An Adaptive Chemistry Reduction Scheme for Reactive Flow Simulations

In numerical simulation of combustion models, solution of the chemical kinetics is often the most expensive part of the calculation, since accurate description of kinetic mechanism involves large number of species and reactions, leading to a large set of coupled ODE's, often too complex to be considered in their entirety along with a detailed flow simulation. Hence the need for representing the complex chemical reactions by simple reduced models, which can retain considerable accuracy while rendering computational feasibility. Realistically, under different conditions and at different points in time, different reactions become important, which has been exploited to develop an adaptive mechanism reduction scheme such that the reduced reaction model adapts itself to the changing reactor conditions. A methodology is developed in this work to automatically construct reduced mechanisms by utilizing mathematical programming techniques, where the objective is to minimize the dimension of the system while retaining sufficient accuracy in the prediction of specific species profiles. The reduced kinetic mechanisms are then analyzed for the range of conditions over which they retain their predictive capacity. Those reduced mechanisms are then coupled with the reactive flow algorithm, by selecting the appropriate mechanism depending on reactor condition and integrating the corresponding reduced set of ODEs for the specified valid range. These ideas are demonstrated using the system of methane combustion in air.

Last modified: Wed May 26 13:11:28 EDT 2004