【作者】 陆鹏波；

【导师】 王巍；

【作者基本信息】 大连理工大学 ， 流体机械及工程， 2012， 硕士

【摘要】 核主泵,即核反应堆冷却剂泵,是核岛中冷却剂循环的驱动设备。作为核岛中唯一运转的部件,核主泵必须在承受高温、高压、强辐射环境下,能够超长使役安全、可靠地运行。空化空蚀作为水力机械中常见的一种破坏原因,它会引发噪声和振动,使水力机械的性能剧烈下降,严重时还会造成叶片的损坏和断裂。所以空化是核主泵在正常运行或者其他灾变工况下极力避免发生的现象。本文首先对核主泵中的空化与一般的混流泵空化进行了对比分析,表明运用已有的空化模型对核主泵空化进行数值计算的可行性。采用一种基于正压关系的状态方程空化模型对二维naca66(mod)翼型进行了定常和非定常的空化流数值模拟,结果表明模拟值与实验值吻合良好,体现了这种空化模型在模拟空化流的准确性。为了对核主泵中的空化进行深入的分析,对分别采用速度系数法和模型变换法设计的5叶片混流式核主泵叶轮进行了空化性能的计算。结果发现,速度系数法设计的叶轮效率为90.866%,临界空化余量为51.93m。而模型变换法设计的叶轮效率为92.844%,比速度系数法高近2个百分点；临界空化余量为16.35m,比速度系数法相对降低了68.5%。为了改善速度系数法设计的叶轮的空化性能,本文对叶轮结构进行了优化。发现原采用速度系数法设计的5叶片叶轮结构并不合理,泵叶轮设计工况下的临界空化余量较高。针对这一问题,增加混流泵的叶片数目为7片,并以效率和扬程作为目标函数,对7叶片混流泵叶片进口边形状、叶片前缘厚度以及叶片厚度变化规律进行了优化设计。对优化前后三种不同叶片结构方案的叶轮空化性能对比分析结果表明：混流泵叶片进口边适当向进口方向延伸,叶片进口边前缘减薄,以及改变叶片厚度的变化规律,将使混流泵的临界空化余量大大降低。优化设计后的混流泵效率为90.857%,扬程为163.86m,优化后的临界空化余量为28.64m,相比优化前降低了45%,有效地改善了混流泵在设计工况下的空化性能。对今后该类高温高压混流式核主泵的设计和优化有一定的参考价值。最后对优化后的核主泵计算了在0.8～1.2倍设计流量范围内的空化性能曲线。结果表明,随着流量的增大叶轮的临界空化余量明显提高,叶轮的空化性能随之变差。更多还原

【Abstract】 Nuclear reactor coolant pump, usually called nuclear main pump, is the driving equipment in the nuclear coolant cycling system. As the only revolving part in the nuclear islands, nuclear main pump must operate in the long term safely and reliably under the circumstances of high temperature, high pressure and strong radiation. As a common causes of damage in hydraulic machinery, cavitation and erosion make the performance of hydraulic machinery drop steeply with noises and vibrations, seriously, it will cause the damage or fracture of the blades. Therefore the cavitation in nuclear main pump should be avoided at the normal or disaster operations.In this paper, the comparison of cavitation phenomenon is carried out between nuclear main pump and ordinary mixed-flow pump, and the results show that it is feasible to simulate cavitation in reactor coolant pump by utilizing the existing cavitation model. Steady and unsteady numerical simulation are implemented for a2d naca66(mod) hydrofoil based on barotropic relationship model, and the simulation results agree well with the experimental data, that indicates the accuracy of this cavitation model in simulation of cavitating flows.In order to have a further analysis on reactor coolant pump cavitation, the characters of5blades impellers designed by velocity coefficient method and model transformation method are calculated in the cavitating flow conditions. The results show that the two types of impeller efficiency and critical net positive suction head(NPSHcr), are90.866%,92.844%, and51.93m, and16.35m respectively. The deviations of efficiency and NPSHcr between two design methods are nearly2%and68.5%.An optimization process is put into effect to improve the cavitation performances of impeller designed by velocity coefficient method. The result shows that the5blades impeller designed by velocity coefficient method, is not reasonable due to higher NPSHcr under design condition. Consequently, the pump impeller blades inlet edge shape, thickness, and the variation of blades thickness along flowing direction are optimized with objective functions of efficiency and head after increasing the impeller blade number to seven,. Cavitation performances among three types of impeller with different blade structures are compared and analyzed. Some useful conclusions are conducted. The NPSHcr is greatly reduced by extending the blade inlet toward the pump inlet properly, attenuating the blade inlet edge and optimizing the blade thickness. The optimized impeller efficiency and NPSHcr are90.857% and28.64m respectively, and NPSHcr is relatively reduced by45%compared with original5blades impeller. The effective improvement of the cavitation performance at the design condition provides helpful directions for further design and optimization of the reactor coolant pump impeller. Finally, cavitation characters are obtained by numerical simulation within the limits of0.8～1.2times design flow rate, the results indicate that the NPSHcr significantly enhance along with the increase of flow rates, meanwhile, the cavitation performance of the impeller goes worse.更多还原