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Chemkin 4.1.1 Chapter 2: Combustion in Gas-phase Processes Figure 2-50 Peaking of NO Concentration Dependent on Temperature in a PFR with an Approximated Mixing Region. Mixing causes a drop in the peak of NO and a lowering shift in the corresponding temperature, similar to the results found in the report. The NO peak shift is attributed to the locations of the reactions in the mixing zone. At temperatures higher than 1300 K, reaction occurs quickly when the oxidizing stream is in low concentrations, thereby decreasing the amount of NO. When the temperature is in the 1200-1300-K range, the reactions occur later in the mixing zone, a location with more oxidizer and consequently more NO. At temperatures lower than 1200 K, the formation of NO is not favored, so the NO concentration drops off. 2.6.5 Co-flowing Non-premixed CH 4 /Air Flame 2.6.5.1 Problem Description By default, the cylindrical shear flow reactor model uses the uniform inlet and initial profile for all variables except axial velocity. The default inlet velocity profile is considered to be fully developed, i.e., parabolic. In this example, we will establish a co-annular flow inlet condition by using the user routine option to override the default inlet profiles. Properties of both jets are assumed to be uniform when they enter the reactor so there is a jump in the inlet profiles at the jet interface. A non-premixed flame will be established downstream as fuel and air are mixed due to diffusion. The co-flowing annular jet configuration is shown in Figure 2-51 and properties of the inner (fuel) and the outer (air) jets are given in Table 2-10. The outer wall is adiabatic. © 2007 Reaction Design 72 RD0411-C20-000-001
Chapter 2: Combustion in Gas-phase Processes <strong>Tutorials</strong> <strong>Manual</strong> Figure 2-51 Confined Co-flowing Annular Jet Configuration. Table 2-10 Properties of the Co-flowing Jets Inner Jet (Fuel) Outer Jet (Air) Radius (cm) 0.8 4.0 Velocity (cm/sec) 10 25 Temperature (K) 600 1000 H2 Mass Fraction 0.05 0 CH4 Mass Fraction 0.45 0 O2 Mass Fraction 0 0.2329 N2 Mass Fraction 0.5 0.7671 2.6.5.2 Problem Setup The project file, cylindrical_shear_flow__profile.ckprj, is located in the samples41 directory. The FORTRAN subroutine used to set up inlet profiles is called CRUPROF and can be found inside the user routine file creslaf_user_routines.f in the user_routines directory. The GRI Mech 3.0, described in Section 2.8.2, is used for the gas phase combustion chemistry. No surface chemistry mechanism is needed because the outer wall is chemically inert. The user routine options are not shown in the graphical User Interface by default. To make these options available from the User Interface, the Display User Routine Options box in the Preferences panel must be checked. Figure 2-52 shows a typical Preferences panel and the Display User Routine Options is located near the bottom of the panel. RD0411-C20-000-001 73 © 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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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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