Investigation of concentration effects on the flame acceleration in vented channels

Propane-air gas explosion experiments were performed in two vented channels of dimensions 1.5 m × 0.3 m × 0.3 m (lab-scale) and 6 m × 1.2 m × 1.2 m (medium-scale). The pressure-time development and flame speed were recorded. Tests were performed with several obstacle configurations. The equivalence ratio ϕ was varied between 0.7 and 1.7, to study the corresponding effects on the flame acceleration and maximum explosion overpressure. The experimental results were compared to numerical simulations performed with the computational fluid dynamics (CFD) tool FLACS, employing two different burning velocity models: (i) the standard burning velocity model in FLACS, (ii) an alternative burning velocity model that incorporates Markstein number effects. Both models gave acceptable predictions of the experimental maximum overpressures for ϕ<1.4. For fuel-rich mixtures, ϕ>1.4, the standard burning velocity model in FLACS generally under-predicted the maximum overpressures. The Markstein number-dependent burning velocity model gave improved results, consistently predicting overpressures within ±10% of the experimental values.