Flame propagation along a vented duct containing grids

A theoretical model has been developed to describe steady flame propagation in pre-mixed fuel-air contained within a partially open duct. The duct contains obstacles in the form of grids to distort the propagating flame front. Both the effects of increasing the number of obstacles in each grid and decreasing the proportion of the roof of the duct open for venting are predicted by the model and compared to laboratory experiments. Although the model is simple, concentrating on the fluid dynamics of the mean flows generated by the volume production within the flame, it demonstrates how to correlate experimental data for both steady flame propagation in a long duct and also for the initial phase of rapid flame acceleration after ignition. These results constitute further evidence that the physical processes which can lead to vapour cloud explosions in petro-chemical plant are dominated by the structure of the underlying fluid mechanics. Thus much of the complex behavior, of propagating flames in partially confined and/or congested regions at least at laboratory scale can be explained using simple but nonlinear fluid mechanics models.