The presented paper deals with the further development of a clogging-affine impeller with the support of optical high-speed video recordings. Development towards a “guide fin” for improved clogging behaviour is presented in 3 configurations. For configuration 1, functional tests are performed which failed at all operating points, even at light textile load. Evaluation of high-speed videos led to the conclusion that the hub shape is responsible for the initiation of a clogging process. To prevent this initiation, in configuration 2 the hub area is provided with a “guide stick” and a cone positioned on the axis of rotation which deflects incoming textiles to a larger diameter and thus away from the hub. The reperformed functional tests showed a significant improvement of clogging behaviour, especially with light and medium textile loads. However, reconsideration of the high-speed videos showed that the design of the guide stick is unsuitable for higher textile loads. This led to further development of the guide fin (configuration 3), whose reperformed functional tests revealed an impeller that was free of clogging in 11 of 12 test scenarios. It can be shown that the use of an optical access provides the possibility to identify and document the beginning of a clogging event in order to derive specific design modifications that can improve the clogging behaviour of a wastewater impeller.
The presented paper focusses on the clogging behaviour caused by the impeller. Further influencing factors, e.g. the volute, are not considered here.