EXPERIMENTAL-EVIDENCE OF SELF-EXCITED RELAXATION OSCILLATIONS LEADINGTO HOMOCLINIC BEHAVIOR IN SPREADING FLAMES

Flame spreading over liquid alcohols has been experimentally character ized by three methods: temperature measurements along the liquid surfa ce, schlieren pictures of the temperature gradients induced in the liq uid by Marangoni flows, and direct video recording of the flame spread ing. Three distinct spreading regimes have been observed: a fast and a slow propagation regime of uniform spreading at high and low values o f the initial fuel surface temperature, and an oscillatory propagation regime at intermediate temperatures. The oscillations start as a Hopf bifurcation from the fast propagation steady state. Moreover, the col lision of the limit cycle with the slow spreading branch originates a homoclinic connection revealed by a logarithmic divergence in the osci llation period, a main feature of generic homoclinic points.