S. Taing et al., PDF CALCULATIONS OF TURBULENT NONPREMIXED FLAMES OF H-2 CO2 USING REDUCED CHEMICAL MECHANISMS/, Combustion and flame, 95(1-2), 1993, pp. 133-150
A three-step chemical kinetic scheme, reduced systematically from a mo
re detailed mechanism is used to represent chemical reaction in the Mo
nte Carlo calculations of the joint velocity-composition probability d
ensity function (pdf) for pilot-stabilized turbulent jet nonpremixed f
lames of H-2/CO2 fuel mixtures. Flames with a range of fuel jet veloci
ties and hence varying degrees of finite rate chemical kinetic effects
have been calculated. The independent variables used are mixture frac
tion, xi and the specific molar abundance of three reactive scalars, G
AMMA(H2O), GAMMA(CO2), and GAMMA(H). Three multidimensional look-up ta
bles are generated for density, other dependent properties and the com
position increments due to chemical reaction. The use of these tables
in all subsequent calculations is computationally efficient. Terms rep
resenting the effects of pressure fluctuations, mechanical dissipation
, and scalar dissipation are modeled using an improved particle intera
ction model. Solutions are obtained on a Sun-Sparc1 station using 30 0
00 Monte Carlo particles for the low jet velocity flames and this numb
er is increased to 50000 at high jet velocities. The calculated veloci
ty and turbulence fields as well as centerline velocity decay rates ha
ve not been compared with measurements but are consistent with recent
experimental data collected in similar piloted jet flames of methane f
uel. The calculated mixing field compares well with experimental data
and the calculated flame length is slightly shorter than the observed
visible flame length. For the low- and intermediate-velocity flames, t
he calculated temperature and mass fractions of the stable species agr
ee reasonably well with instantaneous experimental data collected in s
imilar flames. At high jet velocities, when the flames are close to bl
owoff and the finite rate chemical kinetic effects are very significan
t, discrepancies occur between measurements and computations and the b
lowoff jet velocity is underpredicted by about 20%.