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Chemkin 4.1.1 Chapter 3: Catalytic Processes It is now of interest to vary the sticking coefficients for these rates one by one, and see how such variations will affect predicted temperature profiles in the reactor. A Parameter Study has already been set up to do this in the Mechanism_ParameterStudy project. To see how this is done, go to the Mechanism Parameters tab in the Pre-processing panel. On the Reaction sub-tab, select COMBUST (which is the name of our surface material, so we're selecting reactions related to this material only) from the pull-down menu of the Select Reaction Set and click on the Search Reactions button. The first reaction to show up in the pull-down window under the Search Reactions button is highlighted in blue, indicating that a parameter study has been set up for this reaction rate constant. Click on the Setup Parameter Study button next to the Pre-exponential Factor A value for this reaction to view the Parameter Study Setup. Figure 3-16 Setting Up a Parameter Study for Sticking Coefficients vs. Predicted Temperature Profiles 3.2.1.2 Viewing Results with the Post-Processor Run the Parameter Study by selecting all of the runs in the Run Parameter Study window and clicking the Post-Process button. Once in the Post-Processor control panel, select Line Plot for Plot Type. Under Plot Set, select Solution no 1. Ctrl-click all of the temperature profiles for each of the Parameter Study runs as the Y Variables. Click on Display Plot. © 2007 Reaction Design 110 RD0411-C20-000-001
Chapter 3: Catalytic Processes <strong>Tutorials</strong> <strong>Manual</strong> Figure 3-17 Varying Rate Constants of Reactions 1 and 6. Figure 3-17 demonstrates the results of the Parameter Study displayed by the CHEMKIN post-processor. The results clearly indicate that if we keep the sticking coefficient of reaction 1 constant, and increase the sticking coefficient for reaction 6, the ignition occurs much sooner and the maximum combustion temperature is reached almost as soon as the reactants enter the catalytic reactor. This makes sense, because reaction 6, CH 4 + O(*) + PT(*) → CH 3 (*) + OH(*), is a branching reaction that liberates radicals CH 3 and OH, thus rapidly increasing the radical pool that in turn is responsible for catalytic light-off. On the other hand, increasing the sticking probability of the O 2 +2PT(*)→ O(*) + O(*) reaction delays ignition probably because it is competing with the adsorption of CH 4 on open sites. RD0411-C20-000-001 111 © 2007 Reaction Design
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Chemkin 4.1.1 Contents Table of Con
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Chemkin 4.1.1 Tables List of Tables
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Tutorials Manual 4.1.1 Figures List
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List of Figures Tutorials Manual 2-
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List of Figures Tutorials Manual 4-
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Chemkin 4.1.1 1 1 Introduction The
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Chapter 1: Introduction Tutorials M
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Chemkin 4.1.1 2 2 Combustion in Gas
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Chapter 2: Combustion in Gas-phase
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Tutorials Manual 4.1.1 Index Index
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Tutorials Manual

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