Numerical study on spontaneous ignition of pressurized hydrogen release through a length of tube

Hydrogen is known as one of the green energy sources for fuel cells and hydrogen-fueled cars in the next generation. The storage of high-pressure hydrogen gas conditions is preferred to its storage in cryogenic liquid state. However, cases of unidentified self-ignitions were reported, notably when the high-pressure hydrogen gas suddenly leaked out. Only a few of numerical simulations have shown visually the processes of the self-ignition inside a tube. This paper presents a flow visualization study to investigate the self-ignition mechanism in a test tube i.e. how the ignition process is initiated and the flame propagates. In addition to visualization, measurement of a number of pressure and light sensors installed in the tube supported the analysis of the self-ignition and flame propagation. The test result showed that self-ignition takes place at the boundary layer behind the front center of mixing zone at first, and the flame propagates to the front of mixing zone and tail of the mixing zone along the boundary layer. It showed that self-ignition is accompanied with complex mixing induced by shock interaction with the mixing front. It is also suggested that the self-ignition boundary has a certain critical threshold of static pressure at the boundary layer, based on various burst pressures of hydrogen.

A flow visualization study on self-ignition of high pressure hydrogen gas released into a tube

http://conference.ing.unipi.it/ichs2009/images/stories/presentations/ID265-Bragin_Molkov.pdf

Physics of spontaneous ignition of high-pressure hydrogen release and transition to jet fire

Self-ignition and flame propagation of high-pressure hydrogen jet during sudden discharge from a pipe

Review on hydrogen safety issues: Incident statistics, hydrogen diffusion, and detonation process

The phenomenon of self-ignition and explosion during discharge of high-pressure hydrogen was investigated. To clarify the ignition conditions of high-pressure hydrogen jets, rapid discharge of the high-pressure hydrogen was examined experimentally. A diaphragm was used to allow rapid discharge of the high-pressure hydrogen. The burst pressure was varied from 4 to 30 MPa. The downstream geometry of the diaphragm was a flange and extension pipes, with the pipe length varying from 3 to 300 mm. The diameter of the nozzle was 5 or 10 mm. When short pipes were used, the hydrogen jet did not ignite. However, the hydrogen jet showed an increasing tendency to ignite in the pipe as the length of the pipe became longer. At higher burst pressures, a diffusion jet flame was formed from the pipe. The blast wave from the fireball formed on self-ignition of the hydrogen jet resulted in an extremely rapid pressure rise.

Self-ignition and explosion during discharge of high-pressure hydrogen

Propagation and attenuation characteristics of blast wave pressure generated from an explosion inside an earth-covered magazine

Hydrogen is the most ideal and promising alternative fuel, and fuel cell vehicles that use hydrogen as a fuel are expected to be widely used in public. To use hydrogen commonly, the establishment of proper guidelines for handling safely is required urgently. In a series of research to develop safety data of hydrogen systems, the accurate evaluations of the effect of blast wave from hydrogen explosion were examined. In the case of deflagration, measured blast pressure is influenced largely by thermal strain of the diaphragm of the pressure sensor due to the radiation from the flame. In present work, reduction of the effect of radiation to pressure sensor with recess mount was estimated by calculation using view factor. The natural frequency and the response of the recess mount sensor were also evaluated. The validity of recess mounted sensor was shown through the experiments on the blast waves measurements of hydrogen/air denigration. Blast waves were measured by using both pressure sensors with recess mount and with conventional flush mount. The recess mount method suppressed the effect of radiation remarkably without lacking the accuracy.

Dongjoon Kim

Papers

Self-ignition and explosion during discharge of high-pressure hydrogen

Propagation and attenuation characteristics of blast wave pressure generated from an explosion inside an earth-covered magazine

Measurement of Blast Pressure of Hydrogen/Air Explosion (Investigation of the Effects of Thermal Radiation)

Measurements of flame propagation velocities and blast wave pressures for methane/oxygen gas mixtures

Experimental study on the attenuation of blast waves by a water layer