Flame behavior of a stagnating premixed flame with a vertically impinging vortex tube

The interaction between the premixed flame and vortex tube was investigated experimentally. The vortex tube impinged vertically against the laminar stagnating premixed flame. The vortex tube was formed by rotating the rotational rod which was installed inside the nozzle burner. The flame behavior was observed as a function of the rotational frequency of the rotational rod. The range of the rotational frequency of the rotational rod was varied from 0 rpm to 2000 rpm. The mixture was lean (φ = 0.70) methane/air. The laser tomography method was used, and it gave the two-dimensional time-series flame images. The flame images were binalized to analyze the flame behavior. The unburnt gas velocity along the centerline of the burner was measured by a Laser Doppler velocimetry (LDV). The flame shape became convex to the unburnt gas mixture by the rotation of the rotational rod, and the depth of convex increases with increasing the rotational frequency. The results show three flame behaviors as a function of the rotational frequency of the rotational rod: the stable flame, the oscillating flame, and the double periodic fluctuating flame. The fluctuating flame moved not only up and down but also horizontally. Furthermore, the frequency analysis elucidated the increase in the rotational frequency of the rotational rod increased both frequencies of the unburnt gas velocity and the flame fluctuation. These results indicated the flame behavior was strongly related to the flow field.