Frequency resolved interferometric detection of local density fluctuations in flames

Low NOx strategies usually include lean combustion in order to reduce the flame temperature. Under certain conditions, this interaction can occur periodically as thermo-acoustic coupling, a reason why new premix combustion systems tend to have oscillations. Ongoing developments have pushed the sensitivity for density fluctuation measurements using laser vibrometers. In this experiment a variable geometry burner was enclosed in a liner, with the flame optically accessible through four fused silica windows. By this burner with adjustable flame conditions the cavity of the atmospheric model combustion chamber was excitable at a frequency around 200Hz. Resonant and non-resonant flame conditions were investigated and compared by laser vibrometer interferometry, schlieren visualization and OH*/CH* chemiluminescence.

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