LES/PDF based modeling of soot–turbulence interactions in turbulent flames

Abstract A large eddy simulation (LES)/probability density function (PDF) approach is used to describe the small-scale soot–turbulence–chemistry interactions. The PDF approach directly evolves the joint statistics of the gas-phase scalars and a set of moments of the soot number density function. This LES/PDF approach is then used to simulate a turbulent natural gas jet diffusion flame. Since the PDF equation is high dimensional, a Lagrangian method formulated in cylindrical coordinates is coupled to the Eulerian solution technique for the LES flow equations. The LES/PDF simulations show that soot formation is highly intermittent and is always restricted to the fuel-rich region of the flow. The PDF of soot moments has a wide spread leading to a large subfilter variance. Further, the conditional statistics of soot moments conditioned on mixture fraction and reaction progress variable show strong correlation between the gas phase composition and soot moments.

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