Simulation of Water-Resistance of a Clay Layer During Mining:Analysis of a Safe Water Head

Given previous research and prototypical geological conditions of a mining workface,we simulated fis-sure development in clay layers at the bottom of Quaternary strata and above bedrock,sand and water inrush during mining by model experiments. The results show that V-shaped fissures usually occur in the bottom clay layer at the front top of the active face and that the position of these fissures changes periodically with ground pressure intervals. These fissures occur exactly in the area where the horizontal strain is concentrated. The results also demonstrate that the permeability coefficient of the cracked clay decreases while fissures tend to close. The permeability of the cracked bottom clay layer increases rapidly after a turning point in the permeability coefficient-water head curve (K-H curve) under a certain vertical load. Under static water pressure,the permeability coefficient of cracked clay decreases when load increases. A turning point in the K-H curve showed up and can be seen as a cutoff point to de-cide water inrush under a certain load level. Under an instantaneous water head,the greatest ability of the cracked clay to avoid drastic water inflow is a little higher than that under static conditions.

Multiphase Flow and Wear in the Cutting Head of Ultra-high Pressure Abrasive Water Jet

Abrasive water jet cutting technology is widely applied in the materials processing today and attracts great attention from scholars, but many phenomena concerned are not well understood, especially in the internal jet flow of the cutting head at the condition of ultra-high pressure. The multiphase flow in the cutting head is numerically simulated to study the abrasive motion mechanism and wear inside the cutting head at the pressure beyond 300 MPa. Visible predictions of the particles trajectories and wear rate in the cutting head are presented. The influences of the abrasive physical properties, size of the jewel orifice and the operating pressure on the trajectories are discussed. Based on the simulation, a wear experiment is carried out under the corresponding pressures. The simulation and experimental results show that the flow in the mixing chamber is composed of the jet core zone and the disturbance zone, both affect the particles trajectories. The mixing efficiency drops with the increase of the abrasive granularity. The abrasive density determines the response of particles to the effects of different flow zones, the abrasive with medium density gives the best general performance. Increasing the operating pressure or using the jewel with a smaller orifice improves the coherency of p articles trajectories but increases the wear rate of the jewel holder at the same time. Walls of the jewel holder, the entrance of the mixing chamber and the convergence part of the mixing tube are subject to wear out. The computational and experimental results give a qualitative consistency which proves that this numerical method can provide a reliable and visible cognition of the flow characteristics of ultra-high pressure abrasive water jet. The investigation is benefit for improving the machining properties of water jet cutting systems and the optimization design of the cutting head.

A bull-heading water control technique of thermo-sensitive temporary plugging agent

Aimed at the disadvantages of secondary damage to oil layers caused by the conventional bull-heading water control technique, a thermo-sensitive temporary plugging agent for water control was synthesized by water solution polymerization and applied in the field with a new secondary temporary plugging technique. The optimization and performance evaluation of thermo-sensitive temporary plugging agent were carried out through laboratory experiments. The optimized formula is as follows:(6%-8%) acrylamide +(0.08%-0.12%) ammonium persulfate +(1.5%-2.0%) sepiolite +(0.5%-0.8%) polyethylene glycol diacrylate. The thermo-sensitive temporary plugging agent is suitable for formation temperatures of 70-90 ?C, it has high temporary plugging strength(5-40 k Pa), controllable degradation time(1-15 d), the apparent viscosity after degradation of less than 100 m Pa?S and the permeability recovery value of simulated cores of more than 95%. Based on the research results, secondary temporary plugging technique was used in a horizontal well in the Jidong Oilfield. After treatment, the well saw a drop of water cut to 27%, and now it has a water cut of 67%, its daily increased oil production was 4.8 t, and the cumulative oil increment was 750 t, demonstrating that the technique worked well in controlling water production and increasing oil production.

Effect of Ship Bow Overhang on Water Shipping for Ship Advancing in Regular Head Waves

这份报纸论述处理鞠躬的效果的试验性的调查的结果悬于发货的数量上的延期在在常规头波浪进展的轮船的情况下在前甲板上流水。执行这调查，一系列免费跑的测试在使用一艘多种用途的货物轮船的一个试验性的模型确定的常规波浪被进行装运水的数量。测试在五个弓上被执行悬于有波长和轮船的几联合的变体加速条件。装运水的数量被象波长，轮船速度，和鞠躬形状那样的一些参数以 overhang 扩展影响，这被观察。结果显示出 overhang 延期的重要影响，它与鞠躬闪光形状被联系，在水发货的出现上。这些结果包含联合到来的常规波浪和模型速度。

Evaluation of “C” Values to Head Loss and Water Pressure Due to Pipe Aging: Case Study of Uni-Central Sarawak

Samarahan has transformed from a small village into education hub for the past 2 decades. Rapid development and population growth had led to speedy growth in water demand. The situation is getting worse as the pipes are deteriorating due to pipe aging. Therefore, there is a need to study the adequacy of water supply and relationships among roughness coefficient (C) values in Hazen Williams’ Equation with head loss and water pressure due to pipe aging at Uni-Central, a residential area located at Samarahan Sarawak. Investigations were carried out with Ductile Iron, Abestos Cement and Cast Iron pipes at age categories of 0 - 10 years, 10 - 30 years, 30 - 50 years, 50 - 70 years and >70 years. Six critical nodes named as A, B, C, D, E and F were identified to study the water pressure and head loss. Model was developed with InfoWorks Water Supply (WS) Pro software. The impact of pipe aging and materials to water pressure and head loss was not significant at Nodes A, B, C and F. However, max water pressure at Nodes D and F were only reaching 6.30 m and 7.30 m, respectively for all investigations. Therefore, some improvement works are required. Results also show that Asbestos Cement pipe has the least impact on the head loss and water pressure, followed by Ductile Iron pipe and lastly Cast Iron pipe. Simulation results also revealed that older pipes have higher roughness coefficients, indicated with lower “C” values, thus increase the head loss and reduce the water pressure. In contrast, as “C” values increased, head loss will be reduced and water pressure will be increased.

A LEACH-Head Expected Frequency Appraisal Algorithm for Water-Environment Monitoring Networks

Water-environment monitoring network (WMN) is a wireless sensor network based real-time system, which collects, transmits, analyzes and processes water-environment parameters in large area. Both cluster selection mechanisms and energy saving strategies play an important role on designing network routing protocols for the WMN. Since those existing routing algorithms can not be used directly in the WMN, we thus propose an improved version of LEACH, a LEACH-Head Expected Frequency Appraisal (LEACH-HEFA) algorithm, for the WMN in this paper. Simulation results show that the LEACH-HEFA can balance the energy consumption of nodes, rationalize the clustering process and prolong the network lifetime significantly in the WMN. It indicates that the LEACH-HEFA is suitable to the WMN.

Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low Head Micro Hydro Resources

Theoretical investigation has shown a simple reaction water turbine would perform better when it spins faster. And for the simple reaction turbine water turbine to spin faster under constant water head, its diameter should be smaller. This paper reports on a performance analysis based on the experimental data collected from different performance tests carried on two simple reaction water turbine prototypes. Two new designs of simple reaction water turbines and their manufacturing methods are reported. The two turbines under investigation have different rotor diameters Φ 0.243 m and Φ 0.122 m. In case of the simple reaction water turbine the water enters into the turbine axially and exits tangentially through nozzles located on the outer periphery of the turbine. Further this paper will discuss the performance characteristics of stationary turbine i.e. zero power produced and performance characteristics of turbine producing power. It was found that rotor diameter affects the maximum rotational speed of the simple reaction turbine for constant supply head. It was also found that faster the turbine spins its performance improves. The two turbines were tested between supply head range of 1 m to 4 m.

低水头永磁同步发电机磁极结构的优化设计

文章基于低水头流水发电的工况特点和并网原理,建立了永磁同步发电机的数学模型,并提出了相应的解析算法。采取场路结合的方法,分析不同磁极结构对凸极率、磁阻转矩、电感和波形畸变率等参数的影响。利用上述设计分析方法,对一台30 kW的小型低水头永磁同步发电机进行了优化设计,试验结果表明,该优化设计方案具有可行性和正确性。

有自由面的裂隙网络稳定渗流试验与数值分析

为探究裂隙网络含自由面的稳定渗流特性,设计可视化的二维裂隙网络渗流试验装置,通过调节裂隙网络模型的上、下游水头开展一系列裂隙网络渗流试验,依次记录自由面水头高度和渗流流量大小;同时基于有限元软件COMSOL Multiphysics中的Darcy接口,建立等比例二维裂隙网络数值模型,复现试验工况并与试验结果对比分析。对比发现试验结果与模拟结果基本吻合,这验证了试验结果的有效性以及数值模拟的准确性。研究结果表明:影响自由面变化的主要因素为上、下游水头高度及二者高度差:渗流水力梯度越大,自由面位置的下降越快;渗流水力梯度相同的水力条件,上、下游水头越高,形成的自由面水头越高,自由面降落曲线也越陡。其中,若上、下游水头高度不处于近似的水平,二者对于自由面位置的影响存在较大差异。自由面变化的基本规律符合Dupuit公式的表述。稳定渗流的水力梯度与平均流量仅在流量较小时符合线性相关,随着水力梯度的增加,二者关系呈现明显的非线性。

铅山抽水蓄能电站额定水头选择

水蓄能电站是顺应社会发展潮流的朝阳行业,我国大力提倡和扶持水力发电站的建设,而抽水蓄能电站额定水头的选择直接影响机组的使用效率、使用寿命及可靠性和稳定性。水轮机是一种用于发电的重要设备,其安装质量直接影响发电站的安全和运行效率。研究抽水蓄能电站额定水头是水轮机稳定运行的保障,能确保水蓄能电站安全运行。文章对抽水蓄能电站水泵水轮机额定水头的选取方法进行了探讨,进行了铅山抽水蓄能电站额定水头的选择。

Coupled hydro-mechanical effect of a fractured rock mass under high water pressure

To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test（HPPT）,including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.

长距离有压输水工程整体模型试验管道沿程水头损失替代研究

长距离有压输水工程一般通过设置阻力环的水头损失替代法进行整体模型试验研究。依托深圳市北坑水库输水隧洞工程,对不同雷诺数、环数和布置方式下阻力环的水头损失替代效果及其变化规律进行数值模拟研究发现:当雷诺数Re>0.32×10^(5)后,几乎不会造成阻力环局部水头损失系数与阻力环后旋涡区长度变化;孔径比d/D减小或距径比L/D增大会增强阻力环的水头损失替代效果;当d/D=0.8,L/D=0.5,环数n>2时,阻力环平均局部水头损失系数K_(d)随环数n增加而减小,当环数n>20后K_(d)不再随环数变化。在此基础上推导出环数影响系数ε随环数n的变化规律及其拟合曲线,以及阻力替代段总局部水头损失和替代管道长度计算公式。通过分析环数对漩涡区长度的影响,阻力替代段后需设置不小于2.5D的过渡段才能保证水流流态恢复至未替代状态。

水头衔接的梯级电站水头分配问题研究

对于水头衔接的梯级电站,在两梯级电站总水头不变情况下抬高下游电站运行水位,一方面会增加弃水风险,另一方面会改变两电站利用水头,从而使两电站发电收益发生变化。为了研究抬高下游电站运行水位对梯级电站整体发电收益的影响,计算了抬高下游电站运行水位前后梯级电站收益变化,提出了发电用水增量系数评价指标,并基于弃水损失,研究了改变梯级电站水头分配后电站发电收益变化,给出了改变梯级电站水头分配是否有利于提高梯级电站总收益的判别条件,并以清江隔河岩、高坝洲梯级电站为例进行了探讨。结果表明:鉴于上下游电站电价、综合出力系数的差异,当满足提出的判别条件时,适当抬高下游电站运行水位可增加梯级电站的整体发电收益。研究成果可为梯级电站科学控制水位、平衡弃水风险和水头效益、提高整体发电收益提供理论参考。

缸盖水腔CFD分析及连接钻孔优化

以某柴油机缸盖水腔变动情况为研究对象,对调整前后的缸盖水腔进行CFD仿真。针对缸盖下层水腔、排气道水腔的流速分布云图,结合上水孔及连接钻孔的流量分布,分析流动过程及调整后冷却能力减弱的详细原因。在此基础上,通过调整连接钻孔的直径及位置,提出满足冷却能力要求的优化方案,并对优化方案进行仿真验证。

超大型取水工程取水头部及引水管线设计

为减少水源保护与城市发展的矛盾,同时降低钱塘江盐水入侵对取水安全的威胁,杭州市启动了取水口上移工程。结合杭州市主城区水厂布局调整及千岛湖引水工程事故工况等因素,新建取水工程土建规模按远景300万m^(3)/d考虑,近期设备安装规模为170万m^(3)/d。根据本工程取水口涉水专题研究,取水口上移位置位于富春江石门沙南岸,现状萧山江东取水口上游约250 m处。通过综合比选,采用箱式取水头部,可有效保证取水安全,降低工程投资。根据取水头部和取水泵站两者位置,对引水管线路进行布置,通过水力计算确定采用2根DN3400钢管,全线采用顶管施工。为保障运行安全,设计考虑了引水管防淤积措施和取水头部防护警示设施。

800m以上水头三机式抽水蓄能机组研究

我国的资源禀赋的特点是富煤、贫油、少气,促使我国的能源结构主要以化石能源为主。在“双碳”目标的指引下,以非化石能源为主体的新型能源体系必然是未来大势所趋,光电和风电成为新型电力系统下新能源的主力军,但光电和风电存在随机性和波动性,对电网的冲击相对较大,再加之新能源的定价机制还在探索中,所以出现了弃风、弃光等情况。为高效吸收消纳光电、风电等未来供电主力,避免新能源的浪费,保障电网安全。抽水蓄能水电站必然是未来储能主力,而三机式抽水蓄能机组有着更为独特储能优势,包括适用水头更高、水头变幅更宽、响应电网更快、工程造价更低等。本文就结合光电和风电的实际情况,探讨光电和风电作为供电主力下的储能新方案,三机式抽水蓄能机组高质量消纳新能源的研究和探索。

建筑屋面方形溢流口溢流量计算公式分析及探究

建筑屋面溢流口的设计计算关系到屋面结构安全,对现有国家规范中墙体方形溢流口溢流量计算公式进行了分析对比,通过对水力学不同堰流形式、宽顶堰基本计算公式、流量系数及侧收缩系数等方面的分析推导,得出按现有规范公式计算出的溢流口几何尺寸偏小。结合屋面不同雨水斗对斗前水深的要求及建筑屋面的不同排水形式,提出了墙体方形溢流口属于宽顶堰,明确了溢流口的溢流水位高度和上游坎高度的取值范围,进而采用数学工具推出了屋面方形溢流口溢流量新的计算公式,并从水力学和数学角度对新公式进行了合理性分析,可供设计同行参考。

白象山选矿厂提高产能优化实践

白象山选矿厂为了进一步提高生产效率和产能,针对精矿产品质量、生产作业率等指标进行了生产流程优化,提高设备利用率,采用先进生产设备等研究。通过循环使用淘洗机尾矿溢流水,减轻了尾矿大井负荷,提高了磁选机的选别效果,同时优化湿式筛分预选工艺筛孔尺寸,提高了选厂处理能力;通过优化高压辊辊缝及频率等参数,使用新型侧挡板,延长了高压辊辊面的使用寿命,提高了设备利用率;通过使用凿岩台车、深孔钻机等智能采矿设备,改善了选厂给矿状况。现场生产实践表明,通过上述措施优化,有效提高了白象山选厂的产能。

改进的YOLOv5积水检测算法

为了提升YOLOv5算法的积水检测精准度,提出一种改进YOLOv5网络结构的积水检测算法。通过解耦头代替初始YOLOv5的耦合头,使分类任务与回归任务两者互不干扰,在网络训练到300轮次左右时表现出了良好的收敛效果;利用CIoU损失函数代替GIoU,降低积水检测的误差,提高积水检测精准度。结果表明,相比初始YOLOv5算法的精准度、召回率、m_(AP1)和m_(AP2)分别提升了1.7%、1.8%、1%和0.5%。文中的积水检测算法比初始算法减少了训练损失,收敛速度更快,精准度更高,可为积水区域的检测提供算法支撑。