Development of one-dimensional transient model for predicting flow instability at supercritical pressures

2019 ◽  
Vol 112 ◽  
pp. 162-170 ◽  
Author(s):  
Jiayue Chen ◽  
Hanyang Gu ◽  
Zhenqin Xiong
Keyword(s):  
Flow Instability ◽  
Transient Model ◽  
One Dimensional

One Dimensional Thermal-Hydraulic Stability Analysis of Supercritical Fluid Cooled Reactors

2004 ◽  
Author(s):  
Jiyun Zhao ◽  
Pradip Saha ◽  
Mujid S. Kazimi
Keyword(s):  
Flow Rate ◽  
Single Channel ◽  
Flow Instability ◽  
Density Wave ◽  
Reactor Power ◽  
Rate System ◽  
One Dimensional ◽  
Velocity Amplitude ◽  
System Pressure ◽  
Induced Velocity

A one-dimensional single-channel thermal-hydraulics model has been developed to investigate possible occurrence of density-wave instability in two U. S. Gen-IV reactors cooled by supercritical fluids, i. e., the Supercritical Water-cooled Reactor (SCWR) and Gas-cooled Fast Reactor (GFR). Water density in the SCWR core changes from 780 kg/m3, to 90 kg/m3, whereas the density of supercritical carbon-dioxide in the reference GFR changes from 155 kg/m3 to around 110 kg/m3. The standard frequency domain approach with a decay ratio of induced velocity amplitude of 0.5 has been used to determine the onset of flow instability. With suitable inlet orificing, the hot channel of SCWR has been found to be stable. Sensitivity studies show that the hot channel decay ratio reaches the critical value of 0.5 when either the reactor power is raised to 118% of full power or the core flow rate is reduced to 86% of nominal flow rate. System pressure has only a moderate effect. Detailed 3-D studies, preferably with neutronic feedback, should be carried out for the SCWR design because of its sensitivity to various important parameters. The GFR reference design has been found to be very stable since the density change in the GFR core is rather small compared to that in the SCWR design.

scholarly journals Transient Model for CW and Pulsed Laser Machining of Ablating/Decomposing Materials—Approximate Analysis

1996 ◽  
Vol 118 (3) ◽  
pp. 774-780 ◽  
Author(s):  
M. F. Modest
Keyword(s):  
Three Dimensional ◽  
Pulsed Laser ◽  
Computer Time ◽  
Single Step ◽  
Laser Source ◽  
Laser Machining ◽  
Transient Model ◽  
One Dimensional ◽  
Cpu Time ◽  
Order Of Magnitude

Approximate, quasi-one-dimensional conduction models have been developed to predict the changing shape of holes, single grooves, or overlapping grooves carved by ablation into a thick solid that is irradiated by a moving laser source. For CW or pulsed laser operation a simple integral method is presented, which predicts shapes and removal rates with an accuracy of a few percent, while requiring one order of magnitude less CPU time than a three-dimensional, numerical solution. For pulsed operation a “full-pulse” model is presented, computing the erosion from an entire pulse in a single step, and reducing computer time by another order of magnitude.

A Simple Model for Fluid Flow and Particle Motion Inside the Human Larynx

Volume 4 ◽  
2004 ◽  
Author(s):  
C. Ersahin ◽  
I. B. Celik ◽  
O. C. Elci ◽  
I. Yavuz ◽  
J. Li ◽  
...  
Keyword(s):  
Flow Field ◽  
Particle Deposition ◽  
Flow Distribution ◽  
Axial Direction ◽  
Correction Method ◽  
Accurate Solution ◽  
Two Dimensional ◽  
Transient Model ◽  
One Dimensional ◽  
Dimensional Flow

This study aims to develop a simple and quick, but sufficiently accurate solution method for calculating the air flow and tracking the particles in a complex tubular system, where the flow changes its magnitude and direction in a periodic manner. The flow field is assumed to be quasi-two-dimensional and a pressure-correction method is employed to calculate the spetio-temporal variation of the air velocity inside the larynx. Then, the calculated one-dimensional flow distribution is used to reconstruct a two-dimensional flow field is constructed based on the average velocity along the axial direction. The system geometry is taken as close as possible to the actual larynx for an average person with an average glottis opening. For the current study the walls of the larynx is approximated as rigid walls, but different ways to account for compliant walls are proposed within the context of the one-dimensional mode. The 1-D transient model is validated against a two-dimensional model using a verified commercial code. Particles are introduced into the system and tracked during every time fraction of the respiratory cycle. Then, the histograms of particles that come into contact with the larynx are calculated, and regions with a higher probability for particle deposition are identified.

scholarly journals A Method for the Prediction of Supersonic Compressor Blade Performance

1989 ◽  
Author(s):  
C. Freeman ◽  
N. A. Cumpsty
Keyword(s):  
Flow Instability ◽  
Pressure Rise ◽  
Momentum Equation ◽  
Compressor Blades ◽  
Direction Parallel ◽  
One Dimensional ◽  
Inlet Region ◽  
Small Force ◽  
Surge Line ◽  
The One

A simple model is used to calculate the flow in compressor blades with supersonic relative inlet flow. The one-dimensional model utilises the conservation of stagnation enthalpy, mass flow and momentum in the inlet region. The momentum equation is applied in the direction parallel to the blade surface at inlet and one of the fundamental simplifications adopted is that the projected area of the blades gives such a small force in this direction that a very simple approximation for it suffices. The model is able to predict the loss creation in the inlet region. The level of predicted loss agree well with measured values when the Mach numbers are sufficiently high for the inlet loss to dominate. Furthermore the correct trends of loss with incidence and blade speed are predicted. The pressure rise and flow can also be predicted when the correct deviation and meridional streamtube convergence are given. The method predicts trends usually seen in measurments: the narrowing of the useful operating range between choke and flow instability (surge) as blade speed is increased and a steepening of the surge line at the higher speeds.

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