Computational fluid dynamics (CFD) was used to analyze the performance of the nuclear main pump gas-liquid two-phase flow under loss of coolant accident. The gas distribution of nuclear main pump, the changing of gas under different gas volume fractions, and the effects of coolant containing gas rate and coolant temperature on nuclear main pump head and efficiency were acquired. The conclusions show that the gas inside nuclear main pump impeller under the accident condition is mainly distributed near the impeller hub area. The gas concentrations gradually increase along the axial direction of impeller, and the gas concentrations gradually reduce along the radial direction of impeller. When coolant containing gas rate is less than 15%, with the increase of coolant containing gas rate, head falls from 113 m to 85 m, efficiency drops from 75% to 65% , but the pump still can work normally. When coolant containing gas rate is more than the performance of the pump falls sharply, head fa'ls down to 48 m, efficiency falls down to 31%, and the pump fails to work. When the coolant temperature is within 270 ℃ and 350 ℃ , efficiency and head seldom change with the increase of coolant temperature, however, when the temperature is more than 350 ℃ , the performance of the pump falls sharply and the main pump cannot operate safely.%针对1000 MW压水堆核电站主泵水力性能要求,在对核主泵进行水力设计和三维造型的基础上,采用CFD技术对失水事故工况核主泵气液两相流进行数值计算,并分析了失水事故工况下的核主泵气体分布,不同空泡份额工况下气体在流道内变化,以及空泡份额、冷却剂温度对核主泵扬程、效率的影响.计算结果表明:事故工况核主泵叶轮内气体主要分布在叶轮轮毂附近区域；沿叶轮轴向方向含气量逐渐增高,而沿径向方向含气量逐渐降低；当空泡份额在15％范围内,随着空泡份额的增加,扬程由113 m降低到85 m,效率由75％下降到65％,但仍能正常工作；当空泡份额大于15％,泵性能急剧下降,扬程下降到48 m,效率也降低到31％,泵丧失正常工作能力；冷却剂温度在270～350℃范围内,随着冷却剂温度增加,效率、扬程变化很小,但当温度超过350℃,主泵的性能急剧下降,致使主泵无法安全运行.
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