KEYWORDS: Black bodies, Temperature metrology, Infrared radiation, Monte Carlo methods, Measurement devices, Computer simulations, Thermography, Mouth, Integrated modeling, Ray tracing
With the efficient use of energy, the study of emissivity is considered to be of great importance. In industrial production, temperature measurement technology, and many other fields, emissivity research is performed an important role. The emissivity is considered to be an important quantitative parameter for the infrared radiation characteristics of high-temperature coatings. Although the experimental measurement technique for high-temperature infrared spectral emissivity by the integrated blackbody method has been studied, little research has been reported on the integrated blackbody temperature field measurement and the simulation study of the emissivity of the integrated blackbody cavity. Therefore, in this paper, the temperature distribution of integrated blackbody cavity with the graphite cavity bottom is measured at 800°C, 1000°C. Besides, the above results are adopted, and the effective emissivity of the integrated blackbody is numerically simulated, based on the measurement results and the Monte-Carlo ray-tracing method. Thus, the feasibility of integrating the blackbody is demonstrated, the infrared radiation properties of integrated blackbodies are also studied as influenced by the temperature of the blackbody cavity.
Accurate measurement of the true surface temperature of high-temperature materials is very important in many fields, such as modern industrial systems, solar heat utilization and metrology. At present, passive radiation thermometry is mainly used to measure the real surface temperature of high-temperature materials. This technology cannot get rid of the influence of emissivity on temperature measurement accuracy. The active laser infrared radiation thermometry is a new emissive-free temperature measurement technology. Based on the active thermometry of dual-wavelength infrared laser, with the condition of environmental reflection interference and unknown emissivity, the true surface temperature of high-temperature material is precisely measured and studied. Based on the theoretical model of active dual-wavelength infrared laser thermometry, an active laser thermometry system was built and upgraded in this study. The active temperature measurement experiments of changing laser power were carried out to analyze the influence of laser power on the accuracy of active temperature measurement. Then the active temperature measurement experiments were carried out by changing the laser modulation frequency to analyze the influence of the laser modulation frequency on the active temperature measurement accuracy. The results show that the reasonable selection of laser parameters(laser power and laser modulation frequency) is the key to carrying out precision temperature measurement based on active laser infrared radiation thermometry.
Low size-of-source effect (SSE) infrared optical system design and experimental validation are critically involved. SSE is commonly explored in infrared radiation measurements. The main causes of SSE are the diffraction of the field aperture, the reflection of optical components and objective aberrations. The optical path design and the internal components scattering have an important influence on SSE. Reflective optical system is commonly used in infrared radiation measurements with high temperature region and wide wavelength range, which can eliminate chromatic aberration and reduce coma. A reflective infrared optical system is designed and built based on the high-temperature Fourier transform infrared (FTIR) spectrometer infrared radiation measurement facility at NIM. The ambient scattered radiation and the thermal effect of optical components are controlled via the water-cooled scattered radiation shielding bin and limitation apertures. Experimental validation of the SSE characteristics of the FTIR infrared optical system is carried out via the uniform blackbody radiation source at 500 °C and various sized apertures using the direct measurement method. The corresponding calculation model will be described in the paper. SSE on 3.9 μm is measured via the direct measurement method by using a standard reference blackbody with good temperature uniformity as the radiation source. The effect of reflection is reduced via the high emissivity coating on the apertures. The results show that the effect of the SSE on the FTIR measurement facility at the wavelength of 3.9 μm is less than 2×10-4. Details and results of the infrared optical system SSE measurement will be reported in the paper. All measurements can be traceable to the National Standards of P. R. China.
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