基于双响应波段工作的红外热像仪测温原理与误差分析

为了提高红外热像仪测温的准确性,根据红外辐射理论,从红外热像仪的测温原理出发,分析了基于双响应工作波段的热像仪的测温原理,得出了目标物体的发射率、物体温度计算公式以及相应误差的估算公式,分析了各影响因素对热像仪测量准确度的影响,提供了一种目标物体发射率的测定方法,对利用红外热像仪准确测量内燃机等热能机械表面温度具有重要的意义。     

基于奇异值分解的红外热图像序列处理

在红外热像无损检测中直接获取的原始热像往往信噪比较低、温度对比度较差.为了抑制各种噪声的不良影响,使红外热像无损检测所重构的数字图像有较高的缺陷对比度,从而提高缺陷探测能力,提出了采用奇异值分解法对红外数字图像序列进行处理和增强的方法,并进行了验证.介绍了奇异值分解法的原理;用奇异值分解法对实验中采集的红外热像序列进行处理;以信噪比为指标对图像处理效果进行了定量评定.研究表明奇异值分解法具有抽取红外热像序列中反映试件内部缺陷信息代数特征的能力,可消除加热不均效应、提高图像的信噪比,且缺陷在图像中所处的位置不影响奇异值分解法的使用效果. 因此奇异值分解法是红外热像无损检测中红外热图像序列处理的有效方法.      

压力传感器膜片表面温度的测量和分析计算

用红外热成象技术测量应变式压力传感器工作时的膜片温度分布,以判断由于电阻应变片工作时温度变化对测量准确性的影响。测量中为获得应变片的真实温度,作了表面喷黑处理。对于实用的3MPa和0.6MPa的压力传感器,在不同工作介质(空气和变压器油)及工作电压条件下进行了测量,其结果表明:应变片表面温度随工作电压增高而加大,且不均匀。以空气为介质的温度高于以变压器油为介质的温度。据此可以确定对压力测量准确度的影响。还用有限差分方法对压力传感器膜片表面温度作了数值分析计算。     

基于红外热像仪对珠状凝结换热过程实验

通过非接触式测温装置红外热像仪,观测冷凝液滴的形成、生长以及液滴之间汇聚、滚落过程.实验发现在珠状冷凝过程中,其表面温度变化显著.随着冷凝过程的进行,小液滴逐渐汇聚成大液滴,其液滴单位面积换热量明显下降,液滴表面温度逐渐降低.微纳米级小液滴在珠状冷凝换热中具有至关重要的作用.液滴在洁净表面上的珠状凝结和液滴在汇合后自清理表面上的珠状凝结表现出不同的温度分布,即珠状凝结汇聚后的自清理表面一直被前驱膜所覆盖.      

因子分析法在脉冲红外热无损检测中的应用

为了提高脉冲热像法PT(Pulsed Thermography)的缺陷检测能力,将因子分析法应用于脉冲红外热无损检测的热像序列处理中.介绍了因子分析法的原理,描述了因子分析法处理并重建红外热像序列的步骤.为了考查算法的有效性,对人工内置缺陷的玻璃纤维增强塑料板试件进行了脉冲红外热像检测试验.结果表明:通过因子分析得到的公因子图像可以进行缺陷识别,因子分析法较主分量法处理数据更加灵活;通过公因子重建图像序列后,可增强缺陷信噪比和抑制加热不均效应,从而提高了脉冲热像法的缺陷检测能力.     

视场内导航星分布的预测

给出理想情况下视场内导航星分布模型的基础上,根据敏感器的星等门限和测量精度,进一步实现了存在星等误差情况下导航星分布的预测,使得该模型更为接近真实的情况.实验表明,采用该模型获得的分布与用MonteCarlo方法获得的统计分布极为接近,证明了该模型的正确性和有效性,从而得到了一种事先对视场内导航星分布作出较为准确估计的新的方法.      

铝试件脉冲红外热无损检测的主分量分析

为了提高铝试件脉冲红外热像无损检测的缺陷探测能力,研究了主分量分析法在热像信号处理中的运用方法及效果.结合脉冲热像序列处理论述了主分量分析的数据准备、计算方法和处理效果.为了考查算法的有效性,对铝合金板进行了脉冲红外热像无损检测实验.结果表明,采用第2、第3主分量图像以及由前几个主分量重建的图像均有增强缺陷对比度和抑制加热不均的效应,从而提高了脉冲红外热无损检测的缺陷检测能力;此外,在检测铝板模拟腐蚀时,能使可探测的最小腐蚀率减小10%左右.     

极月轨道上太阳电池阵外热流规律分析

准确的月球表面温度分布模型对于开展月球探测具有重要意义. 目前有关月球表面温 度模型还缺乏对完整月球表面温度分布的计算方法研究. 本文建立了一套计算完整月球表面温度的方法, 其中月球阳面温度采用Racca模型直接计算得到; 对于月球阴面, 将其沿纬度方向划分为若干区域, 每个区域的地表土壤采用一维非稳态热传导模型, 根据嫦娥三号着陆器太阳电池阵在轨环月阶段的温度数据, 修正得到月球表面土壤导热系数、密度及比热容, 通过数值计算求解一维非稳态热传导方程, 得出任意时刻月球阴面表面温度随时间的变化. 嫦娥三号着陆器太阳电池阵环月阶段热分析结果与在轨温度符合较好, 初步说明本文建立的完整月球表面温度计算方法正确可行. 基于本文方法计算得到整个月球表面温度分布, 进一步研究了极月轨道太阳电池阵外热流变化规律.      

烟气覆盖表面红外温度测量的实验分析

为了研究辐射参与性烟气对红外测温法金属壁面温度测量的影响,首先根据实验中红外探测器测量得到的表面温度分布的特点,建立了一维表面红外测温模型;然后根据红外热成像测温原理及辐射传输理论,利用源项多流法分析模型计算了烟气覆盖表面在不同烟气厚度和不同表面温度下红外探测器获得的温度;最后利用马弗炉模拟不同温度的表面,振动筛模拟不同浓度和厚度的烟气环境,在实验室条件下设计搭建了模拟烟气覆盖表面的红外测温实验系统,实验验证了源项多流法分析模型,实验测量得到的温度与分析模型预测的温度吻合较好,并提出了利用反演方法修正红外测温的设想。     

超高频脉冲GTAW熔池表面温度分布

针对5 mm厚Ti-6Al-4V钛合金平板完成焊接熔池红外热成像监测,研究分析了超高频脉冲钨极氩弧焊(UHFP-GTAW)熔池表面温度分布,与常规GTAW(C-GTAW)熔池表面温度分布进行了比较。结果表明,在均为定点加热母材20 s的条件下,与C-GTAW工艺相比,UHFP-GTAW电弧(20 kHz、40 kHz)作用下的熔池中心表面温度测量值增加了10~30 K;分别以不同温度(678 K、823 K和968 K)为参考值测量熔池表面的高温扩散区域,UHFP-GTAW所得试样的高温扩散面积缩小范围为13%~30%。基于热量、力作用和复合散热等要素构建了熔池模型分析其温度场分布特点,计算结果与试验数据基本相符。      

基于多光谱测温优化的材料光谱发射率测量

针对高温材料红外光谱发射率测量中样品表面温度难以准确测量的问题,提出了直接使用光谱仪测量得出样品表面的光谱辐射能量信息,选取其中合适的光谱波段利用多光谱测温方法得到样品表面温度,进而计算出材料的光谱发射率.分析了多光谱测温中发射率模型的阶次和测量波段选取对测温准确度的影响,给出了温度计算的稳健算法,并对其主要不确定度的来源进行了评定.在1 100 K左右温度下以不锈钢材料进行实验验证,得出温度引起的光谱发射率相对不确定度在2～20 μm范围内低于2%,满足红外隐身和辐射测温等领域的要求,适合于导热性能差的材料或涂层材料的高温光谱发射率测量.     

红外加热棒式空间外热流模拟器的数值研究

采用蒙特卡罗法跟踪能束的发射和吸收,提出了一种避免挡板表面能量方程计算的等效反射模型,模拟了红外加热棒式空间外热流模拟器模拟面上的能量分布及其他参数,比较了加热棒为直棒和曲棒时模拟面的热流模拟结果。研究表明,挡板内外表面置换后表面发射率的不同并没有导致模拟面上能量分布的明显变化;增加加热棒根数并不能一直明显地使模拟面的能量分布更趋于均匀;经形状优化后曲棒模拟的热流分布比直棒更均匀。     

临近空间环境下封闭方腔内耦合换热特性

以临近空间浮空器载荷舱为应用背景,对复杂热边界条件下含热源的三维封闭方腔内自然对流、表面辐射和导热的耦合问题进行了数值模拟。综合考虑对流换热、长波辐射、太阳辐射等因素的影响,建立了临近空间热环境模型。通过Fluent软件用户自定义函数（UDF）引入外部非定常的辐射-对流耦合热边界条件,对腔内换热特性的昼夜变化进行研究,并分析了腔壁厚度、发射率和导热系数对其的影响。数值结果表明,腔内平均温度昼夜变化很小,约为12.9 K,但温度场分布随太阳方位变化而变化;腔内对流换热较弱,同一时刻最大温差约为71.3 K;腔壁热阻和发射率增加会削弱自然对流的强度。      

Water surface temperature estimation from Landsat 7 ETM+ thermal infrared data using the generalized single-channel method: Case study of Embalse del Río Tercero (Córdoba,Argentina)

Monitoring of warm distribution in water is fundamental to understand the performance and functioning of reservoirs and lakes. Surface water temperature is a key parameter in the physics of aquatic systems processes since it is closely related to the energy fluxes through the water–atmosphere interface. Remote sensing applied to water quality studies in inland waterbodies is a powerful tool that can provide additional information difficult to achieve by other means. The combination of good real-time coverage, spatial resolution and free availability of data makes Landsat system a proper alternative. Many papers have developed algorithms to retrieve surface temperature (principally, land surface temperature) from at-sensor and surface emissivity data. The aim of this study is to apply the single-channel generalized method (SCGM) developed by Jiménez-Muñoz and Sobrino (2003) for the estimation of water surface temperature from Landsat 7 ETM+ thermal bands. We consider a constant water emissivity value (0.9885) and we compare the results with radiative transfer classic method (RTM).     

Remote sensing based continuous hydrologic modeling

There are two principal ways in which remote sensing can be used with continuous hydrological models: (1) by providing a cost effective way for obtaining input data and (2) by providing synoptic measurements of various state variables. This paper discusses existing hydrologic models and the modifications required to adapt them for using remotely sensed data that may significantly improve their simulation performance. Microwave and thermal infrared measurements show promise for use in hydrologic models because they can measure certain physical properties of the watershed (emissivity and temperature) from which a hydrologic condition can be inferred. Additional applications of remote sensing data include the use of spatial data, mechanisms for extrapolating point data and direct measurement of several hydrologic state variables such as soil moisture, surface temperature, snow water equivalent, frozen soils, and rainfall distribution. Results are presented from several aircraft flights where thermal infrared and microwave data were collected over a small research basin. These results are discussed with respect to their application in continuous hydrologic simulation models.     

三波长辐射温度计

采用辐射法测量物体表面真实温度的最大困难是被测材料表面的发射率难测。三波长辐射温度计能消除发射率对测温的影响,尤其是对抛光表面的测温。本文基于推导多波长辐射温度计的理论,推出了一种三波长辐射测温法的新关系式,并建立了三波长辐射温度计的数学模型。     

Surface temperature estimation in Singhbhum Shear Zone of India using Landsat-7 ETM+ thermal infrared data

Land surface temperature (LST) is an important factor in global change studies, heat balance and as control for climate change. A comparative study of LST over parts of the Singhbhum Shear Zone in India was undertaken using various emissivity and temperature retrieval algorithms applied on visible and near infrared (VNIR), and thermal infrared (TIR) bands of high resolution Landsat-7 ETM+ imagery. LST results obtained from satellite data of October 26, 2001 and November 2, 2001 through various algorithms were validated with ground measurements collected during satellite overpass. In addition, LST products of MODIS and ASTER were compared with Landsat-7 ETM+ and ground truth data to explore the possibility of using multi-sensor approach in LST monitoring. An image-based dark object subtraction (DOS3) algorithm, which is yet to be tested for LST retrieval, was applied on VNIR bands to obtain atmospheric corrected surface reflectance images. Normalized difference vegetation index (NDVI) was estimated from VNIR reflectance image. Various surface emissivity retrieval algorithms based on NDVI and vegetation proportion were applied to ascertain emissivities of the various land cover categories in the study area in the spectral range of 10.4–12.5 μm. A minimum emissivity value of about 0.95 was observed over the reflective rock body with a maximum of about 0.99 over dense forest. A strong correlation was established between Landsat ETM+ reflectance band 3 and emissivity. Single channel based algorithms were adopted for surface radiance and brightness temperature. Finally, emissivity correction was applied on ‘brightness temperature’ to obtain LST. Estimated LST values obtained from various algorithms were compared with field ground measurements for different land cover categories. LST values obtained after using Valor’s emissivity and single channel equations were best correlated with ground truth temperature. Minimum LST is observed over dense forest as about 26 °C and maximum LST is observed over rock body of about 38 °C. The estimated LST showed that rock bodies, bare soils and built-up areas exhibit higher surface temperatures, while water bodies, agricultural croplands and dense vegetations have lower surface temperatures during the daytime. The accuracy of the estimated LST was within ±2 °C. LST comparison of ASTER and MODIS with Landsat has a maximum difference of 2 °C. Strong correlation was found between LST and spectral radiance of band 6 of Landsat-7 ETM+. Result corroborates the fact that surface temperatures over land use/land cover types are greatly influenced by the amount of vegetation present.     

Theoretical performance analysis of electrochromic radiators for space suit thermal control

Variable emissivity electrochromics have been proposed as an enabling technology for integrating a radiator capability into a space suit in order to augment or replace the traditional means of heat rejection achieved via water sublimation. Thermal analysis was performed to establish design trade spaces and to provide operational guidelines and performance specifications for electrochromic technology development. Based on using the available surface area of an entire space suit as a radiator and the projected infrared emissivity modulation capability of state-of-the-art electrochromic material, the proposed application for space suit heat rejection suggests the potential exists to reduce or eliminate reliance on water consumption for thermal control within a defined range of metabolic and environmental boundary conditions.     

月面载荷被动热控技术

由于月面温度环境变化幅度较大,月面载荷需要通过被动热控装置有效控制其与外部环境的换热量,使其本体温度维持在工作或储存温度范围内。文章分析了月面载荷与外部空间环境换热方式;论述了低当量发射率多层隔热组件设计与结构组成;讨论了月面载荷最外表面辐射屏ε和α_s特殊设计及对其表面辐射平衡温度影响;指出利用月壤恒温层及其特性,展开式外多层隔热组件可以在载荷所在月面处形成一个温度相对稳定的月面小环境,其平均温度与当地月壤恒温层温度相当。