Detection technique of the optical and thermoradiative characteristics with compensation effect of reflection and transmittance indicatrices for the semitransparent materials with high subsurface scattering

Abstract

The experimental set-up is developed for detection of reflection and transparence coefficients of semitransparent materials within visible and IR radiation diapasons. The peculiarity of the set-up is using the spectral photometric integrating spheres for effect compensation of reflection indicatrices of tested materials with fixed wavelengths 0.63 µm 1.15 µm (near IR), 2.79 µm and 3.39 µm (middle infrared) of probing laser radiation. In the first case the integrating sphere is a photometric ball which made from porous fluoroplastic with high reflectivity up to 97-99%. For the second range an aluminum sphere (sand blasting) was used. The application of the photometric sphere reduced the measurement error, connected with different sensitivity of photosensors to beam slope angle of detected radiation reflected (transmitted) for flat material samples with different indicatrices of reflection (transmission). The proposed method of experimental measurements of spectral photometric characteristics of reflection and transparent improve the accuracy of theoretical estimations of the optical (thermoradiation) parameters (absorption and scattering indexes), as well as the functions of a thermal radiation heat source for the calculation of temperature fields in semitransparent materials. For the first time, a computational and experimental estimation of scattering and absorption indexes (with an accuracy not less than 1%) were carried out for semitransparent materials with high scattering (porous ceramics based on stabilized zirconium dioxide) in the middle infrared range of wavelengths which is most problematic for optical measurements.

Thermal Mode Optimization of Combustion Chamber Walls for Power-Plants Using Semitransparent Porous Ceramics

“…In the literature [4][5][6][7][8]24,25], there are discrepant data about the optical property and, as a rule, they correspond only to chemically-rectified powders. Stabilized zirconium oxide is distinguished from this line since it has transparence bands up to 0.4-3.4 µm (corresponding to the spectrum of short-wave radiation 1-3 µm of red-hot soot particles) that has previously been measured and proven by the authors [21]. This penetration causes the volumetric reflection r(x), the transmittance τ(x) and the absorption a(x) coefficients, which is dependent on scattering σ and absorption κ indexes for a given semitransparent material-layer thickness H [10,21]:…”

“…In accordance with the proposed optical models and other properties (See Table 2), the heat conductivity Equation 6 Table 2). Model M se3 (14/2400-86) is described by the optical characteristics obtained by the authors using the experimental lasers set up with integrating the photometric sphere sandblasted cast aluminum [21].…”

“…The optical characteristics are presented in Table 2 for semitransparent Y-PSZ samples (curves 1…6) with different optical models Mse(κ/σ-A) and opaque (model polluted) samples Mop with surface reflection R = 30%, large absorption and the same thermal characteristics (curves-7). For a typical heat load inside combustion chamber of high-speed diesel, the use of a semitransparent material (optical model Mse3 [21]) with scattering indices σ = 2400 m −1 at absorption index κ = 14 m −1 (See Figure 3a, curve 3-2) leads to a temperature decreasing by 30 K in surface temperature compared with the non-transparent, opaque one (model Mop7, curve 7-2). The estimates obtained are in good agreement with the qualitative results in [5] and are numerically close to the data in [7].…”

“…However, the optical properties of these ceramic materials and coatings have been poorly studied, primarily experimentally [21,24,27]. These semitransparent materials, unlike opaque ones, are selectively low absorbing and high scattering media in spectral transparent bands of definite wavelength range during an ignited gas mixture in the combustion chamber of high-speed diesel or turbine engines.…”

“…In this paper, the authors continue their theoretical and experimental researches on promising types of ceramics with heat insulation properties both for convective fluxes and thermal radiant ones of model CC walls using ceramics with optical and thermal physical parameters due to different porosity [13,21].…”