Influence of inlet inclined grooves on transient characteristics of axial-flow propulsion pumps during rapid start-up

Abstract:

To improve the transient performance of an axial-flow propulsion pump under rapid start-up conditions and address the drop of head in the saddle region under complex operating environments, this paper proposed a control method for imported inclined groove flow, aiming to enhance the steady-state and transient performance of the pump by optimizing the inflow conditions. Firstly, numerical simulation calculation was conducted on the performance of the axial-flow propulsion pump, and the accuracy of the numerical calculation was verified through experiments. Secondly, the sizes of the inclined groove were designed, and numerical calculations were conducted to investigate the influence of the imported inclined groove on the transient performance of the axial-flow propulsion pump during rapid start-up. Finally, internal flow field analysis was performed to investigate the mechanism of inclined grooves for improving the transient performance of the propulsion pump. The results demonstrate that the inclined groove effectively improves steady-state performance in the saddle zone, achieving a maximum head increase of 56.5%. The rapid start-up process is categorized into four stages based on head evolution: primary development region, saddle region, secondary development region, and stable operation region. The inclined groove improves the drop of head during start-up, with a maximum increase of 27.15%. Localized low-pressure zones in the upstream and downstream of the inclined groove induce reverse flow inside the inclined groove, which is mixed with the main flow to reduce circumferential angular momentum. The optimized inflow conditions improve flow separation, suppress the tip blockage vortex, and reduce pressure fluctuation amplitudes in the rotor-stator interaction zone, thereby enhancing the stability during rapid start-up.