Influence of gas expansion on the velocity and stability limits of stationary curved flames in channels

Abstract

ABSTRACT The influence of gas expansion on the velocity of freely propagating curved stationary premixed flames in channels with free-slip adiabatic walls is studied utilizing 2D computational simulations, with the focus on the strongly nonlinear effects of the Darrieus-Landau instability on the stationary flame shape and velocity. The complete system of unsteady compressible Navier–Stokes equations is solved, including the transport properties (heat conduction, diffusion, and viscosity), and the chemical kinetics in the form of a one-step irreversible Arrhenius reaction. The parametric study focuses on the gas expansion, with a wide yet realistic range of expansion coefficients employed, and on the channel width. It is shown that the stationary curved flame velocity increases with gas expansion coefficient, in line with previous studies. The second critical channel width, at which the stationary curved flame velocity exceeds the one predicted by weakly nonlinear analyses and starts to grow rapidly with channel width, is identified with a sufficient accuracy for a wide range of gas expansion coefficients. The critical channel width for the Darrieus-Landau instability development depends on the gas expansion coefficient non-monotonically. The second critical channel width is found to decrease with the gas expansion coefficient, in a qualitative agreement with previous theoretical predictions.