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Title: Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases

Abstract

Global, simplified analyses of gaseous-hydrogen releases from a high-pressure vessel and liquid-hydrogen pools are conducted for two purposes: (1) establishing order-of-magnitude values of characteristic times and (2) determining parametric dependencies of these characteristic times on the physical properties of the configuration and on the thermophysical properties of hydrogen. According to the ratio of the characteristic release time to the characteristic mixing time, two limiting configurations are identified: (1) a rich cloud exists when this ratio is much smaller than unity, and (2) a jet exists when this ratio is much larger than unity. In all cases, it is found that the characteristic release time is proportional to the total released mass and inversely proportional to a characteristic area. The approximate size, convection velocity, and circulation time of unconfined burning-cloud releases scale with the cloud mass at powers 1/3, 1/6, and 1/6, respectively, multiplied by an appropriately dimensional constant; the influence of cross flow can only be important if its velocity exceeds that of internal convection. It is found that the fireball lifetime is approximately the maximum of the release time and thrice the convection-associated characteristic time. Transition from deflagration to detonation can occur only if the size of unconfined cloudsmore » exceeds by a factor of O(10) that of a characteristic detonation cell, which ranges from 0.015 m under stoichiometric conditions to approximately 1 m under extreme rich/lean conditions. For confined vapor pockets, transition occurs only for pocket sizes larger than the cell size. In jets, the release time is inversely proportional to the initial vessel pressure and has a square root dependence on the vessel temperature. Jet velocities are a factor of 10 larger than convective velocities in fireballs and combustion is possible only in the subsonic, downstream region where entrainment may occur.« less

Authors:
;  [1]
  1. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, M/S 125-109, Pasadena, CA 91109-8099 (United States)
Publication Date:
OSTI Identifier:
20685981
Resource Type:
Journal Article
Resource Relation:
Journal Name: Combustion and Flame; Journal Volume: 144; Journal Issue: 1-2; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; HYDROGEN; CRYOGENIC FLUIDS; GAS SPILLS; LEAKS; PLUMES; EXPLOSIONS; TEMPERATURE DEPENDENCE; SIZE

Citation Formats

Harstad, Kenneth, and Bellan, Josette. Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases. United States: N. p., 2006. Web. doi:10.1016/j.combustflame.2005.07.005.
Harstad, Kenneth, & Bellan, Josette. Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases. United States. doi:10.1016/j.combustflame.2005.07.005.
Harstad, Kenneth, and Bellan, Josette. Sun . "Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases". United States. doi:10.1016/j.combustflame.2005.07.005.
@article{osti_20685981,
title = {Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases},
author = {Harstad, Kenneth and Bellan, Josette},
abstractNote = {Global, simplified analyses of gaseous-hydrogen releases from a high-pressure vessel and liquid-hydrogen pools are conducted for two purposes: (1) establishing order-of-magnitude values of characteristic times and (2) determining parametric dependencies of these characteristic times on the physical properties of the configuration and on the thermophysical properties of hydrogen. According to the ratio of the characteristic release time to the characteristic mixing time, two limiting configurations are identified: (1) a rich cloud exists when this ratio is much smaller than unity, and (2) a jet exists when this ratio is much larger than unity. In all cases, it is found that the characteristic release time is proportional to the total released mass and inversely proportional to a characteristic area. The approximate size, convection velocity, and circulation time of unconfined burning-cloud releases scale with the cloud mass at powers 1/3, 1/6, and 1/6, respectively, multiplied by an appropriately dimensional constant; the influence of cross flow can only be important if its velocity exceeds that of internal convection. It is found that the fireball lifetime is approximately the maximum of the release time and thrice the convection-associated characteristic time. Transition from deflagration to detonation can occur only if the size of unconfined clouds exceeds by a factor of O(10) that of a characteristic detonation cell, which ranges from 0.015 m under stoichiometric conditions to approximately 1 m under extreme rich/lean conditions. For confined vapor pockets, transition occurs only for pocket sizes larger than the cell size. In jets, the release time is inversely proportional to the initial vessel pressure and has a square root dependence on the vessel temperature. Jet velocities are a factor of 10 larger than convective velocities in fireballs and combustion is possible only in the subsonic, downstream region where entrainment may occur.},
doi = {10.1016/j.combustflame.2005.07.005},
journal = {Combustion and Flame},
number = 1-2,
volume = 144,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}