基于VOF模型与动网格技术的油气悬架气液两相流数值模拟

针对某型大吨位矿用自卸车油气悬架为油气两相相互接触的特点,拟从多相流数值仿真的角度对其非线性刚度阻尼特性进行分析。首先,在探讨了现有多相流建模方法适用性、湍流模型适用性的基础上,结合VOF模型和动网格技术,在Fluent软件中建立悬架的气液两相流模型,并采用UDF方法对两相流模型的边界运动形式进行预定义。其次,模拟了悬架拉伸和压缩状态下的内部瞬态流场特性,得到不同时刻相应流道中的速度和压力云图,提取出气室内压力的变化以及悬架内因阀系结构而产生的压力差的变化,进而计算得到其刚度和阻尼特性曲线。再次,将所求力学特性曲线通过Spline函数导入ADAMS/View中,建立了某型矿用自卸车的多体动力学模型,开展了随机道路平顺性仿真分析,并借助实车道路振动测试验证了仿真结果的准确性。最后,通过两相流仿真分析了阻尼孔倒圆大小、开孔角度、不同单向阀开度对悬架阻尼特性的影响。     

混凝土泵车输料管中两相流数值模拟研究

混凝土泵车输送管中的混凝土流动为典型的两相流,目前对其流动特性研究只能通过半经验的实验方法。通过建立基于双流体混凝土两相流模型,进行了输料管多相流场的数值模拟,为混凝土泵车输料管数字化设计和输送性能研究提供了定量化、可视化的设计模型。对混凝土泵车输料管设计和浇筑实验提供了理论基础。     

油田多相流计量方法研究与探讨

分析了多相流分离计量和在线计量方法,总结了多相流计量的核心技术和研究进展,分析了弯管流量计测量油水和气水两相流实验数据,结果表明弯管测量油水两相流准确性较好,测量气水两相流误差较大.探讨了弯管流量计与密度计或与其它流量计配合的测量方案.     

气-液两相流空隙率的测量方法

两相流或多相流参数的测量在各种生产过程和能源系统中愈来愈引起人们的重视。例如,在工业系统和实验室研究中,有时需对下列对象进行测量:油田开采中油一气流量,悬浮液管道,物料的气体输送,流化床,化学反应器,脱盐装置,地热能站,核反应器等。这些测量都涉及到了多相流问题。毫无疑问,多相流参数的测量在各个领域的应用都是很重要的。在与核反应有关的研究中,对多相流参数检测技术的发展起了相当的推动作用。这里不仅仅是为了获取稳态操作下的设计信息,同时也是为了在过渡状态和事     

气油二相流含气率标定方法的研究

气油二相流是工程中常见的一种多相流，如何标定其含气率一直是气油二相流研究中的一个难点。本文通过对几种气油二相流含气流的标定方法研究，结合作者实践，分析了各种方法的特点，认为量筒法，压力法及浮法能力方便，准确地用来对气油二相流含气率进行标定。     

过程层析成像技术的现状与展望

对过程层析成像技术进行了分析,指出过程层析成像技术的产生和发展是与科学研究及工程实践中对两相流或多相流过程内部信息的迫切需求密切相关,过程层析成像技术的发展有着广阔的前景.     

双介质双排量轴向柱塞泵配流窗处液体的泄漏和掺混特性

为进一步提高反渗透海水淡化系统的集成度及其动力元件的工作效率，同时降低该系统的能耗，从理论上推导一种新型反渗透海水淡化变量电机泵中，双介质双排量轴向柱塞泵配流窗处两种不同浓度海水的泄漏和掺混特性。同时，通过有限元模拟的方法，研究分析该柱塞泵在不同结构参数和运行参数下两对配流窗处两种不同浓度海水的泄漏和掺混特性。通过与理论分析结果对比，验证分析模型和所得结果的正确性。分析结果表明：该柱塞泵两侧配流窗处不同浓度海水的泄漏和掺混特性随缸体转速的升高而小幅减弱，随液膜厚度增加而明显增强；该柱塞泵外侧配流窗处不同浓度海水的泄漏和掺混特性几乎不受浓盐水侧压力变化的影响，而其内侧配流窗处不同浓度海水的泄漏和掺混特性则随着浓盐水侧压力的增加而明显减弱。研究结果为海水淡化双介质双排量轴向柱塞泵设计及其配流窗处不同浓度海水的泄漏和掺混特性研究提供参考。     

双轮铣槽机泥浆管内部固液两相流动的仿真分析

应用Fluent数值模拟软件中的Mixture多相流模型、可实现的k-ε湍流模型及SIMPLEC算法,对双轮铣槽机泥浆泵送系统的泥浆管内部固液两相流场进行了数值模拟,初步揭示管内的流动规律,并分析了不同圈数、不同来流速度、不同颗粒体积浓度及不同颗粒直径对流动的影响.仿真结果可以为双轮铣槽机的泥浆泵选型及施工时泥浆泵的控制提供参考.     

基于Fluent的异形油箱内气泡与油液融入规律的研究

液压油箱作为液压系统主要辅件,其结构和充气参数对溶解在油液中的气泡与油液的分离、融入现象等具有重要影响。以紧凑式特种车辆异形油箱为研究对象,利用Fluent多相流模型中的欧拉-欧拉模型,对特种车辆异形油箱内部流场进行气液两相流三维数值模拟,通过油箱出油口气体体积分数变化的监测,研究液压系统油箱内不同充气压力、液压泵不同转速作用下,气泡与油液融入的规律性关系,为液压油箱及系统的设计选型提供参考。     

泥浆脉冲发生器转子水力转矩多相流数值模拟

连续波脉冲发生器是现代油气钻井系统的核心部件之一,脉冲发生器主要部件是其中的定子和转子,定、转子的相对运动会导致钻井液的复杂变化。定转子附近机构复杂,钻井液流速快,有明显的湍流现象,而且实际钻井液主要是由水和细砂组成的多相流混合物。着重考虑多相流对转子水动力特性的影响,使用CFD数值仿真方法比较不同情况下,考虑多相流因素和纯水时的转子水动力特性。研究表明:转子水动力转矩基本不受多相流因素的影响,与来流速度、定转子间隙、相对旋转角度关系密切。研究还发现,流道内固相物质在定转子衔接处有积聚的特性。     

Analysis and modeling of a two-phase jet pump of a thermal management system for aerospace applications

Jet pumps are devices capable of pumping fluids to a higher pressure by inducing the motion of a secondary fluid employing a high-speed primary fluid. The main components of a jet pump are a primary nozzle, secondary fluid injectors, a mixing chamber, a throat, and a diffuser. The work described in this paper models the flow of a two-phase primary fluid inducing a secondary liquid (saturated or subcooled) injected into the jet pump mixing chamber. The model is capable of accounting for phase transformations due to compression, expansion, and mixing. The model is also capable of incorporating the effects of the temperature and pressure dependency in the analysis. The approach adopted utilizes an isentropic constant-pressure mixing in the mixing chamber and at times employs iterative techniques to determine the flow conditions in the different parts of the jet pump.     

A new gas dynamic model for the gas exchange process in two stroke loop and cross scavenged engines

A gas dynamic model is developed to represent the gas exchange process in a cross or looped scavenged engine based on Dedeoglu's⁴ experiments. The scavenge process is considered to be in three phases—a displacement phase, a short-circuiting phase and a mixing phase. The cylinder is subdivided into three zones—an air zone, a gas zone and a mixing zone. Two models are presented to calculate the air and gas flow rates into the mixing zone. One model assumes a constant gas entrainment ratio and the second model a linear variation in the proportion of the cylinder occupied by the gas zone. Calculations presented for a crankcase scavenged engine, show that a good representation may be made of the scavenge process by the new model. The constant entrainment ratio mixing model is less sensitive to input parameters than the second model proposed.     

Effect of superhydrophobic surfaces on bubble column flow dynamics

Bubbly flow in bubble column reactors promotes mixing necessary for many chemical processes. We show that if superhydrophobic-coated material is introduced into a bubble column, there can be a substantial difference in gas holdup and earlier initiation of churn-turbulent flow which can alter larger-scale mixing without a need to change the superficial gas velocity. Addition of superhydrophobic surface can also cause bubbles to (directly or indirectly assisted by the surface) escape faster to the free surface resulting in a reduced void fraction (i.e., reduced gas holdup). As the flow becomes optically opaque at few percent gas phase volume fraction, we utilize two dual plane wire mesh sensors to obtain velocity profiles and bubble size distributions, in addition to the traditional pressure and level based gas holdup measurements to calculate average phase fraction. Additionally, a custom build photon-counting dual energy threshold X-ray computed tomography system is employed to get a higher resolution measurement of the time average phase fraction non-intrusively. We report satisfactory agreement between these techniques with differences arising for understood reasons, and use the insight thus yielded to discuss the effect of superhydrophobic surfaces on bubble column flow dynamics.     

炭黑在水平管道中气力输送的数值模拟与分析

建立了炭黑气力输送水平管道气固两相流的数学模型,采用计算流体动力学方法,对炭黑在不同工况条件下的水平管道中的气力输送进行了模拟。通过模拟与分析,得到了固相的速度和浓度分布、输送气速对固相速度和固相浓度的影响、输送量对固相速度和固相浓度的影响、各种输送量下的压降和最佳经济速度。     

磁场复合电解加工流场分布特性的数值模拟

采用欧拉-欧拉多流体方法,对磁场复合电解加工的气液两相流进行了数值模拟,研究磁场作用下电解质流场流速、气泡体积分数分布等流体力学信息.仿真表明,静液状态时,在磁场的作用下,液相产生了流速,流速呈环状分布,气相呈搅拌状分布.入口添加流速后,在低流速下,液相速度仍呈环状分布,气相呈搅拌状分布;在较高流速下,液相和气相的分布与无磁场时的分布相近.     

Fluid flow signals processing based on fractional Fourier transform in a stirred tank reactor

The analysis of fluid flow signals and the characterization of fluid flow behavior are of great importance for two-phase flow studies. In this work, the fractional Fourier transform (FRFT), which was based on the optimum order calculated by stepping search method, was proposed to extract the characteristics of fluid flow signals. Meanwhile, the largest Lyapunov exponent (LLE), which is an indication of the chaotic degree of mixing process, was adopted to quantify fluid flow behavior. The maximum amplitude (MA) and LLE value were taken together to inquire into the relationship between the characteristics of fluid flow signals and the characterization of fluid flow behavior. In addition, differences between the two adjacent values (AD) and the maximum differences (MD) are employed to further analyze the differences in behavioral characterization with MA and LLE. The results show that the MA value performs the same increasing trend as the LLE value when the gas flow rate and agitation speed increase. AD and MD values of the MA are one to two orders of magnitude greater than those of the LLE. The eigenvalues (MA) solved by the FRFT method is facilitates capturing small changes owing to changes in external conditions. These findings can provide new ideas for the extraction and characterization of fluid flow behavior.     

往复泵气液均相流有效功率计算方法的研究

根据往复泵的理论循环指示图，分别建立了气体按等温过程和多变过程压缩和膨胀时，气液均相流往复泵有效功率与有效扬程的计算公式。同时根据气液均相流能量平衡方程，建立了气液均相流往复泵有效功率与有效扬程的计算公式。两种方法所建立的有效功率与有效扬程的计算公式完全相同。分析结果表明，在气液均相流条件下，往复泵的有效功率由两部分组成：一是对液体作功所消耗的功率；二是对气体作功所消耗的功率，这部分功率取决于气体的压缩与膨胀过程。     

气体对磁流体动力学传感器影响机理的探讨

由于气体和导电流体性质上的差异,导电流体中气体的存在将对磁流体动力学(MHD)传感器的输出特性产生影响。基于电磁感应理论和两相流理论,文章推导并建立了导电流体中含气体的MHD传感器VOF模型。通过ANSYS Fluent对含气体的MHD传感器输出特性进行仿真分析,同时搭建试验平台对不同气体含量MHD传感器进行试验验证。结果表明,导电流体中的气泡在低频时容易被拉伸撕裂成小气泡并随着角振动分散,同时使得流体环流场和电场产生偏移和畸变,角振动频率越低,此现象越明显;当导电流体中不含气体时角振动频率和幅值、重力加速度及偏心等外部因素对MHD传感器的输出特性无影响;当导电流体中含有气体时,MHD传感器的输出特性畸变等随气体含量、重力加速度和偏心的增大而增大,随角振动频率和幅值的增大而减小。文章研究成果能够为MHD传感器导电流体灌装工艺控制提供指导,有助于MHD传感器精度和稳定性的提升。     

Computing gas/melt free interface of gas-assisted injection molding

A solution was put forward to predicate the flow pattern of gas penetration in gas-assisted injection molding. The differential equations that governed the flow field and gas/melt free-interface evolution were analyzed and discretized by Galerkin finite element method, and the free interface was located by the volume of fluid method. The gas was assumed as a fluid phase of constant density and viscosity instead of being simply treated as boundary conditions. The non-Newtonian property of polymer melt was characterized by Carreau model with four parameters. As a case study, different kinds of gas channel were modeled. The gas/melt free interface was captured. The gas front velocity and the pressure of gas/melt front were also computed. The edge shape of gas channel was discussed, which are helpful for the design of gas-assisted injection molding.     

机械搅拌槽内非牛顿流体内流特性研究

在工业生产中获得广泛应用的机械搅拌混合,其流体大都是非牛顿流体,具有与牛顿流体不同的流变性质（弹性效应,剪切稀化以及剪切变稠）,所以急需对非牛顿流体情况下搅拌槽内的内流特性开展研究。基于Lin-A315桨型的粒子图像测速技术（Particle Image velocimetry,PIV）试验结果对搅拌槽内非牛顿流体的流场特性进行定常/非定常数值模拟,研究不同质量分数的黄原胶溶液在不同搅拌速度下的轴面流速分布、湍动能分布、径向截线的流速剖面、所需要的搅拌混合时间以及搅拌能耗。结果表明,数值模拟可以很好地模拟分析机械搅拌槽内非牛顿流体的流场特性;提高搅拌速度可以增加槽内主循环流的范围和强度,搅拌槽内涡的分布和湍动能分布范围也相应变大,与100 r/min相比,300 r/min和500 r/min工况下的轴向速度最大值增加3.6倍和5.9倍,所需要的混合时间缩短0.46倍和0.36倍;增加黄原胶溶液的浓度会减小流场的主循环流范围,增加速度梯度,降低槽底区域循环速度,所以与非牛顿流体溶液浓度的变化相比,所需要混合时间对转速变化更为敏感;另外提高搅拌速度会增加搅拌能耗,因此对低浓度非牛顿流体宜选择中等转速、高浓度非牛顿流体宜选择高转速以有利于溶液混合和能源节约。