid-Vapor Phase Change Process on the Surface of Porous Media for Loop Heat Pipe

Loop Heat Pipe (LHP) performance strongly depends on the performance of a wick that is porous media inserted in an evaporator. In this paper, the visualization results of thermo-fluid behavior on the surface of the wick with microscopic infrared thermography were reported. In this study, 2 different samples that simulated a part of wick in the evaporator were used. The wicks were made by different two materials: polytetrafluoroethylene (PTFE) and stainless steel (SUS). The pore radii of PTFE wick and SUS wick are 1.2 μm and 22.5 μm. The difference of thermo-fluid behavior that was caused by the difference of material was investigated. These two materials include 4 different properties: pore radius, thermal conductivity, permeability and porosity. In order to investigate the effect of the thermal conductivity on wick’s operating mode, the phase diagram on the q-keff plane was made. Based on the temperature line profiles, two operating modes: mode of heat conduction and mode of convection were observed. The effective thermal conductivity of the porous media has strong effect on the operating modes. In addition, the difference of heat leak through the wick that was caused by the difference of the material was discussed.

Two-flow model for piping erosion based on liquid-solid coupling

Previous studies have indicated that piping erosion greatly threatens the safe operation of various hydraulic structures. However, few mathematical models are available to perfectly describe the erosion process due to the complexity of piping. The focus of the present work is to propose a new fluid solid coupling model to eliminate the shortcomings of existing work. A 'pseudo-liquid' assumption is suggested to simulate the particle movement in the erosion process. Then, based on the mass and momentum conservations of the moving particles and flowing water, a new two-flow model is established by using the continuity equations and motion equations. In the model, the erosion rate of soil is determined with a particle erosion law derived from tests results of STERPI. And ERGUN's empirical equation is used to determine the interaction forces between the liquid and the solid. A numerical approach is proposed to solve the model with the finite volume method and SIMPLE algorithm. The new model is validated with the tests results of STERPI. And the soil erosion principles in piping are also explored.

光学舱推进剂补加过程的热分析仿真与试验研究

推进剂补加是确保光学舱在轨长寿命工作的重要功能,补加过程面临的热环境条件比以往任务恶劣,全过程热控制十分必要。针对光学舱推进剂补加过程的复杂传热新问题,建立包含压气机、液冷模块和环路热管等部件的光学舱平台集成热数学模型,进行热分析仿真研究,并开展系统级热试验。对比高温和低温2种补加条件的瞬态热分析和热试验结果,研究传热关系和温度变化规律;针对热试验中垂直热管因重力因素从不运行至运行的瞬态过程,提出一种变热导率仿真方法;提出高温补加优化设计方案并进行在轨预示。结果表明:瞬态仿真结果与试验结果吻合良好,验证了热分析方法和仿真模型的准确性和有效性;在轨补加采用压气机本体预热并启动2套环路热管,压气机的最高温度≤34.1℃,预热总功耗50 Wh,满足指标要求。研究结果对于光学舱停靠空间站期间的推进剂补加流程设计具有一定参考价值。

波纹结构液氮脉动热管传热传质特性研究

低温热管换热器是天然气液化系统中的关键装置,液氮脉动热管作为其核心器件具有体积小、换热效率高等特性,可有效克服系统冻堵及设备紧凑等问题,然而开展相应实验难度较大,因此通过数值模拟方法研究其内部传热传质规律具有重要意义。首先,文章通过UDF(User-Defined Functions)编写自适应相变模型,研究了典型液氮脉动热管的传热传质特性。随后,在冷凝段优化设计了波纹结构,结合相态分布与轴线温度方差值,对比分析了充液率为50%情况三种液氮脉动热管传热传质特性,结2果表明5 mm波纹结构热管两侧方差值为51.49 K与99.22 K2,工质循环速率较快且轴线温度分布均匀。最后,研究了充液率分别为30%、50%与70%情况下5 mm波纹结构的脉动热管的传热性能。结合相态、温度及轴线温度分布分析得出充液率过高或过低均会导致热管内部产生液塞,充液率较高时,轴线温度均匀分布,热管充液率为70%时,综合性能最佳。

充液复杂管道结构损伤程度识别有限元模拟

基于小波包分解法研究充液复杂管道结构损伤程度与损伤指数之间的关系,提出一种针对于充液复杂管道结构的损伤程度识别方法。分别建立相同损伤深度、不同损伤圆心角和不同损伤深度、不同损伤圆心角的充液复杂管道结构模型,研究损伤程度与损伤指数之间的规律。研究发现,当损伤深度为定量时,以损伤面积为变量的损伤程度与损伤指数间呈非线性相关关系,损伤指数随损伤面积的增加而呈先增后减的趋势;当损伤圆心角为定量时,以损伤深度为变量的损伤程度的增加会使得损伤指数值呈先减后增的趋势。结果表明,基于充液复杂管道结构损伤程度与损伤指数之间的关系,可快速实现损伤程度的识别并对损伤程度的发展趋势进行预判。

倾斜管不同黏度气液两相段塞流持液率实验及预测方法

准确预测持液率可为井筒中的流型判断和压降预测提供重要依据,段塞流为稠油井筒中最常见流型,井筒高黏流体将加重气液两相滑脱,导致现有持液率模型应用于高黏流体的预测精度变差。为此,基于多相管流实验平台,在内径为60 mm的测试管段内开展段塞流持液率实验,获取了不同黏度、不同倾角段塞流流型及持液率数据,研究了黏度对持液率和流型转变的影响规律,并结合实验现象和理论推导,提出了倾斜管不同黏度气液两相段塞流持液率新模型。研究结果表明:液相黏度的增加,会增加液相与管壁之间的黏滞力,导致持液率增加;黏度对持液率的影响会改变段塞流与其他流型的转变界限。以Kora液塞区持液率关系式为基础,建立了用混相黏度代替液相黏度的倾斜管气液两相段塞流持液率新模型,并利用实验数据和文献数据进行了验证,证实新模型具有更高的精度。该研究可为预测稠油井井筒压降提供技术支持。

高扬程泵站虹吸式出水流道虹吸形成过程分析

为研究高扬程泵站虹吸式出水流道虹吸形成过程,以某高扬程泵站的出水流道及出水池为研究对象,建立三维模型并使用Fluent仿真计算了虹吸管流态变化。针对3种出水池水位使用VOF模型计算其压力、流速等参数。驼峰段原角度为段前150°、段后160°,在虹吸段顶端使用DN350的真空破坏阀,同时改变驼峰段角度进行优化,发现将段前角度增加10°后,虹吸形成时间为448 s,相较于优化前缩短了56 s,改善了泵启动过程。分析发现,不同水位下虹吸形成时压力分布较为均匀;水位较低时流速分布不均,不良流态产生,低水位造成的负面影响远大于高水位;在驼峰段安装DN350真空阀能减小水力损失,对虹吸形成过程起到促进作用;真空阀会影响经典断面处流速分布,产生高流速区,出水池水位较低时,该现象使得流速分布不均。

高含硫天然气净化装置过滤器液位计引管失效分析

介绍了某大型净化厂脱硫单元原料气过滤器失效的问题,对过滤器液位计引管直管段及焊接法兰进行化学成分、金相组织、断口形貌等分析,探讨失效的主要原因。结果表明,原料气过滤器失效的原因是过滤器的材质不符合要求,长期处于偏低温度和酸性介质环境中导致原料气过滤器氯化物应力腐蚀失效。准确掌握设备失效成因,有针对性地采取防护措施,对于确保装置长周期安全运行具有重要的意义。

强迫振动下垂直管道固液两相流数值模拟研究

粗颗粒固液两相流的管道输运适用于深海采矿工程.扬矿管道在流致振动作用下的内部固液两相流的输运机理尚未被完全探究.因此,采用计算流体动力学(CFD)与离散元(DEM)耦合的方法,分析不同粒径、不同振动频率与振幅和不同浓度工况下在强迫振动管道中的粗颗粒动力学特性以及管内流场变化特性.其中,将管道的振动简化为一维径向振动,将实际工况中的柔性管道假定为刚体管道.研究表明,在管道振动过程中,大颗粒相比小颗粒的惯性更大,而流体也需要更大的速度产生更大的曳力推动大颗粒,导致更大的轴向流场速度以及更大的轴向颗粒速度.随着粒径增大,大颗粒对流场的扰动更大,导致流体与壁面间的作用力更大;并且大颗粒与壁面间的碰撞和摩擦作用力更大,因此壁面剪应力增大.同时,大颗粒与流体间摩擦损耗的能量也更大.因此管道需要更大的能量将其输运,导致振动管道内的压降增加.增大管道振动频率与振幅会导致颗粒在截面上的分布更加分散,同时对流场扰动更大,然而对轴向流场速度的影响相对较小.增大进料浓度使颗粒间、颗粒与流场间的作用更加频繁,导致颗粒分布发生变化,并导致更大的轴向流场速度和湍动能.

Development of ToSPACE for Pipe Wall Thinning Management in Nuclear Power Plants

A number of piping components in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, SPE (Solid Particle Erosion), LDIE (Liquid Droplet Impingement Erosion), etc. Those mechanisms may lead to thinning, leak, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 of USA in 1986 and in Mihama unit 3 of Japan in 1994, the pipe wall thinning management has emerged as one of the most important issues in nuclear power plants. To manage the pipe wall thinning in the secondary system, Korea has used a foreign program since 1996. As using the foreign country’s program for long term, it was necessary to improve from the perspective of the users. Accordingly, KEPCO-E & C has started to develop the 3D-based pipe wall thinning management program (ToSPACE, Total Solution for Piping And Component Engineering management) from eight years ago, and the development was successful. This paper describes the major functions included in ToSPACE program, such as 3D-based DB (Database) buildup, development of FAC and erosion evaluation theories, UT (Ultra-sonic Test) data reliability analysis, field connection with 3D, automatic establishment of long-term inspection plan, etc. ToSPACE program was developed to allow site engineers performing the selection of inspection quantity at each refueling outage, UT data reliability analysis, UT evaluation, determination of next inspection timing, identification of the inspecting and replacing components in 3D drawings, etc., to access easily.

多级液体分布器流动特性分析

新型污水处理工艺的处理效率受到反应池流场扰动影响较大,引起流场扰动的主要因素是液体分布器出流均匀性和出孔湍流强度。目前,关于分布器均匀布水的研究较少,尚未揭示淹没流的孔口阻力特性与沿程阻力特性协同机制。本文提出一种孔径梯度变化的多级液体分布器结构,应用于某示范工程中,建立了基于物质传输模型的淹没流液体分布装置有限元分析方法,将数值模拟结果与试验结果进行对比。结果表明:试验得到2个测试平面内氯离子质量浓度最大偏差为1.97%,有限元模拟得到多级液体分布器的克里斯琴森均匀系数为89.1%。在进水过程中,试验和有限元模拟所得新进水质量分数的变化趋势一致,结果吻合较好,证明了新型污水反应器结构的合理性,且满足工程应用要求。

液体火箭发动机涡轮泵管式扩压器时序效应数值研究

为分析管式扩压器的时序效应对高速涡轮泵性能以及压力脉动的影响并阐明其影响机制,对某液体火箭发动机高速涡轮泵全流域进行三维定常和非定常数值计算,研究了管式扩压器时序效应对涡轮泵外特性的影响规律,采用熵产理论对涡轮泵内部的能量损失进行分析,并通过压力脉动均方根方法对涡轮泵内的压力脉动进行评估。结果表明:随着管式扩压器叶片与蜗壳隔舌夹角的增大,涡轮泵效率和扬程整体趋势均为先升高后降低,两者的变化幅度分别为0.75%、1.68%,当管式扩压器叶片吸力面出口边与蜗壳隔舌的夹角为20.5°、25.5°时,涡轮泵具有较好的性能,其影响机制由蜗壳隔舌下方的扩压管出口附近涡流和能量损失变化决定。动静干涉效应是涡轮泵内压力脉动的主要原因,时序效应对涡轮泵出口和蜗壳隔舌附近压力脉动的变化幅度分别为37.7%、67.6%。蜗壳流道内压力脉动的最大值位于蜗壳隔舌下方扩压管出口区域,时序效应对压力脉动最大值的变化幅度为20.5%。研究结果可为液体火箭发动机涡轮泵性能和振动的优化提供一定的参考。

基于液膜反转的定向井临界携液模型研究

气井积液是苏里格区块大斜井开采中后期面临的一个重要难题,目前适用于定向井的临界携液模型研究较少,且常用携液模型忽略了管径、液体流速和角度的影响。借助多相管流实验开展了定向井携液机理实验,分析了管径、角度、液体流速等因素对气井积液的影响规律,并根据液膜反转机理,在BELFROID模型和WALLIS模型基础上,利用实验数据拟合出了WALLIS模型中参数C和m的计算方法,并考虑管径、气体密度、液体密度、角度、液体表观流速、重力加速度等参数,建立了新的临界携液模型,新模型在预测VEEKEN文献中62口积液气井时结果显示,准确率为91.94%,新模型的建立不仅是液膜反转理论的进一步完善,同时也为定向井积液时机的预测提供理论支撑。

下穿地下构筑物群桩富水砂层盾构通道MJS预加固施工技术研究及应用

下穿地下构筑物群桩富水砂层盾构通道MJS预加固施工技术包括技术原理、实施思路和具体施工步骤,其由密布群桩富水砂层水平引孔、富水砂层水平引孔砂土流失控制、常规水平MJS注浆加固3个环节组成。技术采用引孔机钻杆+外套管进行水平引孔,实现立柱桩和高强度管桩的穿越,以及富水砂层中的长距离成孔,引孔过程中通过双液注浆对注浆线路进行一次加固,同时利用洞口安装的法兰盘+止回阀来进行砂土流失控制,减少引孔对地下构筑物和周边环境的影响,引孔完成后,进行常规MJS注浆加固,达到预加固目标,并形成具体的下穿地下构筑物群桩富水砂层盾构通道MJS预加固施工步骤指导施工,大幅减少对地下构筑物和周边环境的影响,减少泥浆浪费,提高施工效率,经济社会效益较好,具有较好的推广应用价值。

液冷散热式预制舱储能系统冷却液回路设计

随着液冷式预制舱储能推广,亟需冷却液回路设计方法。从工程实用角度出发,针对液冷板,提出了普适于常见3至4排电芯电池包的U形流道结构,分析了流道宽度、高度设计方法;针对液冷管路,提出管路并联式排布和管路变径的方案,阐述了管路流量、节流孔尺寸设计方法。依托1 MW/2 MWh海岛储能工程,分析了工程设计实例。收集并分析了现场运行情况,所设计方案能将电池温度控制至预定区间,电池温差不超过3℃。

次级源和误差传感器布放对带弹性障板的充液直管声振复合有源控制的影响

针对充液管路系统噪声有源控制问题,研究了次级源和误差传感器布放对带弹性障板的充液直管管路系统有源消声与有源消振复合控制效果的影响。基于声固耦合方法建立了带弹性障板的充液直管管路系统的有限元模型,在声激励下对比了次级声源布放对系统有源消声性能的影响,并在组合激励下分析了次级力源、次级声源和误差传感器布放对系统复合有源控制的影响。结果表明,非对称分布的次级声源容易激起管壁振动,进而带动障板振动,导致有源消声效果不佳;采用对称分布的次级声源可使低频段的降噪量提高10 dB以上。复合有源控制可进一步提升全频段的控制效果。通过增加振动误差传感器数量,可使绝大多数频点的降噪量提高1∼20 dB不等。此外,在管壁上布放的两圈次级力源的间距小于管壁振动波长的1/4,且都不位于管壁振动节点附近时控制效果更好。