Self-ignition and Flame Propagation of Pressurized Hydrogen Released Through Tubes

The spontaneous ignition of hydrogen released from the high pressure tank into the downstream pipes with different lengths varied from 0.3m to 2.2m has been investigated experimentally. In this study, the development of shock wave was recorded by pressure sensors and photoelectric sensors were used to confirm the presence of a flame in the pipe. In addition, the development of jet flame was recorded by high-speed camera and IR camera. The results show that the minimal release pressure in different tube when self-ignition of hydrogen occurred could decrease first and then increase with the increase of the aspect of pipe. And the minimum release pressure of hydrogen self-ignition was 3.87MPa. When the flame of self-ignition hydrogen spouted out of the tube, Mach disk was observed. The method of CFD was adopted. The development of shock wave at the tube exit was reproduced and structures as barrel shock, the reflected shock and the Mach disk are presented. Because of these special structures, the flame at the nozzle is briefly extinguished and re-ignited. At the same time, the complete development process of the jet flame was recorded, including the formation and separation of the spherical flame. The flame structure exhibits three typical levels before the hemispherical flame separation.