立式管道泵断电过渡过程内流特性分析

为探究立式管道泵断电过渡过程中内部不稳定流动特性,采用数值模拟的方法,结合Fortran语言编程对CFX进行二次开发,利用角动量微分方程预测了转速变化规律,分析了管道泵断电过渡过程中流量、转速等参数及内流场的变化规律.研究结果表明:断电后转速从正向转速逐渐减小变换为反向转速并增大达到飞逸转速(n_max=1.206 n₀);转速与流量之间存在延迟,前者比后者延迟1.24 s到达零点;压力脉动幅值在飞逸阶段达到最高值;过渡过程初期在进口肘型弯管叶轮流道及蜗壳内产生多个旋涡,中期旋涡逐渐消失,内部流态趋于平稳,后期在第2弯管内侧和叶轮进口边出现小旋涡.研究揭示了管道泵断电停机过渡过程中的内流瞬态特性,为管道泵停机过程的安全运行提供了理论基础.

Analysis of flow characteristics of vertical inline pump during shutdown transition process caused by power failure

In order to explore the inner unsteady flow characteristics of the vertical inline pump during the power-off transition process, the numerical simulation method coupled with a Fortran program based on the commercial CFD code CFX was adopted to predict the flow motions in the pump. The angular momentum differential equation was used to predict the variation law of the rotating speed. The flow rate, rotating speed and other parameters as well as the flow velocity distributions during the transient process of the power-off and shutdown of the pump were analyzed. The results show that after power failure, the speed gradually decreased from positive speed to reverse speed and increased to runaway speed(n_max=1.206 n₀). There was a delay between the speed and the flow rate, the former reached the zero point 1.24s later than the latter; the amplitude of pressure pulsation reached the hig-hest value in the runaway stage. At the beginning of the transition process, several vortices were observed in the inlet passage, impeller channel and volute. In the middle stage, the vortex gradually disappeared, and the flow pattern tended to be stable. In the later stage, small vortices appeared in the inner side of the second bend and the outlet of the curved inlet pipe. The research reveals the transient flow features in the process of the inline pump shutdown, which provides a fundamental theory for the safe operation of pump shutdown.