(40b) Advanced Hydrofoil Impeller Design, ARI-2

Environmental applications require low power high flow impellers with anti-raging properties. The challenge was to design swept back blades that prevent accumulation of fibrous materials while preserving high efficiency. The design effort has produced a high pumping capacity -low power impeller for applications in several industries.  Characteristic impeller constants flow and power number were measured in the laboratory and compared with other impellers.  Power number, N_P, was measured over the turbulent flow regime using a free-floating motor affixed to a load cell.  Flow Number, N_Q, was measured in the turbulent regime using 2D – Particle Image Velocimetry (PIV). Solids suspension and blending performances were evaluated by comparing to standard impellers such as 4PBT45 and hydrofoils. The hydrofoil blades feature a swept back design able to shed and resist fibrous material build ups in waste water treatment (WWTR) applications known as rags.  It was also concluded that the rag shedding ability is sensitive to material surface finish and roughness. The design principles and experimental test data are presented. The impeller features a simplistic design referencing a helix profile to maximize pumping performance along the blade, but also maintain ease of manufacture to reduce production costs.