单吸收罩发射率测量补偿方法

针对表面辐射率的在线长时间测量问题,在前置探测罩的双罩发射率测量方法基础上,研究了一种单吸收罩测量发射率的方法.建立了探头的有效发射率模型,对吸收罩表面发射率和自身辐射能导致的误差进行了分析,归纳出误差参数及误差补偿方法.用实验数据拟合获得了误差参数并应用于测量方程,同时改进了探测罩外形设计,分析比较了误差补偿前后发射率偏差.该方法拓展了测量范围和温度适应范围,实现了发射率低至0.2,温度低至100℃的条件下的有效测量.     

发射率在线测试仪的研制

为了长时在线测量物体表面发射率,设计了一种基于反射率法的发射率在线测试仪,由探测器、硬件电路、上位机和电源4个部分组成。基于反射率法的测量原理,考虑到现场发热和振动等恶劣环境,对测试仪的探测器、硬件电路进行了特殊的设计,并推导了消除热敏电阻红外传感器非线性误差后的发射率求解公式。最后通过试验表明:该测试仪能满足发射率长时在线测量的要求,测量精度达到±0.03。     

基于方向发射率校正的红外测温补偿方法

红外热成像仪具有实时在线、非接触获取被测对象二维温度分布等优点,在钢铁、农业、电力电子等众多领域应用广泛。但是,红外测温结果容易受到干扰因素的影响。针对方向发射率变化引起的红外测温误差,本文提出了基于方向发射率校正的红外测温补偿方法。首先,基于红外测温原理,构建了针对方向发射率变化的红外测温补偿模型。其次,为确定补偿模型中的方向发射率,利用红外热像仪和激光扫描仪构建的三维热成像系统,提出了基于参考体的方向发射率校正方法。然后,通过多项式拟合确定方向发射率随视角变化的规律。实验结果表明所提红外测温补偿方法可以有效降低方向发射率变化造成的红外测温误差,经过补偿温度后,红外测温最大误差由9.64℃降低为2.97℃,标准差由3.57℃降低为0.71℃。     

发射率在线测量系统及其电路设计

针对目前对在线发射率测量的迫切要求,设计了新型的在线发射率连续测量系统.通过对在线发射率测量模型进行误差分析,建立系统误差因素模型,对测量系统进行了总体设计.根据传感器特性及测量要求,墓于ADuC845芯片和磁耦隔离技术对系统电路进行设计,充分考虑了抗电磁干扰(EMI)能力,提高系统的可靠性和电磁兼客性.实验结果证明该测量系统满足一定条件下在线发射率测量需要.     

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%。     

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切削温度是影响切削加工过程中刀具状况和工件表面质量的重要物理量,但切削温度信号的获取与处理存在一些实际问题。针对切削温度测量中的自然热电偶法、人工热电偶法以及红外热图像法,介绍了热电偶的固定、从旋转体上引出测量信号、自然热电偶的标定、工件和刀具表面发射率的标定,以及应用红外热像仪进行测温时切削实验的设计等一些实践做法。实践证明,开槽嵌夹绞丝热电偶方法的测量结果比较可靠;采用集流器引出旋转体热电势信号时所产生的摩擦附加电势可被定量测定并可将其从测温信号中减除;应用红外热像仪测量切削温度时应标定被测材料在各温度段的表面发射率并量化标定环境的影响。     

基于图像测量技术的双波长测温仪在线校准方法

红外测温的方法具有非接触、能够测量极高温度的特点,但其测温精度易受材料自身和环境的影响,针对静电悬浮材料实验装置中双波长测温仪温度测量存在偏差的问题,设计了一种基于图像测量技术的在线校准方法。采用CCD相机获取测温样品的图像,通过边缘提取拟合计算样品体积随温度的变化,与材料自身实际的热膨胀系数对比,修正双波长测温仪的发射率比值。通过对纯金属锆的实验,比对校准后测量的熔点温度,验证了该在线校准方法。     

结构封装式光纤Bragg光栅温度补偿研究

光纤Bragg光栅的中心反射波长λB会随温度的变化而漂移,影响其在波分复用及压力测量等方面的应用.本文通过对石英和有机玻璃两种热膨胀系数不同的材料进行合理的结构设计,提出了一种无源温度补偿装置,探讨了施加预应力对光纤Bragg光栅补偿效果的影响,并对单面封装和双面封装的补偿效果进行了对比研究.该装置在-19℃～60℃的温度范围内,中心反射波长仅漂移0.035nm,温度稳定性大约提高了20倍.     

光电/量热复合式近红外高能激光光斑探测器

为了准确测量高能激光系统远场到靶总能量和功率密度时空分布等参数,本文提出了量热吸收法和光电探测阵列法相结合的复合式测量方法.该方法由热吸收体测量入射激光的总能量,由光电探测阵列测量光斑的时空分布.研制了用于大面积、长脉冲近红外高能激光测量的复合式光斑时空分布探测器.探测器主要由石墨热吸收体、近红外探测器阵列、测温单元和信号处理单元等组成,有效测量光斑面积达到22 cm×22 cm,光斑测量空间分辨力为1.1 cm,时间分辨力为20 ms.该测量系统同时兼顾了光电探测阵列法的高时空分辨能力和量热吸收法的低测量不确定度等优点,适合于高能量、大面积近红外高能激光光斑参数的综合测量,并已成功应用于外场实验.     

SF6气体泄漏环境在线智能检测系统的设计

为实现SF6气体实时在线准确检测,提出了采用红外光谱吸收技术在线检测SF6气体泄漏的设计方案,给出了系统的硬件和软件的设计.通过对传感器信号进行温度补偿和压力补偿,有效提高了传感器的测量精度和灵敏度.利用改进的RS-485通信和数据帧,实现了数据实时、快速、精确传输.现场测试表明,系统性能稳定、寿命长、测量精确、误报率低.测量范围0 ～5000 ppm(1 ppm=10-6),灵敏度1 ppm.可广泛应用于测量SF6气体浓度的场合.     

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.     

Experimental mathematical model as a generalization of sensitivity analysis of high temperature spectral emissivity measurement method

The development of an experimental mathematical model describing temperature state of the sample during high temperature spectral emissivity measurement is introduced. Dimensional analysis of the measurement process gives the physical dimensionless quantities and sensitivity analysis of the measurement process provides the large set of performed model experiments. Evaluated experimental mathematical models are presented including their accordance with model experiments. Established equations are generalization of sensitivity analysis of high temperature spectral emissivity measurement method and can be used for computation of spectral emissivity total uncertainty.     

多光谱测温法的实验研究——发射率模型的自动判别

在多光谱辐射温度计的数据处理中需要假设发射率与波长的数学模型,本文提出一种自动判别发射率与波长数学模型的新方法,并通过实验证明了此方法的确是一种解决目标真温及光谱发射率等测量问题行之有效的方法。     

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.     

Inverse radiation-conduction estimation of temperature-dependent emissivity using a combined method of genetic algorithmand conjugate gradient

The solution of an inverse, conduction-radiation problem in a two-dimensional rectangle is analyzed to determine the temperature-dependent emissivity at the boundary. The medium is gray, absorbing, emitting and isotropically scattering. The bounding surfaces are assumed to be opaque and diffuse. The inverse problem is solved by minimizing the performance function, which is expressed by the sum of square residuals between estimated and exact heat fluxes, using a combined method of genetic algorithm and conjugate gradient. The emissivity is assumed to be represented as a function of boundary temperature with unknown variables. Therefore, the inverse problem is treated by the estimation of these variables. Finally, four examples are presented to show the accuracy of the algorithm. The effect of the measurement errors on the accuracy of the inverse analysis is also investigated. Results show the algorithm can estimate the unknown emissivity when the measurement errors are neglected. Also it is found that increasing the measurement error decreases the accuracy of estimation of temperature-dependent emissivity.     

Dual-band pyrometry for emissivity and temperature measurements of gray surfaces at ambient temperature: The effect of pyrometer and background temperature uncertainties

A dual-band pyrometry model for target temperature (240–360 K) and emissivity measurement was developed, in which two pyrometers with different spectral bands are surrounded by an enclosure at a given background temperature. Nine equal-power spectral bands were selected for the pyrometers from wavelengths between 8 and 14 μm. The Monte Carlo method was used to compute the dual-band measurement uncertainties of temperature and emissivity caused by the propagation of the uncertainties associated with the temperatures of the two pyrometers and the temperature of the background. It was found that the rate of decrease of dual-band measurement uncertainties with increasing difference between target and background temperatures decreases with increasing target temperature. Considering the uncertainty of the background temperature, it was found that dual-band measurement uncertainties are virtually not affected by the background temperature uncertainty when the background temperature is lower than the target temperature, and dual-band measurement uncertainties increase significantly with increasing background temperature uncertainty when the background temperature is higher than the target temperature.     

自动气象站数据采集器温度通道的环境温度补偿

针对自动气象站数据采集器温度通道容易受到环境温度影响限制测量精度的问题,对数据采集器进行了温度漂移检测实验并对实验数据进行了误差分析,提出了基于改进自适应遗传算法优化的最小二乘支持向量机(improved adaptive geneticalgorithm least squares support vector machine,IAGA-LSSVM)的温度补偿方法。改进的自适应遗传算法能够对最小二乘支持向量机拟合过程中的关键参数进行调整从而建立最优模型。与传统LS-SVM相比,IAGA-LSSVM对温度数据的建模均方根误差减小了0.007,有效提高了建模的精度。根据建立的最优函数模型对该数据采集器温度通道进行温度补偿结果表明,经该方法补偿后的数据采集器在任何温度环境下的温度测量误差均小于0.03℃,具有更高的测量精度和稳定性,有效提高了自动气象站的温度观测质量。同时,设计开发了温度补偿界面,为自动气象站观测数据校验和实际业务应用奠定了基础。     

Emissivity estimation for high temperature radiation pyrometry on Ti–6Al–4V

The paper demonstrates a versatile procedure suitable for industrial implementation of temperature measurement on a hot titanium alloy. The driving force has been the need for an accurate temperature measurement during additive manufacturing using laser welding technology where Ti–6Al–4V-wire is melted. The challenges consider both industrial constraints and the varying emissivity of the surface. Measurements makes use of a narrow bandwidth spot radiation pyrometer and a calibration procedure for estimation of the surface temperature through spectral emissivity estimation. The theoretical results are validated through experiments. A number of difficulties in radiation temperature measurements for metals with varying surface properties are discussed; especially the case of surface oxidation. The uncertainty in temperature reading due to the uncertainty in the emissivity estimate is established along with a model that qualitatively describes surface oxidation. The procedure is expected to be useful for several manufacturing applications where it is important to control high temperatures.     

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。