A study of turbulent partially premixed flames based on simultaneous imaging of velocity field and OH radical

Turbulent partially premixed methane flames stabilized in a concentric flow conical nozzle burner have been investigated and presented in this work. The flames are classified in the thin reaction zones regime. The flames were investigated experimentally based on simultaneous measurements of the velocity field and OH-radical. A combined planar imaging velocimetry (PIV) and laser-induced predissociation fluorescence (LIPF) technique was applied. The mean, rms, and instantaneous structure of four flames are presented and discussed in this article. High stability of the investigated flames is partially due to the partial premixing of the jet and mainly to the flow divergence created by the conical nozzle. This creates a stabilization core with lower mean velocity at the center and lower rms of the velocity fluctuations at the flame brush. No significant recirculation could be observed within the stabilization core above the conical nozzle tip. The reaction zone structure in the present partially premixed flames is likely to show double reaction zones in all flames that support earlier theory and experiments.