基于数值试验改善泵站压力水箱内拍门断流性能

The Improvement of Performance on Flow-cutoff of Flap Valves Set in the Pressurized Tank of Pumping Station Based on Numerical Simulation

某大型轴流泵站以压力水箱为出水建筑物,每台泵由并列布置的两扇结构相同、尺寸较小的整体自由式拍门断流,边机组拍门断流性能很差。为改善拍门断流性能,拟对压力水箱内的流场进行数值模拟分析。在泵站停机后压力水箱内的流场CFD数值模拟中,采用Standard k-ε紊流模型与SIMPLEC算法,采用速度进口与自由出流边界条件,按无应力边界条件处理自由水面。以泵站停机拍门断流过程中水泵流量的变化过程为基础设定了3个典型时刻,对泵站停机后压力水箱内的水流流场进行CFD数值试验。对比中间机组与边机组对应的压力水箱内的水流流场,分析了边机组两扇小拍门不同时关闭、后关闭拍门撞击声响很大以及拍门断流性能差的原因。在边机组两扇小拍门之间加设隔墩后,进行了CFD数值试验,与无隔墩情形相比,边机组拍门前水流流态得到了有效调整,从而改善了拍门的断流性能。

Two small free-drop flap valves arranged in parallel for each pump are used as flow-cutoff device in certain large-scale axial flow pumping stations where the pressurized tank was designed as outlet structure.The flap valves of side-set pump has the poorest performance on flow-cutoff in the pumping station.The flow field in the pressurized tank is shown based on numerical simulation in order to improve the flow-cutoff performance of flap valves.The standard k-e turbulence model and momentum equations are solved in the SIMPLEC algorithm with the assumption that the free water surface remains flat as a stress-free plane of symmetry.The velocity distribution and free outflow are prescribed on inlet and outlet boundary respectively.Numerical simulation on the flow field in pressurized tank is done at three typical moments chosen on the basis of the flow variation in the process of shutdown of flap valves.The reason that two flap valves of side-set pump can not be closed simultaneously and the late closing flap valve had a huge force on the wall is analyzed based on the comparison of flow field for side-set pump and middle-set pumps.The result from numerical simulation proves that the division pier with appropriate size which helps to improve the flow distribution uniformity is valid for the two flap valves of side-set pumps to close simultaneously.