Standard thermography vs free emissivity dual color novel CIRA physics technique in the near-mid IR ranges: Studies for different emissivity class materials from low to high temperatures typical of aerospace re-entry

Advances in Material Wide Range Temperature Determination by Dual-Color Emissivity Free Methodology in Long-Mid-near Infrared Ranges at Non-stationary Conditions

“…Finally, in order to increase the sensitivity of the ratio between the signals captured at two close wavelengths, a camera with a working range starting from the near wavelength (NW) spectral range (1.5-5 µm) was chosen. It consists of a FLIR ORION SC 7600 multispectral camera operating in MW and filled out with an internal filter wheel that can rotate fast enough in such a way to consider the object thermal state unchanged, thus, meeting the requirements needed to apply the dual-color technique [7]. The validated numerical model has been used to determine a proper couple of filters in order to make the thermocamera operational in the DC technique experimental applications.…”

“…𝑇(𝑡) = −1216 𝑒 − 1215𝑒 + 2500 (10) the curve is characterized by the total duration of the heating phase up to the maximum value of temperature and a slope, such as to make an evaluation of the change, in a time interval of 5 × 10 −3 s, that corresponds to the time necessary for the wheel to capture the adjacent filters frame. At first, it is necessary to specify that despite the wheel rotation presents a 100 Hz frequency, the wheel balance during rotation and the detection synchronization is guaranteed by filters at close wavelengths positioned in a diametrically opposite wheel position [7], hence half rotation is required to acquire two adjacent frames. In this time interval, a variation in temperature of about 10 −3 °C, at 2500 °C, and of about 2 °C, at 500 °C, can occur (Equation ( 5)).…”

“…A minimum of 3% at 500 • C and a maximum of 9.3% at 2500 • C has been revealed (right side of Figure 11). Finally, a comparison between standard thermography (single color) simulated data and dual-color simulated data for several emissivity classes of materials has been performed [7]. The results are represented in Figure 12.…”

“…To our knowledge, this technique has never been developed to get 2D thermographic images and is also never applied in the aerospace field. So, a state of the art of diagnostic methodology that is applied to thermal conditions compatible with the ones connected to the atmospheric re-entry has been summarized and compacted in several IR spectral ranges (medium [5][6][7], long [6], and near [7] wavelength ranges) for a deeper understanding of the readers. Moreover, as a novelty, the analyses have been performed considering an unsteady temperature scenario for a specific device (FLIR Orion 7600) and for different classes of materials in terms of their emissivity (i.e., low, medium, and high emissivity materials).…”

Novel free emissivity dual color physics methodology at CIRA in the infrared ranges: applicability study from low to high temperature

“…working in 1.5-5 μm) was chosen. It consists of the multispectral camera FLIR ORION SC 7600 operating in MW and equipped with an integrated filter wheel which can rotate fast enough to switch in such a way to consider the thermal state of the object unchanged, thus, meeting the requirements needed to apply the dual colour technique [4,5,6]. The validated model has been used to determinate a suitable couple of filters to make the FLIR ORION SC 7600 operational in the experimental applications of dual colour technique.…”