Abstract
In the present experimental study, the authors try to reveal the effects of the aspect ratio L/D_2 upon the flow around and inside a cross-flow impeller, over a wide parameter range of L/D_2. In order to eliminate the complicated casing factors, the impeller rotates in open space without any casings. As a result, by using hot-wire-anemometer measurements and by conventional flow visualisations, the authors divide the flow around the impeller into three areas, and observe the eccentric-vortex revolution inside the impeller. Using a particle-image-velocimetry technique, the authors quantitatively show velocity distributions, whose accuracy is checked in comparison with the hot-wire-velocimetry results. In addition, the authors define.the outflow rate Q_o out of the impeller and the maximum vorticity ω_<max>. To conclude, the aspect ratio effect upon the outflow-rate coefficient C_<Qo> is not negligible at aspect ratios less than unity. As well, ω_<max> attains the maximum value at L/D_2=0.6.
