Numerical and experimental study of an axially induced swirling pipe flow

In-line flow segregators based on axial induction of swirling flow have important applications in chemical, process and petroleum production industries. In the later, the segregation of gas bubbles and/or water droplets dispersed into viscous oil by swirling pipe flow may be beneficial by either providing a pre-separation mechanism (bubble and/or drop coalescer) or, in the case of water-in-oil dispersions, by causing a water-lubricated flow pattern to establish in the pipe (friction reduction). Works addressing these applications are rare in the literature. In this paper, the features and capabilities of swirling pipe flow axially induced by a vane-type swirl generator were investigated both numerically and experimentally. The numerical analysis has been carried out using a commercial CFD package for axial Reynolds numbers less than 2000. Pressure drop, tangential and axial velocity components as well as swirl intensity along a 5 cm i.d. size and 3 m long pipe were computed. Single phase flow experiments have been performed using a water–glycerin solution of 54 mPa s viscosity and 1210 kg/m³ density as working fluid. The numerical predictions of the pressure drop were compared with the experimental data and agreement could be observed within the range of experimental conditions. The experiments confirmed that swirl flow leads to much higher friction factors compared with theoretical values for non-swirl (i.e. purely axial) flow. Furthermore, the addition of a conical trailing edge reduces vortex breakdown. Visualization of the two-phase swirling flow pattern was achieved by adding different amounts of air to the water–glycerin solution upstream the swirl generator.     

兰州重离子加速器冷却储存环kicker磁铁设计

 介绍了兰州重离子加速器冷却储存环（HIRFL-CSR）CSRm引出kicker磁铁的物理设计、参数计算以及结构设计和加工。为了减小电感,使上升时间达到要求,CSRm引出kicker磁铁采用分布式的传输线方案,同时将无感电容与磁铁并联以满足匹配的问题。磁铁用单匝线圈和铁氧体铁芯来降低电感、减少涡流损耗,并采取两台电源成对供电、导体一端共地的结构形式消除杂散电感和轴向场,这种方式不但消除了过桥的不利影响,而且可通过调节导体间距离方便的调节磁场均匀区宽度和磁铁电感。完成设计后磁铁电感小于1 μH,在140 mm范围内磁场均匀度好于±0. 5%,最高磁场达到0.038 T,最大峰值激磁电流约为2.5 kA。     

Leak detection in water-filled plastic pipes through the application of tuned wavelet transforms to Acoustic Emission signals

A new method to detect leakage in a water-filled plastic pipe is proposed. In this method, a leakage signal-signature in time domain is first captured by monitoring the Short Time Fourier Transforms (STFT) of AE (Acoustic Emission) signals over a relatively long time-interval. The captured signal is then used to find a mother wavelet (tuned wavelet) for the best signal localization in time and frequency domains. The technique for AE signal detection using tuned wavelet is then described. Practical application of the method proposed herein is then presented using a water-filled plastic pipe as a case study. Signals generated from this experimental setup are collected to identify leakage signal-signatures from other interfering signals (background, pipe natural frequency, splash and environmental noise). The results of the experiment prove that using tuned wavelet, AE events can be detected and identified precisely in time. In addition, sources of signals due to leakage and their respective energy levels can also be recognized.     

基于不同波段对成品汽油的模式识别分析

为了实现对输油管道上顺序输送不同牌号汽油(90#,93#,97#)时汽油间界面的区分,根据近红外光谱分析的基本原理,采用主成分分析-马氏距离(PCA-MD)模式识别方法,分析了700—1100nm波段和1100—1700nm波段3种不同牌号成品汽油的近红外光谱,并根据分析结果对汽油进行了分类。结果表明,使用1100—1700nm波段的汽油光谱分类结果较好,该方法可进一步鉴别汽油的质量。     

Liquid refractive index sensor based on slow light in slotted photonic crystal waveguide

A high sensitive and compact refractive index sensor based on slotted photonic crystal waveguide (S-PhCW) is demonstrated. This design is worked on a Mach–Zehnder interferometer (MZI) configuration with S-PhCW as the measuring arm, which can be used to detect any changes in refractive index that correspond to different concentration of the measuring liquid. Combining the slow light enhancement in photonic crystal waveguide (PhCW) with the advantage of excellent optical confinement in slot waveguide, the sensitivity of this simple scheme can reach to 2.3 × 10⁹ nm/RIU with the active region of only 1 mm long.     

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采用一体化安全分析程序,建立了ITER装置第一壁/包层及其主热传输系统、抑压系统的事故分析模型。对真空室内第一壁冷却剂管道双端断裂的失水事故进行计算,并选取单根冷却剂管道双端断裂和多根冷却剂管道双端断裂导致的失水事故工况进行热工水力行为的研究,分析相关系统的热力响应。分析表明,在发生第一壁冷却剂管道断裂事故后,由于冷却剂向真空室内释放,导致真空室内压力升高,之后由于抑压系统爆破盘的开启,可以有效缓解真空室内压力的升高,能够保障真空室系统满足设计限值。     

冲击磁铁回路电感对传输线放电的影响

 分析了脉冲调制器产生短脉冲时冲击磁铁回路电感对脉冲前后沿和宽度不可忽略的影响，从理论上导出了冲击磁铁回路电感与脉冲前后沿的关系，给出并分析了几组实验结果，提出了采用屏蔽结构和适当增加阻抗等两种可行的减小脉冲前沿的方案。     

Symbolic computation of flow in a rotating pipe

A perturbation solution of the fully developed flow through a pipe of circular cross-section, which rotates uniformly around an axis oriented perpendicularly to its own, is considered. The perturbation parameter is given by R = 2Ωa²/ν in terms of the angular velocity Ω, the pipe radius a and the kinematic viscosity ν of the fluid. The two coupled non-linear equations for the axial velocity ω and the streamfunction ? of the transverse (secondary) flow lead to an infinite system of linear equations. This system allows first the computation of a given order ?_n, n ? 1, of the perturbation expansion ? = ∑ Rⁿ?_n in terms of ω_n-1, the (n-1)-th order of the expansion ω = ∑ Rⁿω_n, and of the lower orders ?₁,…,?_{n ? 1}. Then it permits the computation of ω_n from ω₀,…,ω_{n ? 1} and ?₁,…,?;_n. The computation starts from the Hagen–Poiseuille flow ω₀, i.e. the perturbation is around this flow. The computations are performed analytically by computer, with the REDUCE and MAPLE systems. The essential elements for this are the appropriate co-ordinates: in the complex co-ordinates chosen the two-dimensional harmonic (Laplace, Δ) and biharmonic (Δ²) operators are ideally suited for (symbolic) quadratures. Symmetry considerations as well as analysis of the equations for ω_n, ?_n and of the boundary conditions lead to general (polynomial) formulae for these functions, with coeffcients to be determined. Their determination, order by order, implies, in complex co-ordinates, only (symbolic) differentiation and quadratures. The coefficients themselves are polynomials in the Reynolds number c of the (unperturbed) Hagen–Poiseuille flow. They are tabulated in the paper for the orders n ? 6 of the perturbation expansion.     

Friction factor improved correlations for laminar and turbulent gas–liquid flow in horizontal pipelines

We develop improved correlations for two-phase flow friction factor that consider the effect of the relative velocity of the phases, based on a database that includes 2560 gas–liquid flow experiments in horizontal pipes. The database includes a wide range of operational conditions and fluid properties for two-phase friction factor correlations. We classify the experiments by liquid holdup ranges to obtain composite analytical expressions for two-phase friction factor vs. the Reynolds number by fitting logistic dose curves to the experimental data with. We compute the liquid holdup values used to classify the experimental data using correlations proposed previously. The Reynolds number is based on the mixture velocity and the liquid kinematic viscosity. The Fanning friction factor for gas–liquid is defined in term of the mixture velocity and density. Additionally, we sort the experimental data by flow regime and obtain the two-phase friction factor improved correlations for dispersed bubble, slug, stratified and annular flow for different holdup ranges. We report error estimates for the predicted vs. measured friction factor together with standard deviation for each correlation. The accuracy of the correlations developed in this study is compared with that of other 21 correlations and models widely available in the specialized literature. Since different authors use different definitions for friction factors and Reynolds numbers, we present comparisons of the predicted pressure drop for each and every data point in the database. In most cases our correlations predict the pressure drop with much greater accuracy than those presented by previous authors.     

Impact against X65 steel pipes – An experimental investigation

Offshore pipelines subjected to accidental loads, such as impacts from trawl gear or anchors, may experience large global displacements from its initial position and large local strains. The axial forces set up during deformation move the pipeline back towards its initial position, thereby creating a complex local stress and strain history that may lead to fracture in the pipeline. In this study, material and component tests have been carried out on an X65 offshore pipeline material to investigate the behaviour during impact, and to observe if fracture occurs. Pipes were first impacted in a pendulum accelerator at varying velocities before they were pulled straight in a tension machine. Fracture was found in the impacted area of all the pipes. Material tests were carried out to determine the characteristics of the X65 pipeline material. A metallurgical investigation was also conducted, revealing that fracture initiated both inside the pipe wall and on the surface.