Gas Explosion Venting: External Explosion Turbulent Flame Speeds that Control the Overpressure

In most vented explosions the peak overpressure is controlled by turbulent flame propagation external to the vent. This has been known for many years, but a method to predict the overpressure from the external flame speed has not been developed. Current vent modelling is based on the assumption that the unburned gas flow through the vent controls the overpressure and does not address the issue of the external explosion. This work shows that the external flame speeds in a small vented explosion test facility can be predicted from Taylors’s acoustic theory (1946). Vented explosion data is presented for vent coefficients from 3 – 22 for the most reactive mixtures of methane, propane and ethylene in terms of the overpressure and the external flame speed. The overpressure from Taylors’s acoustic theory give a good prediction of the measured overpressure.