Matthias SteffenPaul Uwe Thamsen&nbsp;The increasing load of textiles and fibrous material in wastewater poses special challenges for today's wastewater pumps. A special focus is on the design of the corresponding impeller used. This has a decisive influence on the clogging tendency of a wastewater pump and is of particular interest.At the Chair of Fluid System Dynamics at Technische Universität Berlin, a test rig was developed for investigations of dry-installed wastewater pumps up to a size of DN 250. With the help of artificial wastewater, the clogging behaviour of wastewater pumps can be investigated in a long-term clogging test. The results of these test describe the clogging tendency of a wastewater pump, but it is difficult to draw conclusions about the clogging mechanisms and its sources. Previous studies show that the design aspects of an impeller like hub-, impeller- or blade design play a major role in the clogging behaviour of a wastewater pump. Crucial here is also the question of the beginning of the clogging event, which currently remains unanswered.In order to give a further inside into the actual clogging process and to observe the interaction between impeller and textile, the test rig is equipped with an optical access and a high-speed camera. This allows observations of the impeller in interaction with textiles.To realize such high-speed videos, special requirements for the optical access are necessary. The optical access is realized with an endoscope. With a diameter of 10 mm, it is positioned at an angle of 45 degrees to the flow in order to influence the flow to the pump as little as possible. The high-speed camera is connected to the endoscope via a lens. In order to take smooth pictures at a motor speed of 1500 1/min, at least 1000 pictures per second are necessary. One major challenge is to provide enough light for the camera, because the endoscope provides only little light due to its small design. This was realized with 12 LEDs which are arranged in a ring in front of the suction side of the pump. Each LED has an output of 5500 lm which provides sufficient light for the camera.The described setup allows a deeper insight into the interaction between impeller and textile in order to identify the design aspects of the impeller in detail. These studies will provide a contribution for future design developments of wastewater impellers.

Visualisation of Interactions Between Impeller and Textile in a Wastewater Pump

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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