Experimental analysis of oscillatory premixed flames in a Hele-Shaw cell propagating towards a closed end

Unexpected Propagation of Ultra-Lean Hydrogen Flames in Narrow Gaps

“…However, premixed flames are inherently unstable. The viscosity and thermal expansion gradient across the flame front, the competition between heat conduction and mass diffusion in the fluid, the effect of gravity, the interaction with acoustic waves [12,13], and the heat losses [14] fold and stretch the flame altering some of its dynamic and morphological properties [15].…”

“…From the experimental results, it is unclear both how the flame cells are formed and why hydrogen flames withstand more adverse conditions than heavier hydrocarbon fuels [12]. To investigate the causes that lead to the new propagation regimes identified experimentally, we modeled the propagation of the H 2 -air flame using an in-house finite-element code [14].…”

Premixed-flame oscillations in narrow channels

“…However, most of the experimental research has been performed in vertical tubes [3] under strong buoyancy effects. Here, the first thermoacoustic study reported in a horizontal narrow-channel (Hele-Shaw) vessel, as described in [4], has proved instrumental to further understand the dynamics of the instability.…”

Coupling of vibro-acoustic waves with premixed flame

“…Due to the induced fluctuating heat release, one would expect the emergence of acoustic instabilities involving the acoustic modes of the burner in the same way as it does with the tubes. Surprisingly, acoustic instabilities were reported in the experiments solely when the gap was large enough (more than 7mm), or for glass plates sufficiently thick (19mm) [16,30,31]. For smaller gap or smaller thickness of the glass plates, no oscillating instability was obtained, one possible reason being that viscous losses and acoustic loss at walls are too large to allow pressure fluctuations to excite the acoustic mode of the burner [32].…”