On the Use of Laminar Burning Velocities in Process Safety

This study explores the role of the premixed laminar burning velocity as a global parameter to evaluate the explosion hazard of flammable gases and vapors in chemical process facilities.  Laminar burning velocity is often used to determine the consequence severity of potential fire and explosion scenarios, as well as to select safeguards to mitigate such scenarios.   For instance laminar burning velocity is used by the 2013 version of NFPA 68 Standard on Explosion Protection by Deflagration Venting to calculate the required deflagration vent size of enclosures, correlations to estimate overpressures in unconfined vapor cloud explosions (VCEs), and Computational Fluid Dynamics (CFD) software to model flame propagation.    

Although laminar burning velocities are readily available in the literature for a range of fuels, the pedigree of these values is not always well understood.  Many of these data come from experiments performed over half a century ago and have been somewhat arbitrarily adjusted because the experimental techniques did not provide correct values for well characterized gases like propane.  The uncertainty in the burning velocity values is often not reported, and varies depending on the experimental technique used.

This study provides a historical overview of the experimental methods and uncertainties related to laminar burning velocity measurements.  A number of currently used experimental methods are described, providing information on the strengths and weaknesses of the methods.  Additionally, we describe methods for estimating the laminar burning velocity of gas mixtures from existing pure component data.