CHARACTERISTICS OF TRAILING VORTEX (DISCHARGED WAKE VORTEX) PRODUCED BY A FLAT BLADE TURBINE

The characteristics of the trailing vortex systems generated behind th e blades of a fan turbine (denoted here as discharged wake vortex) wer e elucidated through a simultaneous measurement of the three component s of velocity of the impeller discharge stream. A conditional sampling technique was applied to extract the well developed vortex signals. T otally 373 vortex signals were sampled. It was found that in spite of the scale of the vortex core being small (about one fourth of the impe ller blade width), its rotational and axial velocities reach equal to and higher than the blade tip velocity, respectively. From these resul ts, it was estimated that the discharge velocity of the vortex core is 2.4 times the impeller mean discharge velocity and the kinetic energy carried by the vortex core per unit area is 14.5 times larger than th at of the impeller discharge stream. These results demonstrate how muc h the vortex contributes not only to gas or liquid dispersion but also to mixing in the impeller region.