Fire and explosion - observation of confined deflagration phenomena of flammable gas mixtures under elevated gravity

In order to investigate the effects of gravity on ignition and deflagration of flammable mixtures, we conducted flammable gas explosion experiments using constant volume combustion vessels under several gravity levels from normal gravity (1 G) to elevated gravity up to 50 G. The elevated gravity field was formed by a large-size centrifuge system. We examined flame kernel growth, flame spreading, and explosion pressure in hydrogen-air, methane-air, and propane-air mixtures in an elevated gravity environment. The flammability ranges were determined by the records of the explosion pressures, and it was confirmed that the upper and lower explosion limits were approximately the same regardless of the gravity level. However, the shapes of the propagating flames changed dramatically with increase of gravity level due to strong buoyancy effect especially in lean and rich mixture conditions with slow burning velocity. Moreover, it was found that similar flame spreading phenomena were observed in large-size deflagration of rich mixture under normal gravity and small-size deflagration of stoichiometric mixture under elevated gravity.