Study on Natural Circulation Flow Instabilities in Rod Bundle Channel Under Rolling Condition

2020 ◽  
Author(s):  
Kun Cheng ◽  
Jian Deng ◽  
Rong Cai ◽  
Libo Qian ◽  
Peiyao Qi ◽  
...  
Keyword(s):  
Flow Instability ◽  
Natural Circulation ◽  
Experimental System ◽  
Flow Instabilities ◽  
Rolling Motion ◽  
Two Phase ◽  
Rolling Condition ◽  
Rod Bundle ◽  
System Pressure ◽  
Type Oscillation

Abstract The effects of rolling condition on the flow instability characteristics of natural circulation (NC) in rod bundle channel were experimentally studied. A 3 × 3 rod bundle channel is used as the testing section. The experimental system pressure range is 0.2 to 0.6 MPa, and the range of inlet subcooling is 10 to 70 °C. The ranges of rolling motion amplitude and period are 10 ∼ 20° and 10 ∼ 30s, respectively. Two typical two-phase flow instabilities in rod bundle channel under rolling condition were found in experiments: (a) the trough-type oscillation caused by the vapor generation at the minimum point of flow fluctuation and (b) the compound oscillation formed by the superposition of the trough-type oscillation and DWOI. Experimental results show that the rolling motion can reduce the threshold heating power of trough-type oscillation and cause the occurrence of NC flow instability in advance. But the rolling motion cannot affect the dimensionless boundary of DWOI in rod bundle channel.

Experimental Study on Two-Phase Natural Circulation Flow Instability in Rod Bundle Channel Under Low Pressure Condition

2018 ◽  
Author(s):  
Kun Cheng ◽  
Sichao Tan ◽  
Zheng Liu ◽  
Tao Meng
Keyword(s):  
Flow Instability ◽  
Natural Circulation ◽  
Oscillation Amplitude ◽  
Density Wave ◽  
Low Pressure ◽  
Heating Power ◽  
Pressure Condition ◽  
Two Phase ◽  
Rod Bundle ◽  
System Pressure

An experimental investigation was conducted in a natural circulation (NC) loop to study the characteristics of two-phase flow instability under low pressure condition. A 3 × 3 rod bundle channel was used as the test section. The effects of heating power, inlet subcooling degree and system pressure on the two-phase NC flow instability types and stable boundaries were studied. The experimental results show that three typical flow conditions can occur in rod bundle channel under NC condition, which are single-phase NC flow, subcooled boiling NC flow oscillation and density wave oscillations (DWO). The oscillation amplitude and period of DWO can be enlarged by increasing the heat flux. Increasing the inlet subcooling degree can increase the marginal heating power of flow instability in NC system. The occurrence of DWO can be suppressed by increasing the system pressure. The flow instability boundary presented by the subcooling number and phase change number was also obtained in present work.

Non-Linear Time Series Analysis of the Infuence of Rolling Motion on Natural Circulation System

2010 ◽  
Author(s):  
Wenchao Zhang ◽  
Sichao Tan ◽  
Puzhen Gao
Keyword(s):  
Experimental Data ◽  
Time Series ◽  
Time Series Analysis ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Natural Circulation ◽  
Rolling Motion ◽  
Phase Flow ◽  
Two Phase ◽  
Series Analysis

Two-phase natural circulation flow instability under rolling motion condition was studied experimentally and theoretically. Experimental data were analyzed with nonlinear time series analysis methods. The embedding dimension, correlation dimension and K2 entropy were determined based on phase space reconstruction theory and G-P method. The maximal Lyapunov exponent was calculated according to the methods of small data sets. The nonlinear features of the two phase flow instability under rolling motion were analyzed with the results of geometric invariants coupling with the experimental data. The results indicated that rolling motion strengthened the nonlinear characteristics of two phase flow instability. Some typical nonlinear phenomena such as period-doubling bifurcations and chaotic oscillations were found in different cases.

Study on Natural Circulation Flow Instabilities in Rod Bundle Channel Under Rolling Condition

2021 ◽  
Author(s):  
Kun Cheng ◽  
RONG CAI ◽  
Peiyao Qi ◽  
Bingzheng Ke ◽  
deng jian ◽  
...  
Keyword(s):  
Natural Circulation ◽  
Flow Instabilities ◽  
Circulation Flow ◽  
Rolling Condition ◽  
Rod Bundle

Analysis of Flow Stability Boundaries of ERVC System

2013 ◽  
Author(s):  
Fei Li ◽  
Di Jin ◽  
Xiao Jing Liu ◽  
Xu Cheng
Keyword(s):  
Flow Instability ◽  
Natural Circulation ◽  
Thermal Power ◽  
Management Strategies ◽  
Density Wave ◽  
Flow Stability ◽  
Severe Accident ◽  
Two Phase ◽  
System Pressure ◽  
Calculation Results

ERVC is widely adopted as a part of in-vessel retention (IVR) in severe accident management strategies. In this paper, two-phase flow instability in natural circulation loops of external reactor vessel cooling (ERVC) system in a large size power PWR (CAP 1700 with a thermal power 5000 MWt) is simulated and evaluated by the RELAP5 code. Under certain conditions, flow instability of ERVC system are obtained. It is a kind of density wave oscillation that occurs in non-equilibrium boiling in the heat section and void flashing in the riser at low equilibrium quality and low system pressure. The calculation results show such oscillation course clearly. And several parameters affecting the flow stability are discussed.

Study of Surrogate Data Method for Chaos Identification of Natural Circulation Flow Oscillation Under Rolling Motion

2013 ◽  
Author(s):  
Wenchao Zhang ◽  
Sichao Tan ◽  
Puzhen Gao ◽  
Pengfei Zhang ◽  
Yanguang Yang
Keyword(s):  
Time Series ◽  
Flow Instability ◽  
Natural Circulation ◽  
Principal Component ◽  
Surrogate Data ◽  
Circulation System ◽  
Rolling Motion ◽  
Circulation Flow ◽  
Complex Flow ◽  
Two Phase

The identification of chaos in the two-phase natural circulation system under rolling motion can provide theoretical guidance for forecasting and control of natural circulation flow instability. The surrogate-data technique is one of effective methods to identify the chaos in the time series exactly. It can avoid the limitation of the positively identifying chaos. In this paper, correlation dimension and principal component analysis (PCA) was used as the identification evidence; the surrogate-data technique was used for the identification of chaos in time series of the irregular complex flow oscillations. The results indicate that there is chaos in the natural circulation system under rolling motion and the surrogate-data technique can identify chaos exactly.

Research on Two-Phase Flow Instability in Parallel Multi-Channel Under Rolling Motion Condition

2008 ◽  
Author(s):  
Y. J. Zhang ◽  
G. H. Su ◽  
S. Z. Qiu ◽  
X. B. Yang
Keyword(s):  
Two Phase Flow ◽  
Flow Instability ◽  
Stability Boundary ◽  
Channel Number ◽  
Rolling Motion ◽  
Phase Flow ◽  
Two Phase ◽  
Channel System ◽  
Motion Condition ◽  
High Equilibrium

Two-phase flow instability of the parallel multi-channel system has been studied under rolling motion condition in this paper. Based on the homogeneous flow model with considering the rolling motion condition, the parallel multi-channel model is established by using the control volume integrating method. Gear method is used to solve the system equations. The influences of the inlet and upward sections and the heating power on the flow instability under rolling motion condition have been analyzed. The marginal stability boundary (MSB) under rolling motion condition is obtained and the unstable regions occur in both low and high equilibrium quality regions. The region with low inlet subcooling is also instable. In high equilibrium quality region, the multiplied period phenomenon is found and the chaotic phenomenon appears at the MSB. The oscillation part of mass flow rate (amplitude) may be averaged into other channels so that the influence of rolling motion is weakened. But the stability of multi-channel system is independent of the channel number and the increase of the channel number could only make the amplitude more uniformity in channels.

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