Propagation of high-speed hydrogen-air combustion waves through inert gases

Abstract

The propagation characteristics of high-speed hydrogen-air combustion waves through different inert gases (i.e., nitrogen, argon, and carbon dioxide) are experimentally investigated. Three inlet combustion waves of the transonic deflagration wave, supersonic deflagration wave, and stable detonation are considered. The variation of flame velocity, shock wave pressure and transient flame structures are presented and analyzed. Results indicate that a deflagration-to-detonation transition followed by a velocity decay tends to occur after the high-speed deflagration propagates into the inert gas. The deflagration-to-detonation transition is more likely to occur when the inlet combustion wave is enhanced from a transonic deflagration wave to a supersonic deflagration wave. For the inlet detonation wave case, the velocity decay process can be divided into two stages successively with the sound speed in the corresponding inert gas as the boundary value: nearly linearly decay and slowly decay accompanied by small fluctuations. For all cases, the velocity decay is closely coupled with the flame-inert gas interaction. Carbon dioxide shows the most significant dilution and suppression effects due to its considerable molecular weight and specific heat capacity compared with nitrogen and argon.