Measurements of ensemble averaged flame dynamics using spatially resolved analysis

When applying flame sheet models to predict the dynamics of turbulent flames, it is common to model turbulence using ensemble averaging of the velocity. Measurements of the flame dynamics were made to support use this type of methodology, by measuring the dynamic volume of the flame using phase averaged images of the CH* chemiluminescence. The dynamics agreed with the common behavior described in the literature, namely frequency scaling according to Strouhal number based on flow convective timescales. However, slightly different timescales were observed for the response magnitude and phase, indicating the possibility of different scaling mechanisms at work between these phenomena. The flame heat release rate dynamics were found to be identical to the dynamic response of the flame volume to inlet velocity perturbations, suggesting a simple proportionality between heat release rate and the flame volume. This result supports the use of ensemble averaging for modeling of the turbulent velocity for predictions of flame dynamics.

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