【作者】 杨臧健；

【导师】 程晓舫；

【作者基本信息】 中国科学技术大学 ， 工程热物理， 2009， 博士

【摘要】 自从1900年普朗克黑体辐射定律提出以来,利用热辐射测量温度一直是研究的热点。辐射测温的关键是解决发射率未知的问题,目前已有了一些解决方法,但这些方法在实际运用时存在各种各样的问题,比如要满足特定条件、需要标定等,缺乏一种较为普适、简单、有效、性价比高的温度场测量方法。本实验室经过前期理论研究,发展了一套谱色测温法。该方法通过引入发射率线性模型和同时测量三波段辐射,使温度求解方程组达到封闭,有效解决了发射率未知和需要标定的问题,能有效实现温度场测量。该方法理论已基本发展完善,但还未进入实际应用阶段。本文的主要工作就是以谱色测温法原理为基础,以彩色CCD数字摄像机为硬件,研制谱色测温系统,解决各种技术问题,同时根据实际需要完善理论。首先,本文研究发展了一整套谱色测温系统开发过程。该过程主要包括硬件和软件两方面。硬件方面是指对设备的选择、标定工作。选择是指根据实际需要确定硬件应具有的功能,并以此为标准选择合适的设备。而标定工作主要包含了两个标定实验,分别是对摄像机的控制参数和相对光谱响应曲线的标定。标定的目的是要检验设备是否满足要求,并得到测温计算所需的硬件自身的信息。软件方面是指谱色测温系统应用软件的编制。软件是系统工作的核心,它包括硬件控制、数据获取及其预处理、温度计算数据库设计、数据存储、信息统计及显示等方面的功能。其重点是硬件控制与数据库设计。前者要基于厂家提供的接口函数实现各项功能,而后者是为了实现温度场的实时计算。其次,鉴于谱色测温系统存在噪声且温度场受其影响,本文研究了一套基于数字图像处理的降噪方法。该方法根据谱色测温系统的工作模式和噪声统计特点的不同,采取针对性措施。在单帧分析模式下,采用傅里叶变换滤波法处理周期性噪声,以邻域均值滤波和中值滤波法处理随机噪声;在连续采集模式下,提出了由多图像平均法改进得到的多帧加权平均法来处理各种噪声。再次,由于谱色测温法采用归一化处理和图解法求解温度,导致传统的误差传递分析方法无法得到有意义的结果。因此提出了多通道测量中归一化处理的误差传递分析模型。该模型利用几何的概念分析误差传递,取得了直观和良好的效果。分析指出,不仅支路信号绝对值能影响误差传递,其相对大小关系也会产生影响。鉴于此,有可能利用支路增益调整和抑制误差的放大。因此,本文进一步理论分析了调整支路增益会对归一化坐标平面上的求解坐标系产生的影响,并综合考虑误差传递和求解坐标系两种影响的大小关系,提出可利用支路增益调整抑制归一化平面上某一区域的误差传递,其代价是增加其他区域的误差传递,并给出了典型情况下的分析结果。最后,进行验证实验测试系统的测温准确性,进行实际应用实验验证系统的工作可靠性。验证实验为热电偶加热测温对比实验。该实验用弱可见光辐射热源加热热电偶使之产生可见光热辐射,以热电偶本身为测温目标,有效避免了非热平衡带来的测量误差和热源影响。系统所得平均温度基本符合热电偶测量值,但单像素点温度存在波动。实际应用实验包括安阳钢铁厂的转炉测温实验、低温等离子体应用实验室的一次风加热器燃烧测温实验以及火灾科学国家重点实验室的航空煤油油池火焰温度场测量实验。实验验证了系统测温的可靠性和实际应用的可行性,也揭示了存在的一些问题,为今后的改进积累了第一手资料。更多还原

【Abstract】 Since the Planck’s Law was presented in 1900,the temperature measurement based on thermal radiation has always been emphasized.The key problem in radiation thermometry is that the emissivity is unknown.Although some solutions have been found,various problems present in practical application,such as special requirement, needing calibration,etc.A temperature field measurement method which is general, simple,and efficient,and have high performance-cost ratio is needed.A radiation thermometry which is named "Primary Spectrum Pyrometry"(PSP) has been established in previous theoretical study.By introducing the linear model for emissivity and measuring the radiation in three different wavelength bands at the same time,the PSP can make the measurement equations closed,solve the problems caused by unknown emissivity and calibration,and measure the temperature field efficiently.The theory of the method has almost been mature,but the application,which is indeed needed,is still preliminary.Therefore,the main work is to develop a PSP system based on the theory of PSP and CCD color digital camera for hardware,solve technical problems,and improve the theory if necessary.First,a development process of PSP system composed of hardware work and software work is researched and developed.The hardware work includes the device selection and calibration.The device selection means determining the required functions of the system,and selecting the device which meets the requirements.The calibration mainly consists of the calibration of the effect of control parameters and the calibration of the relative spectral response curve of camera.The main purpose of calibration is to check the device and obtain the information of camera which is needed in calculation.The software work means the programming of application software of PSP system.The software is the kernel of PSP system.It realizes the functions such as controlling of hardware,obtaining,processing and storing of data,designing of the database used in temperature calculation,statistics and display of results.Among them, the key point is the controlling of hardware and designing of database.The former realizes various functions of camera based on the interface functions provided by producer.The later achieves the real-time calculation of temperature field. Second,as the noise exists in PSP system and affects the temperature result,a set of de-noising methods based on digital image process is proposed.According to the difference between different working modes and statistical features of noise,pertinent measures are taken.In single-frame analysis mode,the fourier transform filtering is used to decrease the stripping noise,the neighborhood average filtering and the median filtering is used to decrease the random noise.In continuous acquisition mode, the multi-frame weighted average method,which is improved from the multi-image average method,is proposed to process various noises.Third,as the normalization and graphic method make it meaningless to analyze the error propagation in traditional way,the error propagation analysis model of normalized multichannel measurement is proposed.The model based on geometric concepts is direct and efficient.Analysis shows that not only the absolute value,but also the relative value of different channels can affect the error propagation.So it is possible to decrease error propagation with branch gains.Therefore,the affect of changing the branch gains on the solving coordinates on the normalized plane is analyzed further,and both the affects on normalization and coordinates are comprehensively considered.The result shows that the error propagation in a certain area on the normalized plane can be decreased by changing the branch gains,and the cost is increasing the error propagation in other area.Some detail results in typical conditions are given.Finally,verification experiment is carried out to check the accuracy,and application experiments are carried out to check the reliability of the PSP system.The verification experiment is a contrast experiment of heated thermocouple,in which a heat source with weak visible radiation is used to heat a thermocouple which emits visible thermal radiation.Taking the thermocouple as measurement target avoids the error brought by thermal non-equilibrium and heat source.The average temperature obtained by PSP system meets the thermocouple result,while the temperature of single pixel fluctuates.The application experiments include temperature field measurement of converter, primary air heater and pool fire of aviation kerosene.In these experiments,the reliability and feasibility in practical application have been proved,some problems are revealed,and a lot of firsthand data is obtained for future improvement.更多还原