Frequency Domain Linear Stability Analysis of Simplified Supercritical Water-Cooled Reactor

2009 ◽  
Author(s):  
Pengfei Liu ◽  
Yanhua Yang ◽  
Aijun Xue ◽  
Xu Cheng
Keyword(s):  
Stability Analysis ◽  
Characteristic Equation ◽  
Supercritical Water ◽  
Stability Boundary ◽  
System Model ◽  
Heating Zone ◽  
Critical Number ◽  
Boundary Points ◽  
System Pressure ◽  
The Stability

This paper presents the stability analysis of a supercritical water-cooled system. A model of simplified supercritical water-cooled system is introduced and then its thermal-hydraulic equations, initial conditions and boundary conditions are given. Based on perturbation linearization and Laplace transformation, the transfer function between inlet mass flow rate oscillation and pressure drop oscillation of the simplified system model is established, and the characteristic equation of the simplified system model is derived. Applying control theory to solve the characteristic equation, the stability boundary points are found by judging whether the real parts of all roots solved by characteristic equation are greater than zero. A stability map which consists of these stability boundary points is generated by using both dimensionless sub-pseudo-critical number and trans-pseudo-critical number. An unstable region nearby the pseudo-critical point is determined. The effects of some important parameters on the stability map are investigated also by using decay ratio. The sensitivity analysis shows that the system is stabilized with a higher hydraulic system resistance, fluid inlet velocity or system pressure. It also shows that a longer heating zone, a harder pump characteristics or a larger gravitational acceleration (orientation angle) leads to a larger stability margin of the system. The stability map is also found to be not sensitive to a higher friction resistance or system pressure.

Theoretical Study on the Flow Instability of Supercritical Water in the Parallel Channels

2012 ◽  
Author(s):  
Yali Su ◽  
Jian Feng ◽  
Wenxi Tian ◽  
Suizheng Qiu ◽  
Guanghui Su
Keyword(s):  
Supercritical Water ◽  
Flow Instability ◽  
Stability Boundary ◽  
Physical Models ◽  
Marginal Stability ◽  
Inlet Temperature ◽  
Flow And Heat Transfer ◽  
System Pressure ◽  
Parallel Channels ◽  
The Stability

For the flow of the supercritical water (SCW), the fierce variation of density and specific volume possibly cause flow instability. Based on the structure of parallel channels, mathematical and physical models were established to simulate the flow and heat transfer characteristics of the supercritical water in the parallel channels with semi-implicit scheme and staggered mesh scheme. Flow instability of super-critical water was obtained by using the little perturbation method. Pseudo-subcooling number (NSUB) and pseudo-phase change number (NPCH) are defined based on the property of SCW. The marginal stability boundary (MSB) is obtained with using the NSUB and NPCH. The effects of mass flow rate, inlet temperature and system pressure on the flow instability boundary were also investigated. When increasing the mass flows and system pressure, decreasing the heat flux, the stability in the parallel channels increases. The effect of inlet temperature in the low pseudo-subcooling number region is different from that in high pseudo-subcooling number region.

Instability of Heated Panels in Supersonic Air Flow

2008 ◽  
Vol 33-37 ◽  
pp. 1101-1108
Author(s):  
Zhi Chun Yang ◽  
Wei Xia
Keyword(s):  
Stability Analysis ◽  
Stability Boundary ◽  
Boundary Curve ◽  
Static Stability ◽  
Static Deformation ◽  
Limit Cycle Oscillation ◽  
Aerodynamic Load ◽  
Aeroelastic System ◽  
Aerodynamic Pressure ◽  
The Stability

An investigation on the stability of heated panels in supersonic airflow is performed. The nonlinear aeroelastic model for a two-dimensional panel is established using Galerkin method and the thermal effect on the panel stiffness is also considered. The quasi-steady piston theory is employed to calculate the aerodynamic load on the panel. The static and dynamic stabilities for flat panels are studied using Lyapunov indirect method and the stability boundary curve is obtained. The static deformation of a post-buckled panel is then calculated and the local stability of the post-buckling equilibrium is analyzed. The limit cycle oscillation of the post-buckled panel is simulated in time domain. The results show that a two-mode model is suitable for panel static stability analysis and static deformation calculation; but more than four modes are required for dynamic stability analysis. The effects of temperature elevation and dimensionless parameters related to panel length/thickness ratio, material density and Mach number on the stability of heated panel are studied. It is found that panel flutter may occur at relatively low aerodynamic pressure when several stable equilibria exist for the aeroelastic system of heated panel.

Moment Stability of Stochastic Regenerative Cutting Process

2010 ◽  
Vol 97-101 ◽  
pp. 3038-3041
Author(s):  
Xiao Qin Zhou ◽  
Wen Cai Wang ◽  
Hong Wei Zhao
Keyword(s):  
Stability Analysis ◽  
Stability Boundary ◽  
Cutting Process ◽  
Damping Coefficients ◽  
Cutting Stability ◽  
Stationary Stochastic Processes ◽  
The Stability ◽  
Stiffness And Damping ◽  
Moment Stability ◽  
Stochastic Uncertainties

The stochastic uncertainties of regenerative cutting process (RCP) are taken into consideration, and both cutting stiffness and damping coefficients are modeled as two stationary stochastic processes. The eigenvalue equations are established for the stability analysis of stochastic RCP, corresponding to the differential equations of the first and second order moments. Thus the stability analysis of stochastic RCP is transformed into that of the first two order moments. The influence of stochastic uncertainties on the cutting stability of RCP is discussed. The numerical experiments have verified that with the increase of stochastic uncertainties, the cutting stability boundary was shifted downwards significantly, and the number of lobes was also multiplied.

scholarly journals Three-dimensional modeling and time-delay stability analysis for robotics docking simulation

2019 ◽  
Vol 233 (14) ◽  
pp. 5438-5455
Author(s):  
Prateek Sazawal ◽  
Daniel Choukroun ◽  
Heike Benninghoff ◽  
Eberhard Gill
Keyword(s):  
Stability Analysis ◽  
Time Delay ◽  
Nonlinear System ◽  
Contact Force ◽  
System Model ◽  
Model Parameters ◽  
Force Model ◽  
Hardware In The Loop ◽  
Contact Force Model ◽  
The Stability

Hardware-in-the-loop simulations of two interacting bodies are often accompanied by a time delay. The time delay, however small, may lead to instability in the hardware-in-the-loop system. The present work investigates the source of instability in a two spacecraft system model with a time-delayed contact force feedback. A generic compliance-device-based contact force model is proposed with elastic, viscous, and Coulomb friction effects in three dimensions. A 3D nonlinear system model with time delay is simulated, and the effect of variations in contact force model parameters is studied. The system is then linearized about a nominal state to determine the stability regions in terms of parameters of the spring-dashpot contact force model by the pole placement method. Furthermore, the stability analysis is validated for the nonlinear system by energy observation for both the stable and unstable cases.

Precise Stability Analysis of Stepped Telescopic Booms and Practical Algorithm

2013 ◽  
Vol 395-396 ◽  
pp. 871-876
Author(s):  
Liang Du ◽  
Peng Lan ◽  
Nian Li Lu
Keyword(s):  
Stability Analysis ◽  
Differential Equations ◽  
Characteristic Equation ◽  
Energy Method ◽  
Cross Sectional ◽  
Component Method ◽  
Practical Algorithm ◽  
The Stability ◽  
Precise Expression ◽  
Constant Section

To analyze the stability of stepped telescopic booms accurately, using vertical and horizontal bending theory, this paper established the deflection differential equations of stepped column model of arbitrary sectioned telescopic boom, the stability were analyzed, and obtained the precise expression of the buckling characteristic equation; Took certain seven-sectioned telescopic booms as example, by comparing the results with ANSYS, the accuracy of the equations deduced in this paper was verified. Presented the equivalent component method for the stability analysis of multi-stepped column, the equivalent cross-sectional moment of inertia was deduced by energy method, thus the stability of stepped column equivalent to that of constant section component. By comparing the results with exact value, the precision of equivalent component method was verified which was convenient for stability analysis of telescopic boom.

Analysis of the Chatter Instability in a Nonlinear Model for Drilling

2006 ◽  
Vol 1 (4) ◽  
pp. 294-306 ◽  
Author(s):  
Sue Ann Campbell ◽  
Emily Stone
Keyword(s):  
Stability Analysis ◽  
Hopf Bifurcation ◽  
Nonlinear Models ◽  
Stability Boundary ◽  
Vibration Modes ◽  
Loss Of Stability ◽  
Chatter Vibration ◽  
Cutting Depth ◽  
Stability And Bifurcation Analysis ◽  
The Stability

In this paper we present stability analysis of a non-linear model for chatter vibration in a drilling operation. The results build our previous work [Stone, E., and Askari, A., 2002, “Nonlinear Models of Chatter in Drilling Processes,” Dyn. Syst., 17(1), pp. 65–85 and Stone, E., and Campbell, S. A., 2004, “Stability and Bifurcation Analysis of a Nonlinear DDE Model for Drilling,” J. Nonlinear Sci., 14(1), pp. 27–57], where the model was developed and the nonlinear stability of the vibration modes as cutting width is varied was presented. Here we analyze the effect of varying cutting depth. We show that qualitatively different stability lobes are produced in this case. We analyze the criticality of the Hopf bifurcation associated with loss of stability and show that changes in criticality can occur along the stability boundary, resulting in extra periodic solutions.

scholarly journals Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory

Friction ◽  
2020 ◽  
Author(s):  
Yu Huang ◽  
Haiyin Cao ◽  
Zhuxin Tian
Keyword(s):  
Stability Analysis ◽  
Equilibrium Point ◽  
Journal Bearing ◽  
Stability Boundary ◽  
Initial Point ◽  
Journal Bearings ◽  
Bearing Surface ◽  
Rotating Speed ◽  
Stability Threshold ◽  
The Stability

AbstractIn this study, we observe that there are two threshold speeds (stability threshold speed and second threshold speed) for the long journal bearing, which is different for the short bearing. When the rotating speed is below the stability threshold speed, the stability boundary nearly coincides with the clearance circle, and the journal center gradually returns to the equilibrium point after being released at an initial point. If the rotating speed is between the stability threshold speed and the second threshold speed, after being released at an initial point, the journal center converges to a contour containing the equilibrium point. In this situation, for a higher rotating speed, the corresponding contour is also larger. When the rotating speed exceeds the second threshold speed, the journal gradually moves towards the bearing surface after being released at an initial point.

scholarly journals V/C Digital Controlled DC-DC Converter

2020 ◽  
Vol 9 (3) ◽  
pp. 167-175
Keyword(s):  
Stability Analysis ◽  
Transient Analysis ◽  
Stability Boundary ◽  
Buck Converter ◽  
Sampled Data ◽  
Signal Model ◽  
Stability Range ◽  
Z Domain ◽  
Average Current ◽  
The Stability

In this paper, the switching of dc-dc converter using voltage/current digital control is proposed. It is the combination of existed digital average voltage and digital average current controls. The stability analysis of V/C digital controlled dc-dc converter is derived by using sampled data model. The transient analysis of V/C digital controlled dc-dc converter is also derived by using z-domain small signal model. The proposed V/C digital controlled dc-dc converter has over current protection, fast load transient response, no sub-harmonic oscillations at any value of duty cycle, and wider stability range. The proposed system is analysed with a simple buck converter. The output voltage and inductor current weighting factors influence the stability boundary and transient performances of V/C digital controlled dc-dc converter. The stability analysis and transient analysis is investigated and verified by circuit simulations

D-partition Stability Analysis of a Two-Degree-of-Freedom System with Delayed Restoring Force

1967 ◽  
Vol 9 (3) ◽  
pp. 190-197 ◽  
Author(s):  
B. Porter
Keyword(s):  
Stability Analysis ◽  
Machine Tool ◽  
Algebraic Equation ◽  
Characteristic Equation ◽  
Normal Modes ◽  
Degree Of Freedom ◽  
Central Feature ◽  
Restoring Force ◽  
The Stability ◽  
Two Degree Of Freedom

The method of D-partition is used to analyse the stability of a two-degree-of-freedom system subjected to a delayed restoring force of the kind which causes chatter in certain types of machine tool. The central feature of the analysis is the reduction of a stabliity problem involving a transcendental characteristic equation to a much simpler problem concerning the roots of a related algebraic equation. The results of the exact analysis are compared with approximate results obtained by assuming that the normal modes of the two-degree-of-freedom system can be decoupled.

Analytical Study of Supercritical Water Flow in Two Heated Parallel Channels With Wall Heat Effects

2018 ◽  
Author(s):  
Dhanashree S. Ghadge ◽  
Vijay Chatoorgoon
Keyword(s):  
Supercritical Water ◽  
Power Distribution ◽  
Analytical Study ◽  
Heat Storage ◽  
Stability Boundary ◽  
Numerical Results ◽  
One Dimensional ◽  
Heat Effects ◽  
The Stability ◽  
Frequency Domain Approach

One dimensional (1D) numerical simulations have been carried out of heated parallel channel experiments using the linear frequency domain approach to investigate the effect of wall heat on the system’s stability for supercritical water in vertical heated channels. Oscillatory instability boundaries of the experimental cases with two different wall thicknesses and uniform power distribution are produced, assessed and discussed. These new numerical results with wall heat are compared with experimental data and previous numerical results without wall heat. There is improved agreement on the stability boundary predictions when the wall heat storage effect is included. However, the effect of wall heat storage was small for these experiments.

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