Fundamental mechanisms in premixed turbulent flame propagation via flame–vortex interactions: Part I: experiment

Abstract

A combined experimental and numerical study of the interaction of a two-dimensional vortex with planar laminar premixed flames has been carried out. In such a flow, the flame is subjected to time-varying strain and curvature and, hence, the interaction may be viewed as a model of fundamental processes occurring in premixed turbulent flames. Part I of the paper describes the experimental facility and diagnostics employed and presents results from the experimental investigation of effects of Lewis number, radiative heat losses, and unsteadiness on the interaction. A two-dimensional V-shaped laminar premixed flame is stabilized on a heated wire in a constant-area square duct. A two-dimensional vortex pair, generated from a slot in the duct wall, eventually interacts with one of the flame fronts. Schlieren and smoke flow visualization indicate that the flow field remains two-dimensional over a significant part of the flame–vortex interaction. This feature allows use of line-of-sight diagnostics, and, in particular, a CO ∗ 2 emission imaging technique for determination of quantitative heat release rates. Several fuel and oxidizer mixtures are employed in order to vary the Lewis number from 0.8 to 1.6 and to increase the heat loss parameter by a factor of 2.6. For the conditions investigated, the Lewis and Damköhler numbers are important controlling parameters in the evolution of the heat release rate and radiative losses may be neglected. In Part II of the paper, results from direct numerical simulations of a flame–vortex pair interaction are presented. The simulations were performed using a two-dimensional Navier-Stokes solver in which variable density and temperature-dependent transport coefficients are considered. The simulations utilize the initial conditions of the experiment and were used to investigate the role of multistep chemistry in the flame–vortex interaction.