Effects of the arc-shaped corner on the shock wave and self-ignition induced by sudden release of pressurized hydrogen

The self-ignition is a potential risk during the use of hydrogen, and arc-shaped bends exist in industrial hydrogen pipelines. So the experimental and numerical study were conducted to investigate the shock wave and self-ignition induced by high-pressure hydrogen release via three 90° arc-shaped tubes. The pressure profiles, photoelectric signals and jet flame were recorded. It was found that reflected shock waves generated in the bend would spread both upstream and downstream. And the reflected shock wave propagating downstream can enhance the intensity of the leading shock wave. But the velocity of leading shock wave in the bend decreased faster than that in the straight part. In addition, based on numerous experiments, two processes of self-ignition in the 90° arc-shaped tube were summarized. One was only affected by the strong leading shock wave, the other was affected by the combination of reflected shock wave and leading shock wave. Moreover, the distance from the bend to the burst disc had an effect on the self-ignition. When the distance from the bend to the burst disc was the shortest, it was least likely to cause self-ignition. Besides, the phenomena of flame quenching cannot occur in the bend of arc-shaped tube. The development characteristics of the external flame was studied, including the flame morphology near the Mach disk and the variation in the size of the jet flame.