Temperature Modulation Method for In-situ Measurement of Surface Temperature & Emissivity

对于处于高温下的材料，如果已知材料的光谱发射度，并且可以将发射的辐射与反射或散射的外来辐射区分开来，则电磁辐射的发射光谱是最方便的非侵入式温度探测。第一阶段的计划表明，许多原位温度和发射率测量的问题可以通过一种技术来克服，该技术可以在监测电磁辐射发射光谱的点上调制感兴趣的热表面的温度。通过调节温度，可以区分发射的辐射和反射的辐射。常规计算涉及观测到的调制辐射光谱，然后可以应用于确定温度和发射率。第一阶段演示了对已知发射率表面的温度测量在> ~ 1k以内，对未知发射率表面的温度测量在> ~ 15k以内，发射率测量在> ~ 7%以内。在这个第二期项目中，我们将完成研究，这将使我们能够设计、建造、测试、校准和现场测试一个基于FT-IR光谱仪和二氧化碳激光器调制频率的研究原型系统。我们将对第一阶段的仪器进行改进：1)用FT-IR光谱仪按顺序调制温度，降低测量不确定度，消除长期漂移问题；2)采用更灵敏的探测器降低测量噪声；3)扩展高频限制以适应更高温度的表面；4)使系统用户友好、自动化。该系统的目标规格如下：已知发射率表面的温度测量范围在> ~ 0.25>C；对发射率未知的表面进行温度测量，测量范围在50 ~ 50℃之间；对发射率未知的表面进行发射率测量，发射率在>.2 %以内。该系统将在燃煤中试工厂进行现场测试。

For materials at high temperature, the emitted spectrum of electro-magnetic radiation is the most convenient non- intrusive probe of temperature, if the spectral emittance of the material is known, and if the emitted radiation can be distinguished from extraneous radiation which is reflected or scattered. The Phase I program demonstrated that many of the problems of in-situ temperature and emissivity measurement could be overcome by a technique which modulates the temperature of the hot surface of interest at the point at which the emitted spectrum of electromagnetic radiation is being monitored. By modulating the temperature, it is possible to distinguish emitted from reflected radiation. Routine calculations involving the observed spectrum of modulated radiation can then be applied to determine both the temperature and emissivity. Phase I demonstrated the measurement of temperatures to within > 1 K for surfaces of known emissivity and temperatures to within > 15 K and emissivity to within >7% for surfaces with unknown emissivities. For this Phase II project, we will complete the research which will allow us to design, build, test, calibrate and field test a research prototype system based on an FT-IR spectrometer and a CO2 laser to modulation the frequency. We will improve upon the Phase I apparatus by: 1) decreasing the measurement uncertainty by modulating the temperature in sequence with the FT-IR spectrometer to eliminate problems of long term drift; 2) reduce measurement noise by using a more sensitive detector; 3) extend the high frequency limit to accommodate higher temperature surfaces; and 4) make the system user friendly and automated. The target specifications for the system will be as follows: temperature measurements for surfaces of known emissivity to within > 0.25>C; temperature measurements for surfaces of unknown emissivity to within > 5>C; and emissivity measurements for surfaces of unknown emissivity to within > 2%. The system will be field tested in a coal combustion pilot plant.