Combined application of OH PLIF, HCHO PLIF and stereo PIV to a turbulent premixed swirling flame Free

This paper reports on the investigation of coherent structures in a high-swirl jet with vortex breakdown (Re = 5 000) and combustion of a methane/air mixture (with equivalence ratio equal to 0.7 and 1.4). The measurements were performed by combined application of the stereo PIV, OH PLIF and HCHO PLIF techniques. The velocity data were processed by the proper orthogonal decomposition (POD) and the PLIF data was conditionally sampled according to the POD correlation coefficients. For the non-reacting jet and lean flame, the POD has revealed presence of a coherent structure, consisted of helical vortex structures in the inner and outer mixing layers. Based on the PLIF data it was found that the inner spiraling vortex structure was correlated with positive fluctuations of the local heat release.