Measurement of the Flow Field of Fire Whirl

In this work, a small-scale fire whirl with pool diameter of 5 cm was produced by a fixed-frame type facility with two split cylinders, and the tangential, axial and radial velocity profiles in the central vertical plane of the fire whirl at different gap sizes (2.54 cm, 3.81 cm, 5.08 cm, 6.35 cm, 7.62 cm) of the two split cylinders were measured using stereo particle image velocimetry. A correction method for the effect of flame wander was developed to obtain velocity profiles corresponding to the characteristics of the instantaneous whirl. The magnitudes of the corrected radial velocity are zero to within experimental error. The whirl consists of an inner vortex core and an outer free vortex and the tangential velocity fits well with the model of a Burgers vortex. The profile of axial velocity follows a Gaussian distribution and the maximum axial velocity appears at the flame center. Moreover, at the vortex core radius, the axial velocity is 0.3 times the maximum axial velocity in the same level.