Abstract
Hereafter, we used the Algebraic Flame Surface Wrinkling (AFSW) model to conduct numerical simulations of the Paul Scherrer Institute (PSI) high-pressure, turbulent premixed Bunsen flame experiments. We implemented the AFSW model in OpenFOAM and in Ansys Fluent, and we compared the outcome of both solvers against the experimental results. We also highlight the differences between both solvers. All the simulations were performed using a two-dimensional axisymmetric model with the standard k−ϵ turbulence model with wall functions. Two different fuel/air mixtures were studied, namely, a 100%CH4 volumetric ratio and a 60%CH4+ 40%H2 volumetric ratio. The thermophysical and transport properties of the mixture were calculated as a function of temperature using the library Cantera (open-source suite of tools for problems involving chemical kinetics, thermodynamics, and transport processes), together with the GRI-Mech 3.0 chemical mechanism. It was found that the outcome of the AFSW model implemented in both solvers was in good agreement with the experimental results, quantitatively and qualitatively speaking. Further assessment of the results showed that, as much as the chemistry, the turbulence model and turbulent boundary/initial conditions significantly impact the flame shape and height.
Highlights
The study of premixed turbulent combustion is an area of active research as mastering this technology can directly translate into increased efficiency and reduced NOx and other pollutant emissions
The Algebraic Flame Surface Wrinkling (AFSW) model is an algebraic model originally derived by Muppala et al [8] through curve fitting of the Kobayashi experiments on turbulent flame speed measurements for methane and propane flames [12]
In the AFSW.H header file, we defined the function that implements the computation of the turbulent flame speed St in the AFSW model
Summary
The study of premixed turbulent combustion is an area of active research as mastering this technology can directly translate into increased efficiency and reduced NOx and other pollutant emissions. The solution of Equation (1), together with additional closure models (turbulence, reaction rate source term, and turbulent flame speed) and the thermophysical and transported properties of the unburnt/burnt mixture and flame, gives the propagation of the premixed flame. In Equations (1) and (3), evaluating the mean reaction rate source term ωis the central problem in modeling premixed turbulent combustion. This term can be modeled using algebraic methods or methods based on additional transport equations. We used an algebraic model, in particular the AFSW model [8,11,13,14] By using this model, the reaction rate source term for the progress variable and the regress variable can be expressed as follows, ωc = ρuSt|∇c|, ωb = ρuSt|∇b|,. In order to have a closed-form of Equation (7), the following closure relationships are used,
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