PRESLHY_WP4_D4_3_v1_01

Work package 4 of the PRESLHY project focuses on the ignition phenomena of
cryogenic hydrogen.
This report summarises the results of experiments and analyses carried out as part of the
PRESLHY work package 4 deliverables.
The report is divided into three parts, followed by a conclusions section that summarises
the main conclusions from work package 4.
Part 1: Flammable properties of hydrogen, and hydrogen in air mixtures, at
temperatures ranging from ambient down to cryogenic
In this section the influence of temperature on the flammable limits and minimum
ignition energy of hydrogen, and hydrogen in air mixtures, are considered. The influence
of the concentration of hydrogen in air mixtures, at ambient and low temperatures on the
minimum ignition energy and the hot surface ignition temperature are also assessed.
Part 2: Environmental considerations and interactions regarding cryogenic
hydrogen
In this section the interaction of cryogenic liquids with their environment upon release are
considered. The influence of the substate onto which the cryogenic hydrogen is released,
and the formation and composition of condensed air deposits on the substrate surface are
assessed. The interaction between cryogenic hydrogen pools and water sprays are also
considered.
Part 3: Charge generation and accumulation in cryogenic hydrogen
In this section the generation and accumulation of electrostatic charges in pools of
hydrogen and multi-phase jets are considered. The influence of the initial temperature and
pressure of the hydrogen on electrostatic charge build up during release scenarios are
assessed. The influence of the size of the release orifice, in this case the nozzle diameter,
are also considered.