The Effect of Wear Gap on Cavitation Behavior in Sewage Pump One Channel Impeller

Cavitation is a significant concern in sewage pumps, impacting performance and efficiency. This study explores how different gap configurations; axial gap and radial gap can affect cavitation behavior and pump operation; the investigations were done after designing two different wear rings for the same impeller; one with a radial gap dominant to the axial gap and the other with only an axial gap. The experiments were conducted using a centrifugal pump and a closed-loop test bench with a 2m3 tank connected to a vacuum pump. The setup allowed for measurement of NPSH3% and NPSHic values across various flow rates, cavitation was detected by using an endoscope, a lighting unit and a high-speed camera. The results showed that the radial gap configuration required higher NPSH3% values at higher flow rates compared to the axial gap configuration. At a very low flow rate 0.2 Qopt, both gap configurations exhibited almost similar performance, but as the flow rate increased, the radial gap configuration showed an increase in NPSH values. Furthermore, cavitation inception was observed to occur at higher values for the radial gap configuration compared to the axial gap configuration, also at higher flow rates, the wear ring with radial gap provided less resistance to cavitation initiation. In conclusion, the study highlights how the wear gap could impact cavitation behavior, offering some insight into design changes that could improve sewage pumps performance.