Experimental Study on the Thermal Effect according to the Distance around a Hydrogen Jet Flame

In this study, the safe distance in the case of a hydrogen vehicle fire was analyzed according to the temperature distribution around a hydrogen gas jet flame formed by the thermally activated pressure relief device operation of a hydrogen storage container. The experiment was conducted while 70 MPa hydrogen gas was released from a 1.8-mm-diameter nozzle to a 1.8- × 1.8 m fire-resistant structure wall for distances of 2 and 4 m between the nozzle output and the wall. To analyze the temperature around the hydrogen gas jet flame, five fire-fighting heat-protective hood test samples, certified by the Korea Fire Institute, and temperature sensors were installed every 1 m from the center of the jet flame in the vertical direction to the direction of the flame. In the experiment, the temperature around the jet flame was measured to observe the safe distance for firefighters. The results show that the safe distances at 70°C or less, which is harmless to firefighters, were 5 m without a heat-protective hood and 3 m with a heat-protective hood. In addition, it was confirmed that the direction of the jet flame and blocking by obstacles affect the safe distance during fire-fighting and rescue activities by firefighters.

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.