基于层约束叶片的核主泵空化特性与动力学特性研究

Cavitation characteristics and dynamic characteristics of a nuclear main pump based on the layer constraint of blades

为研究瞬态空化工况下CAP1400核主泵动力学特性,基于层约束设计方法对叶轮叶片进行优化设计,使得产生在后盖板附近的气泡不至快速向前盖板方向发展,即将汽泡发展约束至不同层内。基于雷诺平均动量方程和SST k-ω湍流模型,通过CFX软件对核主泵空化瞬态过程进行定常和非定常数值计算,得到最优层约束叶片模型和空化发展过程中叶轮的瞬态轴向力与径向力变化,对时域信号进行快速傅里叶得到轴向力与径向力的频域特性。模拟结果分析表明:层约束叶片设计能够有效提升泵在小流量工况时的水力效率,而保持其在额定工况区域水力效率基本不变;空化瞬态过程叶轮所受轴向力指向叶轮进口,受空化汽泡带来的叶片表面压力差变化的影响较大;叶轮瞬态径向力合力周向分布规律不受空化程度的影响,而与泵本身的运行状态有关;核主泵在低频范围内径向持续振动明显强于轴向振动,且伴随空化的加剧愈加显著。

In order to study the dynamic characteristics of a CAP1400 nuclear main pump under transient cavitation conditions,the optimization design of blades based on the method of layer constraint was made to ensure the bubbles generated near the back shroud not to develop to the front shroud rapidly and to restrain the development of bubbles only in individual layers. Based on the Reynolds averaged momentum equation and the SST k-ω turbulence model,the steady and unsteady numerical calculation of the cavitation transient process was carried out by using the software CFX. As a result,the optimal layer constrained blade model and the transient axial force and radial force of the impeller during the cavitation were obtained. The frequency domain characteristics of the axial force and radial force were obtained by the fast Fourier transform of time domain signals. The simulation results show that the hydraulic efficiency of the pump can be improved effectively when the blade is in a small flow condition,while the hydraulic efficiency in the rated condition region is still maintained basically unchanged. The axial force of the impeller,which is affected by the surface pressure difference between the blade working face and back,is pointed to the inlet of the impeller during the transient process of cavitation.The radial force circumferential distribution of the impeller is not affected by the degree of cavitation,but is related to the state of the pump. In the low frequency range,the vibration caused by the radial force is stronger than the axial vibration and becomes more and more significant with the strengthening of cavitation.