Abstract

This work investigates experimentally the linear and non-linear dynamics of a ducted, conical, laminar premixed flame under forced acoustic excitation. Upstream travelling acoustic waves hit the flame at varying amplitudes. The flame transfer function is measured. In particular, for velocity disturbance amplitudes close to the mean flow velocity the phase of the transfer function shows significant difference to that at weak excitation. Instantaneous images of the flame under excitation suggest that the non-linearity is associated with the movement of the flame base at high levels
of excitation, which is assumed fixed in the kinematic linear theory. Further work by the group will attempt to explain how non-linearity comes into play at higher forcing amplitudes.