Flame propagation regimes at cryogenic temperature

In the frame of the PRESLHY project more than 100 experiments on hydrogen – air flame propagation regimes in a shock tube at cryogenic temperatures were made with the combustion tube at the KIT HYKA test site. More than half of the experiments were made at cryogenic temperatures (between approx. 90 K and 130 K). The rest experiments were conducted at ambient conditions as the reference data. It was however possible to provide experimental data at various H2 concentrations from 8 to 60 Vol. %H2 and 3 blockage ratios (BR = 0, 0.3 and 0.6). During the course of the experiments, many experimental difficulties and peculiarities specific for cryogenic temperatures were encountered. Critical conditions for flame acceleration to the speed of sound and to the detonation onset at cryo-temperatures were experimentally found. It was also found that the danger of hydrogen combustion and explosion in terms of maximum combustion pressure is much higher than at ambient temperatures because of several times higher density of the combusted substance. Then, even for sonic deflagration at cryogenic temperatures, the maximum pressure might be higher than the detonation pressure at ambient conditions. The data obtained in current work can be used for safety distance assessment for LH2 safety applications.

在PRESLHY项目框架下，于KIT HYKA测试场地的燃烧管中，针对低温激波管内氢-空气火焰传播模式开展了100余次实验。超过半数实验在低温条件下进行（约90 K至130 K之间），其余则在环境条件下开展作为参考数据。此外，实验还获取了8至60体积%范围内多种H₂浓度，以及3种阻塞比（BR=0、0.3和0.6）下的实验数据。实验过程中，遇到了诸多低温特有的实验难点与特性。通过实验确定了低温下火焰加速至声速及爆轰起始的临界条件。研究还发现，由于燃烧物质的密度数倍于环境温度下的密度，低温下氢燃烧与爆炸在最大燃烧压力方面的风险远高于环境温度条件；因此，即便低温下的声速爆燃，其最大压力也可能超过环境温度下的爆轰压力。本研究获得的数据可用于液氢（LH₂）安全应用的安全距离评估。