分类： 物理学 >> 核物理学 提交时间： 2025-05-12
Zhang, Dr. Hong
Wan, Dr. Lingfeng
Wang, Dr. Di
Sun, Prof. Wan
Tang, Prof. Simiao
Pan, Prof. Liangming
Zhu, Prof. Longxiang
摘要： Lead-bismuth Eutectic (LBE) is a promising coolant material for next-generation fast reactors. After a Steam Generator Tube Rupture (SGTR) accident in LBE-cooled Fast Reactors (LFRs), the subcooled water enters the high-temperature LBE and generates bubbles, which may impede the flow of coolant, deteriorate core thermal performance and threaten nuclear safety. For the safety analysis of LFRs, it is necessary to carry out experiments to acquire bubble behavior characteristics in molten LBE. In this paper, a gas-liquid LBE two-phase flow experiment was conducted in circular pipes with diameters of 4 cm, 5 cm, 7 cm and 9 cm. First, detailed radial and axial distributions of void fraction, bubble velocity, interfacial area concentration, chord length and bubble frequency were revealed. We found that the void fraction exhibited a core-peak distribution across the flow cross-section. Bubble velocities stabilized beyond 10 pipe diameters downstream, while bubble chord lengths followed a lognormal distribution whose mean and standard deviation increased with axial flow development. The drift velocity initially increased with channel diameter before reaching a plateau. Furthermore, a positive relationship existed between bubble velocity and chord length in the short chord length range, though this correlation diminished for larger chord lengths. Finally, both the mean value and fluctuation amplitude of differential pressure signals showed strong dependencies on void fraction. Distinct Power Spectral Density (PSD) peaks were observed when void fractions equal 0.38 and 0.47, while spectral entropy and low-frequency energy ratio demonstrated systematic relationships with void fraction, providing potential indicators for flow regime identifications.
分类： 物理学 >> 核物理学 提交时间： 2025-04-05
Zhang, Dr. Hong
Wan, Dr. Lingfeng
Wang, Dr. Di
Sun, Prof. Wan
Tang, Prof. Simiao
Pan, Prof. Liangming
Zhu, Prof. Longxiang
摘要： Lead-bismuth Eutectic (LBE) is a promising coolant material for next-generation fast reactors. After a Steam Generator Tube Rupture (SGTR) accident in LBE-cooled Fast Reactors (LFRs), the subcooled water enters the high-temperature LBE and generates bubbles, which may impede the flow of coolant, deteriorate core thermal performance and threaten nuclear safety. For the safety analysis of LFRs, it is necessary to carry out experiments to acquire bubble behavior characteristics in molten LBE. In this paper, a gas-liquid LBE two-phase flow experiment was conducted in circular pipes with diameters of 4 cm, 5 cm, 7 cm and 9 cm. First, detailed radial and axial distributions of void fraction, bubble velocity, interfacial area concentration, chord length and bubble frequency were revealed. We found that the void fraction exhibited a core-peak distribution across the flow cross-section. Bubble velocities stabilized beyond 10 pipe diameters downstream, while bubble chord lengths followed a lognormal distribution whose mean and standard deviation increased with axial flow development. The drift velocity initially increased with channel diameter before reaching a plateau. Furthermore, a positive relationship existed between bubble velocity and chord length in the short chord length range, though this correlation diminished for larger chord lengths. Finally, both the mean value and fluctuation amplitude of differential pressure signals showed strong dependencies on void fraction. Distinct Power Spectral Density (PSD) peaks were observed when void fractions equal 0.38 and 0.47, while spectral entropy and low-frequency energy ratio demonstrated systematic relationships with void fraction, providing potential indicators for flow regime identifications.
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