Statistics and Dynamics of Instantaneous Leading Point in Nonpremixed Bluff-Body Flames

Abstract

The subtle flow–flame interaction is essential for flame stabilization in propulsion and power systems. In this study, the flamelet/progress variable approach combined with large-eddy simulation is employed to simulate the Sydney nonpremixed bluff-body flame HM1E, for which the leading point concept is employed to reveal the complex flow–flame interaction. The Eulerian data as well as the leading point tracked data are analyzed. The Eulerian data show that compositional structure at axial location ranging from 0.5 to 1.0 has two branches, the unburnt branch and the burning branch. To reveal the underlying physics of the compositional structure, the statistics of leading point are analyzed and show that there are Gaussian-like and non-Gaussian probability density function (PDF) distributions upstream and downstream of about . Further analysis of the flow–leading point interaction shows that the region of ranging from 0.25 and 0.5 is where the instability of the outer shear layer occurs. Two different interaction patterns exist upstream and downstream of corresponding to Gaussian-like and non-Gaussian PDFs, respectively. The core and braid structures developed in the shear layer downstream of are responsible for the non-Gaussian PDF. In addition, the leading point migration in streamwise direction leads to the exhibition of two-branch compositional structure for Eulerian data.