铸造三通的强度计算和使用问题

我国建国初期投入运行的高压高温电厂,主蒸汽管道上的三通多为铸造结构,以后又逐渐发展了焊接、热挤压等结构型式的三通。目前国外大容量高参数机组多采用锻造三通。铸造三通在国内外均日趋减少使用。最近有一些单位对铸造三通做了一些光弹和电阻应变测试试验,对铸造三通的应力     

厚壁等径三通应力分布的有限元分析

本文对厚壁等径三通在弹性范围内、常温静载作用下的应力和强度进行了系统的分析研究。为摸索在各种外载和内压作用下三通的纵横截面、母管与支管相贯线处内外壁的应力分布规律,三通在内压、五种典型外载工况下的应力指数及其与β值的关系曲线,采用 SAP-5有限单元法结构分析程序对几何特征值β=D_外/D_内=1.20、1.35、1.50三种无焊缝加强等径三通进行了三维元计算,并与相应的电测试验比较,证明计算结果是比较准确的。     

焊制三通的应力分析

焊制三通最常见的问题是主管与支管相贯处的连接焊缝开裂而引起泄漏。采用有限元方法对焊制三通的结构进行应力分析,并将应力计算结果进行了线性化处理,等效后成为薄膜应力、弯曲应力及峰值应力,从而获得了焊制三通应力的分布规律。计算结果表明:焊制三通相贯线附近的应力值约比直管段的应力值高出4倍,且最大应力点发生在肩部的内壁。这类焊接结构的应力计算,为设备运行的可靠性和安全性提供了重要的理论依据。     

多结构切换分块式预制电缆井设计浅析

传统电缆井结构改造工艺需在电缆井支线新增侧破坏原有井部分结构并现场绑扎钢筋、浇筑混凝土,存在施工周期长、安全风险大、现场施工噪音、环境污染等问题。以电缆井结构改造中常见的直线井改三通井、三通井改四通井为例,提出了多结构切换分块式预制电缆井设计施工方法,取得了良好的应用效果。     

主汽管三通焊缝开裂泄漏原因分析研究

对主汽管三通焊缝开裂的原因进行研究分析 ,发现由于焊口结构不合理和管路结构的原因 ,造成在焊缝三通侧熔合线处产生较大应力 ,并发生以蠕变损伤为主要损坏形式 ,沿焊接热影响区扩展的损坏开裂     

ZG20CrMoV钢三通裂纹原因分析和焊接修复技术

文章对主蒸汽管道中的铸钢件三通的裂纹产生原因 ,从管系结构、铸造工艺、缺陷性质等环节上进行了分析。叙述了三通的焊接修复技术的焊接工艺以保证焊接质量 ,并对同类问题的处理具有极其重要的参考价值和指导意义     

叉形三通冲压件可靠性能研究

叉形三通冲压件是空调分体内机集气管中常用的组件,其在管路系统中主要为分流、合流及过滤作用。在三通内部加入过滤网,通过定位凹环进行定位,可以起到过滤杂质的作用。传统的冲压模具结构有其局限性,通过实验数据分析现有管路件的失效形式,因零件表面形状不规则而存在应力集中的现象。将模具前端的加工面设计成椭圆形的回转壳体,改变其结构可以有效减少冲压件成型后应力集中。从冲压件的加工工艺着手,分析叉形三通件的失效形式,对原有结构的三通冲压件进行结构优化,增加冲压间距值,提高其壁厚可有效提高受力点的屈服强度。通过以上优化并借助有限元仿真和实验对其进行验证,可以得出更改后的冲压件具有较高的使用寿命,能承受更大的应力。     

干湿灰交换装置设计

介绍一种干湿灰交换装置，该装置由电动隔断门、电动卸灰器、电动三通翻板门三部分组成，由PLC进行控制。该装置采用硬密封技术、封闭式结构，彻底解决传统装置长期以来存在的堵灰、漏灰问题。     

三通道法测量变压器直流电阻的局限性

分析了单通道法与三通道法的测量原理,通过3个直流电阻测量案例,比较了单通道法与三通道法测量值的差异,指出三通道法对变压器中性点引出线的电阻几乎无法正确反映,三通道法对中性点引线上的电阻增大现象反应不灵敏。     

某电厂冷启动蒸汽疏水管道三通开裂问题治理

某电厂3号机组冷启动蒸汽疏水管道与冷启动蒸汽管道连接处三通焊口,运行过程中短时间多次开裂,经过多次补焊处理,效果仍不理想.经分析此三通焊口开裂的主要原因为焊口处二次应力严重超标.经对管道的综合改造,解决了该三通焊口开裂的问题.     

电厂润滑油管焊制三通开裂失效分析

针对广东某发电厂1号机组润滑油管焊制三通开裂的事故,介绍了三通失效的机理,指出存在原始焊接缺陷的焊制三通焊缝尖角处在外力作用下开裂是三通失效的根本原因,为此,提出了今后在工作中应注意的事项及应采取的措施.     

Swarm intelligence based robust active queue management design for congestion control in TCP network

Active queue management (AQM) is an effective solution for the congestion control problem. It can achieve high quality of service (QoS) by reducing the packet dropping probability and network utilization. Three robust control algorithms are proposed in this paper in order to design robust AQM schemes: conventional controller, robust particle swarm optimization (PSO)‐based PID (proportional–integral–derivative) (PSOPID) controller, and robust ant‐colony optimization (ACO)‐based PID (ACOPID) controller. PSO and ACO methods are used to tune the PID controller parameters subject to constraints to achieve the required robustness of the network. Robust PSOPID and ACOPID controllers can achieve desirable time‐response specifications with a simple design procedure and low‐order controller in comparison to the conventional controller. Wide ranges of system parameters change are used to show the robustness of the designed controllers. The ability of the designed controllers to meet the specified performance is demonstrated using MATLAB 7. 11, (R2010b): The MathWorks, Inc.3 Apple Hill Drive Natick, MA USA. On the other hand, to verify the effectiveness of the designed controller, nonlinear simulation is performed using the NS2 package. Finally, it is shown by comparison that the proposed robust ACOPID can achieve more desirable performance than the PSOPID controller and the controllers that have been proposed in previous works. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Excitation and steam‐valving coordinated robust controller design for multi‐machine power systems based on the multi‐index nonlinear robust control approach

This paper proposes a novel multi‐index nonlinear robust control (MNRC) approach for multi‐machine power systems. The MNRC approach combines multi‐index nonlinear control with the control theory. With the multi‐index nonlinear control, which selects the output functions as arithmetic combination of state variables, multiple performance indices of the controlled system can be achieved simultaneously in the nonlinear control framework. The control is able to ensure that the system possess the desired robust performance during disturbance. Then, excitation and steam‐valving coordinated robust controllers are developed based on the MNRC approach for multi‐machine power systems. The effectiveness of the proposed robust controller is evaluated by a six‐machine power system simulation. Simulation results show that the expected dynamic and steady‐state performances of power system can be achieved with the MNRC approach. Meanwhile, it is able to achieve the prescribed system performance despite the presence of disturbances. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Averaging effect on stochastic response prediction in FastADR aggregation for building air‐conditioning facilities

This letter reports on the averaging effect on prediction errors of the fast automated demand response (FastADR) power limitation amount calculated by our autoregressive and neural net models for a large number of multi‐type building air‐conditioning facilities. The standard deviation of prediction error variation decreases with the number of FastADR trials according to the rule. This result will be useful for estimating the averaging effect in the prediction of FastADR for a large number of target facilities. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Proposal of shoplifting prevention service using image analysis and ERP check

In this paper, we propose a software‐as‐a‐service application that prevents shoplifting using image analysis and enterprise resource planning (ERP). In Japan, the total damage due to shoplifting has reached 450 billion per year, and each year more than 1000 small book stores give up their business because of shoplifting damage. Based on the recent advancement in cloud technology and data analysis technology, we propose a shoplifting prevention service with the image analysis of security camera movie and ERP data check for small shops. We also confirm the precision ratio of security camera stream movie analysis using the online machine learning framework Jubatus. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An efficient exact numerical solution for scattering by a circular cylinder

An efficient and exact spectral integral method (SIM) for the general problems of scattering by a circular cylinder is presented, both for acoustic and electromagnetic cases. Fast Fourier transform (FFT) and convolution theorem help us to execute the algorithm efficiently with computational complexity. The Fourier coefficients of the integral kernels are computed in a semianalytical way to accomplish a fast convergence rate with spectral accuracy. Compared with the method not using the semianalytical forms, without the increase of the computing and memory abundance, it saves more than 90% sampling points to achieve about the same accuracy, and with the same number of sampling points, several to more than ten orders of magnitude more accuracy can be achieved. For example, for the tested large wavenumber case with 2 × 10⁶ wavelengths on the boundary, only two sampling points per wavelength are required to achieve a relative error of less than 0.001%. More than 90% computational time is saved compared with the normal summation formula of harmonic cylinder expansions. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A 0.5‐V 5.9‐fJ/conversion‐step SAR ADC in 0.18‐μm CMOS

In this paper, we present a 434‐nW 8‐bit successive approximation register analog‐to‐digital converter (SAR ADC). We mainly consider the optimization of power consumption. A modified split‐capacitor array involving a novel switching scheme is proposed, which reduces the switching power consumption to just 13.8 for the single‐ended scheme without any losses in performance. Based on the SMIC CMOS 0.1 μm EEPROM 2P4M process, the simulation results show that at 0.5 V supply voltage, 300 kS/s sample frequency, and 4.98 kHz input frequency, the ADC achieves an signal‐to‐noise‐plus‐distortion ratio (SNDR) of 49.58 dB and effective number of bits (ENOB) of 7.94, and consumes 434 nW, resulting in a figure of merit of 5.9 fJ/conversion step. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

多区域电网模型在线拼接与合并

介绍了一种基于公共信息模型(CIM)/可扩展置标语言(XML)电网模型和可缩放矢量图形(SVG),以及以联络线路为边界进行多区域电网模型在线拼接与合并的方法.针对各区域系统之间存在T接联络线的情形,提出通过T接分组的方式来解决由于虚拟站命名不统一而造成的T接点不易合并,以及线路信息频繁修改等问题.在模型的增量更新上,除了通过设备的统一命名来更新设备参数外,还通过运行库与待导入模型文件间的连接关系绑定实现模型连接关系的增量更新.通过模型的在线拼接与合并,所开发的电力保障自动化系统根据电网拓扑梳理出从380 V到上级各级电源的供电路径,满足了"全链条式"的电网监视要求,最大限度地保障了对重要用户的可靠供电..     

电力系统分析综合程序功能扩展的设计

就电力系统分析综合程序增加“厂站主接线图”、“交流线‘Ｔ’型接线”和“一个母线持多台发电机”等新功能,进行有关原理、数据结构方面的设计,以电力系统分析综合程序更适合地区及以下电网的计算分析。