Alloyau
I have contacted the administrator to delete my sentence regarding spontenous explosion of hydrogen under pressure, my misstake.
That is right. What does happen is that when highly compressed hydrogen is suddenly released into air auto ignition can happen.
Spontaneous Ignition of Pressurized Releases of Hydrogen and Natural Gas into Air
(Frederick L. Dryer, Marcos Chaos, Zhenwei Zhao, Jeffrey N. Stein, Jeffrey Y. Alpert, and Christopher J. Homer
Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ)
Abstract: This paper demonstrates the ââspontaneous ignitionââ (autoignition=inflammation and sustained diffusive combustion) from sudden compressed
hydrogen releases that is not well documented in the present literature, for which
little fundamental explanation, discussion or research foundation exists, and
which is apparently not encompassed in recent formulations of safety codes
and standards for piping, storage, and use of high pressure compressed gas systems handling hydrogen. Accidental or intended, rapid failure of a pressure
boundary separating sufficiently compressed hydrogen from air can result in
multi-dimensional transient flows involving shock formation, reflection, and
interactions such that reactant mixtures are rapidly formed and achieve chemical
ignition, inflammation, and transition to turbulent jet diffusive combustion, fed
by the continuing discharge of hydrogen. Both experiments and simple transient
shock theory along with chemical kinetic ignition calculations are used to support
interpretation of observations and qualitatively identify controlling gas properties
and geometrical parameters. Although the phenomenon is demonstrated for pressurized hydrogen burst disk failures with different internal flow geometries, similar phenomena apparently do not necessarily occur for sudden boundary failures
of storage vessel or transmission piping into open air that have no downstream
obstruction. However, subsequent reflection of the resulting transient shock from
surrounding surfaces through mixing layers of hydrogen and air may have the potential for producing ignition and continuing combustion. Much more experimental and computational work is required to quantitatively determine the envelope of parameter combinations that mitigate or enhance spontaneous ignition
characteristics of compressed hydrogen as a result of sudden release, particularly
if hydrogen is to become a major energy carrier interfaced with consumer use.
Similar considerations for compressed methane, for mixtures of light hydrocarbons and methane (simulating natural gas), and for larger carbon number hydrocarbons show similar autoignition phenomena may occur with highly compressed
methane or natural gas, but are unlikely with higher carbon number cases, unless
the compressed source and=or surrounding air is sufficiently pre-heated above
ambient temperature. Spontaneous ignition of compressed hydrocarbon gases is
also generally less likely, given the much lower turbulent blow-off velocity of
hydrocarbons in comparison to that for hydrogen.
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