Release and dispersion modeling of cryogenic under-expanded hydrogen jets

- Investigation of release and dispersion of cryogenic under-expanded hydrogen jets.
- HEM model for release and CFD with notional nozzle approach for dispersion.
- Agreement against release data of NASA, large discrepancies against data of KIT.
- Good agreement against dispersion data of KIT at 80 K stagnation temperature.
- Consistency issues for the results against data of KIT at lower temperatures (36 K).

In the present work performed within the framework of the SUSANA EC-project, we address the release and dispersion modeling of hydrogen stored at cryogenic temperatures and high pressures. Due to the high storage pressures the resulting jets are under-expanded. Due to the low temperatures the choked conditions can be two-phase. For the release modeling the homogeneous equilibrium model (HEM) was used combined with NIST equation of state for hydrogen. For the dispersion modeling the 3d CFD methodology was used combined with a) a notional nozzle approach to bridge the expansion to atmospheric pressure region that exists near the nozzle, b) the ideal gas assumption for hydrogen and air and c) the standard (buoyancy included) k-ε turbulence model. Predicted release choked mass fluxes are compared against 37 experiments from literature. Predicted steady state hydrogen concentrations along the jet axis are compared against five dispersion experiments from literature as well as the Chen and Rodi correlation and the behavior of the proposed release and dispersion modeling approaches is assessed.