Compared with the periodic unsteady flow induced by single-stage centrifugal pump, the internal flow state of multistage centrifugal pump is more complicated and the flow is more disordered. In this paper, the start-up process is divided into two stages: the closed-valve transition and the open-valve transition. The transient operation process is simulated numerically, and the pump characteristics and the evolution characteristics of the internal flow field are analyzed. It is found that multistage centrifugal pump start-up process of the closed-valve transition, when the impeller does the same work, compared with the steady state at the same speed, the mechanical energy in the internal flow field is converted into more kinetic energy and less pressure. Compared with the steady state at the same flow rate, in the initial stage of the open-valve start-up process, the stall group in the impeller flow channel is larger and the number of stall groups is more during the transient process, which exacerbates the rotational stall of the internal flow of the impeller, and the flow is more disordered. As a result, the amplitude of the hump fluctuation is greater than that under the same flow steady state. The research on the transient characteristics of the low specific speed multi-stage centrifugal pump during startup conditions is of great significance to the safety and reliability of nuclear power equipment and systems.

与单级离心泵引起的周期性非稳态流动相比，多级离心泵的内部流动状态更加复杂，流动更加混乱。在本文中，启动过程分为两个阶段：闭阀过渡和开阀过渡。数值模拟了瞬态运行过程，分析了泵的特性和内部流场的演变特性。发现闭阀过渡的多级离心泵启动过程中，当叶轮做相同的功时，与相同速度下的稳态相比，内部流场中的机械能转化为更多的动能。和更少的压力。与相同流量下的稳态相比，在开阀启动过程的初始阶段，叶轮流道中的失速组更大，在过渡过程中失速组的数量更多，这加剧了叶轮内部流动的旋转失速，而且流动更加混乱。结果，驼峰波动的幅度大于在相同流动稳态下的波动幅度。低比转速多级离心泵启动过程瞬态特性的研究对核动力设备及系统的安全性和可靠性具有重要意义。而且流动更加混乱。结果，驼峰波动的幅度大于在相同流动稳态下的波动幅度。低比转速多级离心泵启动过程瞬态特性的研究对核动力设备及系统的安全性和可靠性具有重要意义。而且流动更加混乱。结果，驼峰波动的幅度大于在相同流动稳态下的波动幅度。低比转速多级离心泵启动过程瞬态特性的研究对核动力设备及系统的安全性和可靠性具有重要意义。