5通道铁磁探测仪的研发与锅炉管堵塞检测

描述了5通道铁磁探测仪的研发和应用,该仪器能在管外发现发电锅炉过热器管和再热器管内是否有铁锈堆积,并评估堵塞程度,目的是通过检测防止爆管事故。采用磁学探测方法,在管外表面的1条圆周线上布置5个测量点,进行了有限元数值模拟和标定曲线的计算。对计算结果进行了实验验证,与计算值相比较,测量值的标准误差(相对误差)为5.2%。现场检测得到的堵塞面积与管内孔的面积之比,与X射线摄影测得的结果比较,确定铁磁探测仪检测的标准误差(绝对误差)为3.9%。通过为5家热电厂进行过热器管和再热器管堵塞检测,发现超标堵塞30多处,解剖验证无一误报,所以用该仪器进行堵塞检测能够防止上述锅炉管爆管事故。     

热电厂锅炉高温过热器管爆管原因

利用化学成分分析、力学性能测试、显微组织分析和X射线衍射物相分析等方法,对材料为T91钢的热电厂锅炉高温过热器管的爆管原因进行了分析.结果表明:高温过热器管材料的质量合格,异物阻塞管道造成其短时过热是过热器管爆管的主要原因,在距爆口一侧约30 cm处发现有异物残留.     

电站锅炉尾部烟道管子吹损问题探讨

电站锅炉在尾部烟道内往往会布置较多的吹灰装置,在省煤器悬吊管与低温过热器管排或低温再热器管排相交叉位置普遍存在着吹损问题,由于吹损位置隐蔽,往往不易发现,这就对锅炉安全经济运行造成了威胁。现主要针对锅炉定期检验过程中发现的共性问题进行分析探讨,提出合理优化锅炉结构、采取有效措施防止吹损爆管,为存在同类问题的电厂提供了借鉴。     

糖厂25t锅炉过热器爆管的分析及处理

通过对 SHS2 5 - 2 .45 /4 0 0型锅炉热器管爆管的原因分析 ,提出解决锅炉过热器爆管的处理方案     

电站高过爆管分析与焊接修复方案探讨

分析了阿曼萨拉拉独立电厂#5余热锅炉高温过热器模块鳍片管的爆管事故,得出本次爆管原因是多应力作用下金属断裂。然后介绍了焊接修复方案,为电站建设和运行中解决此类爆管事故提供了参考。     

锅炉高温过热器爆管分析

针对某电厂锅炉高温过热器管屏运行过程中出现的爆管事故,采用宏观分析、内窥检查、厚度测试、显微硬度测试、力学性能试验、光谱分析、能谱分析、金相分析等方法进行试验分析,试验结果发现高温过热器管材料组织存在缺陷,产生微裂纹,在运行中进一步发展,最后在钢管薄弱位置(损伤处)造成短时过热爆管。     

锅炉“四管”防磨防爆检查及预防措施

发电厂燃煤锅炉"四管"是指水冷壁管、过热器管、再热器管和省煤器管,这四个部分会受到过热、磨损和腐蚀等因素的影响,很容易出现锅炉泄漏、破裂等现象。这种现象是由于锅炉运行时管外磨损、管内(外)腐蚀、管排超温运行、质量不良等因素造成的。本文对锅炉"四管"爆漏的原因进行了研究分析,并针对这些问题给出了有效的预防措施,为解决同类故障重复出现的情况提供了参考。     

R134a外螺纹管水冷冷凝器研究

采用一种新的冷凝换热模型,对R134a外螺纹管水冷冷凝器进行研究。通过样机设计,并在多功能焓差室标准工况下进行试验,由试验数据反推外螺纹管水冷冷凝器的管外平均冷凝换热系数。通过比较发现,冷凝换热系数的模型计算值比试验值大15%。     

一起锅炉沸腾管爆管事故原因分析及预防措施

分析了锅炉使用的水质不合格及排污不规范所造成的沸腾管爆管原因。根据存在的问题,采取有效的措施,防止了沸腾管再次发生爆管事故的可能,确保了锅炉的安全经济的运行。     

超声波检测技术在锅炉受热面管氧化皮检测中的应用

锅炉受热面管氧化皮检测历来都是预防锅炉爆管的重要手段,主要介绍了超声波检测技术在某电厂锅炉末级过热器管内壁氧化皮检测中的实际应用,通过将超声波检测结果与内窥镜检查以及显微镜下的测量结果进行比较,进一步验证了该技术的准确性和可靠性。同时,将该技术与传统的射线拍片技术、不锈钢氧化皮堆积测量技术和割管取样测量等方法做了比较,指出超声波检测技术的优势及应用前景,对指导锅炉检修及保障锅炉安全经济运行具有一定的指导作用。     

5通道铁磁探测仪的研发与锅炉管堵塞检测

为了提高航空发动机轴承故障诊断的准确率,提出基于改进遗传算法优化（back propagation,简称BP）网络(modified genetic algorithm to optimize BP,简称MGA-BP)的故障诊断模型。针对传统遗传算法易早熟、易陷于局部最优解等缺陷,利用固定个体选择概率、引入三角函数和高斯变异操作对遗传算法进行改进,并用改进遗传算法优化BP网络的权值和阈值。利用优化的BP网络对滚动轴承正常、内圈故障、外圈故障和钢球故障4种工况进行诊断,并考虑到网络输出模式、诊断样本比例等对诊断精度的影响。为了验证MGA-BP在轴承故障诊断中的有效性,将其他改进遗传算法优化BP网络作为对比算法。分析表明：MGA-BP能够较好地适应网络不同的输出模式、不同的样本比例,其抗噪能力、诊断准确率、误差收敛速度和误差收敛值均优于文中其他对比算法。     

基于瑞利-里兹法的低翅片管固有频率数值解

针对低翅片管几何形状复杂,质量和刚度分布不均匀,振动特征值不能有封闭解的问题,采用瑞利-里兹法对低翅片管的固有频率进行了数值研究,获得了低翅片管弯曲振动固有频率的数值计算模型。对于一定规格的低翅片管,应用该数值计算模型可求得其各阶固有频率的数值解。采用共振法测试了低翅片管的固有频率,前三阶固有频率的数值解与实测值相比,误差范围为-3.28%--3.51%。该数值计算模型可用于低翅片管固有频率的求解。     

茹卡乌斯卡斯横掠错排管束实验模型的数值模拟

茹卡乌斯卡斯实验关联式在换热器的设计中有着广泛的应用。针对茹卡乌斯卡斯研究流体横掠错排管束流动与换热特性的实验段为原型,经过适当的简化,建立三维模型,运用大型CFD软件Fluent对该模型内流体的流动与换热特性进行了数值模拟研究。将数值模拟结果与公式计算结果进行对比,误差较小。通过考察特殊管排的局部换热特性,对模型壁面对换热的影响、末排管与中间管排的换热特性差异进行了分析;并将使用茹卡乌斯卡斯公式进行计算的误差与管排数的关系进行分析,在实际的设计计算中有一定的参考意义。     

Smokestack gas velocity measurements using 3D pitot tubes in a coal-fired power plant

On the path to carbon neutrality to reduce greenhouse gas (GHG) emissions, the Korean government has mandated legislation for controlling and monitoring GHG emissions emitted from smokestacks. A continuous emission measurement (CEM) method is considered to be the most reliable for determining CO2 emissions from stationary sources. In Korea, an S-type Pitot tube is the most popular technique to measure the gas velocity in a smokestack, but it will result in a certain error when the non-axial velocity components exist. To vanquish this limitation, Korea Research Institute of Standards and Science (KRISS) developed a nulling smokestack flow measurement (NSFM) instrument equipped with 3D Pitot tubes for taking on-site stack gas velocity measurements. 3D Pitot tubes used in this research, such as prism Pitot tube and sphere Pitot tube, are calibrated in the KRISS airspeed system. The instrument using 3D Pitot tubes with the nulling technique is expected to diminish the restriction on S-type Pitot tubes, and to enhance the quality of the GHG emission measurements in the smokestack. The 3D Pitot tubes can measure both axial and non-axial velocity components of a flow, whereas the S-type Pitot tubes can measure only the axial velocity component. The averaged axial velocity of the stack gas as measured by this instrument has expanded uncertainty of 3.3% (P = 95%, k = 2) for both prism and sphere Pitot tubes.     

A study on the exit flow characteristics determined by the orifice configuration of multi-perforated tubes

A multi-perforated tube indicates the existence of multiple holes in various shapes on the surface of long cylinder-type or rectangular tubes, and the hole installed on the surface is called an orifice as it is relatively small in size, compared with the surface area of the tubes. In this study, flowrate distribution features and changes in discharge angle according to the blockage ratio resulting from the changes in the number of orifices and the thickness of multi-perforated tubes were investigated by means of analysis and experiment, targeting the multi-perforated tubes where rectangular orifices are installed on the both sides of square tubes. In addition, contraction coefficient and flow coefficient between orifices were analytically investigated. The more increase in blockage ratio of multi-perforated tubes, the more uniform flowrate distribution between orifices. The discharge angle becomes more and more perpendicular in the longitudinal direction of multi-perforated tubes as it gets closer to the end of orifices, exhibiting big differences at the entrance if blockage ratio is small. The more increase in the thickness of multi-perforated tubes, the more uniform flowrate distribution between orifices become as contraction coefficient increases. The flow coefficient distribution of orifices using the pressure at the entrance of the orifices of multi-perforated tubes increases in the longitudinal direction of the multi-perforated tubes, exhibiting values ranging from 0.66 to 0.68 as to BR = 0.893 ?? 0.979.     

激光烧蚀ICP-AES中蒸发物输送过程研究

利用Nd:YAG纳秒脉冲激光器烧蚀土壤标样,由氩气作为载气将激光蒸发物质输送到ICP光源,用光电检测法记录元素As、Pb、Cr、Hg和Cd的光谱强度。通过改变炬管与样品蒸发室之间传输管的长度、内径以及载气流量的大小来测量比较重金属元素的光谱强度、信背比和相对标准偏差的变化,以研究激光蒸发物的输送过程对ICP发射光谱的影响。测量结果显示:在传输管长度为60cm,内径为4mm时光谱强度和信背比为最佳;输送激光蒸发物质的载气流量为0.4L/min时,光谱强度和信背比最好;当载气流量保持在0.4L/min不变时,使用内径为4mm的传输管得到的As、Pb、Cr、Hg和Cd分析信号的相对标准偏差(RSD)分别是4.53%,9.08%,7.56%,4.42%和4.24%,而当传输管内径为5.5mm时,其RSD分别是9.72%,9.93%,9.76%,7.07%和7.18%。研究表明,传输管长度尽可能短并且内径合适是提高光谱质量和测量精度的重要条件。     

Q235覆管对AA5052铝合金基管颗粒介质胀形行为的影响

采用AA5052铝合金挤压管作内层基管、Q235碳素结构钢卷焊管作外层覆管的钢铝复合管对复合管颗粒介质胀形行为进行研究。通过塑性理论分析胀形过程中管间切向摩擦力及法向压力对基管应力大小的影响;利用数值模拟分析管间摩擦因数和覆管各向异性对基管的应变成形极限的综合影响,并给出单管、复合管胀形时的壁厚减薄情况和基管的应力、应变分布;通过管材颗粒介质内高压胀形试验,对比单管和复合管胀形条件下铝合金管的极限胀形比,分析复合管的变形协调性。结果表明：通过施加Q235碳素结构钢覆管,减小了AA5052基管胀形区中间截面处的双向拉应力,基管胀形区壁厚减薄变小,胀形比提高了22%,复合管下基管最大减薄率为17.5 %,成形性能显著提高。     

广义Waterbomb折纸管的刚性折叠运动特性

对折叠模式的精确描述是折纸结构工程应用的前提,但现有的理论和方法无法全面地分析大多数折纸结构的刚性折叠过程。以广义Waterbomb折纸管为研究对象,基于球面机构运动学理论系统地分析了其折叠行为与运动协调条件,推导了折叠管刚性收缩和扭转运动的两套解析运动学方程。研究了各种几何设计参数对Waterbomb折纸管刚性折叠行为的影响,并讨论了该折纸结构折叠过程中的分岔行为与可能的物理干涉,及其引起的刚性折叠与结构形变的转化。此工作为基于广义Waterbomb折纸管的可编程超材料、可变形结构和机器人的设计与控制奠定了理论基础和设计依据,同时为复杂折纸结构的运动学分析提供了有效的手段。     

Investigation of the pressure response of different Pitot tubes

Pitot tubes are commonly used to measure gas flow in ducts. The integration of the velocity profile which allows the calculation of the gas flow is described in several international standards such as ISO 3966 or ISO 10780.The common working principle of Pitot tubes is based on the measurement of the differential pressure between the two different pressure taps. The gas velocity is related to this differential pressure through a flow coefficient depending on the Pitot tube type.In case of stable flow, in a pressurized duct, fluctuations of the in-line pressure, even low, can occur. If the response times of the two pressure lines (static and total) between the Pitot tube head and the differential pressure sensor are not equal, these fluctuations can be seen as fluctuations of the measured differential pressure and then of the calculated velocity.This phenomenon is investigated for different design of Pitot tubes and the difference in behaviour of the two pressure lines is highlighted.     

The effect of turbulence on a multi-hole Pitot calibration

Accurate calibrations of multi-hole Pitot tubes require thousands of measurements spanning ranges of the fluid's velocity, and the pitch and yaw angles. When calibrating a commercially-manufactured multi-hole Pitot tube in NIST's low-turbulence wind tunnel, we found hysteresis in certain ranges of airspeed, pitch angle, and yaw angle. In the worst case, the hysteresis caused a calibration error of 30%. We demonstrate that the hysteresis was caused by a flow instability associated with flow separation. A turbulence intensity of only 1% removes the hysteresis; however, the calibration depends on the turbulence intensity over the entire range of our measurements (0.25–2%). Therefore, multi-hole Pitot tubes should be calibrated and used at the same turbulence levels.