Subfilter transport modeling for large eddy simulation of turbulent nonpremixed sooting flames

Suo Yang, Jeffry K. Lew, Michael E. Mueller

Research output: Contribution to conferencePaper

1 Scopus citations

Abstract

Soot is formed by combustion of rich mixtures and is rapidly oxidized before being transported by turbulence into lean mixtures. Furthermore, different soot evolution mechanisms are dominant over distinct regions of mixture fraction (Z). For these reasons, a new subfilter PDF is proposed to account for this distribution of soot in Z space. In this model, the sooting mode of a bimodal soot subfilter PDF is locally activated only at rich mixture fractions where surface growth is locally faster than the oxidation. At the same time, Direct Numerical Simulation (DNS) studies of turbulent nonpremixed jet flames have revealed that Polycyclic Aromatic Hydrocarbons (PAH) are confined to spatially intermittent regions of low scalar dissipation rates due to their slow formation chemistry. The length scales of these regions are on the order of the Kolmogorov scale or smaller, where molecular diffusion dominates over turbulent mixing irrespective of the large-scale turbulent Reynolds number. A strain-sensitive transport model is developed to identify such species. Using a conventional nonpremixed "flamelet" approach, these species are then modeled with their molecular Lewis numbers, while the remaining species are modeled with an effective unity Lewis number. These two models are implemented within a Large Eddy Simulation (LES) framework, applied to a series of turbulent nonpremixed sooting jet flames, and validated via comparisons with experimental measurements of soot volume fraction. Compared to previous models, the soot volume fraction is significantly increased and in much better agreement with the experimental measurements.

Original languageEnglish (US)
StatePublished - Jan 1 2018
Event2018 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2018 - State College, United States
Duration: Mar 4 2018Mar 7 2018

Other

Other2018 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2018
CountryUnited States
CityState College
Period3/4/183/7/18

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Physical and Theoretical Chemistry
  • Chemical Engineering(all)

Keywords

  • Differential diffusion
  • Large Eddy Simulation (LES)
  • Soot
  • Subfilter PDF

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    Yang, S., Lew, J. K., & Mueller, M. E. (2018). Subfilter transport modeling for large eddy simulation of turbulent nonpremixed sooting flames. Paper presented at 2018 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2018, State College, United States.