The Assessment of Multispectral Radiation Thermometry Using Linear and Log-Linear Emissivity Models for Steel

Experiments were performed to measure the spectral intensity values of a variety of steel samples at 700, 800, and 900 K. The experimental work is coupled with two commonly used emissivity models, linear emissivity models (LEMs) and log-linear emissivity models (LLEs), to examine multispectral radiation thermometry (MRT) on inferring surface temperature. Overall, the first-order LEM and the first-order LLE show the best compensation for different alloys, number of wavelengths, temperatures, and heating time. The results reveal that the better the emissivity model suitably represents real surface emissivity behavior, the more accurate is the inferred temperature by MRT.     

Investigation of steel emissivity behaviors: Examination of Multispectral Radiation Thermometry (MRT) emissivity models

Steel emissivity behaviors were investigated in this study. Experiments were conducted to measure emissivity. Six emissivity models were then applied to examine Multispectral Radiation Thermometry (MRT) on inferring surface temperature. The data show that emissivity decreases with increasing wavelength. For steel containing high chromium, emissivity is usually lower than others because of the chromium oxide protection layer. Two emissivity models provide the best overall compensation for different alloys, number of wavelengths, and temperatures. The results reveal that if the emissivity model can well represent the real emissivity behaviors, the more accurate inferred temperature can be achieved.     

激光诱导磷光测温技术在缸内温度测量中的应用

将激光诱导磷光测温技术应用到发动机缸内气体的二维温度测量中.其原理是利用Dy:YAG磷光剂受355 nm波长的激光激发后辐射的458 nm和494 nm磷光强度比进行温度测量,实验在一台侧向换气的光学发动机上进行,测试了该发动机压缩行程的二维温度分布,与由缸压计算的缸内平均温度比较,误差均小于5%.     

Computational Modeling of GMAW Process for Joining Dissimilar Aluminum Alloys

A three-dimensional transient model is developed to solve for heat transfer, fluid flow, and species distribution during a continuous gas metal arc welding (GMAW) process for joining dissimilar aluminum alloys. The phase-change process during melting and solidification is modeled using a fixed-grid enthalpy-porositytechnique, and Scheil's model is used to determine coupling among composition, temperature, and the liquid fraction. The effect of molten droplet addition to the weld pool is simulated using a “cavity” model, in which the droplet heat and species addition to the molten pool are considered as volumetric heat and species sources, respectively, distributed in an imaginary cylindrical cavity within the molten pool. To establish the model for joining dissimilar alloys, results for joining two pieces of a similar alloy are also presented. The dissimilar welding model is demonstrated using a case study in which a plate of wrought aluminum alloy (with approximately 0.5 wt% Si) is butt-welded to an aluminum cast alloy plate (with approximately 10 wt% Si) of equal thickness using a GMAW process. Macrosegregation, along with the associated heat transfer and fluid flow phenomena and their role in the weld pool development, are discussed. The model is able to capture some of the key features of the process, such as differential heating of the two alloys, asymmetric weld pool development, mixing of the molten alloys, and the final composition after solidification.     

基于数据驱动算法的再热蒸汽温度动态预测

锅炉再热蒸汽温度具有强非线性和大滞后特性,为解决其软测量中常规单一模型预测精度不足的问题,提出一种基于自适应提升算法(Adaptive Boosting, Adaboost)和极限梯度提升(eXtreme Gradient Boosting, XGBoost)的数据驱动建模方法。利用变分模态分解对数据进行深度解析,通过XGBoost建立预测模型,将其作为弱学习器,经过Adaboost算法的不断迭代,配合误差动态修正(Error Dynamic Correction, EDC)构造出一种再热蒸汽温度动态数据驱动模型。结果表明：模型最终的精度评价指标均方根误差(Root Mean Square Error, RMSE)和平均绝对误差(Mean Absolute Error, MAE)分别为1.733和1.387,与常规的支持向量回归、随机森林及XGBoost模型相比表现更为优异,可以实现再热蒸汽温度的快速准确预测,为后续再热汽温优化控制问题提供有效的参考。     

发射率结合辐射光强实时测量高温辐射源2维温度场

提出了一种由光纤光谱仪与黑白CCD相机构成的新型实时在线高温温度场测量系统.该系统用光纤光谱仪和黑白CCD相机同时测得高温辐射源的真实发射率和光强场,然后根据发射率和光强场计算得到高温辐射源的温度场.利用该系统对高温发光物体——卤素灯灯丝的温度场进行测量,得到了不同电压值下卤素灯灯丝的温度场分布图,并将所得温度场的最高温度与相应工况下发射光谱法测量得到的最高温度进行比较.结果表明:两者相对偏差在5%以内;所提出的测量方法既弥补了发射光谱法不能获得场分布的缺陷,又避免了比色法测温中单色波长带宽和发射率瞬时变化带来的误差,是一种有效的温度场测量方法.     

Temperature Difference Error Determination for Heat Meter Validation

A method to calculate the maximum value of temperature difference error in heat meters is presented. It is designed for heat meters used for measuring the volume of heat provided to buildings by heating systems using hot water. Validation offices generally use computer-based numerical methods for the calculation of the error over the full temperature range and temperature difference range. Use of these methods is time-consuming due to taking in succession the temperature and temperature difference with a constant gradient as well as selecting the maximum value of error. The author has developed a method that allows the practicing engineer to calculate the maximum error in a short time with his or her own program. This method can also be used for heat meters not conforming to any standard or pairs of temperature sensors not dedicated for heat meters.     

飞灰辐射特性与表面温度关联的实验研究

为降低燃煤、垃圾焚烧和生物质锅炉高温换热器传热管失效泄漏甚至爆管的风险,提出基于高温内窥镜光学测温方法的高温换热器表面积灰和温度状态监测系统.采用多元扩散Hencken燃烧器和细颗粒振荡给粉技术,开展了3种飞灰可见光段辐射特性与温度的关联规律研究.结果 表明:由于3种飞灰理化性质不同,其辐射-温度关联曲线区别明显;光学频道选择不同也会显著影响结果的准确性,在实际应用前应进行系统的实验室标定,以获取更为精确的结果.     

Numerical Evaluation of Radiation Extinction Coefficient Using Fractal Geometry for Vegetation Modeling

This article focuses on the accurate determination of the radiation extinction coefficient (β) for a vegetal set like a tree in the frame of forest fires. Usually, this coefficient is calculated using the De Mestre relationship, not taking into account the leaf orientation and position. In order to evaluate their role, a realistic vegetal structure is numerically created using LAI data, De Wit's models, and IFS geometry. A ray-tracing method is used to simulate the radiative transfer inside the numerical tree. The results show that the leaf distribution and position cannot be neglected in β determination. The use of well-known correlations are not sufficient to predict β: over-estimations of up to 100% have been observed.     

利用PTC材料加热的PID控温研究

PTC电阻是一种具有正温度系数的热敏电阻,利用PTC电阻取代普通电阻作为PID温控的加热元件有可能成为工业加热领域精密温控的一种新手段。利用PTC加热元件,结合PID控温算法,建立了PID精密温控实验系统,研究了PID控温下的PTC加热元件的高精度控温特性,并与固定电阻PID控温进行了对比。研究结果表明:应用PTC材料PID控温可以有效减小超调,但在居里温度之后温度调节过程变得缓慢;PID三参数在一定的范围内,应用PTC材料PID控温明显优于固定电阻,其控温超调减小并且控温精度提高。研究结果对于利用PTC材料PID温控来实现工业加热中的精密温控具有一定的指导价值。     

铝板材退火炉炉温模糊PID控制的仿真研究

针对铝材卷退火炉温度控制过程中的大时滞性,大惯性的特点,应用Matlab模糊推理工具箱,设计了自适应模糊PID温度控制系统,并在Simulink中与传统的PID控制进行了对比仿真.仿真结果表明:采用自适应模糊PID控制后,系统的响应速度加快,超调量减小,且具有较强的鲁棒性和良好的稳定性.     

采用优化算法分析燃烧火焰辐射光谱求取火焰温度

通过对优化算法的尝试利用从气体燃烧火焰发出的辐射光谱拟合分析出火焰燃烧温度的方法,简化了传统测温用双色法所要求的火焰绝对辐射强度的标定,同时有助于了解火焰辐射黑度随波长的变化规律。通过和热电偶测量值的比较,证明经该方法得到的计算结果具有一定的精度,使燃烧火焰温度的在线监测成为可能。     

Heat Transfer Coefficient Correlation for Convective Boiling Inside Plain and Microfin Tubes Using Genetic Algorithms

Two-phase flow heat transfer has been exhaustively studied in recent years. However, in this field, several questions remain unanswered. Heat transfer coefficient prediction related to nucleate and convective boiling has been studied using different approaches—numerical, analytical, and experimental. In this study, an experimental analysis, data representation, and heat transfer coefficient prediction of two-phase heat transfer in nucleate and convective boiling are presented. An empirical correlation is obtained, based on a genetic algorithms search engine, of a dimensional analysis of the two-phase flow heat transfer problem.     

FTIR发射-透射光谱法测量CO_2和碳黑的温度

对傅立叶红外光谱仪发射 透射(FTIRE T)测量技术进行理论和实验研究.理论分析表明,样品厚度为光学薄、颗粒等温、粒径单一和均匀弥散等条件,是应用FTIRE T技术所必须满足的.针对一个改进的傅立叶变换红外光谱仪,以酒精火焰和蜡烛火焰为测试对象,对该机的适用性和误差来源进行详细分析.结果表明,FTIRE T技术所确定的CO2温度和碳黑温度,与其它方法的测量结果符合得较好,可能的相对误差小于±300.     

缸盖水腔表面温度场的确定

为了确定更为准确的缸盖冷却水腔壁面温度场,以车用226B型柴油机缸盖冷却水腔为研究对象,介绍了缸盖水腔流固耦合传热的过程,并给出了使用流固耦合确定水腔壁面温度场的方法和步骤,根据壁面温度场判断出了壁面各区域的传热类型并求解出了壁面的换热系数,结果表明,流固耦合法与集总参数法壁面温差最大可达36K,考虑沸腾传热因素时水腔壁面传热系数最大值为14200W/m2.K,比未考虑沸腾传热时大了近50%。     

缸盖水腔表面温度场的确定

为了确定更为准确的缸盖冷却水腔壁面温度场，以车用226B型柴油机缸盖冷却水腔为研究对象，介绍了缸盖水腔流固耦合传热的过程，并给出了使用流固耦合确定水腔壁面温度场的方法和步骤，根据壁面温度场判断出了壁面各区域的传热类型并求解出了壁面的换热系数，结果表明，流固耦合法与集总参数法壁面温差最大可达36K，考虑沸腾传热因素时水腔壁面传热系数最大值为14200W／m^2·K，比未考虑沸腾传热时大了近50％。     

辐射屏法输热管网隔热保温的参数确定方法及计算结果

在实验和工程应用的基础上,介绍了利用辐射屏法对热网管道进行隔热保温中的确定辐射屏的层数及间隔的方法,并给出了40种不同管径或温度的计算结果,在工程应用中可予以采用。     

铝电解质预焙槽气体焙烧流场与温度场数值模拟

应用κ－ε双方程模型和离散辐射强度法对铝电解槽气体焙烧的流场及温度场进行数值模拟。模型避免了辐射传热的空间积分运算，使温度场的求解简单方便。数值模拟所得到的温度场和流场与工业试验结果吻合较好。本文研究为铝电解预焙槽气体焙烧这一新的焙烧启动方法提供了理论基础。