轴流泵站污物过栅泵内缠堵机理、影响与对策

For trash-blockage of a trash rack at entrance of a pumping station, the trash-blockage resistance and trash-cleaning cost could decrease if small trash is allowed to pass through the rack and enter the pump. However, if a lot of trash winds and blocks flow passages in the pump, the pump system performances will deteriorate rapidly—shaft power will increase, and flow-rate and efficiency will decline dramatically. . Experimental observation and measurement, theoretical analysis and numerical simulation will be used in this research project. The process will be studied that typical trash such as water plants and braided fabric passes through the trash rack, inlet conduit or suction sump and axial flow pump of the pumping station. The position, way, scope and mechanism of trash winding and blockage in the pump will be investigated. The relationship between trash winding and blockage and the size, shape and material properties of trash, the size of the impeller passage and blade shape, the passage structures water flowing through and working condition of the pump will be analyzed. The critical conditions of multiple factors will be determined that trash will not wind and clog flow passage in the pump with different impeller diameters. The influences of position and scope of trash winding and blockage on the internal flow field, flow-rate, lift head, shaft power and efficiency of the pump system will be studied and figured out. The measures reducing trash winding and blockage in the pump will be investigated that backflow rushes the blocked trash off when the pump stops, structures of the pump are improved and the trash blocked by the trash rack is cut short with the knives installed on the trash rack. The optimal bar pitch of the trash rack with a low trash-blockage resistance will be determined through which trash passing will not wind and block flow passages in the pump. Therefore, the goals to reduce and avoid trash winding and blockage in the pump and reduce energy consumption of operation, trash-blockage and trash cleaning of the pumping station will be attained. . This research project can reveal mechanism that trash passes through trash rack, winds and clogs in an axial pump and their influences on pump system performances and ensure high efficient and safe operation for the pumping station, and thus has important science and application significance.

泵站进口拦污，允许小污物进入水泵，可减小拦污阻力，降低清污费用。但如果污物在泵内大量缠堵，则泵装置性能急剧恶化，功率增大，流量和效率大幅度下降，结果触目惊心。.项目采用试验观测、理论分析、数值模拟方法，研究水草、编织物等典型污物通过泵站拦污栅、进水流道或进水池和轴流泵的过程；探明污物在泵内缠绕和堵塞的位置、方式、范围和机理；分析缠堵与污物大小、形状、物性和叶轮叶槽大小、叶片形状、过流结构及工况的关系；确定不同叶轮直径轴流泵污物不缠堵的多因素临界条件。研明泵内污物缠堵位置和范围对内流场、流量、扬程、功率和装置效率的影响。研究停机倒流冲堵、改进泵过流结构、拦污切割污物等减堵措施；确定拦污阻力小、通过的污物在泵内不缠堵的拦污栅最优栅距，达到减少和避免泵内缠堵、降低泵站运行和拦污能耗的目的。.项目揭示污物过栅泵内缠堵机理及其对泵装置性能的影响，保证泵站高效、安全运行，具有重要的科学及应用意义。

大型泵站为阻止水草污物进入水泵，保障安全运行，在进口设施拦污。为减小拦污水头损失，需及时清污，清污量大、处理难。如果允许小污物进入水泵，可减小拦污阻力，降低清污费用。但如果污物在泵内大量缠堵，则泵性能急剧恶化，流量和效率大幅度下降。. 针对上述问题，项目主要研究内容：采用试验观测、理论分析、数值模拟方法，研究水草、编织物等典型污物在拦污栅处被拦截或通过、能否进入进水流道、通过进水流道和轴流泵的过程；探明污物在泵内缠绕和堵塞的位置、方式和机理；分析缠堵与污物大小、形状、物性和过流结构及运行工况的关系；研明泵内污物缠堵位置和范围对内流场、流量、扬程、功率和效率的影响；确定污物不缠堵的临界条件，研究减堵措施，确定拦污阻力小、通过污物在泵内不缠堵的拦污栅最优栅距，达到避免泵内缠堵、降低泵站运行和拦污费用的目的。.主要成果：试验单体污物过栅概率：物距比越大，污物过栅概率越小，当物距比达到一临界值后，过栅概率减小很少。水花生、枯树枝、旧布临界物距比分别为3.22、2.5、2.5。理论预测污物拦截概率与实验一致。数值模拟了不同工况进水流道及泵内流场，分析污物运行轨迹；试验得到不同污物从进水流道进口不同位置进入时到达水泵进口的位置，判断是否通过或卡堵及卡堵位置。应用FLOW-3D数值模拟枯树枝由前池到达拦污栅被拦截或通过的过程，结果与实验一致。确定了拦污栅最优栅距。栅前污物堵塞位置和程度对进水流道流态及水力损失有较大影响；泵污物缠堵后，扬程曲线和功率曲线向左下方移动。设计扬程工况，轮毂处缠堵厚度为叶轮直径4.375%、8.75%时，流量减小13.1%、26.9%，效率下降6.68%、7.46%。在提高清污机可靠性、水草切割、进水偏流、进水池旋涡预测、进水影响水泵空化等方面取得了成果。 . 成果已经在南水北调东线工程泵站得到应用。新的发现正在申报下一个基金项目。. 项目揭示污物过栅泵内缠堵机理及其对泵装置性能的影响，提出对策，保证泵站高效、安全运行，具有重要的科学及应用意义。