Comparison of one-dimensional turbulence and direct numerical simulations of soot formation and transport in a nonpremixed ethylene jet flame

Abstract

Accurate models of soot formation in turbulent flames are important for correctly predicting and simulating flames and fires. Modeling soot formation and transport is challenging due to the complex chemical formation processes, and differential diffusion of soot relative to a flame. Direct numerical simulations (DNS) have highlighted the importance of such transport on soot concentrations, however DNS is computationally expensive. The one-dimensional turbulence (ODT) model is able resolve a full range of length and timescales and solves the evolution of diffusive and reactive scalars in the natural physical coordinate. We present results of soot formation in ODT and compare the model to simulation results from DNS in a temporally-evolving planar ethylene jet flame where the same transport, thermodynamic, and kinetic models are applied. Good agreement is found for the jet evolution in terms of the mixture fraction profiles. Conditional soot statistics (mean and fluctuations) are presented, along with joint soot-mixture fraction PDFs that illustrate the location and motion of soot in the mixture fraction coordinate. Good qualitative agreement between the models is found and the soot behavior is similar. While the ODT cannot capture three-dimensional flow structures, the ODT simulations are less computationally expensive than the DNS suggesting its use in conjunction with DNS for parametric study, model validation, and investigation at parameter ranges not currently available to DNS.