The Effect of Flow and Mixture Inhomogeneity on the Dynamics of Strained Flames by Youssef Mohamed Marzouk

Changes in flow strain and mixture composition on the order of a flame time scale are characteristic of many practical combustion processes. Accurately predicting the unsteady reponse of burning to these changes requires detailed modeling of species transport and chemical kinetics. This thesis formulates a detailed one-dimensional computational model for arbitrary unsteady conditions of strain and mixture, demonstrating its applicability to subgrid modeling of turbulent combustion. A novel numerical formulation, based on a globalized Newton iterative method and a preconditioned Krylov subspace linear solver, ensures efficient and robust convergence despite the stiffness of detailed chemistry. The model is validated via comparison with OPPDIF, a well-benchmarked steady-state strained flame code. The model is then used to characterize the fundamental interactions of flow and mixture inhomogeneityexamining the dynamic response of flame structure and burning to linear variations in mixture equivalence ratio, and capturing the effect of unsteady strain on a flame surface interacting with a vortex in two dimensions. The latter example leads to a redefinition of the appropriate subgrid strain for flame embedding simulation of premixed turbulent combustion. Thesis Supervisor: Ahmed F. Ghoniem Title: Professor of Mechanical Engineering