Tutorials Manual

Chemkin 4.1.1
Chapter 2: Combustion in Gas-phase Processes
third body efficiency for N is set to zero. And we add a new reaction
N 2 + N = N + N + N to explicitly address the different temperature dependence of
nitrogen atom as the third body. Figure 2-32 shows these two reactions in CHEMKIN
format.
Figure 2-32
Nitrogen Atom Reaction in CHEMKIN Format
N2+M=N+N+M 1.92E17 -0.5 224900.
N2/2.5/ N/0/
N2+N=N+N+N 4.1E22 -1.5 224900.
2.5.1.2 Problem Setup
Setting up a shock tube model requires information from the corresponding
experiment. In addition to the conditions of the initial (unshocked) gas mixture, we will
need to provide information on the diameter of the shock tube, the viscosity of the gas
at 300 K, and the velocity of the incident shock. If we do not know the shock velocity
from the experiment, we can estimate it by using the Equilibrium Reactor Model with
the Chapmen-Jouguet detonation option. The shock tube diameter and the gas
viscosity at 300 K are only required when the boundary-layer correction is used in the
shock simulation.
The project file, incident_shock__normal_air.ckprj, is stored in the samples41
directory and the air dissociation mechanism by Camac and Feinberg is located in the
associated working directory.
2.5.1.3 Project Results
The NO mole fraction behind the incident shock is shown in Figure 2-33 as a function
of time. The NO mole fraction profile rapidly rises to a peak value then gradually falls
back to its equilibrium level. Reasons for the greater-than-equilibrium peak NO
concentration can be found in the paper by Camac and Feinberg and references
therein. The predicted peak NO mole fraction is 0.04609 and is in good agreement
with the measured and the computed data by Camac and Feinberg.
© 2007 Reaction Design 56 RD0411-C20-000-001