A Lagrangian analysis of combustion regimes using multi-modal turbulent combustion model

Abstract

High Reynolds number turbulent reacting flows poses a modeling challenge due to the multi-regime, mixed-mode nature of the combustion processes. The present study attempts to provide insights into the complex combustion characteristics in turbulent flames by conducting highly resolved large eddy simulations of the Darmstadt multi-regime burner exhibiting both premixed and nonpremixed combustion regimes with occurrences of local extinction and re-ignition. Massless Lagrangian particles are transported along with the flow in order to monitor the evolution of the local flow-chemistry interaction. The simulations are validated against experimental data, and the Lagrangian properties are compared against the traditional premixed model in progress variable space and a generalized multi-modal manifold model in mixture fraction and generalized progress variable space. The comparison reveals that minor radical species are sensitive to the generalized progress variable dissipation rates, and the multi-modal manifold model is more suitable to reproduce the complex flame structure. Using the multi-modal model framework, the evolution of the combustion regimes is analyzed by the slope of the Lagrangian particle trajectory in the phase space.