Numerical investigations of unsteady flame propagation in stepped microtubes

Abstract

Transient numerical simulations with detailed chemistry have been carried out for premixed stoichiometric CH₄–air and H₂–air flames in two-dimensional stepped microtubes for a range of wall heat transfer conditions. Investigations on such configurations are important from the perspective of the design of micro combustion devices, flame arresters and safety in domestic and industrial combustion devices. Similarities in flame propagation characteristics have been brought out through a detailed analysis for both the fuels. Detailed analysis of the propagating flame near the channel step revealed an interesting phenomenon of sudden increase in flame propagation velocities for a certain range of wall heat transfer coefficient, h. A quantitative value of ratio of heat-loss to heat-generation at the contraction has been proposed which helps predict the flame propagation through sudden channel steps.