Premixed flame propagation in a confining vessel with weak pressure rise

Abstract

AbstractThe propagation of a premixed flame inside of a confining vessel filled with combustible fluid is determined using large-activation-energy asymptotics. The flame structure is analysed assuming that spatial and temporal variations in the transverse direction are weak compared to those in the direction normal to the flame surface. The analysis considers weak pressure rise from confinement and also allows for mixtures that are both near and removed from stoichiometry, non-unity reaction orders, temperature-dependent transport coefficients, and general Lewis numbers. The resulting equations for flame propagation speed are expressed in a coordinate-free form and describe the evolution of an arbitrary shaped flame in a general confining flow. These expressions are specifically applied to the case of a spherical flame propagating inside a spherical chamber. The radius at which the confining vessel influences the flame propagation is determined and the various mechanisms influencing flame behaviour are discussed. The results give rise to a simplified asymptotic relationship that provides an improved equation that may be used to more accurately extrapolate unstretched laminar flame speeds from experimental measurements.