Flame Acceleration in Hydrogen/Air Mixtures in a Vertical Cylinder Filled with Obstacles

Abstract

Experiments were carried out in a cylindrical vessel of 1.5 m i.d. and 5.7 m high to determine the effect of obstacles on combustion for hydrogen/air and hydrogen/air/steam mixtures. A range of hydrogen concentrations from 12 to 20% by volume was studied. At low hydrogen concentrations (<12%), the measured flame speeds were higher (by a factor of two or more) than the calculated laminar flame speeds, but there was no flame acceleration. Flame acceleration occurred for hydrogen concentrations from 14 to 20Y. even when no obstacles were present; the obstacles increased the severity of the flame acceleration.


Experiments performed with eight and fifteen repeated obstacles spaced equally and stacked vertically in the cylinder indicated that increasing the number of obstacles from eight to fifteen had no significant effect on flame speeds. The addition of a diluent such as steam or carbon dioxide completely suppressed flame acceleration for mixtures that exhibited severe flame acceleration.