Research on human blockage effect for indoor 26 GHz mm-wave communications

Based on 26 GHz indoor channel measurements, the blockage attenuation of human bodies was investigated. 2-ray and 4-ray human blockage models were proposed by calculation of the Vogler's multiple knife-edge diffraction field. Results show that 4-ray model fits quite well with measurement data. Human block attenuations are slightly bigger with 1 GHz than with 500 MHz bandwidth. In the blockage measurement of one person moving along the connec-tion line between the transmitter (TX) and receiver (RX), the smallest attenuation is found when the person is located at the middle of the connection line, and the biggest attenuation is observed when the person is nearest from the RX position. In the blockage measurements by multiple human bodies, the attenuation is bigger in the cases which the persons cross the TX-RX connection line with their front faces directed to the horn aperture at the RX than the cases with their lat-eral faces directed to the RX horn aperture. The blockage attenuation is larger with the increase of person numbers, about 5～8 dB more attenuation per person. The results can be used for design of mm-wave 26 GHz indoor communi-cations systems.     

高碳酸盐型铀矿床微酸中性地浸采铀试验

某砂岩铀矿碳酸盐含量高,为避免常规酸法或碱法地浸的化学堵塞,开展了微酸中性地浸试验。以0.3g/L的硫酸溶液为溶浸剂,双氧水、氧气为氧化剂。浸出体系pH控制在6.1~6.7避免了碳酸钙沉淀;Ca~(2+)、SO_4~(2-)分别不超过900mg/L和2 100mg/L,硫酸钙沉淀得到有效控制。酸液与矿石碳酸盐反应可获得400~450mg/L的HCO_3~-作为浸铀剂,在双氧水氧化条件下可使浸出铀浓度达到24~31mg/L,改用300~350mg/L的氧气则使铀浓度进一步升高到48~62mg/L。与常规酸法和碱法工艺相比,微酸中性工艺更有利于在浸铀的同时对硫酸钙和碳酸钙沉淀进行有效控制。     

Blockage effects in wind farms

An experimental study of wind farm blockage has been performed to quantify the velocity decrease that the first row of a wind farm experiences due to the presence of the other turbines downstream. The general perception has been that turbines downstream of the first row are only influenced by the wakes from upstream turbines without any upstream effect. In the present study, an attempt is made to demonstrate the existence of a two‐way coupling between individual turbines and turbines in the wind farm. Several staggered layouts were tested in the wind tunnel experiments by changing the spacing between rows, spacing between turbines in the rows, and the amount of wind turbines involved. The experiments focused on turbines located in the center of the first row as well as the two turbines located in the row edges, usually believed to experience a speedup. The present results show that no speedup is present and that all the turbines in the first row are subjected to a reduced wind speed. This phenomenon has been considered to be due to “global blockage.” An empirical correlation formula between spacing, number of rows, and velocity decrease is proposed to quantify such effect for the center turbine as well as for the turbines at the edges.     

Validation of a CFD model with a synchronized triple‐lidar system in the wind turbine induction zone

A novel validation methodology allows verifying a CFD model over the entire wind turbine induction zone using measurements from three synchronized lidars. The validation procedure relies on spatially discretizing the probability density function of the measured free‐stream wind speed. The resulting distributions are reproduced numerically by weighting steady‐state Reynolds averaged Navier‐Stokes simulations accordingly. The only input varying between these computations is the velocity at the inlet boundary. The rotor is modelled using an actuator disc. So as to compare lidar and simulations, the spatial and temporal uncertainty of the measurements is quantified and propagated through the data processing. For all velocity components the maximal difference between measurements and model are below 4.5% relative to the average wind speed for most of the validation space. This applies to both mean and standard deviation. One rotor radius upstream the difference reaches maximally 1.3% for the axial component. © 2017 The Authors. Wind Energy Published by John Wiley & Sons, Ltd.     

滑坡–堵江–涌浪灾害链模拟的DEM–CFD耦合分析方法及其应用

滑坡-堵江-涌浪灾害链的演化过程涉及复杂的滑坡-河流相互作用。为了真实再现这一演进过程,本文提出了一种扩展的离散元法（DEM）与计算流体动力学（CFD）耦合数值方法,通过在局部平均DEM-CFD耦合方法中引入流体体积法（VOF）建立了一套能够描述河流自由水面演化的扩展DEM-CFD耦合数值框架,实现了对滑坡涌浪形成及传播过程的追踪;并提出了一种新的局部孔隙率计算方法即虚拟球模型,来克服网格颗粒临界尺寸比的限制,从而实现复杂地形建模要求;进一步通过多个典型算例验证其准确性和有效性。在此基础上,开展了滑坡-堵江-涌浪灾害链演化模拟,并应用至白格滑坡坝形成过程复演,深入分析了滑坡-河流动态演化过程及耦合作用机理。结果表明：所提出的方法能够准确模拟滑坡-河流相互作用;滑坡-河流-河谷地形的耦合作用驱动了灾害演化,滑坡体驱动了涌浪的传播,而河流则增加了滑坡体的动能耗散,且对其沉积过程在河流流向上产生相反影响;模拟得到的白格滑坡运移路径、沉积形态及涌浪侵蚀面积与实地调查结果吻合度较高,成功再现了2018年10月11日白格滑坡堵江事件。本文所提出的扩展DEM-CFD耦合数值方法为深入研究滑坡-堵江-涌浪灾害链演化机制提供了有力的数值工具,对于灾害预测及防灾减灾策略的制定具有一定的参考价值。     

氧化皮脱落导致的过热器管爆管分析

某电厂高温过热器运行5万h后连续发生爆管,通过对爆管及割管样品的宏观形貌、机械性能、金相以及材料状态等进行综合分析,确定爆管原因与氧化皮脱落导致的堵塞有关。对此,提出了杜绝快速起停,适当延长停炉后的打开炉门时间,安装锅炉管寿命管理系统等建议和措施。     

EH供油系统油泵出口滤网堵塞原因分析及污染防控

某发电机组EH供油系统主油泵出口滤网频繁堵塞,滤网前后压差异常升高,给机组安全运行带来隐患。为查明原因,采用扫描电子显微镜、傅里叶变换红外光谱、X射线能谱等手段并结合抗燃油的油质全分析试验,对EH供油系统油泵出口滤网污染物成分进行分析。结果表明,污染物是系统中的磨损产物、抗燃油的过滤滤料及其他颗粒杂质。解决此类问题的方法包括合理选用抗燃油过滤器,以及加强油质和油系统的污染防控。同时,为促进液压系统过滤技术的发展与提高,提出了意见和建议。     

塔河油田稠油井解堵抑堵剂研制

塔河油田稠油井在掺稀开采过程中常常出现井筒堵塞的情况,严重影响正常生产。堵塞物的四组分分析结果表明,其主要成分为沥青质,所占质量分数达57%。考察了不同类型化合物对堵塞物的溶解性能,并考察了助剂的复配效果,研制了复合解堵抑堵剂RPDA-02,该剂对堵塞物的饱和溶解量达2.0 g/g,显著优于现场使用的对比剂。考察了RPDA-02的抑堵效果,结果表明,该剂对沥青质沉积的抑制时间超过60 天。研究了现场工况条件对该剂解堵抑堵性能的影响,结果表明,使用温度变化对其性能影响很小。开发了掺稀连续加剂工艺,可较好地解决稠油井堵塞问题,并对采出液的后续处理无不利影响。     

障碍物阻塞率梯度对甲烷爆炸特性影响研究

通过自主设计并搭建小型实验平台,研究障碍物阻塞率梯度依次为0、0.05、0.1、0.15时,甲烷火焰传播过程的火焰结构变化、火焰前锋动力学以及压力演变。结果表明：阻塞率梯度为0和0.05的工况,经过障碍物后的火焰前锋会由模糊逐渐变得清晰,随后火焰前锋会向燃烧区凹陷;而阻塞率梯度为0.1和0.15工况的火焰在经过障碍物后,前端始终模糊,随后湍流燃烧加剧,迅速在整个管道爆燃,并无火焰前锋凹陷现象。阻塞率梯度对火焰瞬时速度影响较大,而对平均速度并无太大影响。随着阻塞率梯度从0增大到0.15,最大火焰速度会明显提升,而平均火焰速度却近似一致。此外,高阻塞率梯度的障碍物组有利于压力积聚,随着阻塞率梯度的增大,峰值超压也呈现规律性的增大,达到峰值超压所需的时间也相应延长。     

常压塔塔顶压降升高的原因分析

某常压蒸馏装置掺炼轻质原油或回炼轻污油时常压塔负荷变大,当常压塔塔顶（简称常顶）回流量大于22 t/h时,常顶和进料段压差由20 kPa增加到40 kPa以上,常顶油和常一线油出现馏程重叠。现场调研发现,常压塔上数第9~16层塔盘、浮阀有大量结垢沉积物,几乎堵塞整块塔盘。对现场堵塞位置垢样进行采样,元素分析、XRD、XRF表征结果表明,常压塔一中段处垢样的主要成分是NH4FeP2O7。通过高温缓蚀剂模拟结垢试验确定了塔顶结垢堵塞的原因,并针对性提出优化解决措施。