Some Fundamental Combustion Properties of "Cryogenic" Premixed Hydrogen Air Flames

Because of the emergence of the U.E. “green deal” and because of the significant implication of national and regional authorities throughout Europe, the “hydrogen” economy is emerging. And with it, numerous questions and experimentations. One of them, perhaps a key point, is the storage and transport of hydrogen. Liquid hydrogen in cryogenic conditions is a possibility already used in the space industry but under a lot of constrains. What may be acceptable in a well-controlled and restrained domain may not be realistic in a wider application, closer to the public. Safety should be ensured and there is a need for a better knowledge of the flammable and ignition properties of the “cold” hydrogen mixtures following a cryogenic spillage for instance to select adequate ATEX equipment. The purpose of PRESLHY project [4] is to investigate the ignition, fire and explosion characteristics of cryogenic hydrogen spillages and to propose safety engineering methods. The present work is part of it and addresses the measurement of the laminar burning velocity (Sl), flammability limits (FL), minimum ignition energy (MIE)… of hydrogen air mixtures at atmospheric pressure but down to -150°C. To do this, a special burner was designed with details given inside this paper together with the experimental results. It is found that the FL domain is reduced when the temperature drops, that MIE increases slightly and Sl decreases.