立式轴流泵出水流道流场试验研究

EXPERIMENTAL INVESTIGATION ON FLOW FIELDS IN OUTLET DIVERGENT PASSAGE OF VERTICAL AXIAL-FLOW PUMP

大型低扬程水泵采用渐扩出水流道,比水流道水力损失占泵扬程的15%～20%左右。为立式轴流泵设计制作了不同扩散角、无中隔板和有中隔板多种透明出水流道,采用五孔探针测定和丝线观测出水流道内流场,研究流场形成机理,分析流动规律,并与等圆出水管内流动比较。结果表明,由于后导叶出流环量、泵轴旋转诱导、出水弯管二次流和扩散的影响,出水流道内为复杂的螺旋流,断面轴向流速和周向流速分布不均匀、不对称,不均匀程度大于等圆出水管内流动,断面环量有向周边集中的趋势。成果对大型轴流泵装置出水部分的优化水力设计,提高泵装置效率有重大意义。

Outlet divergent passages are adopted in large, low head pumping stations whose hydraulic losses are 15%～20% of pump water head. Several divergent angle clear outlet divergent passages with central partitions and without partitions are designed and made for vertical axial-flow pump, in which flow fields are measured and determined with five-hole probes and visualized with ligament. Formation mechanism of the flow is studied and flow regularity is analyzed, which is compared with the flow in pump outlet circle pipe. The results indicate that： under the influence of the outlet circulation of guide vane, induction of pump axis, secondary flows in the outlet curved pipe and the divergence of the passage, the flow in the passage is complex spiral flow. The axial and circumferential velocities of the flow on cross sections of the passage are neither even nor symmetrical, and more uneven than that in the outlet pipe, the circulation on the section has a tendency of concentrating to outer areas of the section. Results mean much to optimum design of outlet parts of large axial-flow pump assemblies and increasement of pump assembly efficiency.