Numerical investigation of flame propagation in small thermally-participating, adiabatic tubes

摘要

This study investigates the behaviour of flames propagating in small adiabatic tubes where the wall acts as a heat-recirculating medium. First, a simple analytical model is used to map global system behaviour at various inlet flow velocities, tube diameters, and for specific wall conditions and mixture composition. Regimes identified in the analytical model are verified with detailed numerical simulations. Providing a more accurate representation of the system is a two-dimensional model solving the low Mach number Navier-Stokes equations and the wall energy equation, with axisymmetry, implemented with a 2-step chemical kinetics mechanism. Results from this model are compared to those obtained with a 1-D formulation at similar conditions. Predictions of flame structure and burning and propagation rates are compared, and dissimilarities between model formulations are used to explain discrepancies in the results. As expected, two-dimensional effects are observed to become more significant as tube diameter and inflow velocity are increased, which influences the global behavior of the system. As 1-D models are predominant tools for the study of flames in small flow channels, their accuracy is assessed, and their range of applicability discussed.