Abstract
In order to address the impact of the concentration gradients on the chemistry – turbulence interaction in turbulent flames, the REDIM reduced chemistry is constructed incorporating the scalar dissipation rate, which is a key quantity describing the turbulent mixing process. This is achieved by providing a variable gradient estimate in the REDIM evolution equation. In such case, the REDIM reduced chemistry is tabulated as a function of the reduced coordinates and the scalar dissipation rate as an additional progress variable. The constructed REDIM is based on a detailed transport model including the differential diffusion, and is validated for a piloted non-premixed turbulent jet flames (Sandia Flame D and E). The results show that the newly generated REDIM can reproduce the thermo-kinetic quantities very well, and the differential molecular diffusion effect can also be well captured.
Highlights
An accurate modeling of the interaction between mixing processes and the chemical kinetics is an important issue in numerical simulations of turbulent non-premixed flames [1, 2, 3]
If we provide the scalar gradient into the Reaction-Diffusion Manifolds (REDIM) from flame scenarios with different scalar dissipation rates, the REDIM reduced chemistry can incorporate the influence of turbulent mixing process on the chemical kinetics in terms of the scalar dissipation rates, and the impact of the concentrations gradients on the chemistry – turbulence interaction can be represented
To validate the generated REDIM reduced chemistry and to investigate whether the effect of the turbulent mixing process on the REDIM can be re-produced if one considers the scalar dissipation rate as additional progress variable, the wellknown piloted non-premixed methane/air diffusion flames, Sandia Flames [35], are selected as representative validation flames
Summary
An accurate modeling of the interaction between mixing processes and the chemical kinetics is an important issue in numerical simulations of turbulent non-premixed flames [1, 2, 3]. One of the challenges is the modeling of the chemical source terms, since they are strongly introduced by the turbulent mixing process and molecular transport. Manifold-based simplified chemistry is one of the the application of the manifold-based simplified chemistry can largely reduce the computational cost, one additional problem arises when they are applied to model turbulent flames: It is well known that the turbulent mixing can significantly affect the chemical reactions [14, 15]. It is important to know whether the simplified chemistry can reproduce the effect of the turbulent mixing on the chemical kinetics correctly
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