Experimental studies on the erosion rate of different heat treated carbon steel economiser tubes of power boilers by fly ash particles

The experimental investigations on the effect of the fly ash particle size, velocity, impingement angle, and feed rate were done with an emphasis on the effect of erosion on annealed SA 210 GrA1 (A) and normalized SA 210 GrA1 (N) carbon steel economizer-tube materials. Erosion rates were evaluated with different impingement angles ranging from 15° to 90°, at four different velocities of 32.5, 35, 37.5, and 40 m/s, and at four different feed rates of fly ash particles of 2, 4, 6 and 8 g/min. The erodent used was fly ash particles, sizes ranging from 50-250 μm of irregular shapes. Erosion rate is found to be the maximum at the impingement angle of 30°. Erosion rates of the carbon steel tube in different heat treatment conditions, annealed and normalized, at a constant velocity of 32.5 m/s with different angles were studied. In all cases of feed rates, impingement angles, particle sizes, and velocities of fly ash particles, it has been found that the erosion rate of the annealed tube is less than that of the normalized tube. Empirical correlations for erosion rate relating the velocity, size, feed rate, and impingement angle of the particles and elongation property of the target materials were arrived. Morphologies of the eroded surface were examined by scanning electron microscope (SEM).     

Coastal erosion in China under the condition of global climate change and measures for its prevention

The general characteristics of coastal erosion in China are described in terms of the regional geography, the form of erosion, the causes of erosion, and the challenges we are facing. The paper highlights the relationship between coastal erosion and sea level rises,storm waves and tides, and the influence of global climate changes on coastal erosion along the coastal zone of China. The response of the risk of coastal erosion in China to climate changes has obvious regional diversity. Research into and the forecasting of the effects of climate changes on coastal erosion are systemic work involving the natural environment, social economy, and alongshore engineering projects in the global system. Facing global warming and continual enhancement of coastal erosion, suggestions for basic theoretical study, prevention technology, management system assurance, and strengthening the legal system are presented here.     

浅谈某水库安全监测设计

本文从分析影响大坝安全的各种因素入手,在时空两个方面拓宽了大坝安全监测的概念,即大坝安全监测应在时空上将影响大坝安全的因素考虑在内。在此基础上,提出：①大坝安全监测要有明显的针对性;②重视对溃坝的分析;⑥大坝安全监测应和设计及大坝安全定检结合起来,以方便资料分析和相互校核;④加强对大坝安全监测（包括监测系统）,特别是自动化系统的效益评估,要求大坝安全监测系统成为水库运行调度的依据,真正为提高水库效益服务;⑤通过网络技术,实现大坝安全监测的网络化,以方便经验交流,提高监测技术。     

钻柱振动条件下的钻井液冲蚀引起的钻柱失效*

钻柱失效问题已经成为高压喷射钻井技术发展和推广的瓶颈。建立了一种钻柱失效的新理论模型,利用振动的知识研究钻柱的失效情况,分析钻柱在振动条件下的位移和速度,在此基础上利用冲蚀理论对钻柱的失效进行研究,分析得出钻井液对钻柱的冲蚀磨损量和最大冲蚀角。根据算例计算与分析,对应算例参数进行室内实验和井场实验设计,完成实验的验证与结果分析。结果表明:在考虑钻柱振动条件下,钻井液对钻柱的冲蚀磨损量要远大于未考虑钻柱振动条件下钻井液对钻柱的冲蚀磨损量;同时得知最大冲蚀角与冲蚀理论中的规定是完全吻合的以及钻井液对钻柱冲蚀所发生的最大角度在钻柱有无振动的条件下是相同的。研究结论对于在石油钻井中如何减少钻柱的失效及如何提高钻柱的使用寿命具有一定的理论参考意义。     

基于输水隧洞泵送混凝土管道的冲蚀机理

采用数值模拟方法对龙开口水电站1号输水隧洞混凝土泵送过程中管道冲蚀磨损问题进行研究。利用DPM离散相模型分析泵送管道的冲蚀磨损机理,结合1号隧洞实际泵送混凝土的情况来验证数值模型是否正确。通过模拟结果从整个管道固相体积分数分布与弯管出口处的压强变化等特征理解其内在的多相流动规律。模拟得到的弯管最大冲蚀磨损部位,与实际泵送过程中的磨损部位吻合较好。说明DPM冲蚀模型能准确预测泵送管道的磨损特性,可为类似的泵送混凝土施工提供有益参考。     

渐缩型气动喷砂喷嘴冲蚀模拟分析

为研究气动喷砂枪喷嘴喷射颗粒对自身造成的冲蚀磨损情况,通过选取渐缩型气动喷砂喷嘴为研究对象,运用CFD软件对其内部流场及颗粒运动特性进行模拟分析;通过改变收缩角度、颗粒粒径及颗粒质量流率进一步分析影响喷嘴冲蚀速率变化的规律。结果表明:喷嘴的冲蚀区域主要集中在收缩段及收缩段与出口段交界面处;以收缩角度为30°、45°、60°的喷嘴为例,随收缩角度的增加,冲蚀区域出现"逆向发展";随颗粒粒径的增加,喷嘴最大冲蚀速率呈现先下降后上升的"U"形变化趋势,且其最低点所对应的粒径与收缩角度成反比;随颗粒质量流率的增加,喷嘴最大冲蚀速率呈上升趋势,但并未呈现线性关系。     

齿轮电蚀现象的研究进展

介绍了齿轮电蚀现象以及国内外对齿轮电蚀的研究情况与进展;明确了齿轮电蚀系统是一个特殊的磨擦学系统,所涉及到的相关学科与理论错综复杂,各种现象相互并存耦合,因此造成了实验研究的复杂性与难度;统计了国内典型的齿轮电蚀范例,并在此基础上总结了齿轮电蚀现象的特征与研究方法、手段。     

硅各向异性腐蚀技术

论述了硅各向异性腐蚀技术在国内外的水平和友展趋势,攻关成果的推广应用前景。     

Erosion and sediment delivery in rills on steep loess slope

Sediment delivery in rills on the loess slope was studied by inflow experiments. Relationships between sediment delivery rate in rills and flow shear stress, discharge and slope gradient, maximum sediment and unit runoff power, and discharge and slope gradient were analyzed. A relationship is presented for calculating the erosion rate in rills .     

水电站AGC中的惩罚函数及虚拟机组技术

针对影响水轮机使用寿命与运行安全的气蚀和振动问题,从经济角度出发,用惩罚函数方法,有效地避开了机组的气蚀和振动区.在水电站自动发电控制AGC中,为避免负荷调整时频繁通过气蚀和振动区,以及机组的频繁开停,将机组的安全运行区以虚拟机组形式加入电厂的AGC优化计算中.