Tutorials Manual

More documents

Recommendations

Info

Chemkin 4.1.1 Chapter 2: Combustion in Gas-phase Processes In Figure 2-9, there is an obvious difference (about a factor of four) between the ignition time values as defined by the two chosen criteria. This plot demonstrates why one should be mindful of ignition time definitions used in computations. The dark line is the temperature profile and the light line is the OH mole fraction. Finally the ignition times vs. the inverse of temperature, are shown in Figure 2-10 on a semi-log plot. Here the difference between the two ignition time definitions is obvious. Figure 2-10 Ignition Times vs. Inverse of Temperature (Semi-log) 2.3.4 Burner-stabilized Flame 2.3.4.1 Project Description This user tutorial presents a simulation of a burner-stabilized laminar premixed flame of hydrogen and air at low pressure. This project uses the chemistry set for hydrogen combustion described in Section 2.8.1. Burner-stabilized laminar premixed flames are often used to study chemical kinetics in a combustion environment. Such flames are effectively one-dimensional and can be made very steady, facilitating detailed experimental measurements of temperature and species profiles. Also, laminar flame speed is often used to characterize the combustion of various fuel-oxidizer combinations. Therefore, the ability to model chemical kinetics and transport © 2007 Reaction Design 32 RD0411-C20-000-001
Chapter 2: Combustion in Gas-phase Processes <strong>Tutorials</strong> <strong>Manual</strong> 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. RD0411-C20-000-001 33 © 2007 Reaction Design
Page 1 and 2: August 3, 2007 1:53 am Release 4.1.
Page 3 and 4: Chemkin 4.1.1 Contents Table of Con
Page 5 and 6: Chemkin 4.1.1 Tables List of Tables
Page 7 and 8: Tutorials Manual 4.1.1 Figures List
Page 9 and 10: List of Figures Tutorials Manual 2-
Page 11 and 12: List of Figures Tutorials Manual 4-
Page 13 and 14: Chemkin 4.1.1 1 1 Introduction The
Page 15 and 16: Chapter 1: Introduction Tutorials M
Page 17 and 18: Chemkin 4.1.1 2 2 Combustion in Gas
Page 19 and 20: Chapter 2: Combustion in Gas-phase
Page 31: Chapter 2: Combustion in Gas-phase
Page 83 and 84:
Chapter 2: Combustion in Gas-phase
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Chemkin 4.1.1 3 3 Catalytic Process
Page 93 and 94:
Chapter 3: Catalytic Processes Tuto
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Chemkin 4.1.1 4 4 Materials Problem
Page 117 and 118:
Chapter 4: Materials Problems Tutor
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Chemkin 4.1.1 5 5 Chemical Mechanis
Page 163 and 164:
Chapter 5: Chemical Mechanism Analy
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Tutorials Manual 4.1.1 Index Index
Page 179 and 180:
Index Tutorials Manual normalized s
show all

Tutorials Manual

Create successful ePaper yourself

Delete template?

Save as template?