Critical radius for hot-jet ignition of hydrogen-air mixtures Articles uri icon

publication date

  • March 2013

start page

  • 3105

end page

  • 3109

issue

  • 7

volume

  • 38

international standard serial number (ISSN)

  • 0360-3199

electronic international standard serial number (EISSN)

  • 1879-3487

abstract

  • This study addresses deflagration initiation of lean and stoichiometric hydrogen&-air mixtures by the sudden discharge of a hot jet of their adiabatic combustion products. The objective is to compute the minimum jet radius required for ignition, a relevant quantity of interest for safety and technological applications. For sufficiently small discharge velocities, the numerical solution of the problem requires integration of the axisymmetric Navier&-Stokes equations for chemically reacting ideal-gas mixtures, supplemented by standard descriptions of the molecular transport terms and a suitably reduced chemical-kinetic mechanism for the chemistry description. The computations provide the variation of the critical radius for hot-jet ignition with both the jet velocity and the equivalence ratio of the mixture, giving values that vary between a few tens microns to a few hundred microns in the range of conditions explored. For a given equivalence ratio, the critical radius is found to increase with increasing injection velocities, although the increase is only moderately large. On the other hand, for a given injection velocity, the smallest critical radius is found at stoichiometric conditions.

keywords

  • deflagration initiation; hydrogen–air mixtures; hot-jet ignition; transient jets