A Numerical Investigation into the PAT Hydrodynamic Response to Impeller Rotational Speed Variation

The utilization of pump as turbines (PATs) within water distribution systems for energy regulation and hydroelectricity generation purposes has increasingly attracted the energy field players' attention. However, its power production efficiency still faces difficulties due to PAT's lack of flow control ability in such dynamic systems. This has eventually led to the introduction of the so-called variable operating strategy or VOS, where the impeller rotational speed may be controlled to satisfy the system-required flow conditions. Taking from these grounds, this study numerically investigates PAT eventual flow structures formation mechanism, especially when subjected to varying impeller rotational speed. CFD-backed numerical simulations were conducted on PAT flow under four operating conditions (1.00 Q(BEP), 0.82 Q(BEP), 0.74 Q(BEP), and 0.55 Q(BEP)), considering five impeller rotational speeds (110 rpm, 130 rpm, 150 rpm, 170 rpm, and 190 rpm). Study results have shown that both PAT's flow and pressure fields deteriorate with the machine influx decrease, where the impeller rotational speed increase is found to alleviate PAT pressure pulsation levels under high-flow operating conditions, while it worsens them under part-load conditions. This study's results add value to a thorough understanding of PAT flow dynamics, which, in a long run, contributes to the solution of the so-far existent technical issues.

Automated summary

This study investigates the flow structures formation mechanism of PATs under varying impeller rotational speed through CFD-backed numerical simulations. The results show that PAT flow and pressure fields deteriorate with decreasing machine influx, with increased impeller rotational speed alleviating pressure pulsation levels under high-flow conditions but worsening them under part-load conditions. These findings contribute to a better understanding of PAT flow dynamics and help in solving existing technical issues in the long run.