A numerical study on the acoustic forcing of a laminar premixed saturated spray flame

This paper presents a numerical investigation into the interaction between a laminar premixed saturated spray flame and periodic acoustic forcing. A two-phase model is adopted that implements the Euler-Euler governing equations for the liquid and gaseous phases, enabling the flame dynamics to be examined in detail, particularly in terms of the flame transfer function (FTF). Three distinct mechanisms are identified: (1) a direct perturbation of the flame by a velocity-coupled mechanism, (2) a secondary effect acting via perturbations of the advection velocity of the liquid fuel droplets and (iii) a tertiary effect caused by local variations in the droplet concentration due to droplet clustering. The FTF gain at low-frequency approaching is FTF approximate to 2. The phase difference between the processes acting in the second and third coupling mechanisms is found to be a key parameter governing the flame response. At low forcing frequencies, the third coupling mechanism is found to dominate over the first two.