Investigation on the effect of forward skew angle blade on the hump characteristic in a mixed flow pump using modified partially averaged Navier-Stokes model

A mixed flow pump is regarded as an important power facility in the hydropower field for renewable energy. Pump impeller design shows a great attempt to alleviate the hump characteristic and suppress the severe pressure fluctuations as the mixed flow pumps operate under part-load conditions. In this respect, an advanced turbulence model, i.e., modified SST k-ω partially averaged Navier-Stokes (MSST PANS) model, was adopted to numerically investigate the effect of forward skew angle blade on the hump characteristic using different impeller blades. Both experimental and numerical results indicate that the pump with forward skew angle blade shifts the hump region to the deeper part-load region. In the pump impeller with the forward skew angle blades, a synchronous stall cell is observed near the blade leading edge and near the hub side, while typical rotating stall cell evolution is observed in the conventional pump impeller. Analysis on the blade loading also indicates that under the unstable condition, the forward skew angle blade could switch the mid-loaded distribution to the fore-loaded distribution. Finally, the low frequency pressure fluctuations induced by the rotating stall cell evolution could be also eliminated successfully as the forward skew angle impeller blades are adopted.