红外热像仪精确测温技术

为实现红外热像仪对温度的精确测量,根据热辐射理论和红外热像仪的测温原理,推导了计算被测物体表面真实温度的通用计算公式;讨论了发射率对测温精度的影响,分析了用红外热像仪进行精确测温的条件,探讨了环境、大气和热像仪本身对测量精度的影响,并绘制了各种因素对测温精度影响的理论曲线。结果表明:发射率为0.7时,真实温度为50℃,发射率偏离0.1时,对于3~5 μm热像仪来说,测温结果偏离真实温度0.76~0.89 ℃; 对于8~14 μm热像仪来说,测温结果偏离真实温度1.56~1.87℃。本研究结果对提高热像仪测量温度和表面发射率的准确性,减小不必要的测量误差具有实际意义。     

大型空间反射镜发射率测量及误差分析

为了准确测定空间相机主镜毛坯件的表面发射率以便定量分析相机热控效果,本文在分析热像仪测温原理的基础上,利用现有测量条件,提出一种利用两种已知发射率材料作为参考的发射率测量方法.根据测量试验,得到主镜表面发射率为0.565.为定量反映各因素对测量精度的影响,对测量公式进行了误差分析.分析结果表明,与被测件表面发射率接近的材料的热像仪测温误差及发射率标称误差对测量精度有较大影响,同时得到本次试验因热像仪测温误差及参考材料发射率标称误差带来的测量误差为±0.028.最后,结合相机热平衡试验的数据对测量结果进行了验证,结果表明测量得到的主反射镜的发射率基本反映了热平衡试验的主镜表面状态,证明本文的方法对主反射镜发射率的测量是适用有效的.     

红外热像仪外场测温的大气透过率二次标定

为了实现测温红外热像仪的外场精确测温,研究了大气透过率的二次标定。建立了红外热像仪的外场远距离测温标定模型,采用一个标准面源黑体和红外热像仪对大气透过率进行了二次标定。首先,用标准面源黑体的设置温度标定大气透过率的二次修正系数;然后,在已知目标感兴趣区域发射率的情况下,用二次修正系数对未知辐射源测量值进行修正,实现未知辐射源目标辐射温度的准确测量。实验显示,随黑体设置温度从50℃不断升高(二次大气透过率近似为1),大气二次透过率修正系数在50～100℃内迅速下降,在100～200℃内下降趋势减缓,逐渐接近于约为0.7的常数。实验结果为测温红外热像仪外场精确测温提供了保证。     

An emissivity-corrected method for the accurate radiometric measurement of transient surface temperatures during braking

The main difficulty encountered in brake disc infrared temperature measurements is the lack of knowledge of the disc surface emissivity, which is nonuniform and varies during braking. To provide information on the nonuniformity and variations of emissivity, brake disc surface temperatures were investigated by an original two-colour fibre optic pyrometer and an infrared camera. The first result is the measurements of the accurate surface temperature. Besides, it is shown that the local emissivity varies with friction due to modifications of surface properties. Thermal phenomena observed on the disc track are correlated with temporal changes of normal and tangential frictional forces.     

低温状态下的材料法向发射率测量

研究了在-60~50℃条件下准确测量材料法向发射率的方法。基于发射率定义建立了材料法向发射率测量模型。为屏蔽环境杂散辐射与大气吸收的影响,利用真空液氮背景通道搭建了低温状态下材料发射率测量装置。测量了氧化铜与高发射率陶瓷两种样品的法向发射率随温度、波长的变化情况。结果表明:两种样品的法向光谱发射率均随波长增加而降低;随温度的升高,氧化铜样品法向积分发射率稳定为0.850±0.012,陶瓷样品的法向积分发射率降低了0.124。最后,实现了低温状态下红外光谱辐射的高精度采集,对低温状态下材料法向光谱发射率测量结果的不确定度进行了评定,得到的结果显示其相对扩展不确定度小于6.0%。     

Lifetime prediction of low infrared emissivity coatings in 3 wt% NaCl solution

Low infrared emissivity coatings were prepared by using epoxy-polyurethane (EPU) and aluminum (Al) as adhesives and fillers, respectively. The change of coating emissivity was studied by using immersion testing in 3 wt% NaCl solution to assess the corrosion resistance. It was found that the emissivity increased with increasing heating temperature and time, and that the emissivity of coating failure increased with decreasing Mach number. Moreover, the Arrhenius relationship was employed to calculate the lifetime of low infrared emissivity EPU/Al composite coatings. The calculated results when compared with observation data validate the effectiveness of the model predictions. The current work showed that the low emissivity EPU/Al composite coatings exhibited favorable lifetime, and the Arrhenius relationship was effective and showed a potential in engineering applications.     

图像配准技术在红外温度检测中的应用与研究

针对电器温升检测,运用图像配准算法对红外图像和光学图像进行配准,从而借助光学图像的高分辨率来解决红外图像分辨率低的问题,在Matlab环境下配准效果较好.该配准算法已嵌入红外测温软件,多次使用表明其准确度高,能有效地综合利用光学图像的高分辨率和红外图像的温度显示功能,从而使红外测温技术在电器温升检测中发挥出更好的效果.     

复杂背景下三维弯曲表面红外测温修正

航空发动机涡轮叶片的断裂脱落与叶片温度密切相关,准确测量涡轮叶片温度对航空发动机的安全运行具有重要意义。针对涡轮叶片材料发射率不均匀、周围高温物体反射严重以及探测角度变化等因素导致传统红外辐射测温方法精度难以保证的问题,基于辐射传输理论与红外热成像测温原理,分析了对红外测温结果影响的主要因素,提出了复杂背景下三维弯曲表面红外辐射测温的修正模型。通过设计实验测量获得弯曲表面的发射率、双向反射分布函数、角系数等重要参数,根据提出的温度修正模型,得到弯曲表面红外修正温度。通过与典型位置上热电偶的测温结果对比,测温误差由修正前的4%左右下降到1%以内,证明了所提的修正模型具有较高的精度和适应性,可为涡轮叶片气动传热试验技术的提升和航空发动机等重大装备的研制提供支撑。     

近室温样品加热炉温度的模糊PID控制研究

根据红外隐身材料光谱发射率测试方法的要求,提出了一种基于半导体制冷器的近室温样品加热炉系统。在对加热炉系统特性进行分析的基础上,建立了基于模糊PID控制的系统仿真模型。经仿真及实验可知,在加热和制冷条件下,实际温度与设定温度之间的误差分别为±0.20℃和±1.00℃。结果表明,系统稳定性好,响应时间短,解决了近室温样品加热炉抗干扰能力弱、不易控制等问题。     

Measurement technology for material emissivity under high temperature dynamic heating conditions

The thermal dissipation of radiation is main heat shield mechanism for non-ablative thermal protection materials on hypersonic vehicles withstanding high temperature dynamic heating cycle during endo-atmospheric ascent, cruise and reentry. Therefore, it is necessary to know the thermal radiative properties of the material under the simulated high temperature dynamic heating conditions on the ground. The emissivity depends on the surface state and its temperature. A new simultaneous measurement technology of emissivity and varying surface temperature is proposed under high temperature dynamic heating conditions. This new technology solved synchronous measurement problems by utilizing spectral signal of Fourier transform infrared (FTIR) spectroscopy. The calibration of different temperature ranges, the background disturbances, the influences on temperature measurement by wavelength range and its corresponding fluctuations of measurement signal, were thoroughly investigated. The measured results of steel and graphite as reference materials proved the effectiveness of this simultaneous measurement technology and showed great potential in engineering applications under high temperature dynamic heating conditions.     

Calibrated Thermal Microscopy of the Tool-Chip Interface in Machining

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool-chip interface during the steady-state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all-reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond-turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control-volume approach; and 2) a simplified finite-difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.     

端面滑动摩擦副接触界面波段发射率研究

为研究滑动摩擦过程中接触界面波段发射率的变化规律,设计并开展了一系列实验。以端面滑动摩擦副的接触界面为研究对象,在含二硫化钼的脂润滑条件下,开展定载荷、定转速实验,利用热像仪和自制装置测量了不同摩擦时间后的波段发射率,并根据发射率变化规律对红外测温仪测得的接触界面辐射亮温进行了修正。结果表明：测量装置能够较准确地实现摩擦接触界面波段发射率的测量;含有润滑脂和磨屑的接触界面发射率总体上在一定范围内波动,在摩擦过程中,具有先下降后上升的趋势;在稳定摩擦阶段,对辐射亮温的修正精度较高。     

Error analysis on measurement temperature by means dual-color thermography technique

Dual color thermography is a non-contact measurement temperature technique used mainly when the emissivity of surface is unknown; it is based on ratio of monochromatic emissive power calculated by means Planck’s radiation equation and allows measuring the temperature of gray body surface objects without being assigned their emissivity and without approximations.For real surfaces, the emissivity varies with the temperature of surface as well as the wavelength and the direction of radiation. In this case, the dual color thermometry is executed by equipping the IR camera of two narrow band pass filters, so as to consider the surface emissivity of a quite constant value. This allows calculating the ratio between the radiative fluxes of the two different emission wavelengths that is almost independent to the surface emissivity.One of the crucial factor in this technique is the choice of the two narrow filter wavelengths. In fact the measurement errors depends directly on the two wavelengths and the variation of spectral emissivity related to the wavelength chosen and it also depends inversely on distance between central value of filters.In this paper, the authors have developed and validated a mathematical model of experimental setup to measure object surface temperature by means IR thermo-camera. This mathematical model was used to quantify the temperature measurement error in the dual-color technique. A novel correlation to estimate temperature measurement error was provided.     

基于全域红外热成像的空预器积灰监测技术

空气预热器是燃煤火力机组的核心换热元件,由于氨逃逸引起的空预器堵灰现象,对其安全稳定运行会产生严重影响。针对堵灰问题,提出了一种基于全域红外热成像的空预器换热元件局部堵塞状态监测方法,运用高分辨率红外热成像测温技术实现换热元件温度的准确观测,同时采用多点协同观察和视角优化设计方法,达到换热元件全域观察能力,并设计集成边缘计算监测系统,对多点全域红外热像图进行实时智能识别与积灰诊断,红外画面与诊断结果经光纤通讯传输至机组监控中心。该方法可有效解决火力发电机组空预器积灰监测精准难题,确保机组空预器安全稳定运行。     

Calibrated Thermal Microscopy of the Tool–Chip Interface in Machining

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool–chip interface during the steady‐state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all‐reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond‐turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control–volume approach; and 2) a simplified finite‐difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.     

金属切削刀具和工件的波段发射率标定

使用红外热像仪对切削加工中常见的工件材料碳钢和模具钢、常用的刀具材料硬质合金和涂层硬质合金在300～900 ℃进行表面发射率的标定,并考虑加热箱内环境热辐射对试样的作用,分析温度、表面结构、几何形状对试样表面发射率的影响。结果表明钢材表面发射率随温度升高而增大,但模具钢在较宽的温度范围内保持较小的表面发射率;试样表面平整性影响表面发射率;涂层刀具的表面发射率在比较宽的温度范围内一直稳定在相当低的值。     

Methodology for spectral emissivity measurement by means of single color pyrometer

The application of non-intrusive optical devices, such as infrared pyrometers able to measure the temperature of surfaces, makes possible the evaluation of emissivity curve of the tested materials at different temperature values. In this paper the authors propose a methodology for the spectral emissivity measurement by means of a single color pyrometer providing a semi-empirical formula, obtained experimentally at CIRA’s laboratory. The semi-empirical formula allows to know the actual emissivity value of the sample’s surface for whatever emissivity value set up on the pyrometer. The agreement between the experimental emissivity and the emissivity predicted by semi-empirical formula was verified.     

Adaptive spectral band identification method in noncontact temperature measurement based on dynamic programming

An adaptive method based on dynamic programming is proposed to identify the spectral band for noncontact measurement of surface temperature of heatshield materials when Fourier transform infrared (FTIR) spectrometer is used to collect the radiation spectrum in the dynamic heating environment of a high-frequency plasma wind tunnel. First, the radiation spectrum is converted to a time series. Then, high-frequency parts of the measurement spectral signal are obtained by multi-resolution analysis of one-dimensional discrete wavelet and then the suitable spectral band required by a noncontact temperature measurement is adaptively identified based on dynamic programming. Eventually, surface temperature and its corresponding emissivity can be determined. Results of the experiment conducted on a benchmark material (graphite) in the dynamic heating environment of high frequency plasma wind tunnel show the proposed method to be practical.     

空间光谱成像仪热设计参数的灵敏度

针对空间光学遥感器在轨运行期间其热物理属性的实际参数与热设计参数之间存在一定的偏差,从而影响整机热设计的问题,本文基于系统灵敏度理论,对空间光学遥感器的热设计进行了分析,并建立了在轨条件下的热平衡方程组.通过分析热平衡方程组的设计变量,总结出影响整机温度分布的热设计参数.以某空间光谱成像仪热设计为例,分析了上述影响整机温度分布的设计参数的灵敏度.灵敏度分析结果表明:整机平均温度对太阳吸收系数的灵敏度几乎为零;对红外半球发射率的灵敏度为2.2～14.55℃;对内部热源的灵敏度为1.8～2℃/W;对导热率的灵敏度为2.25×10-3～4.39×10-2 m℃2/W:对接触导热系数的灵敏度为0～1.1×10-3 m2℃2/W.试验验证结果表明,基于灵敏度分析结果的热控设计方案有效且可行.     

Design, construction, and analysis of a continuous-temperature infrared calibrator for temperature measurement using an infrared scanner

A continuous-temperature infrared calibrator is designed and constructed for providing reference video signals in temperature measurement using an infrared scanner. The calibrator can be controlled for a wide range of temperature settings and to present a continuous span of reference signals for calibration purposes. Both analytical and experimental methods are used to evaluate the performance of the calibrator. Results show that the calibrator has a normal total emissivity of at least 0.984, which is about 1% lower than the predicted value. Methods to improve the emissivity of the calibrator are also discussed. The paper provides for analytical equations useful for parameters estimation in the future design of the calibrator.