PRESLHY Experiment series E3.1 (Cryogenic Hydrogen Blow-down/Discharge) results – part A "high pressure"

In the frame of the PRESLHY project more than 200 hydrogen blow-down experiments were made with the DisCha-facility at KIT and about half of the experiments were made at cryogenic temperatures (approx. 80 K). During the experimental campaign the facility was continuously improved and extended, since several problems with the facility and instrumentation were encountered. However, the tests showed very good reproducibility. Although the actual exploitation of the data is left for the further modelling work in the work packages WP3 and WP4, some interesting observations are: not a single test showed a spontaneous ignition, although the cold jets generated relative strong electrostatic fields. This static electricity seems to be generated by ice crystal which form on the release nozzle before the tests. The cold tests with large diameter and high pressure show strong temperature decay in the reservoir close to the boiling point of hydrogen and quite a huge fraction of “particles” entrained in the released jet were recorded. It is assumed that this is ice from ambient humidity and frozen on the nozzle before the actual test. However, there might be condensed hydrogen involved, as the acceleration of the gas through the nozzle might bring down the temperature below the boiling point. ... mehrOnly detailed multi-phase simulations accounting for non-equilibrium effects of the real gases’ behaviour might clarify this issue.