四电极电导传感器敏感场的理论分析

针对水为连续相条件下的油水两相流含水率测量问题，首先分析了环形四电极电导传感器敏感场正问题的数学模型。之后在此模型基础上，利用分离变量法推导了均匀媒质时传感器内部电势、轴向电流和径向电流的分布，并得到了简单非均匀媒质时场域内各点电压的数学理论解。最后，建立了油水两相环状流型下电导传感器含水率测量模型。结果表明，该模型与Begovich＆Watson经典公式吻合，为进一步深入研究电导传感器的响应特性奠定了基础。     

基于质子导体的燃料电池型气体传感器

某些质子导体如固体高分子膜、磷酸氢锆和锑酸等在室温下对化学传感器有足够的离子电导，研究和开发了在室温下可以检测H₂、CO、C₂H₄等可燃气体的质子导体传感器，研究其结构、敏感机理和特性，并研究温度、湿度、催化电极材料和复合电极制备技术对传感器性能的影响.     

一种新的电容层析成像电极组合激励测量模式

电容层析成像图像重建为非线性不适定反问题,其敏感场分布不均匀,可获得的测量数据有限,中心处物体的成像效果不佳。增加电极数目,可获得更多的电容测量数据,减小其不定性,同时改善敏感场分布。但同时导致电容测量值变小,测量精度下降。在保证电容测量精度的前提下,提出了24电极组合式电容层析成像传感器结构,研究了两种激励测量方案,并与传统12电极电容层析成像传感器进行了对比分析,包括电容测量值的大小及其动态测量范围、灵敏场分布的均匀性以及不同流型下的重建图像。仿真结果表明,与12电极电容层析成像传感器相比,采用24电极组合式电容层析成像传感器,其电容测量值大,可较好地保证测量精度,其灵敏度分布更加均匀,对中心处物体的成像质量明显提高。     

屏蔽电极可行性的理论分析与实验研究

在使用传统四电极电导传感器对油井产出液的含水率进行实际测量时,由于传感器两端电位近似为零而造成激励电流漏失,导致含水率测量精度下降.提出在原有四电极基础上增加两个屏蔽电极的改进方案,建立了含屏蔽电极电导传感器内电流密度分布的理论模型,并对屏蔽电极的宽度和间距进行了优化设计,理论上漏失程度可由原来的31.5%下降到0.36%.环状流型下的实验结果表明,屏蔽电极可有效减少漏失条件下激励电流的漏失,传感器测量精度有较大提高.大庆油田现场试验结果表明,传感器测量相对误差小于5%.     

沸石及其复合物气体传感器的研究与应用

半导体金属氧化物是一种常见的气敏材料,以该类型材料作为敏感材料可以设计出具有不同传感原理的气体传感器,但选择性和灵敏度不佳却一直是该类气体传感器的不足。为了解决该问题,常将气敏材料与沸石进行复合,制备金属氧化物/沸石气体传感器,利用沸石独特的物理、化学特性来改善金属氧化物的气敏特性。近年来,许多研究者对金属氧化物/沸石气体传感器进行了研究,使该类传感器对目标气体的选择性与灵敏度均有了提升。为了更好地总结已有的研究内容,以气体传感器的检测原理为主线,对金属氧化物/沸石气体传感器进行了总结,结合沸石对气敏特性的改善进行归纳梳理,从传感器的制备方法、气敏特性和敏感机理等多方面进行了详细的整理和分析,为后续此类工作的开展提供基础。     

柱状气液旋流器压力场和速度场模拟分析

利用计算流体动力学(CFD)方法,采用流体力学软件FLUENT,针对柱状气液旋流分离器进行了内部流场、压力场和气相浓度的分析,得到了柱状气液旋流分离器的压力降分布特性和速度分布特性。揭示了入口位置及溢流口直径对柱状气液旋流分离器分离性能的影响。经研究发现:要使柱状气液旋流分离器具有低压力损失和高分离效率的综合性能,需要将入口位置和溢流口直径控制在一定范围。     

催化燃烧蒸发器内气体浓度冷态分布规律

催化燃烧蒸发器作为一种强化传热的有效手段,具有高效、结构紧凑和易放大等优点.催化燃烧蒸发器中的浓度场分布对其传热性能具有重要的影响.运用多空介质模型对燃烧蒸发器内部流体分布特性进行了CFD模拟,分析计算了冷态时N₂和H₂ 在混合腔内浓度的分布特性,同时进行了实验验证.模拟和实验结果具有相同的变化趋势,而且结果表明不同空速下燃烧蒸发器中存在较大的浓度分布不均匀性,改变出口位置对浓度场的分布具有一定的改善作用.通过对燃烧腔中浓度场分布的模拟为燃烧蒸发器的进一步优化设计提供了理论依据.     

沸石及其复合物气体传感器的研究与发展

近年来大量文献报道了沸石及其复合物气体传感器的研究和设计.该类型传感器在选择性、稳定性、灵敏度以及响应范围上均表现出了优异的特性.本文以沸石的基本特性为主线,从沸石基气体传感器的制备方法和测试手段入手,总结了近些年主流沸石基气体传感器的气敏特性和敏感机理,并对未来沸石基气体传感器的发展趋势进行了阐述.     

三相流化床和两相鼓泡塔内的压强径向分布

利用应变片压力传感器测定了三相流化床和气-液鼓泡塔内压强的径向分布,比较了不同操作条件下床层内不同轴向位置上压强径向分布的特征,初步探讨了体系的流体湍动特性。     

气升式外环流反应器流体力学参数的轴径向分布

在气升式外环流反应器（Φ 0.09 m×1.8 m）内,利用压差法和双探针电导探头技术考察了不同表观气速下空气-水两相体系中气含率及气泡参数随轴径向位置的变化规律,测得了平均及局部气含率、气泡尺寸及分布、气泡上升速度、气泡频率以及气液相界面积,并从气液流场特征及气泡间相互作用等方面对实验结果作出分析。基于实验数据拟合出局部气含率随表观气速和轴径向位置的关联式。     

Wall effects in point probe measurements of radial bubble distributions

The point properties of bubbling systems have been calculated for various assumed bubble frequency and size distributions. Flat, linear and parabolic radial frequency distributions were considered for both uniform and non-uniform bubble size distributions.The point bubble frequency distribution, which is equivalent to the distribution measured by a probe inserted into the system, may not be representative of the distribution which actually exists in the bed. Due to a boundary effect, the theoretical probe output for larger bubbles is found to yield a peak in the bubble frequency toward the bed centre, even if the actual distribution is flat, the magnitude of the bias increasing as bubble size increases. Caution in using radial frequency profiles obtained by point probe methods is thus indicated.     

Application of the double optic probe technique to distorted tumbling bubbles in aqueous or organic liquid

The optic probe technique is widely used to investigate bubble reactors. To derive values of bubble local velocities and bubble local sizes, a specific signal treatment is usually applied under severe assumptions for bubble path and shape. However, in most industrial reactors, bubble motion is chaotic and no common shape can be assumed.In this work, the reliability of the signal treatment associated with the optic probe technique is examined for distorted and tumbling bubbles. A double-tip optic probe is settled in a glass tank and the rise of bubbles is filmed simultaneously. Several trains of bubbles are studied, interactions between bubbles being gradually increased.Referring to image analysis, several ways to derive mean bubble velocities from optic probe data have been compared. Crenels from front tip and rear tip raw signals are associated and individual bubble velocities are derived. Nevertheless, complete velocity distributions are difficult to obtain, as they depend on the choice of the time within which the bubble is searched on the second tip. Using a simpler approach it is shown that the most probable velocity, calculated through the raw signals inter-correlation, is a correct estimation of the average bubble velocity.Concerning bubble size, bubble chord distributions show too high values due to bubble distortion and deviation. A simplified estimation of bubble mean Sauter diameter, using the most reliable measurements only (i.e., local gas hold-up, local mean bubbling frequency, and most probable bubble velocity), was tested for highly distorted bubbles; this method was validated both in water and cyclohexane.     

Hydrodynamik in Blasensäulen – Messung von relativem Gasgehalt und Blasengröße

In bubble column reactors mass transfer kinetics are determined by local hydrodynamic processes (bubble formation, velocity, coalescence, break‐up, etc.). For a better understanding of the influence of pressure and particle load on these processes, a measurement system for detection of local bubble size distributions in opaque bubbly flows is needed. Therefore, in this work an optical needle probe was applied in a bubbly flow. In a first step, the needle probe was validated by means of single‐bubble measurements. The measurement technique shows high potential for application in more complex and opaque systems.     

矩形薄腔中聚合物熔体非等温注气充填的数值模拟

采用五参数Cross粘度模型,利用有限元和控制体积法对矩形薄腔中聚合物熔体非等温注气充填过程中不同时刻的气泡边界、熔体前沿、熔体压力场、温度场和速度场等进行了数值模拟,结果表明:气泡主体边界平行于模壁方向生长,其前沿总是先向中心线附近移动,再向中心线两边移动;熔体压力在气泡周围某一区域内保持不变且等于气压;对于充模时间很短的情况,除气泡附近外,温度在各处相差不大。     

Bubble Size Distributions for Dispersed Air – Water Flows in a 100 mm Horizontal Pipeline

The bubble size distributions of air dispersed in water flowing in a 100 mm horizontal pipeline were studied. Size distributions were obtained with a high‐speed digital camera at axial positions 0.5, 15.3 and 42.3 m from the air injection point. Air was injected into the pipeline through a narrow tube extending into the pipe, perpendicular to the pipe axis. The effects of average water velocity, air concentration, and injection nozzle diameter on the evolution of bubble size distribution with axial pipe position were studied. For the lowest air concentration of 0.07%, equilibrium bubble size distributions were dependent only on water velocity. Nozzle injection diameter did not affect the downstream bubble size distributions at air concentrations of 0.07% and 0.3%. Levich's break‐up theory was found to over‐predict the experimental d_max for each test condition.     

BUBBLE SIZES AND HOLDUP STRUCTURE IN BUBBLE COLUMNS DETERMINED BY DYNAMIC GAS DISENGAGEMENT

A new model for determining bubble size distributions in bubble columns by the dynamic gasdisengagement(DGD)technique is developed.It is based on an idea of non-uniform steady statedirstribution of bubble dispersion.Interpreting the axial non-uniformity,this model gives axial gasholdup distributions.If assuming an axially homogeneous dispersion,a radial gas holdup distributioncan be obtained.The Sauter mean diameters or specific interfacial areas for several systems areestimated by the technique.The results for an air-water system agree with those measured by afive-point conductivity probe technique.The obtained axial gas holdup distributions agree well withreported measurements and the radial gas holdup distributions are also reasonable.     

The measurement of bubble parameters in two-phase dispersions—I: The development of an improved probe technique

An improved probe technique for the measurement of bubble size and velocity in turbulent bubble dispersion has been developed. The technique makes use of fast real-time data processing methods to identify the bubble orientation during measurement and to accept readily interpretable data for only those bubbles whose central axes are coincident with the probe axis. The method is evaluated experimentally using well defined single bubbles and shown to be accurate as well as rapid.     

Bubble size distribution in bubble columns

The bubble size distributions are measured for the air-water system as a function of air velocity at room temperature in two bubble columns. High speed cinephotography and fiber optic probe techniques are used to measure the bubble size. Our limited measurements suggest that the bubble size may be independent of gas velocity in the range 3.6 to 9.2 cm/s and may be dependent on column diameter with smaller bubbles for narrower columns. The bubble size appears to be smaller at the column wall than at distances away from the wall.     

Distribution of bubble properties in a gas-liquid-solid fluidized bed

The behavior of bubbles in a cocurrent gas-liquid-solid fluidized bed was investigated in a column of 76.2 mm ID in this study. The particles used were glass beads of 3 and 6 mm and a binary mixture of these particles. A novel dual electrical resistivity probe system was developed and utilized to obtain bubble properties including bubble size and rise velocity. The distributions of the bubble properties in the gas-liquid-solid fluidized bed were evaluated for three flow regimes: the dispersed bubble flow regime; the coalesced bubble flow regime; and the slug flow regime.     

加热上升管内过冷流动沸腾数值模拟

采用计算流体动力学（CFD）程序CFX4.4对加热上升管内过冷流动沸腾工况下气水两相流动局部两相流参数（空泡份额和汽泡尺寸）进行了数值模拟。对数值差分方法、相关模型（界面力和气泡诱导的紊流）和汽泡尺寸进行了敏感性分析。空泡份额分布计算结果与实验结果比较表明，在低空泡份额工况下，两者符合较好，在高空泡份额工况下两者存在一定偏差，并且气相速度和汽泡尺寸的计算结果不理想。计算结果与实验结果之间的差异说明程序模型对于加热上升管内过冷流动沸腾模拟并不完善，建立更为合理的汽泡尺寸模型，考虑汽泡的合并和撕裂是必要的。