Abstract
In the present experimental study, the authors try to clarify the characteristics of the flow around and inside a cross-flow impeller in a typical geometry, over a wide parameter range of an aspect ratio 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. Then, the authors define the outflow rate Q_o but 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 (L/D_2)'s less than unity. As well, ω_<max> attains the maximum value at L/D_2 = 0.6. In addition, at L/D_2 = 0.6, we futher reveal minute fluctuating pressures on an impeller's end wall.
