厚煤层一次采全高煤壁失稳原因及控制技术

针对成庄煤矿四盘区层一次采全高煤壁失稳问题,对观测统计数据进行分析,发现片帮主要表现形式分五种:顶部、腰部、顶底部、底部以及斜切片帮,据此采用对顶板超前预爆破和煤壁超前预加固技术来控制大采高煤壁稳定性,不仅对煤壁失稳的控制取得了良好的效果,而且经济效益显著。可为相似条件下的厚煤层一次采全高煤壁失稳控制提供借鉴。     

金沙江上游水电站应对白格堰塞湖灾害的措施及经验

2018年10月、11月,西藏自治区昌都市江达县白格村两次发生山体滑坡造成金沙江断流并形成白格堰塞湖,给金沙江上游沿岸人民生产生活设施造成巨大安全威胁和超过百亿元的经济损失。华电金沙江上游水电开发有限公司组织所属企业及参建单位快速应对,采取撤离避让、工程防护、人工干预、生产恢复,推动后续处置、风险评估等措施,最大限度减轻了对金沙江上游叶巴滩、拉哇、巴塘、苏洼龙等在建水电站的灾害损失和后续影响,为类似灾害的处置提供借鉴经验。     

Three‐dimensional computational comparison of mini pinned heat sinks using different nanofluids: Part one—the hydraulic‐thermal characteristics

The hydraulic‐thermal characteristics of 3D pinned heat sink designs have been numerically compared as the first part of a three‐part investigation. Five different pin geometries (circular, square, triangular, strip, and elliptic pins) and an unpinned heat sink with three types of nanofluids (Al₂O₃–H₂O, SiO₂–H₂O, and CuO–H₂O) are considered for laminar forced convection. The range of Reynolds number is from 100 to 1000, and volume fractions vary between 0% and 5%. The finite volume method is employed to solve the Navier–Stokes and energy equations by employing a SIMPLE algorithm for a computational solution. Three parameters are presented—the Nusselt number, the bottom temperature, and the hydrothermal performance of the heat sink with pressure drop data. The findings indicated that the overall hydrothermal performance of elliptic‐pinned (EP) heat sinks produces the most substantial value of 3.10 for pure water. For different nanofluids, the SiO₂–water nanofluids with EPs have the most significant hydrothermal performance. Also, this factor is enhanced with an increase in nanofluid concentration up to nearly 3.34 for 5% of SiO₂–water. Consequently, applying the elliptic‐pinned heat sinks is recommended with pure water for considering an increase in the pressure drop, with 5% of SiO₂–water nanofluids, regardless of an enlargement of pressure drop for heat‐dissipation applications.     

Experimental investigation of Al2O3–MgO hot hybrid nanofluid in a plate heat exchanger

Exergy–energy analysis of the plate heat exchanger is experimentally performed with different Al₂O₃–MgO hybrid nanofluid (HyNf) as a hot fluid. There were six combinations of fluids, namely, deionized (DI) water, ethylene glycol–DI water brine (1:9 volume ratio), propylene glycol–DI water brine (1:9 volume ratio), base fluids and their respective Al₂O₃–MgO (4:1 particle volume ratio) HyNfs of 0.1% total volume concentration. The effects of different flow rates and hot inlet temperatures on the heat transfer rate, heat transfer coefficient, pump work, irreversibility, and performance index (PI) are investigated. It is witnessed that the heat transfer rate, heat transfer coefficient, pump work, and irreversibility enhances with the flow rate and nanoparticle suspension. While the PI declines with a rise in the flow rate, the heat transfer rate, heat transfer coefficient, PI, and irreversibility rise up maximum for MgO–alumina (1:4) DI water HyNf upto 11.8%, 31.7%, 11.1%, and 4.05%, respectively. The pump work enhances upto 1.6% for MgO–alumina (1:4)/EG–DI water (1:9) HyNf.     

低阶煤颗粒-气/油泡间的诱导时间研究

为表征低阶煤颗粒-气/油泡间矿化过程的差异,通过Sutherland理论下固体颗粒进入泡沫产品的总概率(E)和浮选速率常数(k)之间关系,并结合低阶煤颗粒-气/油泡的浮选速率试验,求得了低阶煤颗粒-气/油泡间的诱导时间。浮选实验研究表明,在相同的捕收剂消耗量下低阶煤-油泡浮选产率均高于低阶煤-气泡浮选产率。诱导时间测试表明,低阶煤颗粒-油泡间的诱导时间(35 ms)要明显低于低阶煤颗粒-气泡间的诱导时间(93 ms)。上述实验结果表明,油泡表面的疏水性要强于传统浮选气泡表面的疏水性。然而,进一步利用Sutherland理论中固体颗粒进入泡沫产品的总概率和浮选速率常数之间的数学关系,并结合低阶煤颗粒-气/油泡的浮选速率试验求得的低阶煤颗粒-气/油泡间的诱导时间分别为9.67和8.46 ms,其与诱导时间测试仪分别测量的诱导时间差异很大。这主要是由于在实际浮选过程中气/油泡的上升速度分别为23.26和22.68 cm/s,其远高于2015EZ型诱导时间仪测试过程中气/油泡碰撞速度(2.0 cm/s)。因此,诱导时间理论计算表明气泡-颗粒间的碰撞速度对颗粒-气泡间的诱导时间影响很大。上述研究结果表明油泡浮选效果优于传统浮选的内在原因在于低阶煤颗粒-油泡间的诱导时间小于低阶煤颗粒-气泡间的诱导时间。     

全自动集装箱码头装卸系统质量管理

全自动集装箱码头装卸系统集成了当今世界各项先进技术,在研发、制造、调试过程中,都要坚持质量第一、安全第一的原则,确保各项技术参数可靠,设备运行稳定。在总结国内几个全自动码头装卸系统的质量管理方法与经验的基础上,结合自动化码头自身特点,给出全自动集装箱码头装卸系统主要质量管理方法,进一步丰富发展自动化码头装卸系统建造过程中的“不欠债离岸”质量管理理念。     

Discrete element method study on hopper discharge behaviors of binary mixtures of nonspherical particles

This study is aimed at unveiling the influence of binary mixtures of nonspherical particles on hopper discharge behavior, which remains poorly understood. The discrete element method (DEM) is employed to simulate seven particle types with aspect ratios between 0 and 2 (namely, a sphere, two ellipsoids, two cylinders, and two cuboids) with the same volume. Seven monodisperse systems and twelve binary-shape mixtures are assessed. For the monodisperse systems, particle shape is the dominant factor dictating discharge rate, compared to other factors like aspect ratio, preferential orientation, and packing. Regarding the binary-shape mixtures, the discharge rates are similar for all twelve mixtures, reflecting a surprising lack of shape effects, which in turn means the negligible impact of solid volume fraction, aspect ratio, and segregation extent. Moreover, collision force is generally negatively correlated with discharge rate.     

复杂流道结构料仓的下料流率预测

在实验室搭建的有机玻璃料仓下料平台上，分别以自由流动粉体玻璃微珠和黏附性粉体煤粉和聚氯乙烯为实验介质，针对无改流体(No-In)、封闭改流体(Con-In)和开放改流体(Ucon-In)三种情况所形成的不同流道结构，开展了粉体料仓下料及其流率建模研究，定量分析了改流体对粉体下料流率的促进作用，对比给出了玻璃微珠、煤粉和聚氯乙烯在不同流道结构料仓内的下料特性。研究表明，改流体的引入有利于提高料仓下料流率，Con-In促进流动效果最明显，对于流动性弱的煤粉，下料流率提升幅度达到最大的58%。基于剪切摩擦区的概念，提出流率校正因子F对最小能量理论方程进行了修正，将理想的料仓下料模型拓展至实际下料过程。进一步，对于Con-In，根据流道结构特征结合对粉体的受力分析，修正了模型中的锥角项；对于Ucon-In，基于粉体下料流动竞争机制，提出分阶段下料模式并关联了内层和夹层的下料流率，最终建立了复杂流道结构料仓的下料流率预测模型。该模型综合考虑了粉体物性、下料流型和流道结构的影响，可有效预测自由流动粉体和黏附性粉体流经传统料仓(No-In)和改流体料仓(包括Con-In和Ucon-In)的粉体下料流率，且预测偏差<10%。     

铁素体/贝氏体双相钢循环载荷作用下变形行为的模拟研究

为了避免铁素体/贝氏体双相钢管线管在服役过程中的交变载荷作用下引起的塑性损伤，采用有限元模拟方法，建立了Chaboche随动强化模型，研究了铁素体/贝氏体双相钢在循环应变载荷作用下的变形行为。结果显示，在循环应变作用下，应变优先在铁素体中形成累积，并在铁素体、贝氏体界面集中；随应变幅的增大，应变带在铁素体中形成，而贝氏体内累积应变增加不大，两相界面应变差增大。研究表明，铁素体内应变和两相应变差的增加将降低双相钢的塑性变形能力。     

月柿提取物体外抗氧化活性研究

目的以月柿提取物为原料,研究其对2,2-联苯基-1-苦基肼基(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基的清除能力,并测定其多酚类物质没食子酸的含量。方法检测波长为518 nm,反应时间为40 min条件下,以IC_(50)值(清除率为50%时,抗氧化剂的浓度值)作为抗氧化能力评价指标,并采用高效液相色谱法测定其没食子酸含量。结果月柿提取物对于DPPH自由基有良好的清除作用,其IC50值为0.1868 mg/mL,与常用抗氧化剂作用相当,且月柿提取物中没食子酸含量为1.65 g/kg。结论月柿提取物具有很强抗氧化活性,作为化妆品及功能性食品原料有广阔的开发前景。