转速对核主泵空化特性的影响

Effect of rotating speed on cavitation performance of nuclear reactor coolant pump

为研究转速对核主泵空化性能及进口流态的影响,应用理论分析、数值计算和试验研究的方法,对AP1000核主泵进行不同转速下的数值模拟和空化试验,得到3种频率30,40,50 Hz下不同流量(0.7Qd,1.0Qd,1.3Qd)时的空化特性,并对叶轮进口截面静压分布与泵流动性能的影响关系进行分析.结果表明:转速对小流量工况下泵的空化性能影响较大;随着转速的降低,小流量工况下,空化性能曲线趋势变化比大流量工况下明显;在不同转速的额定流量下,转速较大时,模型核主泵在装置临界空化余量(NPSHC)减小时更容易接近临界空化状态;在转速较小时,临界空化余量(NPSHC)较小,且一旦发生空化,其扬程曲线斜率下降也相对平缓;在额定转速下,模型泵在大流量时更容易接近临界空化状态;随着转速和流量的减小,更容易造成模型泵在开始试验阶段进口处产生回流,扰乱进口的流场,从而造成局部空化严重.

To study the effect of the rotating speed on cavitation performance and inlet flow pattern of the nuclear reactor coolant pump,the numerical simulation and cavitation test at different speeds were conducted for AP1000 nuclear reactor coolant pump by using theoretical analysis,numerical calculation and experiments,then cavitation characteristics with different frequences（ 30,40,50 Hz） and different flow rates（ 0. 7Qd,1. 0Qd,1. 3Qd） were obtained. The relationship between the static pressure distribution of the impeller inlet section and flow performance of the pump was analyzed. The results show that the rotating speed has a greater impact on pump cavitation performance under low flow conditions. With rotating speed reduced,cavitation trend curve change under low flow conditions is more apparent than under high flow conditions. The model can more easily get access to critical cavitation when the NPSHC reduced at a high rotating speed under rated flow at different rotating speeds.The NPSHC is lower when the model pump is at a low rotating speed,and the slope of lift curve declines slowly in cavitation. At a rated rotating speed,the model pump in high flow more easily gets ac-cess to the critical cavitation. With the rotating speed and flow decreasing,the flow rate decreases,a reflux at the inlet of the model at the beginning of the pilot phase is caused,which disrupts the inlet flow field,thus resulting in local severe cavitation.