叶轮中心淹没深度对特低扬程下立式泵装置流道水力性能的影响

为提高特低扬程泵站立式轴流泵装置的水力性能，该研究对叶轮直径为3.0、2.5、2.0、1.5 m的立式轴流泵装置在不同叶轮中心淹没深度下的进、出水流道流场分别进行了三维湍流流动数值计算，并对流道流场和水头损失进行了分析比较；对某特低扬程泵站在叶轮中心淹没深度为3.08、2.38、1.68 m下的立式轴流泵装置水力性能分别进行了数值计算及比较，并进行了泵装置模型试验验证。研究结果表明：叶轮中心淹没深度对肘形进水流道的水流流态及水头损失的影响很小，但对虹吸式出水流道的流态和水头损失影响较大；随着叶轮中心淹没深度的增大，虹吸式出水流道内的流态逐渐改善，流道水头损失基本呈下降趋势，泵装置效率逐渐增大，特低扬程工况下泵装置模型试验最优工况点的效率达75.92%，泵装置能量性能数值模拟结果与模型试验结果基本一致。研究结果可为特低扬程泵站采用立式泵装置的设计提供一定参考依据。

Influence of the submerged depth of impeller center on the hydraulic performance of flow channel in vertical pump system with extra-low head

Vertical axial-flow pumps have been widely used in the low head pumping station, due to their simple structure, excellent ventilation and heat dissipation, convenient installation, maintenance, and operation. But it is rarely used in the extra-low head pumping station, because the hydraulic performance is less than that of tubular pump. This study aims to improve the hydraulic performance of the vertical axial-flow pump system in the extra low head pumping stations. The numerical simulation was also carried out on the three-dimensional turbulent flow using the Reynolds time mean Naiver-Stokes equation and RNG turbulence model. The flow field of the inlet and outlet channel was calculated in the vertical axial-flow pump system. different submerged depth of the impeller center was selected for each impeller diameter of 3.0, 2.5, 2.0, and 1.5m. Meanwhile, the flow field and hydraulic loss of the flow channel were compared to the hydraulic performance of the vertical axial-flow pump system in the extra low head pumping stations. The submerged depth was set as the pump impeller center of 3.08, 2.38, and 1.68. Finally, the test had validated the simulation. The results show that the submerged depth of the impeller center shared little effect on the flow pattern and hydraulic loss of the elbow inlet channel. The same flow pattern was found in the inlet channel. The hydraulic loss of the channel was basically unchanged under the same impeller diameter and different submerged depths. The flow velocity changed gently and evenly, indicating the orderly turning flow in the elbow inlet channel. There was no bad flow pattern in the elbow inlet channel; There was a large impact of the submerged depth of the impeller center on the elevation arrangement of the vertical axial-flow pump system and the hydraulic performance of the siphon outlet channel. The layout space of the outlet channel increased in the direction of the façade with the increase of submerged depth of the impeller center. The flow pattern was gradually improved in the siphon outlet channel, where the current turned more gently. The hydraulic loss of the siphon outlet channel basically tended to decrease. There was an increase in the efficiency of the pump system. The efficiency was 75.92% at the optimal operating point of the model test under extra low head conditions. The energy performance of the pump system was also consistent with the model test. The increasing submerged depth of the pump impeller center also led to an increase in the investment in the civil engineering of the pumping station. The pumping station can be required to increase the submerged depth of the impeller center, according to the added value of civil investment and the reduced value of operating cost. The finding can provide a sound reference to design the vertical axial-flow pump system in the extra-low head pumping stations.