摘要
核反应堆蒸汽发生器二次侧的流动不稳定现象不仅会影响控制系统,而且会使设备结构的压力边界疲劳损坏。两相流不稳定性的表现形式多样、影响因素众多、机理复杂、研究方法种类多,一直是蒸汽发生器和两相流领域的经典问题之一。首先,该文介绍了两相流不稳定性的常见分类和3种典型不稳定性的机理,包括流量漂移、密度波型脉动和压力降型脉动。其次,从守恒方程出发,总结了各种研究方法。再次,系统性总结了3种典型不稳定性的研究现状,并重点介绍了清华大学核能与新能源技术研究院堆工团队的工作。然后,该文提出了使用新无量纲数描述复杂过热系统,包括两相数、过热数、无量纲泵数和无量纲旁通数,明确和统一了Froude数、摩擦数、管长和管径等对密度波型脉动的影响规律,并解释了此前研究中矛盾的结论。同时,该文给出了有关模型简化和边界条件对稳定边界影响的理论推导和证明,并明确了实验室小规模单管或简化并联管试验段及工程验证试验回路与实际核电厂蒸汽发生器及二回路系统之间的替代条件。最后,该文介绍了高温气冷堆示范工程(high temperature gas-cooled reactor-pebble bed module, HTR-PM)蒸汽发生器如何通过设计来避免不稳定性问题。
[Significance]Two-phase flow instability is a classic problem in the field of steam generators and other two-phase flows.Therefore,it has been studied extensively.In nuclear reactor steam generators,two-phase flow instability may occur on the secondary side and interfere with the control system,causing fatigue-induced damage to the equipment.While two-phase flow instability can have different complex mechanisms and many influencing factors,there are various methods to research and analyze this phenomenon.[Progress]The phenomenon of two-phase flow instability can be classified into two types.The mechanisms of flow excursion(LE),density wave oscillation(DWO)and pressure drop oscillation(PDO)are introduced.LE and PDO can occur in conditions corresponding to the region of negative slope in the hydrodynamic characteristic curve(mass flow rate vs.pressure drop curve)in the heated tube and can be avoided by eliminating the negative slope region.However,DwO can also occur in the positive slope region due to the phase difference between two transient processes.One of these is the mass flow rate variation caused by variation in the driving pressure difference,which is controlled by the rate of momentum transfer.The other is the transient variation of the subcooled water region length and the density of saturated two-phase region fluid,which is caused by heat transfer.Changes caused by heat transfer are slower than changes in flow and pressure.Various research methods of two-phase flow instability are systematically summarized,including the theoretical time-domain method(nonlinear and linear methods),theoretical frequency-domain method,and discrete numerical method,starting from the conservation equations.The mathematical criterion obtained from the theoretical time-domain model can analyze the parameters'influence exactly over a wide range.The spatial distribution of density,enthalpy,and other physical parameters in the frequency domain can be obtained using the theoretical frequency-domain method,and the stability boundary it predicts is more accurate than that predicted by the theoretically simplified linear time-domain method.In addition,the research status of LE,DWO,and PDO is systematically summarized,with a particular focus on the work of our research group.New dimensionless numbers(two-phase number,superheated number,dimensionless pump number,and dimensionless bypass number)are proposed to describe the stability of the complex,superheated,two-phase flow boiling systems.A law unifying the influence of the Froude number,friction number,and geometric parameters(tube length,tube diameter,etc.)on DWO was developed.Previous contradictory conclusions are explained.A rigorous theoretical derivation and proof of the effects of model simplification and boundary conditions are presented.The requirements for conservatively modeling a real nuclear power plant steam generator and secondary loop system using a test section consisting of a single or multiple parallel small-scale heated tubes and a simplified engineering verification test loop in the laboratory are clarified.Finally,methods to avoid LE and DWO in the steam generator of the high-temperature gas-cooled reactor are introduced based on reactor design.To predict the stability of the high-temperature gas-cooled reactor-pebble bed module(HTR-PM)engineering test facility-steam generator(ETF-SG),theoretical time-domain method,theoretical frequency-domain method.RELAP5 model,and one-dimensional transient program are developed,which are in good agreement with the experiments.[Conclusion and Prospects]The results from the ETF-SG can conservatively predict the stability boundary of the steam generator and secondary loop of the HTR-PM nuclear power plant.The conditions for the occurrence of in-phase and out-of-phase DWO in ETF-SG are revealed,and methods for eliminating them are recommended.The above achievements are applied in the design,commissioning,and operation of the HTR-PM steam generator.
作者
苏阳
李晓伟
吴莘馨
张作义
SU Yang;LI Xiaowei;WU Xinxin;ZHANG Zuoyi(Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education,Collaborative Innovation Center for Advanced Nuclear Energy Technology,Institute of Nuclear and New Energy Technology,Tsinghua University,Beijing 100084,China)
出处
《清华大学学报(自然科学版)》
EI
CAS
CSCD
北大核心
2023年第8期1184-1203,共20页
Journal of Tsinghua University(Science and Technology)
基金
国家重点研发计划资助项目(2020YFB1901600)
国家科技重大专项资助项目(ZX06901)。
关键词
高温气冷堆
蒸汽发生器
两相流不稳定性
时域法
频域法
high-temperature gas-cooled reactor
steam generator
two-phase flow instability
time-domain method
frequency-domain method
