Analysis of ethylene-oxygen combustion in micro-pipes

Propagation of premixed stoichiometric ethylene-oxygen flames in cylindrical pipes of sub/near-millimeter radii is investigated-computationally, analytically and experimentally. Namely, various stages of flame evolution such as quasi-isobaric, exponential acceleration; its moderation due to gas compression; and eventual saturation to the Chapmen-Jouget deflagration are consdiered. Specifically, we have determined the dynamics and morphology of the flame front, its propagation velocity and acceleration rate. Due to viscous heating, the entire process can be followed by the detonation initiation ahead of the flame front. The computational component of this research includes numerical solution of the hydrodynamics and combustion equations with chemical kinetics represented by one-step Arrhenius reaction. The theoretical model accounts for small, but finite Mach number; and it assumes a plane-parallel flame-generated flow, zero flame thickness as well as large thermal expansion and flame-related Reynolds number. The overall study bridges the gap between the experiments of Wu et al. [Proc. Combust. Inst. 31 (2007) 2429] and the analytical formulation of Akkerman et al. [Combust. Flame 145 (2006) 206].