Instability Analysis of Once-Through Steam Generator

2013 ◽  
Vol 756-759 ◽  
pp. 4596-4599
Author(s):  
Su Xia Hou ◽  
Ji Jun Luo ◽  
Jun Xu ◽  
Qing Hua Zhang
Keyword(s):  
Frequency Domain ◽  
Steam Generator ◽  
Moving Boundary ◽  
Stability Boundary ◽  
Feedback System ◽  
Frequency Domain Analysis ◽  
Frequency Domain Method ◽  
Two Phase ◽  
Instability Analysis ◽  
Major Factors

Considering the characteristic of Once-Through steam generator, the simplified dynamic model with lumped parameters moving boundary is used to describe two-phase flow feedback system in this paper. The feedback system and transfer-function for instability analysis are derived from the model. The instability analysis of the system is based on the frequency-domain analysis method. The Matlab software and its simulink tools are used to analyze the instability of the system. Then the stability boundary under the effect of some major factors is obtained. The results of stability boundary are compared to the concerned experiments by frequency-domain method.

The application of pulsation ratio preprocessing method in researching density wave instability

2018 ◽  
Vol 10 (3) ◽  
pp. 140-145
Author(s):  
Yefei Liu ◽  
Yang Liu ◽  
Xingtuan Yang ◽  
Haijun Jia
Keyword(s):  
Frequency Domain ◽  
Density Wave ◽  
Annular Channel ◽  
Frequency Domain Analysis ◽  
Wave Instability ◽  
Two Phase ◽  
Transform Method ◽  
Modified Method ◽  
Fast Fourier Transform Method ◽  
Dc Component

A modified Fast Fourier Transform method based on the pulsation ratio preprocessing is carried out in this study. When the density wave instability occurs, the method is applied to capture the characteristic signals in the frequency domain. Thus, the stable boundary in two-phase flow can be recognized accurately. In this paper, experiments are conducted in a system based on a narrow annular channel. The method is verified through two groups of experimental data collected in different conditions. The results indicate that the modified method can avoid the problem of DC component spectrum leakage in traditional frequency-domain analysis with the false value interference eliminated. Accordingly, it can improve the accuracy of boundary identification effectively when the instability occurs.

Frequency-Domain Analysis for Prediction of Seasickness on Ships

2005 ◽  
Vol 42 (04) ◽  
pp. 192-198
Author(s):  
Segundo Esteban ◽  
Jose M. Giron-Sierra ◽  
Joaquin Recas ◽  
Jesus M. De la Cruz
Keyword(s):  
Mathematical Model ◽  
Frequency Domain ◽  
Transfer Functions ◽  
Frequency Domain Analysis ◽  
Ship Design ◽  
Ship Motion ◽  
Frequency Domain Method ◽  
Motion Data ◽  
Response Amplitude Operators ◽  
The Mathematical Model

Oscillatory vertical motions of ships cause seasickness. There is a mathematical model that can be used to compute the percent of passengers who will get sick caused by vertical motions. However, the application of the mathematical model requires obtaining 2 hours of records of experimental or simulated ship motion data. Based on a filters analogy, this article proposes a new frequency-domain method for the calculation of seasickness incidence. The method can be applied to any sea power spectrum and any ship. Because it is based on response amplitude operators or transfer functions, which can be obtained with seakeeping simulation programs, the method can be applied even before the ship is built. The results of the method can be useful for ship design and for the analysis of best operation for passenger comfort.

Comparison of Time and Frequency Domain Analysis With Full Scale Data for the Horn Mountain Spar During Hurricane Isidore

2006 ◽  
Author(s):  
Arcandra Tahar ◽  
John Halkyard ◽  
Mehernosh Irani
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Full Scale ◽  
Frequency Domain Method ◽  
Drag Forces ◽  
The Time Domain ◽  
Scale Data

The Horn Mountain Spar is located in 1,654 m of water about 135 km from Venice, Louisiana in the Gulf of Mexico. The facility was instrumented extensively to measure key spar and riser response parameters (Edwards et. al. 2003). Halkyard et. al. (2004) and Tahar et. al. (2005) have compared measured spar responses such as motion and mooring line tensions with numerical predictions. This paper extends the work done on comparison of the full scale data during hurricane Isidore. All previous numerical simulations were based on a time domain analysis procedure. One concern related to this method is that it is computationally intensive and time consuming. In the initial stages of a project, a frequency domain solution may be an effective tool compared with a fully coupled time domain analysis. The present paper compares results of time domain and frequency domain simulations with field measurements. Particular attention has been placed on the importance of the phase relationship between motion and excitation force. In the time domain analysis, nonlinear drag forces are applied at the instantaneous position. Whereas in the frequency domain analysis, nonlinear drag forces are stochastically linearized and solutions are obtained by an iterative procedure. The time domain analysis has better agreement with the field data compared to the frequency domain. Overall, however, the frequency domain method is still promising for a quick and approximate estimation of relevant statistics. With advantages in terms of CPU time, the frequency domain method can be recommended as a tool in pre-front end engineering design or in a phase where an iterative nature of design of an offshore structure takes place.

A Moving Boundary Analysis for Start-Up Performance of a Nuclear Steam Generator

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
S. Paruya ◽  
P. Bhattacharya
Keyword(s):  
Heating Rate ◽  
Void Fraction ◽  
Steam Generator ◽  
Moving Boundary ◽  
Density Wave ◽  
Flow Reversal ◽  
Phase Zone ◽  
Two Phase ◽  
Boundary Analysis ◽  
Start Up

Thermohydraulic phenomena of a steam-water natural-circulation (SWNC) system are very complicated, particularly, during its start-up and shutdown. Its performance strongly depends on the circulation inside it. Accurate quantification of the flow, void fraction, two-phase level, boiling boundary, etc., is difficult at both steady state and transient states like load variation, start-up, and shutdown. Attempts have been made to develop a high-fidelity thermohydraulic model (five-equation scheme) that caters to nonhomogeneous and thermal nonequilibrium flow to derive the dynamic effect of heating rate on the performance of the SWNC loop of steam generator of an Indian nuclear reactor during steaming-up period. The proposed work also attempts to predict boiling height, flow reversal, and density-wave oscillation (DWO). The boiling channel of the SWNC loop is modeled based on the moving boundary analysis using finite volume method. In this moving boundary problem, both control volumes of single-phase zone and two-phase zone change with time. Numerical results have been presented in this paper. The results indicate that both circulation flow variation and two-phase level variation in steam drum have strong dependency on void fraction in the boiling channel. Flow-reversal phenomenon is identified during the initial stage of boiling. Two-phase swelling and collapse that occur during the start-up are predicted. Above a critical heating rate, DWO has been observed. All these phenomena have been explained.

Frequency-domain analysis of intermittent control

2009 ◽  
Vol 223 (5) ◽  
pp. 591-603 ◽  
Author(s):  
P J Gawthrop
Keyword(s):  
Frequency Domain ◽  
Balance Control ◽  
Design Method ◽  
Feedback System ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Theoretical Explanation ◽  
Intermittent Control ◽  
Sampled Data ◽  
Data Feedback

Intermittent control is a feedback control design method that combines both continuous-time and discrete-time domains. A recent result shows that this form of intermittent control can be rewritten as a sampled-data feedback system with a particular vector generalized hold. This paper builds on this result to give, for the first time, a frequency-domain analysis of the closed-loop system containing an intermittent controller. This analysis is illustrated using two examples. The first example is related to the human balance control system and is thus physiologically relevant. The second example gives a theoretical explanation of the phenomenon of self-induced oscillations in intermittent control systems.

Analysis of Two-Phase Flow Instability for Steam Generator

2008 ◽  
Author(s):  
Su-Xia Hou ◽  
Yun Tai ◽  
Fu-Yu Zhao
Keyword(s):  
Steam Generator ◽  
Nuclear Reactor ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Computer Code ◽  
Frequency Domain Method ◽  
Phase Flow ◽  
Steam Generators ◽  
Two Phase ◽  
The Stability

Two-phase flow instability is an important problem that affects the running of steam generators in nuclear reactor systems. In this paper, two-phase flow instability in parallel channels of a steam generator are analyzed to disclose the mechanism of flow instability by using the frequency domain method. The mathematical expressions of heat transfer and flow for a steam generator are proposed, and the transfer function of the closed-loop system is deduced by using linearization and Laplace transfer. The steam generator’s stability is judged according to Nyquist stability criterion. Depending on this fundamental principal, the computer code is developed to analyze the stability of steam generators. The results displayed two conclusions; firstly, the increase of inlet orifices or mass flow rate enhances the stability of generator steam; secondly, the coupling interactions between channels and their external loop effects on the stability of generator steam are not ignored. The result show that the effects are non-monotonic on the stability of generator steam.

Study on two-phase flow instabilities in internally-ribbed tubes by using frequency domain method

2014 ◽  
Vol 65 (1-2) ◽  
pp. 1-13 ◽  
Author(s):  
Yifan Zhang ◽  
Huixiong Li ◽  
Liangxing Li ◽  
Xianliang Lei ◽  
Tai Wang
Keyword(s):  
Frequency Domain ◽  
Two Phase Flow ◽  
Flow Instabilities ◽  
Frequency Domain Method ◽  
Phase Flow ◽  
Two Phase ◽  
Domain Method

scholarly journals Two-phase transport in a cemented waste package considering spatio-temporal evolution of chemical conditions

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Yonghui Huang ◽  
Haibing Shao ◽  
Erich Wieland ◽  
Olaf Kolditz ◽  
Georg Kosakowski
Keyword(s):  
Chemical Reactions ◽  
Feedback System ◽  
Cementitious Materials ◽  
Transport Processes ◽  
Gas Generation ◽  
Two Phase ◽  
Waste Package ◽  
Barrier Materials ◽  
Dry Conditions ◽  
Major Factors

AbstractThe long-term evolution of cemented waste packages is governed by (bio)chemical reactions between waste, cement, and barrier materials, and by transport processes inside the waste package and through openings in the waste package hull. Inside a waste package, gases can be generated by pH-dependent anoxic corrosion of metals and the degradation of organic matter. The (bio)chemical reactions consume water and will not proceed under dry conditions. The degradation of cementitious materials lowers the alkaline pH of the pore water. The modeling of such a complex feedback system shows that the internal structure of a waste package and the exchange of mass with the environment (boundary conditions) are major factors that determine the importance of process couplings. The (bio)chemical reactions are controlled by internal re-distribution of water predominantly via vapor transport. Calculated gas generation rates were found to be affected by dry-out processes inside the drum.

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