Tutorials Manual

Chemkin 4.1.1
Chapter 2: Combustion in Gas-phase Processes
Figure 2-30 gives the comparisons of the measurement and the predictions. In
general, the profiles show similar trends as observed in the temperature profiles
except that the pressure results are less sensitive to heat loss.
Figure 2-30
HCCI Engine—EGR Pressure Comparison
We can examine the heat-release rate profile for the timing and the magnitude of heat
generated by combustion. Since the temperature profile predicted by the nonadiabatic
model is in good agreement with the measurement, we can “reverseengineer”
to determine how much thermal energy is dissipated to the environment,
i.e., the heat loss rate, during the combustion/expansion period. The heat-release rate
and the heat loss rate profiles predicted by the non-adiabatic model are shown in
Figure 2-31. Since the solution file provides the heat production rate (heat_gas_rxn,
you must change the units from erg/cm 3 -sec to cal/sec-cm 3 ) instead of the heatrelease
rate (heat_loss_rate, cal/sec), we need to export the solutions to a text file
and use a utility program such as Microsoft Excel to obtain the heat release rate
(= heat production rate x volume). We then import the manipulated text data file back
to the Post-Processor to get the plot in Figure 2-31. Note that the heat-release profile
usually contains narrow spikes. If we want to calculate the total heat-release from the
heat release rate profile, we must make sure the profile has enough time resolution to
reduce numerical error.
© 2007 Reaction Design 54 RD0411-C20-000-001