Effects of pressure waves on the stability of flames propagating in tubes

Abstract Numerical simulations were performed to study the effects of pressure waves on the evolution and stability of flames propagating in tubes. The model is the fully compressible reactive Navier–Stokes equations coupled to a calibrated one-step chemical-diffusive model for combustion in a stoichiometric hydrogen–air mixture. The numerical solution method is high order in space and time, and adaptive mesh refinement provides adequate resolution of flames, boundary layers, acoustic waves, and all of their interactions. The influence of tube length scale and aspect ratio was examined for a range of tube sizes that produce tulip flames (TFs) and series of distorted tulip flames (DTFs). The simulations show that pressure waves and acoustic properties of the tube play an important role in the flame evolution, specifically in the formation and evolution of the series of increasingly wrinkled DTFs. A time scale and pressure wave analysis of the results, combined with a linear analysis to give the growth rate of the Rayleigh–Taylor instability (RTI), shows that the RTI is a primary cause for the initiation of DTFs.