Optical diagnostics of hydrogen-air diffusion flame

Work motivation – adaptation of optical Hilbert diagnostic methods for visualization and study of optical density and phase temperature fields in the structure of an axisymmetric diffusion hydrogen-air flame. The diagnostic complex is implemented on the basis of the IAB-451 device with modified blocks of optical filtering, information source and processing. A laminar jet flame H2/N2 in still air is considered. The investigated torch is oriented vertically. Visualization of phase disturbances induced by the medium under study in a multi-wavelength probing (λ1 = 636 nm, λ2 = 537 nm and λ3 = 466 nm) light field is performed using polychromatic Hilbert and Foucault-Hilbert transformations in combination with registration and pixel-by-pixel processing of the dynamic RGB image structure. The dynamic phase structure of the diffusion flame is visualized. The initial temperature approximation, based on the assumption of an air mixture, is corrected so that the calculated hilbertogram matches the measured one as closely as possible. The data obtained are in good agreement with the results of thermocouple measurements. The temperature was recorded by thermocouples at reference points. The phase function is reconstructed in axisymmetric sections from RGB-hilbertograms. The reliability of the results is confirmed by comparing the experimentally obtained hilbertograms and hilbertograms reconstructed from phase structures using the Abel transform.