Quantitative visualization of the structure of swirl burner flows

The quantitative visualization of swirl burner flows is performed in the present study. A two-dimensional digital laser sheet image processing technique is employed to enhance the qualitative flow visualization images and to obtain quantitative results of the flows. The calibration of the errors due to the distortion of the camera and the nonuniformity of the laser sheet is made. The unsteady characteristics of the jet mixing behavior in the swirling flow can clearly be analyzed from the sequential instantaneous images. In the central fuel jet in weak swirling flow cases, the CTRZ can not be generated. However, because of the effect of the centrifugal force, the jet spread angle in swirling flow is larger than that in nonswirling flow. It is found in the central fuel jet in strong swirling flow cases that the presence of the stagnation region of the recirculation zone has the dominant effect on the jet mixing in the swirling flow. As the axial velocity ratio of the central jet over the annular air is equal to 4.75, the vortex breakdown of the swirling flow will not happen because of the large momentum of the central jet. Better mixing between the jet(s) and the swirling flow can be obtained in the annular fuel jet cases as compared with the central fuel jet cases.