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

Harstad, Kenneth and Bellan, Josette (2006) Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases. Combustion and Flame, 144 (1-2). pp. 89-102. ISSN 0010-2180. doi:10.1016/j.combustflame.2005.07.005.

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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.

Item Type:Article
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Bellan, Josette0000-0001-9218-7017
Additional Information:© 2005 The Combustion Institute. Published by Elsevier Inc. Received 22 December 2004, Revised 21 June 2005, Accepted 3 July 2005, Available online 31 August 2005. This study was conducted at the Jet Propulsion Laboratory, California Institute of Technology, and was sponsored by the U.S. Department of Energy under the Hydrogen Program, with Mr. Neil Rossmeissl, Mr. Patrick Davis, and Dr. Jay Keller as Program Managers, under an interagency agreement with the National Aeronautics and Space Administration.
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:Hydrogen-safety global analysis
Issue or Number:1-2
Record Number:CaltechAUTHORS:20171019-095150347
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Official Citation:Kenneth Harstad, Josette Bellan, Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases, In Combustion and Flame, Volume 144, Issues 1–2, 2006, Pages 89-102, ISSN 0010-2180, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82480
Deposited By: Tony Diaz
Deposited On:19 Oct 2017 18:19
Last Modified:15 Nov 2021 19:50

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