| 摘要 |
The invention relates to an improvement of a spiral aerator according to DE-C 2461032 which is used in particular for aerobic-biological cold or thermophilic treatment of waste waters. At the free end of its hollow shaft, it carries a propeller composed of at least two screw-shaped spirals evenly distributed about the periphery of the shaft. At this end, which is to be submerged, an ejector action occurs at an axial gas outlet orifice as a result of the liquid flow directed through the spiral towards the end of the hollow shaft. The spirals which are concave at the front side have transition surfaces running from each of these front surfaces to the backs of the leading spirals in the direction of rotation, so that concave-curved vortex chambers are formed, in which string-shaped vortices are axially and centrifugally accelerated. As a result of particular shaping and arrangement of the transition surfaces and spirals towards the hollow shaft and axially beyond the gas outlet orifice, spreading out of the string-shaped vortices at the shaft end is prevented, the vortices meeting at a certain distance from the hollow shaft end in a node.
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