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核主泵是反应堆冷却剂系统的主要设备和压力边界的设备之一,对安全可靠性要求极高。由于核主泵叶轮与导叶的动静干涉作用,以及运行过程中偏离设计工况时,其流道内流体会产生非常复杂的压力脉动,并会对核主泵水力单元零部件产生复杂的附加动态应力而导致疲劳破坏。为提高核主泵的安全可靠性,采用对混流式核主泵进行全流道非定常数值模拟途径来探究核主泵水力单元,在不同运行工况下的瞬态流场,通过研究叶轮、导叶流道压力的时域变化规律,并利用快速傅里叶变化的频域分析方法对压力脉动特性进行特点分析。结果表明:在设计工况下压力脉动幅值最小,若运行工况的流量远远低于设计工况,流道内的压力脉动幅值将大幅度上升,压力脉动最为剧烈点位于叶轮出口。流量的减小对叶轮出口流动影响较小,但对叶轮进口影响较大。压力脉动的频率与叶轮叶片数和导水机构的导叶数有关,叶轮与导水机构的压力脉动主要发生在主频及谐波位置,且为低频压力脉动。
The nuclear main pump is one of the major equipment and pressure boundary equipment of the reactor coolant system, and it requires extremely high safety and reliability. Due to the static and dynamic interference between the main pump impeller and the guide vane and the deviation from the design conditions during operation, the fluid in the flow passage will have very complicated pressure pulsations and will generate complicated additional dynamics on the components of the hydraulic unit of the nuclear main pump Stress caused fatigue damage. In order to improve the safety and reliability of the nuclear main pump, the unsteady numerical simulation of full flow channel of Francis core main pump was used to explore the transient flow field of hydraulic unit of nuclear main pump under different operating conditions. The time-domain variation of guide vane flow pressure is analyzed. The characteristics of pressure pulsation characteristics are analyzed by using the fast Fourier transform frequency-domain analysis method. The results show that the pressure pulsation amplitude is the smallest under the design conditions. If the flow rate in operation condition is much lower than the design condition, the pressure pulsation amplitude in the runner will increase drastically and the pressure pulsation will be the most intense at the exit of the impeller. The decrease of flow has little effect on the outlet flow of the impeller, but it has a great influence on the import of the impeller. The frequency of pressure pulsation is related to the number of impeller blades and the number of guide vanes of the guide mechanism. The pressure pulsations of the impeller and the guide mechanism mainly occur at the fundamental frequency and the harmonic position, and are low-frequency pressure pulsations.