Numerical study on the shock wave and vortex and their coupling effect on the behavior of the flame induced by the spontaneous ignition of high-pressure hydrogen release

Abstract

High-pressure hydrogen storage is currently the mainstream way of hydrogen storage. However, the risk of spontaneous ignition and subsequent jet flame are serious obstacles to the wide application of hydrogen energy. To further reveal the interaction of shock waves, vortices and flame induced by the spontaneous ignition of high-pressure hydrogen release under the effect of release process and burst pressure, a numerical study is conducted by employing LES, RNG, EDC models and detailed hydrogen/air combustion mechanism. The qualitative and quantitative comparison of flow field and flame splitting process outside the tube between this numerical study and previous experimental results validate the numerical results. It is found that an initial vortex is formed at the edge of the jet. Then, several vortices are generated at the edge of the jet and ahead of the Mach disk. The number of vortices in the outer side of the barrel shock is larger when the opening time is shorter. After moving out of the tube, the flame front becomes hemisphere and the lateral edge has a hemispherical bulge which is induced by the initial vortex. The temperature is low and the hydrogen concentration is high in the high-speed region which is induced by the reflected shock wave, leading to the splitting of the flame into two parts: the first and the second half of the flame. However, the flame cannot be formed at the initial stage when the opening time increases to 150 μs and the flame area is larger than with smaller opening times. After splitting, under the affection of the vortices generated at the lateral side, the first half of the flame rotates backward and gradually merges with the second half of the flame, finally forming a complete hydrogen jet flame.