LINEAR EDDY MODELING OF REACTANT CONVERSION AND SELECTIVITY IN TURBULENT FLOWS

The linear eddy model (LEM) is used for statistical predictions of stationary, homogeneous turbulent flows under the influence of isothermal chemical reactions. Nonpremixed reacting systems are considered with two reaction mechanisms: a binary, irreversible single-step reaction A+B-->P; the series-parallel reaction A+B-->R, A+R-->P. In both systems, the influence of various flow parameters on the reactant conversion rate is elucidated For the second reaction scheme, effects of the flow parameters on the ''selectivity'' are also investigated. The trends predicted by the LEM agree with those produced previously by direct numerical simulation (DNS) at moderate values of the Reynolds number, Schmidt number and Damkohler number. An important feature of the LEM is its capability to extend the parameter range well beyond that currently attainable by DNS. The LEM generated results for a wide range of Schmidt and Damkohler numbers are discussed as well as their effects on the selectivity. These results assess the performance of some of the existing closures for modeling of the selectivity. None of the closures are capable of reproducing the LEM results.