红外热成像技术在多联机故障检测中的应用

制冷管路堵塞是多联机系统运行中的重要故障现象之一,严重影响了系统的正常工作。常规的检测方法是依据技术人员的经验,配合在管路上布置热电偶所获得的数据,进行综合分析,从而判断故障原因及故障点位置,检测效率低。本文采用红外热成像技术,通过最大负荷制冷工况、名义制冷工况、最大负荷制热工况和名义制热工况试验,研究了多联机在制冷管路堵塞情况下的红外数据、图像及其与热电偶测试数据的比较。研究结果表明,红外热成像技术能够快速、直观、准确地定位故障位置,可应用于多联机的故障检测并提高检测效率。     

自动变形气塞压力成型多层管材技术

采用自行设计的自动变形气塞定型装置生产了多层复合管材，调节自动气塞压力与成型压力的比值控制制品的质量。通过对管材内、外壁质量以及气塞使用寿命的对比发现，当调节自动气塞压力与成型压力的比值为1．25时，管材的内应力最小，内外壁光滑且平整，气塞的寿命最长，达到了700h。同时对自动变形气塞成型与真空定型法相比所具有的优点进行了分析，采用自动变形气塞生产管材不仅可以节省费用，而且可以将爆破压力提高0．3MPa。     

多元解堵技术在白于山区块的研究与应用

长庆油田白于山区块经过多年开采,目前部分油井产量递减迅速,分析认为主要是由于该区块井温相对偏低,原油开采过程中有机和无机沉淀析出（结垢）导致储层部分孔喉堵塞。室内对该区块原油和堵塞物成分分析,结果显示堵塞物成分复杂。针对堵塞物不同特性,开发出一套多元解堵体系,实验结果表明反应4h时,多元解堵体系对该区块垢样溶蚀率比土酸体系溶蚀率提高了14%,对白于山区块岩心平均伤害率为-17.1%。现场试验表明多元解堵技术对白于山区块油井堵塞有明显针对性,能有效提高该区块油井单井产量。     

水平管道中瓦斯爆炸火焰传播速度测量

在煤炭工业中, 瓦斯爆炸事故经常发生, 造成了巨大的人员伤亡以及材料性能的破坏. 在研究瓦斯爆炸机理过程中, 火焰前端传播速度是最重要的因素之一. 根据中北大学水平管道实验装置设计了一套火焰速度测量系统, 用于研究在密闭管道内圆环障碍物的数量和阻塞比对火焰传播速度的影响. 结果表明, 障碍物对瓦斯爆炸产生的火焰具有明显的加速作用. 随障碍物数量和阻塞比的增加, 火焰加速更加明显且持续更剧烈. 其中, 障碍物数量对火焰加速持续的作用更大, 而障碍物阻塞比的作用不明显.     

立体结构障碍物不同阻塞比对火焰传播的影响

通过运用自行设计的火焰加速系统,文章研究了立体结构障碍物对预混甲烷火焰传播过程中火焰传播速度和超压的影响。选用五种立体结构障碍物,平板、长方体、三棱柱、四棱柱和圆柱,其阻塞比分别有20%、40%和60%。结果表明在相同阻塞比下,平板、三棱柱对增加火焰传播速度和超压相对较大,长方体居中,圆柱、四棱柱影响相对有限。研究有助于对矿井瓦斯爆炸预防控制以及为工业安全设计提供参考。     

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.     

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。