空化过程对核主泵外特性变化的影响与分析

为研究空化发展对核主泵外特性及内部流场的影响,基于连续性方程、雷诺时均N-S方程和RNG k-ε湍流模型,对核主泵模型泵在设计工况下进行全流场空化模拟.研究中选择四种空化工况,通过对比模拟结果,得出核主泵在发生空化时,其性能变化规律及内部流场变化规律.模拟结果表明:核主泵发生空化时,泵的外特性对有效空化余量降低的敏感程度不同.随着空化程度的加剧,扬程下降最快,功率下降最慢.空化状态下,由于空化产生的气泡对叶轮流道产生排挤作用,使得过流断面面积减小,流体相对速度增大.此外,由于空化产生的气泡改变了空化区域流体状态,使流体动力黏度减小,导致空化区域湍流耗散率减小,湍流耗散损失降低.

Study on the influence of cavitation on the performance of reactor coolant pump

In order to study the effect of cavitation development on the external characteristics of a nuclear main pump and related internal flow region, this study, based on the continuous equation, the Reynolds time-average N-S equation and the RNG k-ε turbulence model, simulates cavitation behaviors occurred in full-flow region of a nuclear model pump under the design condition. Four cavitation conditions were selected in the study. By comparing simulation results with each other, the performance variation and the variation of internal flow region of the nuclear main pump were predicted when cavitation occurred. The simulation results show that when the nuclear main pump is cavitated, the external characteristics of the pump are sensitive differently to reduction of the effective airspace margin. As the degree of cavitation increases, the head decreases sharply and the power decreases more slowly. In cavitation state, the area of flow section is reduced and the relative velocity of fluid is increased due to the squeezing effect of air bubbles generated by cavitation on the flow path of impeller. In addition, because the bubbles generated by cavitation change the fluid state in the cavitation region and decrease the hydrodynamic viscosity, the turbulent dissipation rate and the turbulent dissipation loss in the cavitation region are reduced respectively.