Tutorials Manual

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.
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