Thermal Runaway and its Control in Microwave Heated Ceramics

1992 ◽  
Vol 269 ◽  
Author(s):  
Gregory A. Kriegsmann
Keyword(s):  
Microwave Power ◽  
Initial Conditions ◽  
Physical Phenomenon ◽  
Three Dimensional ◽  
Control Process ◽  
Independent Solution ◽  
Cylindrical Sample ◽  
Thermal Runaway ◽  
Amplitude Equation ◽  
Heating Process

ABSTRACTThe heating of a ceramic slab under TEM illumination is modeled and analyzed in the small Biot number regime. The temperature distribution is almost spatially uniform in this limit and its evolution in time is governed by a first order nonlinear amplitude equation. This equation admits a time independent solution which is a multivalued function of the microwave power. The dynamics of the heating process are deduced, from the amplitude equation and the multivalued response, and are dependent upon the microwave power and initial conditions. The results of this analysis give a plausible explanation of certain difficulties arising in sintering experiments, such as thermal runaway. A simple control process is presented and analyzed which mitigates against these deleterious effects. Abbreviated parameter studies are performed showing trends in the controlled heating process.A quasi-three-dimensional problem modeling the heating process of a thin cylindrical sample in a waveguide applicator is also presented. For certain excitations the physical phenomenon deduced from this model and the required control process are the same as those obtained for the slab. For other excitations there is a strong spatial structure along the axis of the sample. For a certain choice of parameters the middle portion of the sample is at an elevated temperature while the remaining portion is at a much lower temperature. This phenomenon may be useful in joining applications.

CFD Analysis of Batch-Type Reheating Furnace With Regeneratve Burners

2008 ◽  
Author(s):  
Bin Wu ◽  
Tom Roesel ◽  
Andrew M. Arnold ◽  
Zhaojiang Xu ◽  
Eugene Arnold ◽  
...  
Keyword(s):  
Product Quality ◽  
Three Dimensional ◽  
Control Process ◽  
Flow Characteristics ◽  
Steel Production ◽  
Value Added ◽  
Heating Process ◽  
Cfd Analysis ◽  
Reheating Furnace ◽  
Quality Control Process

A reheating furnace is a critical component in value-added steel production. These furnaces can have a significant impact on product quality and total cost. Due to the higher efficiency of regenerative burners, a growing number of reheating furnaces are using this technology. To better understand the regenerative burner operation, a Computational Fluid Dynamics (CFD) analysis has been conducted to examine the transient and three dimensional flow characteristics in the No.3 reheating furnace at ArcelorMittal Steelton. Simulation results with traditional burners and regenerative burners have been analyzed to understand the effect of retrofitting a furnace with these more modern burners. The temperature distribution on the billets has also been monitored throughout the simulated heating process providing insight into the optimization of billet residence time and improvement of the product quality control process.

Motion planning and trajectory tracking for three-dimensional Poiseuille flow

2009 ◽  
Vol 626 ◽  
pp. 307-332 ◽  
Author(s):  
JENNIE COCHRAN ◽  
MIROSLAV KRSTIC
Keyword(s):  
Motion Planning ◽  
Performance Metrics ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Independent Solution ◽  
Planning Problem ◽  
Reference Trajectory ◽  
Special Role ◽  
Motion Planning Problem

We present the first solution to a boundary motion planning problem for the Navier–Stokes equations, linearized around the parabolic equilibrium in a three-dimensional channel flow. The pressure and skin friction at one wall are chosen as the reference outputs as they are the most readily measurable ‘wall-restricted’ quantities in experimental fluid dynamics and also because they play a special role as performance metrics in aerodynamics. The reference velocity input is applied at the opposite wall. We find the exact (method independent) solution to the motion planning problem using the PDE (partial differential equation) backstepping theory. The motion planning solution results in open-loop controls, which produce the reference output trajectories only under special initial conditions for the flow velocity field. To achieve convergence to the reference trajectory from other (nearby) initial conditions, we design a feedback controller. We also present a detailed examination of the closed-form solutions for gains and the behaviour of the motion planning solution as the wavenumbers grow or the Reynolds number grows. Numerical results are shown for the motion planning problem.

A Quasi-three-dimensional Finite-volume Shallow Water Model for Green Water on Deck

2013 ◽  
Vol 57 (03) ◽  
pp. 125-140
Author(s):  
Daniel A. Liut ◽  
Kenneth M. Weems ◽  
Tin-Guen Yen
Keyword(s):  
Shallow Water ◽  
Finite Volume ◽  
Time Domain ◽  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Green Water ◽  
Water Model ◽  
Ship Motions ◽  
Shallow Water Model

A quasi-three-dimensional hydrodynamic model is presented to simulate shallow water phenomena. The method is based on a finite-volume approach designed to solve shallow water equations in the time domain. The nonlinearities of the governing equations are considered. The methodology can be used to compute green water effects on a variety of platforms with six-degrees-of-freedom motions. Different boundary and initial conditions can be applied for multiple types of moving platforms, like a ship's deck, tanks, etc. Comparisons with experimental data are discussed. The shallow water model has been integrated with the Large Amplitude Motions Program to compute the effects of green water flow over decks within a time-domain simulation of ship motions in waves. Results associated to this implementation are presented.

Efficient Algorithms for Inspection and Reforming of Double-Curved Plates in Line-Heating Process

2006 ◽  
Vol 22 (03) ◽  
pp. 184-193
Author(s):  
Yujun Liu ◽  
Zhuoshang Ji ◽  
Yanping Deng ◽  
Jun Zhang ◽  
Ji Wang
Keyword(s):  
Manufacturing Process ◽  
Three Dimensional ◽  
Efficient Algorithms ◽  
Heating Process ◽  
Line Heating ◽  
Technical Parameters ◽  
Error Analyses ◽  
Metal Plates ◽  
Plate Formation ◽  
Prospective Application

Line heating is an effective and economical method for forming metal plates into three-dimensional shaped plates for ships, trains, and airplanes. When a curved plate subject to deformation is formed in line-heating process, the deformed shape is repeatedly inspected and reformed to reach the designed shape. Efficient automatic inspection and reforming processes are essential to enhance productivity in the whole manufacturing process. In this paper, efficient algorithms for inspection and reforming of double-curved plates are introduced. These algorithms have been developed to automatically inspect the transverse and longitudinal shape of plate surfaces and provide technical parameters to reform the unformed plates. The longitudinal shape of the plate surface is examined based on a shell plate development with plastic deformation during the plate formation, and the transverse shape is inspected through error analyses of transverse curvature radiuses. How to use the inspection results to reform unformed plates is discussed. In the end, experiments are performed with comparison to the current industrial plate manufacture, and results show a prospective application of our algorithms to the practical manufacturing of doublecurved plates. The methods presented in this study may play a role in realizing the automation of the entire curved-plate manufacturing process.

A Combined Eulerian and Lagrangian Method for Prediction of Evaporating Sprays

2002 ◽  
Vol 124 (3) ◽  
pp. 481-488 ◽  
Author(s):  
M. Burger ◽  
G. Klose ◽  
G. Rottenkolber ◽  
R. Schmehl ◽  
D. Giebert ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Lagrangian Method ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Lagrangian Methods ◽  
Eulerian Method ◽  
Lagrangian Modeling

Polydisperse sprays in complex three-dimensional flow systems are important in many technical applications. Numerical descriptions of sprays are used to achieve a fast and accurate prediction of complex two-phase flows. The Eulerian and Lagrangian methods are two essentially different approaches for the modeling of disperse two-phase flows. Both methods have been implemented into the same computational fluid dynamics package which is based on a three-dimensional body-fitted finite volume method. Considering sprays represented by a small number of droplet starting conditions, the Eulerian method is clearly superior in terms of computational efficiency. However, with respect to complex polydisperse sprays, the Lagrangian technique gives a higher accuracy. In addition, Lagrangian modeling of secondary effects such as spray-wall interaction enhances the physical description of the two-phase flow. Therefore, in the present approach the Eulerian and the Lagrangian methods have been combined in a hybrid method. The Eulerian method is used to determine a preliminary solution of the two-phase flow field. Subsequently, the Lagrangian method is employed to improve the accuracy of the first solution using detailed sets of initial conditions. Consequently, this combined approach improves the overall convergence behavior of the simulation. In the final section, the advantages of each method are discussed when predicting an evaporating spray in an intake manifold of an internal combustion engine.

Computational Characterization of Passive Fluid Mixing in Microfluidics

Volume 3 ◽  
2004 ◽  
Author(s):  
Erik D. Svensson
Keyword(s):  
Stokes Equations ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Fluid Mixing ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fluid Systems ◽  
Sensitive Dependence ◽  
Microfluidic Mixers

In this work we computationally characterize fluid mixing in a number of passive microfluidic mixers. Generally, in order to systematically study and characterize mixing in realistic fluid systems we (1) compute the fluid flow in the systems by solving the stationary three-dimensional Navier-Stokes equations or Stokes equations with a finite element method, and (2) compute various measures indicating the degree of mixing based on concepts from dynamical systems theory, i.e., the sensitive dependence on initial conditions and mixing variance.

Coupling Numerical Simulation of Resin Matrix Composites about Temperature and Degree of Cure Fields by Hot-Press Forming

2013 ◽  
Vol 788 ◽  
pp. 43-47
Author(s):  
Fei Sun ◽  
Dun Ming Liao ◽  
Peng Xu ◽  
Chang Chun Dong
Keyword(s):  
Three Dimensional ◽  
Exothermic Peak ◽  
Resin Matrix ◽  
Transient Temperature ◽  
Heating Process ◽  
Curing Process ◽  
Hot Press ◽  
Degree Of Cure ◽  
Resin Matrix Composite ◽  
The Impact

In this paper, a coupled numerical model of three-dimensional transient temperature field and degree of cure field for resin matrix composite curing process was developed. Using this model the hot-press curing process of the plate-shaped composite parts were simulated with considering the impact of tools and auxiliary materials. Thus, the temperature and degree of cure fields distribution in the entire process cycle were obtained. Numerical results show that the curing of the composite has a certain sequence. At the beginning, the composite is first curing at the boundary and gradually to the center. At the end stage, because of the higher curing rate, the center released a large amount of heat which makes the boundary curing simultaneously with center. In addition, there is a significant exothermic peak during the curing process. And the peak temperature is higher when it was closer to the center. This research effectively provides reference for optimizing the heating process parameters to improve product quality.

Effect of Initial Velocity Field on Smoke Diffusion Characteristic in Subway Tunnel

2009 ◽  
Author(s):  
Hui Yang ◽  
Li Jia ◽  
Lixin Yang
Keyword(s):  
Velocity Field ◽  
Field Condition ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Wind Effect ◽  
Diffusion Characteristic ◽  
Subway Tunnel ◽  
Air Velocity ◽  
Initial Field ◽  
Fire Disaster

In this paper, piston wind effect on smoke diffusion characteristic in subway tunnel is studied by using three-dimensional transient computational fluid dynamics (CFD) method. In the first simulation case, fire disaster is simulated with homogeneous resting initial field condition. In the second simulation case, the train’s decelerating process till stopping in the tunnel is simulated for getting three-dimensional tunnel air velocity field distribution. Then the final heterogeneous air velocity field when the train stops in the tunnel is taken as initial field condition and the same fire scenario as the first case is simulated again. The data obtained under both initial conditions are compared by detecting people evacuation safety and the influence of initial air velocity field is analyzed. The results show that the inertial air velocity field caused by train’s movement has significant influence on smoke diffusion at the first few minutes of fire disaster, which is the key time for people’s evacuation. The adopted method in this paper and the simulation result could be used in establishing more effective subway fire evacuation plan.

Fanno Design of Blow-Off Lines in Heavy Duty Gas Turbine

2013 ◽  
Author(s):  
Marco Cioffi ◽  
Enrico Puppo ◽  
Andrea Silingardi
Keyword(s):  
Gas Turbines ◽  
Gas Flow ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Design Procedure ◽  
Flow Equation ◽  
Heavy Duty ◽  
Cross Sectional ◽  
Pipe Length ◽  
Choked Flow

In typical heavy duty gas turbines the multistage axial compressor is provided with anti-surge pipelines equipped with on-off valves (blow-off lines), to avoid dangerous flow instabilities during start-ups and shut-downs. Blow-off lines show some very peculiar phenomena and somewhat challenging fluid dynamics, which require a deeper regard. In this paper the blow-off lines in axial gas turbines are analyzed by adopting an adiabatic quasi-unidimensional model of the gas flow through a pipe with a constant cross-sectional area and involving geometrical singularities (Fanno flow). The determination of the Fanno limit, on the basis of the flow equation and the second principle of thermodynamics, shows the existence of a critical pipe length which is a function of the pipe parameters and the initial conditions: for a length greater than this maximum one, the model requires a mass-flow reduction. In addition, in the presence of a regulating valve, so-called multi-choked flow can arise. The semi-analytical model has been implemented and the results have been compared with a three-dimensional CFD analysis and cross-checked with available field data, showing a good agreement. The Fanno model has been applied for the analysis of some of the actual machines in the Ansaldo Energia fleet under different working conditions. The Fanno tool will be part of the design procedure of new machines. In addition it will define related experimental activities.

scholarly journals PARALLEL COMPUTATIONS IN STUDIES OF DEPENDENCE OF GAS DYNAMIC PARAMETERS OF UPWARD SWIRLING FLOW OF GAS ON BLOWING VELOCITY

2016 ◽  
pp. 92-97
Author(s):  
R. E. Volkov ◽  
A. G. Obukhov
Keyword(s):  
Stokes Equations ◽  
Swirling Flow ◽  
Initial Conditions ◽  
Exact Analytical Solution ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Heat Conducting ◽  
Computational Domain ◽  
Navier Stokes Equations ◽  
Gas Dynamic

The rectangular parallelepiped explicit difference schemes for the numerical solution of the complete built system of Navier-Stokes equations. These solutions describe the three-dimensional flow of a compressible viscous heat-conducting gas in a rising swirling flows, provided the forces of gravity and Coriolis. This assumes constancy of the coefficient of viscosity and thermal conductivity. The initial conditions are the features that are the exact analytical solution of the complete Navier-Stokes equations. Propose specific boundary conditions under which the upward flow of gas is modeled by blowing through the square hole in the upper surface of the computational domain. A variant of parallelization algorithm for calculating gas dynamic and energy characteristics. The results of calculations of gasdynamic parameters dependency on the speed of the vertical blowing by the time the flow of a steady state flow.

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