Single-blade impeller development using the design of experiments method in combination with numerical simulation

This paper concerns the optimization of single-blade impellers as used in the waste-water industry. When considering wastewater pump hydraulics, both the ability to handle solids and hydraulic efficiency become essential criteria for optimization. An innovative approach was taken to this optimization problem through the combination of two separate tools: design of experiments (DOE) and computational fluid dynamics (CFD). Through the use of DOE, it was possible to investigate the effect on hydraulic performance of five key parameters identified as being critical to solids handling. The designed experiment required 32 runs only, as compared with 243 runs (3⁵), which would have been necessary using the traditional 'trial-and-error' approach. For each DOE0 run, unique impeller geometry was created. A transient numerical methodology was adopted for the performance evaluation of each impeller. The methodology was validated and verified on several single-blade impellers covering a range of design specific speed (N_s = 32 to 77). In all benchmark models, excellent agreement with experimental data was observed. The models, resulting from the designed experiment, have advanced the state of the art in terms of single-blade impeller design, quantified relationships between solids handling parameters and led to the development of new higher efficiency single-blade impellers with improved solids handling ability over conventional designs.