Investigation of the Influence of Tubercles on the Operating and Cavitation Behavior of an Axial Pump

Previous investigations have already shown the delay of flow separation at critical angles of attack as an effect of tubercles on the flow around airfoils both, numerically and experimentally. However, concerning axial pump impellers, the knowledge about the influence of tubercle modification along the leading edge is not yet sufficient. Therefore, the aim of this investigation is to understand the influence of a sinusoidal tubercle leading edge geometry on the operating behavior as well as the cavitation behavior of an axial pump using numerical and experimental methods. For this purpose, an unmodified reference impeller with a Gö11K profile is designed, which serves as the basis for the impeller modified with tubercles. Using a steady-state simulation, the characteristics of each impeller are investigated. The operating behavior of both impellers is then investigated on a test rig according to EN ISO 9906. The experimental investigations lead to the finding that the presented tubercle modification causes a reduction of the head at part load and an increase at overload. Furthermore, the experiments show that the tubercle modification increases maximum efficiency. The experimental investigation of the cavitation behavior of both impellers shows that the introduced tubercle modification generally leads to the onset of cavitation-induced head drop at significantly lower NPSH values, thus improving the cavitation behavior.