Analysis of the flamelet concept in the numerical simulation of laminar partially premixed flames

Numerical computations and optical diagnostics of unsteady partially premixed methane/air flames

“…When G = 0 is at Z < 1 the level-set G-equation is not needed since both the premixed flame zone structure and diffusion flame structure can be well tabulated as a function of mixture fraction and scalar dissipation rate. This is consistent with the finding of Consul et al [12]. The present simple and computationally efficient model is shown to well capture the fundamental aspect of the structures and dynamics of partially premixed flames.…”

“…Thus, the change of temperature and concentration can not be tabulated as a function of mixture fraction, and the position of the premixed flame can not be decided from the mixture fraction. This explains the observation of Consul et al [12] that the flamelet library model based on mixture fraction and scalar dissipation rate becomes inaccurate for partially premixed flames at low scalar dissipation rate. The present model employed a premixed flame propagation model (the level-set G-equation) to remedy this difficulty.…”

“…Consul et al [12] presented an evaluation of stationary flamelet library model (based on mixture fraction and scalar dissipation rate) for numerical simulations of two-dimensional steady partially premixed and non-premixed flames. It was shown that for non-premixed flames the stationary flamelet library model can give results in excellent agreement with the results from fully coupled chemistry and flow simulations.…”

“…Detailed flame chemistry can be obtained through a precomputed flamelet manifold tabulation, also known as a flamelet library, containing a profile of a 1-D premixed or non-premixed laminar flame, a method that is justifiable as long as a scale separation exists between the chemistry and the flow. Recently, the applicability of the flamelet approach for laminar steady partially premixed flames was analyzed [12]. It was shown that the method can give results in agreement with the experiments at a rather low computational cost.…”

An implicit relation between temperature and reaction rate in the SLFM

“…Pitsch et al [3] used the unsteady flamelet model with Lagrangian time scale to discuss the transient effect in modeling diffusion flame. Claramunt et al [4] and Cònsul et al [5] analyzed the application of the SLFM in nonpremixed laminar flames and laminar partially premixed flames, and compared the SLFM with the unsteady laminar flamelet model. It was found that the SLFM is incapable of predicting unsteady reaction processes such as pollutant formation, local extinction and reignition, lift-off or blow-out.…”