CORRELATION OF SWIRL NUMBER FOR A RADIAL-TYPE SWIRL GENERATOR

An experimental investigation was undertaken to derive a new correlati on for the swirl number of a radial-type swirl generator under various Reynolds numbers and various vane angle conditions. A radial-type swi rl generator with 16 rotary guide vanes was used to generate an annula r swirling jet flow. The Reynolds numbers ranged from 60 to 6000, and the vane angles from 0 degrees to 56 degrees. Quantitative measurement s for the velocities were made by using an optical method of laser-Dop pler anemometry (LDA). Three-component velocity profiles of axial, rad ial, and azimuthal components at the swirling jet exit were measured f or various flow conditions. A flow visualization method using smoke-wi re and still photography was also applied to observe the flow patterns of the recirculation region behind the circular bluff body. Under low Reynolds number conditions, the swirl strength was found to be strong ly dependent on the Reynolds number as well as on the guide vane angle . Based on the experimental results, a modified swirl number S is deri ved to characterize the swirling flow, which is useful for the design of a swirl generator.