Dynamic properties of unstable motion of swirling premixed flames generated by a change in gravitational orientation.

The dynamic behavior of swirling premixed flames generated by the effect of the gravitational orientation has been experimentally and numerically investigated. When the gravitational direction relative to the flame front is changed, i.e., in inverted gravity (-1G), an unstable flame is formed in a limited domain of equivalence ratio and swirl number. The time history of flame front fluctuation shows that high-energy chaotic motion is superimposed on a periodic oscillation generated by unstable vortex motion in the combustion products. This results in the dynamic motion of the unstable flame becoming deterministically chaotic. This is clearly demonstrated by sophisticated nonlinear time series analysis, which has not been widely applied to the investigation of combustion phenomena.