Flame propagation and acceleration in narrow channels: sensitivity to facility specific parameters

Abstract

Flame propagation experiments in stoichiometric H 2 -air are conducted in a smooth 482-mm long, 10-mm × 10-mm square cross section channel, closed at the ignition end and open at the opposite end. Direct observation is used to track the flame acceleration dynamics. The effect of facility specific parameters (i.e. ignition energy, boundary conditions near the ignition end, window material and settling time between filling and ignition) on flame propagation and acceleration is assessed. The absolute mean deviation is used as a metric to determine the effect of the aforementioned parameters on the collected front position data, and Response Surface Methods for experimental design is applied to examine inter-parameter interactions. Results show that the boundary conditions near the ignition end (i.e. large/small ignition offset) have the largest influence on the recorded front position with the remaining parameters playing a less important role. The early stages of flame propagation is compared against theoretical predictions to understand the discrepancies observed in the data; a simple acoustic model was found sufficient to explain the increased acceleration rates observed for the large ignition offset cases. Finally, a link between the observed front oscillations during flame acceleration and the flow rate dynamics at the channel's open end is highlighted.

Flame acceleration and detonation onset in narrow channels: Simultaneous schlieren visualization

“…In addition, the waiting time between filling and ignition is controlled to 15 s as this was found sufficient to avoid any impact of initial flow unsteadiness on the early stages of flame propagation [27]; (v) to remove any visible condensation from the burned gases the channel is vacuumed for at least three minutes after each test. each direction viewed.…”

A Study on the Influence of Steel Structures in Concrete Subgrades on the Detection of Subgrade Distresses by Ground-Penetrating Radar

“…The identification of subgrade problems in ballastless track railways involves a range of methodologies, including direct observations, external and internal inspections, and comprehensive evaluations [10,11]. The direct observation method relies on manual inspection for the visual assessment of subgrade defects and distresses [12]. The external inspection method utilizes advanced non-destructive detection techniques, including laser scanning, radar sensing, and thermal imaging, to monitor deformations, cracks, and other visible subgrade distresses.…”