核主泵空化流动对能量转换的影响

为研究核主泵内部空化流动对能量转换的影响,采用RNG k-ε湍流模型和Rayleigh-Plesset空化模型对设计工况下核主泵模型泵进行了全流场空化模拟,得到核主泵发生空化时叶轮内气泡分布规律.选取叶片吸力面的前盖板流线和后盖板流线,通过分析不同空化工况下这两条流线上的动扬程与静扬程变化规律,研究核主泵发生空化时,空化流动对叶轮内能量转换的影响.结果表明:核主泵内流体的能量主要由叶轮中后段提供,且从前盖板到后盖板,叶片做功能力逐渐减弱;空化干扰叶轮内流体流动,导致空化区域相对速度增大,压力减小,在气泡密集区域,叶片做功能力几乎为0;随着空化程度加剧,无空化区动扬程增大,静扬程减小,且静扬程减小幅度大于动扬程增大幅度,从而引起泵扬程和效率下降;随着空化程度加剧,动、静扬程突变程度加剧,增大了叶轮内的流动损失,进而导致泵扬程及效率进一步下降.

Effect of cavitation flow on energy transfer in nuclear main pump

In order to study influences of cavitating flow on energy transfer in nuclear main pumps, the cavitating flow field in a nuclear main pump model was carried out under design condition using the RNG k-ε turbulence and Rayleigh-Plesset cavitation models, then vapour bubble distribution features in the impeller were attained. The influences of cavitating flow on the energy transfer in the impeller were studied under different cavitation conditions by analysing variations of fluid kinetic and sta-tic heads along the two streamlines on the shroud and hub. Results showed that the energy of fluid was provided by the impeller in the middle and after-middle portions of blade, and the working capacity of blades decreased gradually from the shroud to the hub. Cavitation interfered with the flow in the impeller, leading to an increased relative velocity and a decreased pressure in cavities, and the working capacity of blades was almost zero in a zone with dense vapour bubbles. In non-cavitation zones, the kinetic head rose but the static head declined along the streamlines with the development of cavitation. Because the decrease in the static head was greater than the increase in the kinetic head, the pump head and efficiency had to be reduced. In addition, with the development of cavitation, the sudden change in both heads were intensified in the cavitation zones, resulting in an increased hydraulic loss in the impeller, eventually, the pump head and efficiency dropped off even further.