Propagation of hydrogen-oxygen flames in Hele-Shaw cells

Flame propagation in Hele-Shaw cells with a micro-sized gap was experimentally investigated. The evolution of flame front morphology was recorded via Schlieren photographs as the hydrogen-oxygen (H-2-O-2) mixture was ignited at ambient temperature and pressure. By varying gap size, two different regimes of flame propagation are identified: 1) the non-accelerating flame in narrow gaps; 2) the self-accelerating flame in relatively wide gaps. For the former, the initial flame front is globally circular, and subsequently evolves into branches separated from the surface, exhibiting dendritic-growth and fingering shapes. In the latter regimes, the flame front exhibits a cellular structure and accelerates nearly sonic speed due to hydrodynamic instabilities. It is found that the flame acceleration depends non-monotonically on the gap size due to the competing mechanisms of viscosity friction and heat loss through the walls. The effect of equivalence ratio on the non-accelerating flame is studied to identify the mechanism controlling the local extinction flame. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Experimental investigation was conducted on flame propagation in Hele-Shaw cells with a micro-sized gap. Different regimes of flame propagation were identified based on gap size, leading to various flame front morphologies and speeds. The non-accelerating flame in narrow gaps exhibited distinct behaviors compared to the self-accelerating flame in wider gaps, influenced by hydrodynamic instabilities.