LINEAR-EDDY MODELING OF NONEQUILIBRIUM TURBULENT REACTING FLOWS WITH NONPREMIXED REACTANTS

Interactions between turbulent mixing and finite-rate chemistry effect s leading to highly nonequilibrium behavior of nonpremixed flames in i ncompressible, homogeneous turbulence are simulated by utilizing the l inear-eddy model (LEM). Computations reveal that as turbulent mixing i ncreases the local scalar dissipation rate, the mean temperature and r eaction rate decrease rapidly at the flame location and, depending on the activation energy, the flame either reignites or extinguishes. The LEM results are also compared to predictions from the conditional mom ent closure (CMC) model and reveal interesting differences between the se models near conditions of flame extinction. Specifically, for the c hemistry under consideration and within the context of the comparisons to the LEM simulations, the results highlight the importance in the C MC approach of modeling the conditionally averaged mixture-fraction di ssipation rate and accounting for conditional fluctuations in the chem ical reaction rate term in nonpremixed combustion systems near extinct ion. (C) 1997 by The Combustion Institute.