Premixed flames introduce kinetic energy at the scales of the flame, which has the potential to alter the classical turbulent energy cascade through energy backscatter. This paper presents an experimental analysis of the cross-scale turbulent kinetic energy transfer in turbulent premixed swirl flames at turbulent Reynolds numbers between 830 - 3,800. Simultaneous tomographic particle image velocimetry and formaldehyde planar laser induced fluorescence measurements are used to obtain high-resolution velocity and progress-variable fields in reacting and non-reacting flows. Filtering is performed on the velocity fields using a spatial box filter of size Δ = 750 μm and the amount of sub-filter-scale kinetic energy and cross-scale energy flux were quantified on instantaneous and mean basis. Results indicate that instantaneous energy backscatter is more prominent in the presence of the flame, forming a coherent structure at low turbulence intensities and the early stages of combustion. Nevertheless, the flux of turbulent kinetic energy across the filter scale in the presence of the flame is observed to approach that of a non-reacting flow at higher turbulence intensities. These results suggest that premixed flames may affect the mean flux of energy across the filter scale, especially at lower turbulence intensities.
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