An experimental study on pyro-acoustic amplification of premixed laminar flames

Abstract A premixed, laminar methane-air flame was excited by a speaker-driver unit, and the gain and the phase of pyro-acoustic amplification were measured with microphones located both upstream and downstream of the flame for parameters of burner port radius, flow velocity, and mixture strength. It has been found that the plot of amplification versus excitation frequency shows a jagged shape with peaks and valleys. To describe this experimental behavior, an equation has been derived using a mathematical model of an axially symmetric premixed flame and the concept of “transfer function” of the flame. The results of calculation with this equation are shown to be in good agreement with experimental data. Furthermore, the transfer function obtained in the present work is compared with those suggested by other investigators.