Transactions of the Korean Society of Pressure Vessels and Piping (한국압력기기공학회 논문집)

Korean Society of Pressure Vessels and Piping (한국압력기기공학회)
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Numerical Analysis on the Transient Load Characteristics of Supersonic Steam Impinging Jet using LES Turbulence Model

LES 난류모델을 이용한 초음속 증기 충돌제트의 과도하중 특성에 대한 수치해석 연구

  • Received : 2018.11.21
  • Accepted : 2018.12.18
  • Published : 2018.12.30
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Abstract

In the case of high-energy line breaks in nuclear power plants, supersonic steam jet is formed due to the rapid depressurization. The steam jet can cause impingement load on the adjacent structures, piping systems and components. In order to secure the design integrity of the nuclear power plant, it is necessary to evaluate the load characteristics of the steam jet generated by high-energy pipe rupture. In the design process of nuclear power plant, jet impingement load evaluation was usually performed based on ANSI/ANS 58.2. However, U.S. NRC recently pointed out that ANSI/ANS 58.2 oversimplifies the jet behavior and that some assumptions are non-conservative. In addition, it is recommended that dynamic analysis techniques should be applied to consider transient load characteristics. Therefore, it is necessary to establish an evaluation methodology that can analyze the dynamic load characteristics of steam jet ejected when high energy pipe breaks. This research group has developed and validated the CFD analysis methodology to evaluate the transient behavior of supersonic impinging jet in the previous study. In this study, numerical study on the transient load characteristics of supersonic steam jet impingement was carried out and amplitude and frequency analysis of transient jet load was performed.

Keywords

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Fig. 1 Qualitative behavior of critical mass flux

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Fig. 2 Schematic of the rupture pipe and target plate

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Fig. 3 Mach number contour of steady-state free jet

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Fig. 4 Snapshot of pressure contour (impinging jet)

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Fig. 5 Snapshot of Mach number contour (impinging jet)

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Fig. 6 Time-averaged impinging force

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Fig. 7 Normalized amplitude(RMS) of impinging force

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Fig. 8 Variation of the jet impingement load with respect to time

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Fig. 9 FFT results (load amplitude vs. frequency)

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Fig. 10 Dominant frequency of the jet impingement load with respect to the axial distance of the target plate

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Fig. 11 Time-averaged impinging pressure

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Fig. 12 Normalized amplitude(RMS) of impinging pressure

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Fig. 13 Normalized amplitude(RMS) of impinging pressure

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Fig. 14 Variation of the impinging pressure with respect to time (R/D=0)

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Fig. 15 FFT results (pressure amplitude vs. frequency, R/D=0)

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Fig. 16 Variation of the impinging pressure with respect to time (R/D=1)

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Fig. 17 FFT results (pressure amplitude vs. frequency, R/D=1)

Table 1 Dominant frequency of the jet impingement load

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Table 2 Dominant frequency of impinging pressure

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References

  1. ANS, 1998, "Design Basis for Protection of Light Water Nuclear Power Plants against the Effects of Postulated Pipe Rupture," ANSI/ANS-58.2-1988(W1998).
  2. USNRC, 2007, "Determination of Rupture Locations and Dynamics Effects Associated with the Postulated Rupture of Piping(Rev.2)," U.S. Nuclear Regulatory Commission, Washington, DC, NUREG-0800.
  3. Wallis, G., 2004, "The ANSI/ANS Standard 58.2-1988: Two Phase Jet Model".
  4. Ransom., V., 2004, "Comments on GSI-191 Models for Debris Generation".
  5. Oh, S., Choi, D. K., Kim, W. T., Chang, Y. and Choi, C., 2017, "Numerical Analysis on Feedback Mechanism of Supersonic Impinging Jet using LES," Trans. of the KPVP, Vol. 13, No. 2, pp. 51-59.
  6. Johnson, R. W., 1998, "The Handbook of Fluid Dynamics," Springer, pp.17-32-17-33.
  7. ANSYS, Inc., 2010, "ANSYS Fluent User Guide".