The Glass Furnace Model (GFM)

The Glass Furnace Model (GFM) Version 4.0, a computational fluid dynamic (CFD) glass furnace simulation code was developed at Argonne National Laboratory with assistance and guidance from the glass industry to provide a powerful cost-effective tool that can be used to analyze and optimize existing furnaces or investigate new furnace designs. GFM 4.0 is a major upgrade, newly available in 2007.

The GFM consists of three major computational models:

1. A combustion space model
2. A radiation heat transfer model
3. A multiphase glass melt model.

Because radiation is the dominant mode of heat transfer in the combustion space, a new, computationally efficient, hybrid model of radiant heat transfer was developed and applied throughout the furnace volume. The radiation model calculates the spectral radiation heat transfer from the combustion gases and soot to all surfaces including walls, crown, burner and exhaust inlet/exit planes, and the glass melt surface. A separate surface radiation exchange computation accounts for radiation coming from the combustion space volume and radiation exchange between the crown, walls, and the melt surface

Combustion Space Model

The combustion space model uses a three-step partially decoupled computational scheme and divides the combustion species into two groups: major species and subspecies. The three-step scheme computes

1. Combustion hydrodynamics through the calculation of the major species (species that significantly affect the computed temperature, pressure, and velocity fields)
2. Formation and transport of pollutants and soot (these subspecies calculations do not have a major effect on the flow field)
3. Net radiation heat fluxes based on the temperature field and species concentration distributions.

A combustion space computation cycles through these three sub-computations to obtain the heat flux at the melt surface, which is the major heat input boundary condition in the melt computation.

Glass Melt Model

A multiphase (solid, liquid, gas) reacting flow model of the glass melt has been developed. All phases are treated with an Eulerian formulation. Batch is treated as distribution (number density) of solid particles (for both cullet and batch raw materials) with various size groups. The transport and melting of these particles is computed, thus allowing the computation of the batch coverage. The gas phase is evaluated in a similar manner to the batch by calculating bubble number density distributions along with models that compute the transport of the gas injected at bubblers.

Solution Methodology

An iterative three-step procedure generates the coupled simulation solution. The local flow properties (pressure, temperature, density, velocity, and species concentrations) in the combustion space are computed by solving the associated coupled transport equations. The emitted energy from each cell is calculated each iteration. After a preset number of iterations, the time-consuming radiation absorption calculation is performed, followed by a surface radiation exchange computation, and the updated local heat fluxes are returned to the combustion flow calculation. These combustion calculations continue until convergence or a preset number of iterations that triggers a switch over to the melt computation. The combustion space results provide the melt calculation with net radiation heat flux (the balance of emission and absorption) on the melt surface. Then, the calculated surface radiation heat flux is used by the glass melt model to compute batch melting and other local flow properties in the glass melt. The calculated local glass surface temperature is fed back to the combustion flow calculation and thus completes an iteration cycle between the melt and combustion spaces. The iteration is repeated until the computational results converge.

Validated and Ready to Use

The GFM code was extensively validated against a comprehensive database acquired from in situ measurements in three different types of operating furnaces. The data acquisition program conducted by the DIAL Laboratory of Mississippi State University provided spatial distribution data on the gas temperature, gas velocity, gas species concentration, wall temperatures, and directional radiation heat fluxes in the combustion space and glass melt surface temperatures and velocities.

GFM 4.0 Sample Test Problem

A solved sample test problem is included in the GFM 4.0 release. This test problem simulates a hypothetical 20 ton/day regenerative glass melting furnace coupled to the glass melt. Round Robin Test 4 and 4a (RRT 4 and 4a) defined by Technical Committee 21 (TC21) of the International Commission on Glass (ICG), form the basis of this solved sample problem. TC21 is the ICG committee for Modeling of Melting Processes.

New Version 4.0 Capabilities

The latest version, GFM 4, comes with a modern installer and major enhancements to all of the GFM components.

Major enhancements that increase the usability and power of GFM are:

1. A greatly simplified user interface based on furnace simulation cases that performs the file handling operations automatically. The user now defines, saves, copies, runs, post processes, and deletes simulation “cases,” and need no longer know the details of data saved in files. Case operations apply to all of the numerous files that make up a case. For example, copying a case to do a series of parametric runs that vary an operating parameter creates a copy of all of the case files renamed with a new case number in a new case folder.
2. A new hybrid radiation heat transfer algorithm that increases both the speed and fidelity of the radiation computation.
3. An automated cycling capability that automatically transfers melt surface boundary condition files between the melt and combustion codes and starts up the next iteration of the melt or combustion space when the previous one finishes in a coupled melt and combustion furnace simulation. The automated cycling capability can reduce the running time for coupled simulations from several weeks to several days or less depending on the size of the furnace and coarseness of the grid.
4. An automated soot model calibration procedure.
5. A new progress monitoring program and progress data gathering capabilities in melt and combustion space program modules. The progress monitoring program plots equation residuals, mean temperatures, and energy distribution that easily allow users to identify problems in a simulation or verify progress toward convergence. Output from the data gathering includes summary files that give detailed mass and energy balance information for the combustion space and the melt.
6. Numerous other enhancements to increase the fidelity and improve convergence in the melt and combustion space computations.

Technical Requirements

If you have an appropriate engineering and glass technology background, you can learn to use GFM in a relatively short time. GFM was designed to run efficiently (on the order of a day or two for the largest furnaces and overnight for smaller furnaces) on high end PCs. The GFM has an easy-to-use graphical interface that allows quick construction of a model of a glass furnace by using the preprocessor. The postprocessor facilitates display of the simulation results.

The GFM will run on Windows 2000 and later computers. The code requires a 2 GHz Pentium IV or better with at least 512 MB RAM. Faster machines or more RAM will decrease the run time and allow use of more refined grids.

Licensing Information

Argonne is offering a free, six-month trial license (as of June 2007, and may change without notice) to encourage companies and universities to use the GFM. To try the GFM software, please fill out a trial license and return it to the address noted below.

After the free trial period, a license is required to use and operate GFM.

• U.S. or foreign commercial license
• U.S. or foreign university/non-profit license

Please print a copy of the agreement, fill in the appropriate information, have an authorized representative of your organization sign it, and send the signed license agreement to the address noted below. Pricing for the GFM is noted in the Appendix of the license. Payment can be made by credit card, check, or bank wire. An invoice will be provided if requested.

Cynthia Wesolowski
Software Licensing Coordinator
Office of Technology Transfer-201
Argonne National Laboratory
9700 S. Cass Ave.
Argonne, IL 60439

Please contact Cynthia Wesolowski(630-252-7694) weso@anl.gov. to let her know that you are sending the agreement.