Parametric study on improving stability of axial-flow pumps with self-circulating casing
In order to explore ways to effectively expand the stable operating range of axial-flow pumps,a single-channel steady numerical simulation of the self-circulating casing treatment was carried out on an axial-flow pump to analyze the influence of the circumferential coverage ratio,suction port position and throat height on the expansion and stability performance of water pumps,and to as well reveal the influence law and improvement mechanism of the self-circulating casing on the expansion and stability of axial-flow pumps.The results show that the self-circulating casing can effec-tively expand the flow range of the axial-flow pump,keeping the position of the suction port un-changed,increasing the circumferential coverage ratio and throat height can increase the flow margin,but the design point efficiency is reduced.The flow margin of the self-circulating casing with a throat height of 1.8 mm first increases and then decreases with the backward movement of the suction port po-sition,and the efficiency first decreases and then increases,indicating that there is an optimal position above the blade tip.Within the scope of the study,the flow margin reaches a maximum of 5.93%,and the efficiency at the design point is reduced by a minimum of 1.12%.Through the self-circulating ca-sing treatment,the area of the blockage area formed by the interaction between the blade tip leakage flow and the main flow above the blade tip is reduced,which is responsible for the extended flow range and increased efficiency of the axial-flow pump for small flow conditions.This study provides a reference for the expansion and stability of axial-flow pump under the end wall treatment of self-circulating casing.
axial-flow pumpself-circulating casing treatmentflow margindesign point efficiencytip leakage flow
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