PRESLHY_D4.2_v1.0

Work package four of the PRESLHY project focuses on ignition phenomena. This report
summarises computational modelling work which was carried out to complement the
experimental programme. Three particular scenarios have been considered: firstly, the
determination of the MIE in hydrogen-air mixtures at arbitrary composition and initial
temperature; secondly, the effect of hydrogen temperature decrease on pressure limit leading to
spontaneous ignition in a T-shaped channel and thirdly, the investigation of the condensation of
oxygen over an evaporating LH2 pool and its potential to cause highly energetic events after
ignition.
The CFD model was seen to predict accurately experimentally measured MIE for both ambient
and cryogenic temperature hydrogen-air mixtures. Thus, the model can be used as a means of
calculations of potential hazards in hydrogen safety engineering.
A LES approach was employed to investigate the effect of hydrogen temperature decrease on
pressure limit leading to spontaneous ignition in a T-shaped channel. For cryogenic hydrogen
(80 K), it was found that a pressure approximately 4 times larger than for warm hydrogen is
required to trigger ignition and sustain combustion outside the T-shaped channel, which could
likely lead to a hydrogen jet fire.
CFD modelling can be used to investigate the formation of cryogenic hydrogen and condensed
oxygen mixtures. CFD simulations can be used to support experimental investigations where it
may not be possible to exactly define the underlining cause of highly energetic events following
combustion of cold hydrogen/oxygen mixtures.