垂直螺旋输送机气固两相流场输送研究

针对垂直螺旋输送机内散粒物料输送效率低下问题,提出气体对物料输送的影响。应用气固两相流动原理,建立空气相与颗粒相的湍流模型,并通过Fluent软件进行数值模拟,建立内流场域,分析得出不同粒径物料输送过程受气体影响程度不同,为今后散料输送提供理论基础。     

粉煤调节阀内气固两相流动的研究

以煤气化系统中的粉煤调节阀为研究对象,采用CFD数值模拟方法对阀门内部的气固两相流动进行了数值模拟研究,得到了粉煤流量随阀门开度的变化情况及内流场特性。分析了粉煤输送过程中随着阀门开度增大,介质出口附近存在粉煤堆积的现象。给出了阀门节流元件结构改进,增大阀门的可调比,以减少流体卡塞满足大流量工况的使用需求。     

煤粉浓缩器内气固两相流动特性的数值模拟

利用气固两相计算模型(IPSA模型),对水平浓淡煤粉燃烧器关键部件——百叶窗煤粉浓缩器内部压力、速度、浓度场进行了数值模拟,得出了浓缩器内气固两相流动规律,进一步分析了浓缩器的煤粉浓缩机理。计算结果表明,在浓缩器叶片上部出现高煤粉浓度的带状结构,并且在浓侧出口中心位置的煤粉浓缩带内,形成局部的煤粉高浓度区域,这是百叶窗式煤粉浓缩器的主要特点,与试验研究中观察到的气固两相流动现象一致。同时在不同分流挡板开度k下对煤粉浓缩器内部流动进行了数值模拟,得到了浓缩器性能参数,给出其变化趋势,与试验结果对比吻合较好。     

基于流态化技术的振动流化床气固两相流动分析

在对基于流态化技术的振动流化床气固两相流动的欧拉（Euler）方法的双流体模型研究的基础上,利用专业流体力学分析软件Fluent对褐煤颗粒床层进行数值模拟．研究振动、风速、褐煤颗粒粒度等参数对振动流化床床层中褐煤颗粒均匀流化的影响．实验结果表明：振动及气流的交互作用,可有效抑制褐煤颗粒在床层中的返混现象,使得振动流化床褐煤颗粒干燥均匀;选择双流体模型,将Fluent用于振动流化床气固两相流动数值模拟,是一种行之有效的数值模拟方法．     

型内孕育硅铁块熔化过程的数值模拟研究

建立了描述硅铁块在型内熔化过程中传输现象的数学模型,在固相、液相和糊状区中的流体流动、热量和溶质传输用统一方程描述,用控制容积差分法耦合求解质量、动量、能量和溶质守恒方程,计算结果与试验结果进行了对比,两者基本一致,表明所建立的数学模型和采用的计算方法能够用于模拟型内孕育硅铁块的熔化过程,实现型内孕育工艺的优化设计。     

垂直管内气固两相流数值模拟计算--颗粒动力学理论方法

基于气固两相流体动力学模型、颗粒动力学理论的颗粒脉动动能模型（ＫＴＧＦ）和气体湍流动能模型（ＳＧＳ）,对气固两相垂直上升流动进行数值计算,模拟计算结果得到了与试验研究所揭示的环—核流动结构。模拟计算与Ｍｉｌｌｅｒ和Ｇｉｄａｓｐｏｗ （１９９２）试验结果进行了比较,颗粒相浓度、速度和颗粒相动力粘性系数分布与试验值基本吻合     

基于DPM模型的立磨局部流场数值模拟分析

采用CFD理论中的离散相模型(DPM模型)和雷诺应力方程涡粘模型(RSM模型)对立磨内复杂的气固两相流流场的分布特性进行数值模拟分析。分别从速度、温度、压强等两相流的流场讨论分析立磨磨腔内的气固相的相互耦合作用。研究表明,立磨磨腔流场是一个剧烈的三维旋转湍流流场,流场呈现出不对称性和强烈的湍流脉动性。通过对磨辊磨盘耦合区、选粉机中心回料锥筒处强烈的湍涡现象的模拟分析,为合理设计立磨壳体、喷嘴环、中心回料锥筒等结构,提供理论依据。     

L型气固两相流管道输送有限元分析

针对颗粒在密相输送过程中经常会出现的堵塞问题,运用气固两相流动理论中的欧拉—欧拉模型和湍流模型,使用流体有限元软件Fluent,对L型管道中的颗粒浓度分布规律进行数值模拟。分析和讨论气体风速、进口处颗粒的体积含量对L型管道内颗粒浓度分布以及出口处颗粒速度的影响。     

小粒径固液两相流在旋流泵内运动的数值模拟

为了分析旋流泵内固液流动特性,采用Eulerian多相流模型,扩展的标准κ-ε湍流方程与SIMPLEC算法,应用流体动力学软件FLUENT对旋流泵叶轮内固液两相湍流进行了数值模拟。分析了多种粒径及浓度条件下的固相体积浓度分布规律。在旋流泵叶轮固液两相流动中,固体颗粒还是主要集中于叶轮工作面,因而会加剧叶轮工作面磨损破坏速度。数值结果表明,泥沙颗粒直径变大以及泥沙浓度的加大都会使旋流泵扬程和效率下降,其中浓度的变化对扬程和效率的影响更明显。     

油泥清洗器内液固两相流的数值模拟研究

油泥清洗器的作用是将油水固三相充分混合,由于浮油浆含量较少,且搅拌器内主要是罐底的固体泥沙和水的混合过程,所以将研究物系简化为水和固体泥沙的两相体系。本文采用Fluent中的欧拉两相流模型对油泥清洗器内的液-固混合情况及流场分布进行数值模拟研究,得到了油泥清洗器内液固两相流的速度云图及流场分布。模拟结果表明:油泥清洗器最底层的搅拌叶片周围的两相流动最均匀,液固两相的混合效果较好。     

Flow uniformity in a multi-intake pump sump model

The head-capacity curves for pumps developed by the pump manufacturer are based on tests of a single pump operation in a semi-infinite basin with no close walls or floors and with no stray currents. Therefore, flow into the pump intake is with no vortices or swirling. However, pump station designers relying on these curves to define the operating conditions for the pump selected sometimes experience reductions of capacity and efficiency, as well as the increase of vibration and additional noise, which are caused by free air mixed with the pump inlet flow. Therefore, sump model test is necessary in order to examine the flow structure around pump intake. In this study, flow uniformity according to the flow distribution in the pump intake channel is examined to find out the cause of vortex occurrence in detail. A multi-intake pump sump model with 7 pump intakes and a single-intake pump sump model are adopted for the investigation. Furthermore, effectiveness of anti-submerged vortex device (AVD) for the suppression of the vortex occurrence in a single pump intake, as well as in a multi-intake pump sump model has been examined by the methods of experiment and numerical analysis. The results show that most high value of flow uniformity is found at the inlet of pump intakes #3 and 5 in the multi-intake pump sump with 7 pump intakes. Therefore, when the pump station is designed, the flow patterns at the upstream region of pump intake inlet in the forebay diffusing area should be to consider in detail because the unbalanced flow at the channel inlet region gives considerable influence on the vortex occurrence around bell-mouth. Strong submerged vortex can be successfully suppressed by AVD installation on the bottom of pump intake channel just below the bell mouth.     

Study of process parameters effect on the filling phase of micro-injection moulding using weld lines as flow markers

Micro-injection moulding (micro-moulding) is a process which enables the mass production of polymer micro-products. In order to produce high-quality injection moulded micro-parts, a crucial aspect to be fully understood and optimised is the filling of the cavity by the molten polymer. As a result, the relationships between the filling pattern and the different process parameter settings have to be established. In this paper, a novel approach based on the use of weld lines as flow markers to trace the development of the flow front during the filling is proposed. The effects on the filling stage of process parameters such as temperature of the melt, temperature of the mould, injection speed and packing pressure have been investigated. An optical coordinate measuring machine has been employed for the investigation. The micro-cavity, which presents micro-features ranging from 600 μm down to 150 μm, has been manufactured by micro-electrodischarge machining. A commercially available polystyrene grade polymer has been moulded using a high-speed injection moulding machine. The design of experiment technique was employed to determine the effect of the process parameters on the filling phase of the micro-cavity. In addition, extensive measuring uncertainty analysis was performed to validate the experimental plan. Results show that the temperature of the mould and the injection speed are the most influencing process parameters during the injection moulding of a micro-component.     

磁力搅拌湍流场的PIV测量及流场演变的POD分析

为了解磁力搅拌过程湍流特性,对其开展了激光粒子图像测速(PIV)试验,并进行了本征正交分解(POD)分析.分析表明,在测量平面转子外部区域,除平均流动,含能量较高的流动结构为循环剪切流和转子旋转的尾涡结构.在搅拌槽底部具有较高的旋涡强度,有利于固体颗粒悬浮.流体与转子之间的流-固耦合作用使转子产生振荡,随转速升高,系统...     

两相脉冲爆震发动机的燃油喷射、混合及其雾化研究

两相爆震燃烧近来得到了广泛的重视和关注,但在它走向应用之前仍有很多问题需要解决。燃油的喷射、混合和雾化对两相爆震燃烧的影响就是其中之一。本文利用激光喷雾测量仪分别就直射喷嘴与气动喷嘴研究了汽油的喷射雾化与混合雾化,得到了汽油的雾化粒度与供油量、供气量间的关系。利用CFD程序对混合室中油、气的混合特性进行了模拟,结果与试验结果非常吻合。结合脉冲爆震发动机模型机多循环爆震试验,发现汽油的粒度大小对脉冲爆震模型机的油气当量比、燃油填充比有显著的影响。     

蜂窝密封流场和泄漏特性的实验研究

利用烟线法,显示了蜂窝腔中空气的流动情况,揭示了蜂窝腔中旋涡的结构特点。表明在相同的入口条件下,间隙越小,进入蜂窝腔的气流与水平面的夹角越大,且旋涡体积越大、中心位置越靠近底面。同时,在不改变实验其它参数的情况下,改变蜂窝的深度,通过实验观察蜂窝密封的泄漏量。结果表明,在不同的入口压力情况下,蜂窝深度与蜂窝对边距的比值为0.52左右时,蜂窝密封的泄漏流量最小。     

高速轴向柱塞泵柱塞腔空化机理研究

针对高速轴向柱塞泵内的空化问题,以某型号高速轴向柱塞泵为研究对象,搭建了其CFD数值仿真模型,研究柱塞泵旋转过程中的空化机理及演变规律。首先,对额定工况下柱塞泵的空化现象进行可视化分析,揭示空化的发生位置及在该位置处产生空化的机理;其次,以转速为变量,研究转速对空化的影响规律及其影响机理。结果表明:空化主要发生在柱塞腔内,充液率不足和流体漩涡影响是空化的主要原因;空化程度随着转速的升高而不断升高,这是由于流体流速的提高导致静压低,另一方面流体的离心力增大造成了充油率不足,同时还使流体进入柱塞腔的射流角增大;最后,根据空化机理对柱塞缸体底孔进行结构改进。在额定工况下,改进后柱塞腔内的空化程度与改进前相比下降了59.3%,空化抑制效果显著。     

基于分段线性MPCA的充液氨过程建模及监控

为深入分析晶变改性装备中反应釜充液氨工艺过程特性,同时也为了进行更精确、有效的过程监控,提出了一种分段线性多向主元分析(MPCA)方法,实现该间歇过程的建模及故障诊断。首先将三维建模数据降维展开并进行主元分析(PCA),得到采样点数据特征矩阵;然后基于间歇过程的多操作时段特性,根据特征矩阵相似度最大隶属原则,通过设定窗口长度可调的滑动聚类器,在系统运行轨迹上分别从数据变异的方向和幅值对采样点进行2次聚类划分,将间歇过程操作周期分割为一系列运行特性相同的子时段,最后利用各个子时段的线性MPCA模型逼近系统非线性运行过程,实现间歇生产过程建模及在线监测。通过反应釜充液氨工艺过程的实际应用,结果表明提出的建模方法能够对该间歇生产进行合理的、易于从过程特性角度解释的时段划分,所建模型具有可靠的监控性能,能及时准确检测出系统运行过程中的异常情况。     

Diagnosis of the behavior characteristics of the evaporative diesel spray by using images analysis

In this study, the effects of change in injection pressure on spray structure have been investigated on the high temperature and pressure field. To analyze the structure of evaporative diesel spray is important in speculation of mixture formation process. Also emissions of diesel engines can be controlled by the analyzed results. Therefore, this study examines the evaporating spray structure in a constant volume chamber. The injection pressure is selected as the experimental parameter, is changed from 72 MPa to 112 MPa with a high pressure injection system (ECD-U2). The PIV (Particle Image Velocimetry) technique was used to capture behavior variation of the evaporative diesel spray. Analysis of the mixture formation process of diesel spray was executed by the results of flow analysis in this study. Consequentially the large-scale vortex flow could be found in downstream spray and the formed vortex governs the mixture formation process in diesel spray.     

A proposal for diesel spray model using a TAB breakup model and discrete vortex method

A hybrid model consisting of a modified TAB (Taylor Analogy Breakup) model and DVM (Discrete Vortex Method) is proposed for numerical analysis of the evaporating spray phenomena in diesel engines. The simulation process of the hybrid model is divided into three steps. First, the droplet breakup of injected fuel is analyzed by using the modified TAB model. Second, spray evaporation is calculated based on the theory of Siebers’ liquid length. The liquid length analysis of injected fuel is used to integrate the modified TAB model and DVM. Lastly, both ambient gas flow and inner vortex flow of injected fuel are analyzed by using DVM. An experiment with an evaporative free spray at the early stage of its injection was conducted under in-cylinder like conditions to examine an accuracy of the present hybrid model. The calculated results of the gas jet flow by DVM agree well with the experimental results. The calculated and experimental results all confirm that the ambient gas flow dominates the downstream diesel spray flow.     

调压式真空注型充型速度智能调控方法研究

针对真空注型(Vacuum casting,VC)浇注件由于充型速度不稳定所导致的翘曲变形质量缺陷,提出调压式真空注型工艺,并分析压力充型机理,论证压力差是影响充型速度的关键工艺参数,并通过分析阀口开度和充型速度的关系制定了充型速度控制策略。详细介绍该控制策略的实现过程,包括：对浇注件的STL模型进行体素化,并获取模腔的体积及横截面面积等特征;采用控制体积法对充型过程进行数值模拟,获得理论的阀口开度调节曲线;构建阀口开度模糊控制器,并利用二维查询表实现模糊推理过程,提高了控制器的响应速度,减小超调量。利用自主研制的试验平台结合具体实例进行试验,试验结果充分体现了调压式真空注型工艺的优势,证明了控制策略的可行性,大大提高了浇注件质量,为真空注型技术提供了一种新的工艺方法。