Tutorials Manual

Chapter 2: Combustion in Gas-phase Processes
Tutorials Manual
processes in these flames is critical to interpreting flame experiments and to
understanding the combustion process itself. Examples of the use of flame modeling
to interpret experimental observations and to verify combustion chemistry and
pollution formation can be found in Miller, et al. 9
2.3.4.2 Project Setup
The project file is called pre-mixed_burner__burner_stabilized.ckprj. The data files
used for this sample are located in the
samples41\pre-mixed_burner\burner_stabilized directory. This reactor model is
simple and contains only one gas inlet and one premixed-burner reactor.
On the Reactor Physical Properties tab of the C1_ Pre-Mixed Burner panel, the
problem type is selected as Fix Gas Temperature because a measured temperature
profile is used rather than computing the gas temperatures from the energy equation.
For these laminar flames, the gas temperatures are often obtained from experiment
rather than by solving an energy conservation equation. This is because there can be
significant heat losses to the external environment, which are unknown or difficult to
model. For cases where the heat losses are known or negligible, the user can solve a
burner-stabilized flame problem in which the temperatures are determined from the
energy conservation equation. Even if the energy equation is to be solved for the
temperatures, the iteration converges more reliably if the species profiles are first
computed using a fixed temperature profile. In any case, the user needs to input an
estimate of the temperature profile. For this example, a temperature profile called
pre-mixed_burner__burner_stabilized_TPRO.ckprf is input on the Reactor Physical
Properties tab and only the species transport equations are solved using the
temperature as a constraint. The system pressure (25 Torr) is also input on this panel,
along with the choice of Mixture-averaged Transport and the use of the Correction
Velocity Formalism.
The Ending Axial Position (10 cm) for the simulation is input on the Initial Grid
Properties tab of the C1_ Pre-Mixed Burner panel, along with a number of parameters
concerning the gridding of the problem. A few of the grid parameters have been
changed from the default values. The pre-mixed burner reactor model has adaptive
gridding. The initial simulations are therefore done on a very coarse mesh that may
have as few as five or six points. After obtaining a solution on the coarse mesh, new
9. J. A. Miller, R. E. Mitchell, M. D. Smooke, and R. J. Kee, in Proceedings of the Nineteenth
Symposium (International) on Combustion, The Combustion Institute, Pittsburgh,
Pennsylvania, 1982, p. 181. J. A. Miller, M. D. Smooke, R. M. Green, and R. J.
Kee, Combustion Science and Technology 34:149 (1983). J. A. Miller, M. C. Branch,
W. J. McLean, D. W. Chandler, M. D. Smooke, and R. J. Kee, in Proceedings of the
Twentieth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh,
Pennsylvania, 1985, p. 673.
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