20210802-PRESLHY_D3_3_ReleaseMixingExperiments_V1p0

Within the experimental program of PRESLHY 4 experimental campaigns address the nonreactive phenomena release and mixing. The DISCHA experimental campaign (E3.1a) consisted
of more than 200 hydrogen high pressure blow-down experiments applying the DISCHA-facility
at KIT. About half of the experiments were made at cryogenic temperatures (approx. 80 K). With
the new built CRYOSTAT facility of KIT 12 similar hydrogen blow-down experiments were
performed with LH2 (E3.1b). Not a single test showed a spontaneous ignition, although at least
the cold high pressure jets generated relative strong electrostatic fields. This static electricity
seems to be generated by ice crystals which form on the release nozzle before the tests and are
broken and entrained when the discharge is initiated.
With the POOL experiments (E3.4) at KIT the influence of ground materials and side wind on
the evaporation rates of LH2 was assessed. Four different ground materials were tested:
concrete, sand, gravel and water. The results were used to validate corresponding models. The
gravel material caused highest evaporation rate and accordingly largest flammable mixtures
above the pools.
The RAINOUT experiments (E3.5) of HSE demonstrated the little potential for rain-out and
pool formation even at massive release rates. Field measurements for concentration and
temperature measurement revealed a useful correlation for cryogenic releases. Similar as for
the DISCHA experiments the generated electrical fields and currents turned out to be too small
to represent a credible ignition source.