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Progress in numerical modeling of non-premixed combustion

Citation

Xuan, Yuan (2014) Progress in numerical modeling of non-premixed combustion. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05292014-112456783

Abstract

Progress is made on the numerical modeling of both laminar and turbulent non-premixed flames. Instead of solving the transport equations for the numerous species involved in the combustion process, the present study proposes reduced-order combustion models based on local flame structures.

For laminar non-premixed flames, curvature and multi-dimensional diffusion effects are found critical for the accurate prediction of sooting tendencies. A new numerical model based on modified flamelet equations is proposed. Sooting tendencies are calculated numerically using the proposed model for a wide range of species. These first numerically-computed sooting tendencies are in good agreement with experimental data. To further quantify curvature and multi-dimensional effects, a general flamelet formulation is derived mathematically. A budget analysis of the general flamelet equations is performed on an axisymmetric laminar diffusion flame. A new chemistry tabulation method based on the general flamelet formulation is proposed. This new tabulation method is applied to the same flame and demonstrates significant improvement compared to previous techniques.

For turbulent non-premixed flames, a new model to account for chemistry-turbulence interactions is proposed. %It is found that these interactions are not important for radicals and small species, but substantial for aromatic species. The validity of various existing flamelet-based chemistry tabulation methods is examined, and a new linear relaxation model is proposed for aromatic species. The proposed relaxation model is validated against full chemistry calculations. To further quantify the importance of aromatic chemistry-turbulence interactions, Large-Eddy Simulations (LES) have been performed on a turbulent sooting jet flame. %The aforementioned relaxation model is used to provide closure for the chemical source terms of transported aromatic species. The effects of turbulent unsteadiness on soot are highlighted by comparing the LES results with a separate LES using fully-tabulated chemistry. It is shown that turbulent unsteady effects are of critical importance for the accurate prediction of not only the inception locations, but also the magnitude and fluctuations of soot.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Combustion, non-premixed flame, numerical modeling, flamelet
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Blanquart, Guillaume
Thesis Committee:
  • Meiron, Daniel I. (chair)
  • Shepherd, Joseph E.
  • Pullin, Dale I.
  • Blanquart, Guillaume
Defense Date:12 May 2014
Funders:
Funding AgencyGrant Number
U.S. Department of Energy-Basic Energy SciencesDE-SC006591
National Energy Research Scientic Computing Center (Office of Science of the U.S. Department of Energy)DE-AC02-05CH11231
Extreme Science and Engineering Discovery Environment (NSF)OCI-1053575
Record Number:CaltechTHESIS:05292014-112456783
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05292014-112456783
ORCID:
AuthorORCID
Xuan, Yuan0000-0001-9326-2197
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8421
Collection:CaltechTHESIS
Deposited By: Yuan Xuan
Deposited On:30 May 2014 21:31
Last Modified:20 Apr 2017 16:41

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