小型泵站吸水井进水管位置数值模拟

Numerical simulation of water supply pipe position to intake of small-sized pumping station

为了探究二次供水泵站吸水井内流动不稳定问题,研究了吸水井进水管位置对吸水井及泵吸水管内流动特性影响.采用Ansys-CFX流体仿真软件,对包括吸水井、进水管和泵吸水管在内的水体域进行三维定常数值模拟,对具有相同供水规模但进水管位置布置不同的2个泵站进行计算.分析了水泵进水条件和进水流道水力损失,结合其内部各断面速度分布情况,提出将进水条件差的泵站进水管位置进行更改的方案,并对更改后的水泵进水条件、水力损失以及内部流动情况进行对比分析.结果表明,泵站A吸水井进水管正对泵吸水管,吸水管内存在旋涡和扰流,并且各断面的轴向流速均匀度较小,平均流速偏流角较大,内部流动不稳定,水泵进水条件较差.将该泵站进水管位置分别向相邻2个泵位偏移1.375 m之后,该泵吸水管流道水力损失由6.579 cm分别降为3.301和3.258 cm,各断面处的轴向流速均匀度提高,平均流速偏流角降低,水泵进水条件得到改善.因此,为了改善水泵进水条件的稳定性,在小型泵站设计时应避免吸水井进水管正对泵的吸水管.

To explore the flow instability in an intake of secondary water supply pumping station and study effects of water supply pipe position to the intake on flow patter in pump suction pipes,Ansys-CFX fluid simulation software was used to calculate the three-dimensional steady turbulent flow in the intake. The fluid domain includes the water supply pipe,intake,and a few pump suction pipes. In the simulations,the water supply flow rate was kept the same,and the supply pipe had two positions.Based on the obtained flow condition in the pump suction pipes and the hydraulic loss in the suction pipes as well as the velocity distribution in several cross-sections,an improved design was proposed.The flow condition in that design was checked accordingly. The results show that vortex and flow turbulence exist,and the uniformity of axial velocity is poor as well as the flow average derivation angle islarger in the pump suction pipes of pump intake A,where the water supply pipe is opposite to suction pipe,suggesting an unsatisfactory inlet flow condition to the pumps. When the water supply pipe position was altered to the left and right sides by 1. 375 m,the hydraulic loss in suction pipe was only3. 301 cm and 3. 258 cm,respectively,in comparison with 6. 579 cm loss in the original design. Furthermore,the uniformity of axial velocity increased,and the flow average derivation angle decreased,showing an improved inlet flow condition. Therefore,in order to improve the flow instability at pump inlet,the water supply pipe to the intake should prevent from being rightly against a pump suction pipe.